2021 Vol. 20 No. 6 Previous Issue    Next Issue

    Special Focus: High quality and high efficiency fertilization of rice
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Agricultural Economics and Management

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    Advancements in plant regeneration and genetic transformation of grapevine (Vitis spp.)
    ZHANG Xiu-ming, WU Yi-fei, LI Zhi, SONG Chang-bing, WANG Xi-ping
    2021, 20(6): 1407-1434.  DOI: 10.1016/S2095-3119(20)63586-9
    Abstract ( )   PDF in ScienceDirect  
    Grapevine (Vitis spp.) is one of the most economically important fruit crops worldwide, and there is considerable interest in improving its major agronomic and enological traits in response to ever-changing agricultural environments and consumer demands.  Molecular genetic techniques in particular, associated with rapid technological advancements, provide an attractive alternative to conventional breeding approaches for developing new grapevine varieties with enhanced yield performance, quality, stress tolerance and disease resistance.  To date, several grapevine varieties have been transformed with genes associated with diverse functions through biolistic bombardment and/or Agrobacterium-mediated transformation, and transgenic grape lines have been obtained using established regeneration systems.  Nevertheless, a wide range of factors, including genotype, explant source and culture medium, have been shown to affect the efficiency of plant regeneration.  Moreover, the selection and use of acceptor materials, bacterial strain and cell density, selectable markers and selection methods also influence transformation efficiency.  This paper provides an overview of recent advances in grapevine regeneration and genetic transformation and in-depth discussion of the major limiting factors, and discusses promising future strategies to develop robust plant regeneration and genetic transformation in grapevine.
    Special Focus: High quality and high efficiency fertilization of rice
    Editorial - High quality and high efficiency fertilization of rice
    LI Gang-hua
    2021, 20(6): 1435-1437.  DOI: 10.1016/S2095-3119(21)63683-3
    Abstract ( )   PDF in ScienceDirect  
    Rice (Oryza sativa L.), one essential staple cereal, feeds over 60% of the world’s population (FAO 2020).  As the global population grows, improving rice yield becomes an effective strategy to achieve food security (Deng et al. 2019).
        The use of chemical fertilizer, especially nitrogen (N) fertilizer, has historically played a critical role in the growth of rice yield (Zhang et al. 2015; Wood et al. 2020).  However, poor N management, especially excessive fertilizer application rate, has caused a number of adverse effects, such as, rice quality deterioration, yield instability, environmental degradation, and so on (Zhang et al. 2015, 2020; Guo et al. 2020; Hu et al. 2020).  Therefore, worldwide scientists have increasingly focused on how to increase the utilization rate and decrease the input of N fertilizer without compromising rice yield and quality (Zhang et al. 2015; Deng et al. 2019; Hu et al. 2020; Wood et al. 2020).
        The core of high quality, efficient and precise fertilization for rice is to improve the N-use efficiency (NUE) and rice quality depending on the characteristics of different varieties.  There are three aspects to improve NUE: breeding rice varieties with high NUE, precisely managing N fertilizer application and adopting new fertilization methods for high efficiency fertilizers.
        First, breeding rice varieties with high NUE is one fundamental method to improve NUE (Varshney et al. 2020; Liu et al. 2021).  However, nitrogen-efficient genes are still a long way from common use in rice breeding.  For current varieties, especially hybrid rice varieties, the use of restorer line is undoubtedly more direct and effective.  Therefore, it is worthwhile to explore restorer lines with a high yield and high NUE (HYHN) property, and their common agronomic traits.  Tian et al. (2021) select a number of highly efficient HYHN-type restorer lines and find that the advantages of HYHN restorer lines include a high level of nutrient accumulation and distribution to the panicles, and smooth flows of nutrients along the transportation channels.  This finding provides important guidance for the crossbreeding of existing varieties.
        Second, precision management of N fertilizer application is the fastest and most effective way to improve NUE, which includes soil testing and fertilizer recommendation (Chen et al. 2014), real-time and site-specific N management (Peng et al. 2006, 2010), precise and quantitative fertilization (Ling et al. 2005), and so on.  The precise and quantitative fertilization is the most typical among these approaches.  It uses systematic technical methods and parameters for the determination of total N rate, the N fertilizer ratio of base and tillering fertilizer to panicle fertilizer, and accurate leaf color diagnosis of N panicle fertilizer (Ling 2007).  In recent decades, precision management of N fertilizer has been rapidly developing.  There are three examples  in this issue.
        The first example is that total N rate depends on rice varieties and cultivation methods.  Ratoon rice cropping is an important component of the rice cropping system in USA, and has expanded to Asian countries in recent years.  N is the most effective nutrient for promoting regrowth and development of ratoon tillers, and improving N use efficiency of ratoon rice production will likely enhance the economic sustainability of rice production.  Based on an experiment test spanning several years, Wang et al. (2021) find that main crop N rate significantly affects rice main crop.  However, given N applied at 99 kg ha–1 at pre-flood after main crop harvest, the yield of rice ratoon crop is not significantly affected by main crop N rate.  In addition, neither main crop N nor ratoon crop N has a significant effect on the head rice yield of ratoon crop. 
        The second example suggests that N rate might be related to rice grain quality.  Few studies have examined the relationship between grain-filling characteristics of superior and inferior grains, and the grain quality of mid-season hybrid indica rice is still unclear.  Zhang et al. (2021) conducted a field experiment to ascertain the critical grain-filling characteristics that contribute to rice milling quality, appearance quality and cooking and eating quality under different N applications.  The results indicate that the prolonging grain-filling duration and increasing grain weight at the maximum grain-filling rate of inferior grains contributed to improved milling quality, appearance quality and cooking and eating quality of mid-season indica rice under appropriate N applications. 
        The third example is the development of diagnostic techniques for panicle N fertilizer.  Yao et al. (2021) developed a new critical N dilution curve for hybrid indica rice under the mechanical pot-seedling transplanting system.  This curve is able to determine more accurately and reliably the N nutrition status in pot-seedling mechanical transplanting (PMT) of hybrid indica rice than the existing curves, which can improve the management of real-time and dynamic rice fertilization.
        Finally yet importantly, the adoption of new fertilization methods for high efficiency fertilizers is the latest breakthrough in improvement in NUE (Lam et al. 2018; Liu et al. 2020).  Slow and controlled-release fertilizer as a new type of fertilizer has been the research subject of researches worldwide (Chen et al. 2018; Wei et al. 2018).  In order to meet the long-term nutrient needs of crops, this type of fertilizer slows down the release of nutrients by employing different coating materials and adding inhibitors (Timilsena et al. 2015).  Theoretically, it can greatly improve NUE by making the supply of N fertilizer synchronized with the demand of rice crops, which is achieved by the usual practice of splitting application of fertilizer according to crop nutrient requirements (Yuan et al. 2016).  However,  explicit methods are particularly important that reduce the number of fertilizer applications and increase NUE under the context of increasing agricultural labor costs (Ke et al. 2018; Li et al. 2018; Mi et al. 2019; Sun et al. 2019).  The side-dressing placement fertilizer application of new high-efficiency fertilizers meet this demand and become the latest breakthrough in improvement in NUE (Zhang et al. 2016; Pan et al. 2017).
        For side deep placement of N fertilizer in paddy rice, Zhao et al. (2021) conducted a field experiment and find that two fertilization models (RTN3RNR1) could achieve the dual goals of increasing grain yield and NUE.  These two fertilization models are worth further investigations.
        For slow and controlled-release fertilizers suitable for rice, Wu et al. (2021) conducted experiments to examine the N release characteristics of seven different slow and controlled release fertilizers, and their impacts on rice grain yields and yield components, in order to provide a theoretical basis for their further use.  They find that the N release characteristics of different types of slow and controlled release fertilizers were significantly different and proposed that the fertilizer type with a stronger N supply capacity and a longer effective duration was more conducive to dry matter accumulation at the later growth stage, thus promoting higher rice yield.
        In summary, studies in this special focus engage in a new research topic on high quality, efficient and precise fertilization of rice.  The findings offer valuable guidance and reference  for the management of high quality and high efficiency N fertilizers for rice.
    Indica rice restorer lines with large sink potential exhibit improved nutrient transportation to the panicle, which enhances both yield and nitrogen-use efficiency
    TIAN Qing-lan, HE Lian-hua, LIAO Shuang, LI Wu, DENG Fei, ZHOU Wei, ZHONG Xiao-yuan, REN Wan-jun
    2021, 20(6): 1438-1456.  DOI: 10.1016/S2095-3119(20)63309-3
    Abstract ( )   PDF in ScienceDirect  
    The yield and nitrogen use efficiency (NUE) of hybrid rice combinations are closely related to restorer line.  Therefore, it is essential to evaluate the agronomic characteristics of restorer lines with high yield and high NUE (HYHN).  However, it is unclear which restorer lines are HYHN, and neither have the common agronomic traits of the HYHN restorer lines been identified.  Aiming to address this issue, we conducted two filed experiments using three nitrogen applications, which screened five HYHN restorer lines from 15 indica restorer lines.  Yield, NUE and nutrient transportation of restorer lines with different yields and NUE types were examined.  Yield and total nitrogen absorption in aboveground biomass (TNA) increased, whereas NUE for grain production decreased with increasing nitrogen application levels.  The HYHN restorer lines had large spikelets and high weight per panicle that were significantly positively correlated with yield and NUE.  Therefore, large sink potential may be beneficial for both yield and NUE.  We further studied the differences in nutrient transportation to panicles between the HYHN and low yield and low NUE (LYLN) restorer lines and found that the former had a higher nitrogen absorption level and dry matter weight ratios of panicle in maturity.  Moreover, the HYHN lines also had a higher root and neck-panicle node bleeding intensity per stem after heading and more developed vascular bundles of neck-panicle nodes and leaves than the LYLN lines, which could contribute to the transportation of nutrients from root to ground and from stem and leaf to spike.  Therefore, the advantages of large sink potential of the HYHN restorer lines include large nutrient accumulation in and distribution to the panicles and smooth flow of nutrients along the transportation channels.
    Effects of nitrogen management on the ratoon crop yield and head rice yield in South USA
    WANG Yue-chao, LI Xiu-fen, Lee Tarpley, PENG Shao-bing, DOU Fu-gen
    2021, 20(6): 1457-1464.  DOI: 10.1016/S2095-3119(20)63452-9
    Abstract ( )   PDF in ScienceDirect  
    Ratoon rice cropping is an important component of the rice cropping system in Texas and south Louisiana, USA, and expanding in Asian countries.  Two field studies were conducted with widely planted rice (Oryza sativa L.) cultivars at Eagle Lake, Texas, USA to determine the effects of nitrogen (N) management in main (first) crop (MC) and ratoon (second) crop (RC) on RC yield.  In 2012 and 2013, one cultivar (Presidio) was adopted to determine the effects of RC N management on ratoon yield and head rice yield.  In 2016 and 2017, CL153, CL163 and CL272 in addition to Presidio were adopted to examine the effect of MC N management on ratoon yield and head rice yield.  N applied at preflood after MC harvest considerably improved RC yield.  Application of 99 kg N ha–1 at preflood after MC harvest was practically adequate for RC regrowth, development and approaching the yield potential for Presidio.  RC could produce quite high average grain yields of 5.90 to 6.53 t ha–1 in 2012 and 2013, respectively.  Main crop N rate only significantly affected MC yield; however, given N applied of 99 kg ha–1 at preflood after MC harvest, ratoon yield was not significantly affected by MC N rate.  Neither the main nor ratoon crop N management had a significant effect on RC head rice yield.  Considerable RC head rice yields (55–65%) were observed in all of the four cultivars and 4 years except for CL272 in 2016.  These results indicat that without very high N fertilizer application, rice ratoon crop could produce a considerable grain yield and an expectative head rice yield.  Rice ratooning could be a practical way to increase rice yields with the minimal input in south Texas and regions with a similar climate.
    Response of grain-filling rate and grain quality of mid-season indica rice to nitrogen application
    ZHANG Jing, ZHANG Yan-yan, SONG Ning-yuan, CHEN Qiu-li, SUN Hong-zheng, PENG Ting, HUANG Song, ZHAO Quan-zhi
    2021, 20(6): 1465-1473.  DOI: 10.1016/S2095-3119(20)63311-1
    Abstract ( )   PDF in ScienceDirect  
    Nitrogen is one of the important factors for high yield of rice.  Apart from high yield, high quality has become the current urgent demand for rice production.  Grain-filling stage is crucial for rice yield and quality formation.  However, the effect of nitrogen on grain-filling characteristics and the relationship of grain-filling characteristics and rice quality of mid-season indica rice were still unclear.  A field experiment was carried out to ascertain the critical grain-filling characteristics that contribute to rice milling quality, appearance quality and cooking and eating quality under nitrogen applications.  The results showed that nitrogen applications prolonged the duration of superior and inferior grain filling.  The mean grain-filling rate (Gmean) and the maximum grain-filling rate (Gmax) of the inferior grains were positively correlated with chalky kernel rate, chalkiness, and amylose content.  The time reaching the maximum grain-filling rate (Tmax G) of the inferior grains was positively correlated with brown rice rate, milled rice rate, and head milled rice rate.  Chalky kernel rate and chalkiness were negatively correlated with peak paste viscosity and breakdown viscosity.  Less amylose content and more crude protein content were detected in nitrogen application of Liangyoupei 9 and Y Liangyou 2 both in 2016 and 2017.  According to the correlation analysis, better cooking and eating quality of Y Liangyou 2 which had less amylose content might result from its higher Gmax and Gmean of inferior grain than that of Liangyoupei 9 in the treatments of nitrogen application.  These results indicated that the prolonging grain-filling duration and increasing grain weight at the maximum grain-filling rate of inferior grains contributed to the improvement of milling quality, appearance quality, and cooking and eating quality of mid-season indica rice under appropriate nitrogen applications.
    Determining nitrogen status and quantifying nitrogen fertilizer requirement using a critical nitrogen dilution curve for hybrid indica rice under mechanical pot-seedling transplanting pattern
    YAO Bo, HE Hai-bing, XU Hao-cong, ZHU Tie-zhong, LIU Tao, KE Jian, YOU Cui-cui, ZHU De-quan, WU Li-quan
    2021, 20(6): 1474-1486.  DOI: 10.1016/S2095-3119(21)63622-5
    Abstract ( )   PDF in ScienceDirect  
    Field experiments of nitrogen (N) treatment at five different application rates (0, 75, 150, 225, and 300 kg ha−1) were conducted under pot-seedling mechanical transplanting (PMT) in 2018 and 2019.  Two high-quality and high-yielding hybrids of indica rice, Huiliangyou 898 and Y Liangyou 900, were used in this study.  The N nutrition index (NNI) and accumulated N deficit (Nand), used to assess the N nutrition status in real-time, were calculated for the indica cultivars under PMT with a critical nitrogen concentration (Nc) dilution model based on shoot dry matter (DM) during the whole rice growth stage.  The relationships between NNI and Nand with relative yield (RY) were determined, and accurate N application schemes were developed for hybrids indica rice under PMT.  The results indicated that high application rate of N-fertilizer significantly increased the concentrations of shoot DM and N in aboveground organs during the observed stages in the two cultivars for two years (P<0.05).  The Nc dilution model of hybrid indica cultivars was Nc=4.02DM−0.42 (R2=0.97) combining the two cultivars under PMT.  Root-mean-square error and normalized root-mean-square error of the curve verification were 0.23 and 10.61%, respectively.  The NNI and Nand ranged from 0.58 to 1.31 and 109 to –55 kg ha−1, respectively, in the two cultivars for all N treatments.  NNI showed a linear relationship with Nand during the entire growth stage (0.53<R2<0.99, P<0.01).  In addition, NNI showed a linear-plateau relationship with RY (0.73<R2<0.92, P<0.01) throughout the observed stages.  These results suggest that the models can accurately diagnose the N-nutrition status and support effective N-fertilizer management in real-time for hybrid indica rice under PMT.
    Effect of side deep placement of nitrogen on yield and nitrogen use efficiency of single season late japonica rice
    ZHAO Can, HUANG Heng, QIAN Zi-hui, JIANG Heng-xin, LIU Guang-ming, XU Ke, HU Ya-jie, DAI Qi-gen, HUO Zhong-yang
    2021, 20(6): 1487-1502.  DOI: 10.1016/S2095-3119(20)63362-7
    Abstract ( )   PDF in ScienceDirect  
    Side deep placement of nitrogen plays an important role in improving rice yield and nitrogen use efficiency.  Few studies have examined the effects of reducing the times of nitrogen (RTN) application and reducing the nitrogen rate (RNR) of application on rice yield and nitrogen use efficiency under side deep placement of nitrogen in paddy fields.  Therefore, a field experiment of RNT and RNR treatments was conducted with nine fertilization modes during the 2018–2019 rice growing seasons in a rice–wheat cropping system of the lower reaches of the Yangtze River, China.  Rice yield and nitrogen use efficiency were investigated under side deep placement of nitrogen.  We found that under the same nitrogen application rate, the yield of RTN3 increased by 9.64 and 10.18% in rice varieties NJ9108 and NJ5718, respectively, compared with the farmers’ fertilizer practices (FFP).  The nitrogen accumulation of RTN3 was the highest at heading stage, at 11.30 t ha–1 across 2018 and 2019.  Under the same nitrogen application rate, the N agronomic use efficiency (NAE), N physiological efficiency (NPE) and N recovery efficiency (NRE) of RTN3 were 8.1–21.28%, 8.51–41.76% and 0.28–14.52% higher than those of the other fertilization modes, respectively.  RNR led to decreases in SPAD value, leaf area index (LAI), dry matter accumulation, nitrogen accumulation, and nitrogen use efficiency.  These results suggest that RTN3 increased rice yield and nitrogen use efficiency under the side deep placement of nitrogen, and RNR1 could achieve the goals of saving cost and increasing resource use efficiency.  Two fertilization modes RTN3 and RNR1 both could achieve the dual goals of increasing grain yield and resource use efficiency and thus are worth further application and investigation.
    Effects of different types of slow- and controlled-release fertilizers on rice yield
    WU Qiong, WANG Yu-hui, DING Yan-feng, TAO Wei-ke, GAO Shen, LI Quan-xin, LI Wei-wei, LIU Zheng-hui, LI Gang-hua
    2021, 20(6): 1503-1514.  DOI: 10.1016/S2095-3119(20)63406-2
    Abstract ( )   PDF in ScienceDirect  
    This experiment explored the effects of single application of seven types of slow- and controlled-release fertilizers on rice yield and various population characteristics.  Based on a study of the nitrogen (N) release characteristics of these fertilizers, pot experiments were conducted in 2018 and 2019 with split fertilization (CK, urea applied split equally at basal and panicle initiation stages, respectively) as control, which assessed the effects on SPAD value, yield and yield components, dynamic changes of rice tillers and dry matter accumulation.  The results showed that the N release characteristics of different types of slow- and controlled-release fertilizers were significantly different.  Polymer-coated urea (PCU) showed a controlled-release mode and provided sustained release throughout the whole growth stages.  Sulfur-coated urea (SCU) exhibited a slow-release mode, providing insufficient release at the middle and late stages.  Urease inhibitor urea (AHA) and urea-formaldehyde (UF) yielded a rapid-release mode, with an explosive N release at the early stage and no release at the middle and late stages.  These results showed that PCU delayed the peak seedling stage.  Compared with CK, dry matter accumulation and SPAD showed no significant differences, and due to the continuous release of N throughout the growth stages, rice yield, spikelets per panicle, seed setting rate, and 1 000-grain weight were all increased.  Owing to the lack of N supply at the late stage and the low number of spikelets, SCU led to a reduction of rice yield, which is nevertheless not statistically significant.  AHA and UF were susceptible to environmental factors and had varying effects on rice yield.  The results of this experiment indicated that given a fixed amount of N applied in a pot, the stronger the N supply capacity and the longer the effective duration time of the fertilizer, the higher the dry matter accumulation at the late growth stage, and the higher the rice yield.
    Functional analysis of the nitrogen metabolism-related gene CsGS1 in cucumber
    XIN Ming, QIN Zhi-wei, YANG Jing, ZHOU Xiu-yan, WANG Lei
    2021, 20(6): 1515-1524.  DOI: 10.1016/S2095-3119(20)63305-6
    Abstract ( )   PDF in ScienceDirect  
    Glutamine synthetase (GS) plays an important role in nitrogen (N) metabolism in cucumber.  In this study, we cloned and sequenced the CsGS1 gene, and analyzed the expression patterns and subcellular localization of the GS1 protein in response to different N conditions in order to determine its role in low-nitrogen (LN) tolerance.  CsGS1 was abundantly expressed in the leaves of the low N-requiring cultivar D0328, while the high N-requiring cultivar D0422 showed similar expression levels across different tissues including leaves, shoots and roots.  Furthermore, the GS1 protein was primarily localized in the cytoplasm of plant cells.  Both cultivars were then transformed with the CsGS1 coding sequence or antisense sequence via Agrobacterium tumefaciens in order to overexpress and silence GS1 expression, respectively.  Overexpression of CsGS1 significantly improved LN tolerance and photosynthetic parameters, and increased chlorophyll b content, biomass, plant height, root length, N accumulation and GS activity under LN condition compared to the control.   CsGS1 silencing on the other hand significantly reduced the above indices.  Taken together, CsGS1 is crucial for maintaining N metabolism in cucumber plants during N deprivation, and is a promising target for generating novel transgenic breeds with increasing nitrogen utilization efficiency. 
    Differences of aroma development and metabolic pathway gene expression between Kyoho and 87-1 grapes
    JI Xiao-hao, WANG Bao-liang, WANG Xiao-di, WANG Xiao-long, LIU Feng-zhi, WANG Hai-bo
    2021, 20(6): 1525-1539.  DOI: 10.1016/S2095-3119(20)63481-5
    Abstract ( )   PDF in ScienceDirect  
    Aroma is an important quality trait of grapes and often the focus of consumers, viticulturists and grapevine breeders.  Kyoho is a hybrid between Vitis vinifera and Vitis labrusca with a strawberry-like scent, while 87-1 is an early-ripening mutant of Muscat hamburg, belonging to Vitis vinifera, with a rose scent.  In this study, we compared their aroma compositions and concentrations during berry development by headspace-SPME combined with gas chromatography-mass spectrometry (GC-MS), and analyzed the expression differences of enzyme-encoding genes in the LOX-HPL, MEP and MVA metabolic pathways by qRT-PCR.  Twelve esters were detected in Kyoho during the whole berry development and they were abundant after veraison, but no esters were detected in 87-1 berries.  Linalool was the dominant terpene among the 14 terpenes detected in 87-1 berries, while limited amounts of terpenes were detected in Kyoho berries.  qRT-PCR analysis indicated that the low expression of VvAAT might explain the low content of ester volatiles in 87-1 berries, and the low expression of coding genes in the MEP pathway, especially VvPNLinNer1, might be the reason for the low content of volatile terpenes in Kyoho berries.  The results from this work will promote our understanding of aroma metabolic mechanisms of grapes, and offer some suggestions for grape aromatic quality improvement.
    The transcriptional landscape of cultivated strawberry (Fragaria×ananassa) and its diploid ancestor (Fragaria vesca) during fruit development
    LI Yong-ping, LIU Tian-jia, LUO Hui-feng, LIU Sheng-cai
    2021, 20(6): 1540-1553.  DOI: 10.1016/S2095-3119(20)63376-7
    Abstract ( )   PDF in ScienceDirect  
    Cultivated strawberry (Fragaria×ananassa) originated from four diploid ancestors: F. vesca, F. viridis, F. iinumae and F. nipponica.  Among them, F. vesca is the dominant subgenome for cultivated strawberry.  It is not well understood how differences in gene expression between diploid and octoploid strawberry contribute to differences during fruit development.  In this study, we used comprehensive transcriptomic analyses of F. vesca and Fananassa to investigate gene expression at the different stages of fruit development.  In total, we obtained 3 508 (turning stage) and 3 958 (red stage) differentially expressed genes with pairwise comparisons between diploid and octoploid.  The genes involved in flavonoid biosynthesis were almost upregulated in the turning stages of octoploid, and we also discovered a ripe fruit-specific module associated with several flavonoid biosynthetic genes, including FveMYB10, FveMYB9/11, and FveRAP, using weighted gene coexpression network analysis (WGCNA).  Furthermore, we identified the species-specific regulated networks in the octoploid and diploid fruit.  Notably, we found that the WAK and F-box genes were enriched in the octoploid and diploid fruits, respectively.  This study elucidates new findings on flavonoid biosynthesis and fruit size of strawberry with important implications for future molecular breeding in cultivated strawberry. 
    Plant Protection
    Two novel gene-specific markers at the Pik locus facilitate the application of rice blast resistant alleles in breeding
    TIAN Da-gang, CHEN Zi-qiang, LIN Yan, CHEN Zai-jie, LUO Jia-mi, JI Ping-sheng, YANG Li-ming, WANG Zong-hua, WANG Feng
    2021, 20(6): 1554-1562.  DOI: 10.1016/S2095-3119(20)63272-5
    Abstract ( )   PDF in ScienceDirect  
    Blast, a disease caused by Magnaporthe oryzae, is a major constraint for rice production worldwide.  Introgression of durable blast resistance genes into high-yielding rice cultivars has been considered a priority to control the disease.  The blast resistance Pik locus, located on chromosome 11, contains at least six important resistance genes, but these genes have not been widely employed in resistance breeding since existing markers hardly satisfy current breeding needs due to their limited scope of application.  In this study, two PCR-based markers, Pikp-Del and Pi1-In, were developed to target the specific InDel (insertion/deletion) of the Pik-p and Pi-1 genes, respectively.  The two markers precisely distinguished Pik-p, Pi-1, and the K-type alleles at the Pik locus, which is a necessary element for functional genes from rice varieties.  Results also revealed that only several old varieties contain the two genes, of which nearly half carry the K-type alleles.  Therefore, these identified varieties can serve as new gene sources for developing blast resistant rice.  The two newly developed markers will be highly useful for the use of Pik-p, Pi-1 and other resistance genes at the Pik locus in marker-assisted selection (MAS) breeding programs.
    Identification of eight Berberis species from the Yunnan-Guizhou plateau as aecial hosts for Puccinia striiformis f. sp. tritici, the wheat stripe rust pathogen
    LI Si-nan, CHEN Wen, MA Xin-yao, TIAN Xia-xia, LIU Yao, HUANG Li-li, KANG Zhen-sheng, ZHAO Jie
    2021, 20(6): 1563-1569.  DOI: 10.1016/S2095-3119(20)63327-5
    Abstract ( )   PDF in ScienceDirect  
    Puccinia striiformis Westend. f. sp. tritici Erikss. (Pst) infects wheat and causes stripe rust.  The rust is heteroecious with wheat as the primary uredinial and telial host and barberry (Berberis spp.) as the alternate pycnial and aecial host.  More than 40 Berberis species have been identified as alternate hosts for Pst, and most of these are Chinese Berberis species.  However, little is known about Berberis species or their geographic distributions in the Yunnan-Guizhou plateau in southwestern China.  The Yunnan-Guizhou plateau is considered to be an important and relatively independent region for the evolution of the wheat stripe rust pathogen in China because the entire disease cycle can be completed within the region.  In this study, we conducted a survey of barberry plants in the Yunnan-Guizhou plateau and identified the eight Pst-susceptible Berberis species under controlled conditions, including B. julianae, B. tsienii, B. veitchii, B. wilsonae, B. wilsonae var. guhtzunica, B. franchetiana, B. lepidifolia and B. pruinosa.  These species are reported here for the first time to serve as alternate hosts for the wheat stripe rust pathogen under controlled conditions. 
    Identification of genes involved in regulating MnSOD2 production and root colonization in Bacillus cereus 905
    GAO Tan-tan, DING Ming-zheng, LI Yan, ZENG Qing-chao, WANG Qi
    2021, 20(6): 1570-1584.  DOI: 10.1016/S2095-3119(20)63247-6
    Abstract ( )   PDF in ScienceDirect  
    sodA2-encoding manganese-containing superoxide dismutase (MnSOD2) in Bacillus cereus 905 plays an essential role in antioxidative stress, nutrition utilization, rhizosphere and phyllosphere colonization.  However, the genes involved in regulating the sodA2 expression have not been clearly elucidated in B. cereus.  In this study, a genome-wide random insertion mutagenesis was constructed by using transposon TnYLB-1 to identify novel genes regulating the sodA2 expression.  Seven mutants that changed the sodA2 expression at both mRNA and protein levels were finally obtained.  Sequence analysis and BLAST data showed that the genes disrupted by TnYLB-1 in B. cereus 905 shared high conservations with those in the B. cereus type strain, ATCC 14579.  These genes encode heat-inducible transcription repressor, chloride channel protein, recombinase A, ferrous iron transport protein, nucleoside diphosphate kinase, and histidine ammonia-lyase.  Besides, we also provided the evidence that the genes regulating the sodA2 expression could influence colonization ability of B. cereus 905 on wheat roots.  Specifically, those genes downregulating the sodA2 expression significantly reduced bacterial colonization on wheat roots, and mutants with increased MnSOD2 activities could enhance bacterial population densities on wheat roots to a certain degree.  Our work provided information that multiple genes are involved in MnSOD2 production and wheat root colonization.  The molecular regulatory pathways through which these genes modulate the sodA2 expression and root colonization need to be investigated extensively in the future.
    Molecular characterization of the ryanodine receptor from Adoxophyes orana and its response to lethal and sublethal doses of chlorantraniliprole
    SUN Li-na, LIU Yan-di, ZHANG Huai-jiang, YAN Wen-tao, YUE Qiang, QIU Gui-sheng
    2021, 20(6): 1585-1595.  DOI: 10.1016/S2095-3119(20)63356-1
    Abstract ( )   PDF in ScienceDirect  
    The insect ryanodine receptor (RyR) is a novel target of the anthranilic and phthalic insecticides, which have high activity against lepidopteran insects.  Several diamide insecticides have been used to control pests in orchards in China.  To enhance our understanding of the effects of diamides on RyRs, full-length cDNAs were isolated and characterized from the summer fruit tortrix moth, Adoxophyes orana, which is the most severe pest of stone and pome trees worldwide.  In addition, the modulation of AoRyR mRNA expression by diamide insecticides was investigated.  The AoRyR mRNA obtained had an open reading frame (ORF) of 15 402 bp nucleotides encoding 5 113 amino acids, and shared high and low identity with its orthologs in other insects and mammals of 77–92 and 45–47% identity, respectively.  One alternative splice site with two exclusive exons was revealed in AoRyR (a/b).  The usage of exon was more frequent in eggs and larvae than in pupae and adults.  Quantitative real-time reverse transcription PCR (qRT-PCR) showed that AoRyR mRNA was expressed at all developmental stages, especially in eggs, male pupae and male adults.  The expression levels of AoRyR mRNA in the whole body were up-regulated markedly after 3rd instar larvae were treated with chlorantraniliprole at LC10, LC20 and LC50 dosages.  The results could provide the basis for further functional studies of AoRyR and for the development of new chemicals with selective activity against insects. 
    Cuticular protein gene LmACP8 is involved in wing morphogenesis in the migratory locust, Locusta migratoria
    ZHAO Xiao-ming, YANG Jia-peng, GOU Xin, LIU Wei-min, ZHANG Jian-zhen
    2021, 20(6): 1596-1606.  DOI: 10.1016/S2095-3119(20)63248-8
    Abstract ( )   PDF in ScienceDirect  
    Cuticular proteins (CPs) are major components of the insect cuticle-associated organs such as integument and wings, although the importance of CPs for wing development and function in hemimetabolous insects remains understudied.  In the present study, a wing cuticular protein LmACP8 was identified from Locusta migratoria, which belongs to the RR-2 subfamily of cuticular protein R&R consensus (CPR) chitin-binding proteins.  LmACP8 was mainly expressed in the wing pads and showed high expression levels before ecdysis of third-, fourth-, and fifth-instar nymphs, with its encoded protein located in the procuticle of wing pads and adult wings.  Depletion of LmACP8 by RNA interference markedly reduced the amount of its protein, which consequently caused abnormal wing morphogenesis in the transition from nymph to adult of L. migratoria.  We further demonstrated that the abnormal morphogenesis was caused by severe damage of the endocuticle in the wings.  LmACP8 was suppressed by 20-hydroxyecdysone (20E) in vivo, however, its expression was significantly up-regulated after knocking down the hormone receptor gene LmHR39.  Thus, the LmACP8 that is negatively regulated by the LmHR39-mediated 20E signaling pathway is involved in wing development during the nymph to adult transition.
    Animal Science · Veterinary Medicine
    Identifying the complex genetic architecture of growth and fatness traits in a Duroc pig population
    ZHANG Zhe, CHEN Zi-tao, DIAO Shu-qi, YE Shao-pan, WANG Jia-ying, GAO Ning, YUAN Xiao-long, CHEN Zan-mou, ZHANG Hao, LI Jia-qi
    2021, 20(6): 1607-1614.  DOI: 10.1016/S2095-3119(20)63264-6
    Abstract ( )   PDF in ScienceDirect  
    In modern pig breeding programs, growth and fatness are vital economic traits that significantly influence porcine production.  To identify underlying variants and candidate genes associated with growth and fatness traits, a total of 1 067 genotyped Duroc pigs with de-regressed estimated breeding values (DEBV) records were analyzed in a genome wide association study (GWAS) by using a single marker regression model.  In total, 28 potential single nucleotide polymorphisms (SNPs) were associated with these traits of interest.  Moreover, VPS4B, PHLPP1, and some other genes were highlighted as functionally plausible candidate genes that compose the underlying genetic architecture of porcine growth and fatness traits.  Our findings contribute to a better understanding of the genetic architectures underlying swine growth and fatness traits that can be potentially used in pig breeding programs. 
    Evaluation of a povidone-iodine and chitosan-based barrier teat dip in the prevention of mastitis in dairy cows
    ZHANG Hui-min, JIANG Hong-rui, CHEN Dai-jie, SHEN Zi-liang, MAO Yong-jiang, LIANG Yu-sheng, Juan J. LOOR, YANG Zhang-ping
    2021, 20(6): 1615-1625.  DOI: 10.1016/S2095-3119(20)63418-9
    Abstract ( )   PDF in ScienceDirect  
    Postmilking teat dip is an important tool used to prevent mastitis in the modern dairy industry.  In this study, we evaluated the in vitro and in vivo efficacies of a barrier teat dip containing povidone-iodine and chitosan for the prevention of mastitis.  In experiment 1, we evaluated the antibacterial effects of chitosans with different molecular weights against six mastitis-causing bacteria based on the minimal inhibitory concentration test.  The results showed that 50 kDa chitosan had the maximum antibacterial activity compared with 5, 150 and 350 kDa chitosans.  In experiment 2, the inhibition zone test indicated that the barrier teat dip with 4.0% povidone-iodine and 1.0% chitosan had higher (P<0.05) in vitro antibacterial efficacy against most tested mastitis-causing bacteria than the barrier teat dip with 4.0% povidone-iodine and no chitosan.  In experiments 3 and 4, we evaluated the efficacies of two postmilking teat dips, 1) a barrier teat dip containing 1.0% chitosan and 4.0% povidone-iodine and 2) a conventional nonbarrier product containing 10% povidone-iodine in a field trial at two commercial dairy herds (1 and 2).  A 56-d split-udder experiment (experiment 3) was conducted using 47 lactating Chinese Holstein cows in herd 1.  Both left teats were immersed in barrier postmilking dip, and both right teats were dipped with nonbarrier postmilking dip.  During a 56-d split-herd experiment (experiment 4), a total of 139 lactating Chinese Holstein cows from herd 2 were allocated to two groups: 1) all teats of 67 cows were dipped in the nonbarrier teat dip, and 2) all teats of 72 cows were dipped in the barrier teat dip.  Milk samples were collected and analyzed for somatic cell count (SCC), fat content, protein content, and fat-to-protein ratio prior to the start of sampling (0 d), and at 28 and 56 d after initiation.  Bacteriological analysis was only performed on milk samples with SCC≥200?000 cells mL–1.  In experiment 3, no differences (P>0.05) in SCC, somatic cell score (SCS) or other milk quality indicators were observed between nonbarrier and barrier teat dip treatment teats throughout the experiment.  At the end of experiment 4, compared with nonbarrier teat dip group, a reduction (P<0.05) of 29% was observed for subclinical mastitis infection prevalence in the barrier teat dip group.  In the barrier teat dip group, the subclinical mastitis infection prevalence on 56 d was lower (P<0.05) than 0 d.  No differences (P>0.05) in milk qualities or clinical mastitis incidence were detected between groups.  Bacteriological analysis demonstrated that the barrier product containing povidone-iodine and chitosan reduced the subclinical mastitis infection prevalence induced by mastitis pathogens.  This effect was mainly due to the reductions in Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia fergusonii infections.  Overall, the data indicated that a barrier teat dip containing 4% povidone-iodine and 1% chitosan was more effective than 10% povidone-iodine in preventing subclinical mastitis. 
    Effects of 105 traditional Chinese medicines on the detection of β-agonists in medicine extracts and swine urine based on colloidal gold immunochromatographic assay
    WANG Zi-lin, FENG Ke-ying, GE Xiu-feng, MAI Jia-cheng, WANG Han-chuan, LIU Wen-zi, ZHANG Jia-hui, SHEN Xiang-guang
    2021, 20(6): 1626-1635.  DOI: 10.1016/S2095-3119(20)63265-8
    Abstract ( )   PDF in ScienceDirect  
    Colloidal gold immunochromatographic assay (CGIA) is commonly used for the on-site detection of β-agonists that are sometimes used illegally as feed additives in swine diets.  However, few studies have evaluated the causes of false-positive results that sometimes occur when applying CGIA in agricultural settings.  In this study, we investigated if this false-positive phenomenon is related to the addition of certain traditional Chinese medicines (TCMs) to swine feed.  We established and verified an extraction method for TCMs, and then applied CGIA to detect β-agonists in the extracts of 105 TCMs and in the urine of swine dosed with TCMs, respectively.  Liquid chromatography-tandem mass spectrometry was used to validate the results of the urine samples tested positive for β-agonists using CGIA.  The results were also verified using TCMs and colloidal gold test strips produced by different manufacturers.  The extracts of Citri Reticulatae Pericarpium Viride, Citri Reticulatae Pericarpium, Magnoliae Officinalis Cortex, Chaenomelis Fructus, and Rhodiolae Crenulatae Radix Et Rhizoma were tested positive for β-agonists.  Meanwhile, the addition of Citri Reticulatae Pericarpium Viride and Citri Reticulatae Pericarpium to swine feed resulted in false-positive results for β-agonists in swine urine.  The results provide a new way to explain false-positive CGIA results and provide valuable information for livestock feeding programs. 
    Agro-ecosystem & Environment
    Organic matter fractions within macroaggregates in response to long-term fertilization in calcareous soil after reclamation
    CAO Han-bing, XIE Jun-yu, HONG Jie, WANG Xiang, HU Wei, HONG Jian-ping
    2021, 20(6): 1636-1648.  DOI: 10.1016/S2095-3119(20)63354-8
    Abstract ( )   PDF in ScienceDirect  
    Soil organic carbon (SOC) plays a key role in improving soil quality and optimizing crop yield.  Yet little is known about the fate of macroaggregates (>0.25 mm) under long-term fertilization and their relative importance in SOC sequestration in reclaimed calcareous soil.  Therefore, the effects of mineral fertilizers and organic manure on the mechanisms of organic carbon (OC) stabilization in macroaggregates were investigated in this study.  Four treatments were used: unfertilized control (CK), mineral fertilizer (NPK), compost chicken manure alone (M), and mineral fertilizers plus manure (MNPK).  Samples from the 0–20 cm layer of soil receiving 11-year-long fertilization were separated into four fractions based on the macroaggregates present (unprotected coarse and fine particulate organic matter, cPOM and fPOM; physically protected intra-microaggregate POM, iPOM; and biochemically protected mineral associated OM, MOM) by the physical fractionation method.  Compared with the control, the long-term application of NPK had little effect on SOC content, total nitrogen (TN) content, and OC and TN contents of macroaggregate fractions.  In contrast, incorporation of organic manure (MNPK) significantly increased SOC (45.7%) and TN (24.3%) contents.  Application of MNPK increased OC contents within macroaggregate-extracted fractions of cPOM (292.2%), fPOM (136.0%) and iPOM (124.0%), and TN contents within cPOM (607.1%), fPOM (242.5%) and iPOM (127.6%), but not the mineral associated organic carbon (MOM-C) and nitrogen (MOM-N) contents.  Unprotected C fractions were more strongly and positively correlated with SOC increase than protected C fractions, especially for cPOM-C, indicating that SOC sequestration mainly occurred via cPOM-C in the studied calcareous soil.  In conclusion, MNPK increased the quantity and stability of SOC by increasing the contents of cPOM-C and cPOM-N, suggesting that this management practice (MNPK) is an effective strategy to develop sustainable agriculture.
    Microbial community dynamics during composting of animal manures contaminated with arsenic, copper, and oxytetracycline
    Ebrahim SHEHATA, CHENG Deng-miao, MA Qian-qian, LI Yan-li, LIU Yuan-wang, FENG Yao, JI Zhen-yu, LI Zhao-jun
    2021, 20(6): 1649-1659.  DOI: 10.1016/S2095-3119(20)63290-7
    Abstract ( )   PDF in ScienceDirect  
    Effects of the heavy metal copper (Cu), the metalloid arsenic (As), and the antibiotic oxytetracycline (OTC) on bacterial community structure and diversity during cow and pig manure composting were investigated.  Eight treatments were applied, four to each manure type, namely cow manure with: (1) no additives (control), (2) addition of heavy metal and metalloid, (3) addition of OTC and (4) addition of OTC with heavy metal and metalloid; and pig manure with: (5) no additives (control), (6) addition of heavy metal and metalloid, (7) addition of OTC and (8) addition of OTC with heavy metal and metalloid.  After 35 days of composting, according to the alpha diversity indices, the combination treatment (OTC with heavy metal and metalloid) in pig manure was less harmful to microbial diversity than the control or heavy metal and metalloid treatments.  In cow manure, the treatment with heavy metal and metalloid was the most harmful to the microbial community, followed by the combination and OTC treatments.  The OTC and combination treatments had negative effects on the relative abundance of microbes in cow manure composts.  The dominant phyla in both manure composts included Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria.  The microbial diversity relative abundance transformation was dependent on the composting time.  Redundancy analysis (RDA) revealed that environmental parameters had the most influence on the bacterial communities.  In conclusion, the composting process is the most sustainable technology for reducing heavy metal and metalloid impacts and antibiotic contamination in cow and pig manure.  The physicochemical property variations in the manures had a significant effect on the microbial community during the composting process.  This study provides an improved understanding of bacterial community composition and its changes during the composting process. 
    Synergistic effect of Si and K in improving the growth, ion distribution and partitioning of Lolium perenne L. under saline-alkali stress
    FAN Yuan, SHEN Wu-yan, Pino VANESSA, CHENG Fang-qin
    2021, 20(6): 1660-1673.  DOI: 10.1016/S2095-3119(20)63277-4
    Abstract ( )   PDF in ScienceDirect  
    The application of Si or K has proven to be beneficial for the growth of plants under saline-alkali stress.  However, the synergistic effect of Si and K in improving the growth, ion distribution, and partitioning in Lolium perenne L. under saline-alkali stress remains unclear.  In this study, the growth characteristics and ion-selective absorption of ryegrass (Lolium perenne L.) exposed to different levels of saline-alkali stress were evaluated.  The growth parameters of ryegrass were significantly improved when Si was applied by itself or coupled with K under low saline-alkali stress.  Under a high saline-alkali level, only simultaneous application of Si and K could significantly improve the growth of ryegrass.  When Si and K were applied together, the K+/Na+ and Ca2+/Na+ ratios in root, stem, and leaf of ryegrass were maximally improved as compared to the individual treatments and control.  The K+ and Ca2+ concentrations in the vacuole, cell wall, and organelle of leaf were increased dramatically.  This improvement was due to the ability of applied ions to compete with Na+, allowing the plant to maintain osmotic potential and leaf water content.  The concentration of Na+ was significantly reduced when Si and K were applied and mainly concentrated in the soluble fraction and cell wall.  The Si concentration in ryegrass increased markedly by the combined application of Si and K, and most of it was accumulated in the cell wall and soluble fraction, which could help in chlorophyll synthesis, reduce membrane injury, and increase water absorption under saline-alkali stress.  This study emphasized the advantage of Si and/or K on the growth of plants under different saline-alkaline levels and provided a guide for the production of Si-K fertilizer and its application in saline-alkali soil. 
    Changes in bacterial community and abundance of functional genes in paddy soil with cry1Ab transgenic rice
    SONG Ya-na, CHEN Zai-jie, WU Ming-ji, LI Gang, WANG Feng
    2021, 20(6): 1674-1686.  DOI: 10.1016/S2095-3119(20)63271-3
    Abstract ( )   PDF in ScienceDirect  
    A field experiment involving cry1Ab transgenic rice (GM) and its parental non-cry1Ab rice (M) has been on-going since 2014.  The diversity of the bacterial communities and the abundance of the microbial functional genes which drive the conversion of nitrogen in paddy soil were analyzed during the growth period of rice in the fifth year of the experiment, using 16S rRNA-based Illumina MiSeq and real-time PCR on the amoA, nirS and nirK genes.  The results showed no differences in the alpha diversity indexes of the bacterial communities, including Chao1, Shannon and Simpson, between the fields cultivated with line GM and cultivar M at any of the growth stages of rice.  However, the bacterial communities in the paddy soil with line GM were separated from those of paddy soil with cultivar M at each of the growth stages of rice, based on the unweighted UniFrac NMDS or PCoA.  In addition, the analyses of ADONIS and ANOSIM, based on the unweighted UniFrac distance, indicated that the above separations between line GM and cultivar M were statistically significant (P<0.05) during the growth season of rice.  The increases in the relative abundances of Acidobacteria or Bacteroidetes, in the paddy soils with line GM or cultivar M, respectively, led to the differences in the bacterial communities between them.  At the same time, functional gene prediction based on Illumina MiSeq data suggested that the abundance of many functional genes increased in the paddy soil with line GM at the maturity stage of rice, such as genes related to the metabolism of starch, amino acids and nitrogen.  Otherwise, the copies of bacterial amoA gene, archaeal amoA gene and denitrifying bacterial nirK gene significantly increased (P<0.05 or 0.01) in the paddy soil with line GM.  In summary, the release of cry1Ab transgenic rice had effects on either the composition of bacterial communities or the abundance of microbial functional genes in the paddy soil.
    The water-saving potential of using micro-sprinkling irrigation for winter wheat production on the North China Plain
    ZHAI Li-chao, Lü Li-hua, DONG Zhi-qiang, ZHANG Li-hua, ZHANG Jing-ting, JIA Xiu-ling, ZHANG Zheng-bin
    2021, 20(6): 1687-1700.  DOI: 10.1016/S2095-3119(20)63326-3
    Abstract ( )   PDF in ScienceDirect  
    The shortage of groundwater resources is a considerable challenge for winter wheat production on the North China Plain.  Water-saving technologies and procedures are thus urgently required.  To determine the water-saving potential of using micro-sprinkling irrigation (MSI) for winter wheat production, field experiments were conducted from 2012 to 2015.  Compared to traditional flooding irrigation (TFI), micro-sprinkling thrice with 90 mm water (MSI1) and micro-sprinkling four times with 120 mm water (MSI2) increased the water use efficiency by 22.5 and 16.2%, respectively, while reducing evapotranspiration by 17.6 and 10.8%.  Regardless of the rainfall pattern, MSI (i.e., MSI1 or MSI2) either stabilized or significantly increased the grain yield, while reducing irrigation water volumes by 20–40%, compared to TFI.  Applying the same volumes of irrigation water, MSI (i.e., MSI3, micro-sprinkling five times with 150 mm water) increased the grain yield and water use efficiency of winter wheat by 4.6 and 11.7%, respectively, compared to TFI.  Because MSI could supply irrigation water more frequently in smaller amounts each time, it reduced soil layer compaction, and may have also resulted in a soil water deficit that promoted the spread of roots into the deep soil layer, which is beneficial to photosynthetic production in the critical period.  In conclusion, MSI1 or MSI2 either stabilized or significantly increased grain yield while reducing irrigation water volumes by 20–40% compared to TFI, and should provide water-saving technological support in winter wheat production for smallholders on the North China Plain.
    Agricultural Economics and Management
    Impacts of household income on beef at-home consumption: Evidence from urban China
    ZHU Wen-bo, CHEN Yong-fu, ZHAO Jing, WU Bei-bei
    2021, 20(6): 1701-1715.  DOI: 10.1016/S2095-3119(20)63582-1
    Abstract ( )   PDF in ScienceDirect  
    Beef consumption in China has increased substantially from 5.0 million tons in 2000 to 7.7 million tons in 2019 thanks to rapid income growth, but still remains low compared to pork and poultry consumption.  Improving the understanding about the impacts of household income on beef consumption in China is necessary to forecast future beef demand and inform the domestic beef industry, especially in the context of unprecedented expansion of middle income class in China.  Based on survey data of 32 878 urban households collected by the National Bureau of Statistics of China, we employed the inverse hyperbolic sine (IHS) double-hurdle model to estimate income elasticities of beef demand across different income groups and simulated possible trends of future beef consumption of Chinese urban residents.  The empirical results showed that the unconditional income elasticities of beef consumption at home vary between 0.169 for the low-income group and 0.671 for the high-income group.  The simulated results indicated that beef consumption is expected to increase by 12.0 to 38.8% in 10 years and by 18.6 to 70.5% in 15 years under distinct income growth scenarios.  Our findings provide practical insights for policy makers and other stakeholders about future beef demand, such as potential opportunities embedded in rising beef demand for domestic producers and world beef exporters as well as the urgency of improving the supply chain resilience of beef in China.
    Do cooperatives participation and technology adoption improve farmers’ welfare in China?  A joint analysis accounting for selection bias
    YANG Dan, ZHANG Hui-wei, LIU Zi-min, ZENG Qiao
    2021, 20(6): 1716-1726.  DOI: 10.1016/S2095-3119(20)63325-1
    Abstract ( )   PDF in ScienceDirect  
    This study examines the impact of farmers’ cooperatives participation and technology adoption on their economic welfare in China.  A double selectivity model (DSM) is applied to correct for sample selection bias stemming from both observed and unobserved factors, and a propensity score matching (PSM) method is applied to calculate the agricultural income difference with counter factual analysis using survey data from 396 farmers in 15 provinces in China.  The findings indicate that farmers who join farmer cooperatives and adopt agricultural technology can increase agricultural income by 2.77 and 2.35%, respectively, compared with those non-participants and non-adopters.  Interestingly, the effect on agricultural income is found to be more significant for the low-income farmers than the high-income ones, with income increasing 5.45 and 4.51% when participating in farmer cooperatives and adopting agricultural technology, respectively.  Our findings highlight the positive role of farmer cooperatives and agricultural technology in promoting farmers’ economic welfare.  Based on the findings, government policy implications are also discussed.
    Low glycemic index: The next target for rice production in China?
    HUANG Min, HU Li-qin
    2021, 20(6): 1727-1729.  DOI: 10.1016/S2095-3119(20)63299-3
    Abstract ( )   PDF in ScienceDirect  
    China has 22% of the world’s population but only 7% of the world’s arable land.  Food security has been a chief mission of the Chinese state since the beginning of the dynastic era and remains a primary objective in the early 21st century.  As a result, high yield has been the first priority of farmers, researchers and agricultural agencies in China for a long time.
        Rice is the most important food crop in China, feeding about 65% of the national population.  Rice self-sufficiency has been achieved in China by increasing grain yields by more than 50% since 1980, and this trend is likely to be sustained assuming current yield and consumption trajectories without reduction in production area (Deng et al. 2019).
        As living standards improve, the demand for high quality rice, especially good taste rice, increases in China.  In general, rice with low amylose content and soft texture is preferred by Chinese rice consumers.  This preference has driven considerable changes in rice production of China: (1) in single-season rice cropping regions such as Jiangsu and Heilongjiang provinces, the planting area of soft japonica rice with low amylose content (<15%) has increased substantially while that of non-soft japonica rice with relatively high amylose content has decreased considerably (Zhu et al. 2015); (2) in single- and double-season (early and late seasons) rice mixed cropping regions such as Hunan and Jiangxi provinces, the planting area of early-season indica rice, which is dominated by cultivars with high amylose content (Yin et al. 2020), has decreased sharply (Peng 2016), whereas the planting area of single- and late-season indica rice with moderate to low amylose contents has increased significantly.  Increasing eating quality of rice has also been a focus for Chinese rice researchers and agricultural agencies. New tasty (soft texture) indica and japonica rice cultivars have been increasingly developed and grown in China to cater to consumer preferences (Zeng et al. 2019).
        Improved living standards are also driving up the demand for healthy food in China.  However, rice is generally categorized as a food with high glycemic index (GI).  There is an evidence that rice consumption is significanlty positively associated with the increase in risk of type II diabetes, especially in Asian populations including Chinese (Hu et al. 2012).  Based on the dose-response relation between rice intake and relative risk of type II diabetes plotted by Hu et al. (2012), Song et al. (2017) found that the relative risk of type II diabetes was significantly elevated above 1.00 in China under the current rice intake, i.e., 213 and 256 g d–1 for women and men, respectively.  In addition, China currently has the highest number of people with diabetes (mainly type II diabetes) in the world, with 114 million or 12% of Chinese adults being diagnosed with diabetes and an additional 493 million with pre-diabetes (Xu et al. 2013).  It is well known that diet management is very important for diabetes care (Sami et al. 2017).  Choosing low-GI foods in place of high-GI foods is a clinically useful way to control glycemic levels in people with diabetes (Brand-Miller et al. 2003).  Therefore, it is meaningful and urgent to produce low-GI rice in China to reduce risk of type II diabetes.  In this regard, it has been found that there is a large variability in GI among rice cultivars.  For example, Fitzgerald et al. (2011) reported that the GI of cooked rice ranged from 48 to 92 in a set of 235 cultivars.
        Our concern is that the current rapid development of tasty rice with soft texture (low amylose content) may increase rather than reduce the risk of type II diabetes in China, because the lower the amylose content of rice, the lower the resistant starch contents (Rahman et al. 2007), the less the resistance to digestion (Hu et al. 2004), and the higher the GI (Fitzgerald et al. 2011).  This concern can be supported by a human diet study of Ohtsubo et al. (2016), who observed that a more drastic increase of postprandial blood glucose occurred in the case of eating low-amylose rice than in the case of eating high-amylose rice and thus concluded that the high-amylose rice is promising for the purpose of diabetes prevention.  Our concern is also supported by a population-based study of 3 918 Chinese adults aged 23–69 years (Cheng et al. 2017), which showed that the consumption of rice with high GI was detrimentally associated with glucose homeostasis and suggested that the preferred choice of rice with lower GI should be advocated.  These also highlight that the cultivar change should be included when modeling the risk of type II diabetes associated with rice intake.
        There is no doubt that low-GI rice with high amylose and resistant starch contents is not preferred by most Chinese consumers in the terms of palatability.  However, in the age of increasing prevalence of non-communicable diseases, most rice consumers are expected to choose health over taste.  Therefore, we appeal that China should begin to consider human health as a target for rice production.  Taken into considerations that (1) GI of rice is not only closely related to its amylose and resistance starch contents but also affected by its other starch traits (e.g., starch gelatinization and retrogradation properties, the particle size of starch granule, the ratio of amylose to amylopectin, the crystallite structure of amylopectin, the starch resistance against enzymatic hydrolysis, and the interactions of starch with other components) and external factors such as cooking conditions (Frei et al. 2003; Rahman et al. 2007; Kaur et al. 2016); and (2) GI of foods and some starch traits such as the resistance starch contents are different depending on measurement method (Brand-Miller and Holt 2004; Walter et al. 2005), we therefore suggest promoting collaborative studies among researchers from various disciplines (crop science, food science and public health) to permit a full understanding of low-GI rice (Fig. 1).  The collaborative studies are not difficult to arrange given that China has established a batch of collaborative innovation centers at national and local levels and has accumulated a wealth of experience.  The studies can start by (1) investigating the digestive properties and glycemic impact of existing rice cultivars with different grain physicochemical characteristics across a wide range of environments, crop management practices and cooking conditions; and (2) considering the minimal extent of desirable palatability for the development of low-GI rice cultivars with high amylose and resistance starch contents in breeding programs.  In addition, it is also important to facilitate the collaboration among academy, government and business to enhance the consumer acceptance of low-GI rice (Jones and Jew 2007).  These works will provide useful information to guide the evaluation, production and promotion of healthy rice in China in the near future.