2020 Vol. 19 No. 7 Previous Issue    Next Issue

    Crop Science
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
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    Environmental risks for application of magnesium slag to soils in China
    WANG Xiao-bin, YAN Xiang, LI Xiu-ying
    2020, 19(7): 1671-1679.  DOI: 10.1016/S2095-3119(19)62835-2
    Abstract ( )   PDF in ScienceDirect  
    Magnesium slag (MS) is one of the main industrial solid wastes produced by the magnesium industry.  Solving the problem of its disposal has attracted much attention with increasing amounts of solid wastes generated in the production of metallic magnesium.  Because MS contains calcium (Ca), magnesium (Mg), and silicon (Si), some have tried to use MS as Si-Ca-Mg fertilizer or for soil amendment in agriculture.  However, in the magnesium metallurgical process, some pollutant elements are introduced into MS, resulting in the enrichment of these pollutants in MS, such as arsenic (As), chromium (Cr), cadmium (Cd), mercury (Hg), copper (Cu), nickel (Ni), fluorine (F) and chlorine (Cl).  Research indicates that the enrichment of these pollutants can result in high levels, especially for Cd, Hg, Cu, Ni, F and Cl (0–4, 0–0.74, 20–127, 100–170, 2 277–14 800 and 133–1 000 mg kg–1, respectively) in some MS in China.  These levels are often far beyond the limits (≤0.3, ≤0.5, ≤50 and ≤60 mg kg–1 for Cd, Hg, Cu and Ni, respectively) of the Chinese Risk Screening Values for Soil Contamination of Agricultural Land based on the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land (GB 15618-2018) or the critical reference values (≤800 and ≤200 for F and Cl, respectively).  The elements Hg, Cu, Cr and F (detected in MS leachate at 0.00023–0.0052, 0.043–3.89, 0.026–0.171, and 1.43–8.52 mg L–1, respectively) also exceed the limits (Class IV–V) of the Chinese Standard for Groundwater Quality (GB/T 14848-2017).  Based on the above results, it is suggested that without any pretreatment for reducing harmful pollutants MS should not be allowed to be applied for soil remediation or conditioning directly into farmlands in order to ensure soil health, food safety and environmental quality. 
    Biofumigation: An alternative strategy for the control of plant parasitic nematodes
    Rebecca Jean Barnes BRENNAM, Samantha GLAZE-CORCORAN, Robert WICK, Masoud HASHEMI
    2020, 19(7): 1680-1690.  DOI: 10.1016/S2095-3119(19)62817-0
    Abstract ( )   PDF in ScienceDirect  
    Plant-parasitic nematodes wreak havoc on the yield and quality of crops worldwide.  Damage from these pests is estimated to exceed US$100 billion annually but is likely higher due to misdiagnosis.  Nematode damage may be catastrophic, but historically the solution has been damaging as well.  Use of the synthetic nematicide methyl bromide (MBr) poses risks to the environment and to human health.  Biofumigation, the use of plant material and naturally produced compounds to control pests, is an increasingly feasible method of pest management.  The process acts through the growth or incorporation of plant material into the soil, that, over the course of its degradation, releases glucosinolates that break down into nematotoxic isothiocyanates.  These secondary plant metabolites exist naturally in commonly grown plants, most of which belong to the Brassicaceae family.  Research endeavors have increasingly explored the potential of biofumigation.  The reaction of target pests, the selection of biofumigant, and ideal environments for efficacy continue to be evaluated.  This review seeks to provide a cost and benefit assessment of the status of biofumigation for the control of plant-parasitic nematodes as an alternative to conventional methyl bromide usage. 
    Crop Science
    Mapping quantitative trait loci associated with starch paste viscosity attributes by using double haploid populations of rice (Oryza sativa L.)
    Tahmina SHAR, SHENG Zhong-hua, Umed ALI, Sajid FIAZ, WEI Xiang-jin, XIE Li-hong, JIAO Gui-ai, Fahad ALI, SHAO Gao-neng, HU Shi-kai, HU Pei-song, TANG Shao-qing
    2020, 19(7): 1691-1703.  DOI: 10.1016/S2095-3119(19)62726-7
    Abstract ( )   PDF in ScienceDirect  
    The paste viscosity attributes of starch, measured by rapid visco analyzer (RVA), are important factors for the evaluation of the cooking and eating qualities of rice in breeding programs.  To determine the genetic roots of the paste viscosity attributes of rice grains, quantitative trait loci (QTLs) associated with the paste viscosity attributes were mapped, using a double haploid (DH) population derived from Zhongjiazao 17 (YK17), a super rice variety, crossed with D50, a tropic japonica variety.  Fifty-four QTLs, for seven parameters of the RVA profiles, were identified in three planting seasons.  The 54 QTLs were located on all of the 12 chromosomes, with a single QTL explaining 5.99 to 47.11% of phenotypic variation.  From the QTLs identified, four were repeatedly detected under three environmental conditions and the other four QTLs were repeated under two environments.  Most of the QTLs detected for peak viscosity (PKV), trough viscosity (TV), cool paste viscosity (CPV), breakdown viscosity (BDV), setback viscosity (SBV), and peak time (PeT) were located in the interval of RM6775–RM3805 under all three environmental conditions, with the exception of pasting temperature (PaT).  For digenic interactions, eight QTLs with six traits were identified for additive×environment interactions in all three planting environments.  The epistatic interactions were estimated only for PKV, SBV and PaT.  The present study will facilitate further understanding of the genetic architecture of eating and cooking quality (ECQ) in the rice quality improvement program.
    Genome-wide identification and transcriptome profiling reveal great expansion of SWEET gene family and their wide-spread responses to abiotic stress in wheat (Triticum aestivum L.)
    QIN Jin-xia, JIANG Yu-jie, LU Yun-ze, ZHAO Peng, WU Bing-jin, LI Hong-xia, WANG Yu, XU Sheng-bao, SUN Qi-xin, LIU Zhen-shan
    2020, 19(7): 1704-1720.  DOI: 10.1016/S2095-3119(19)62761-9
    Abstract ( )   PDF in ScienceDirect  
    The Sugars Will Eventually be Exported Transporter (SWEET) gene family, identified as sugar transporters, has been demonstrated to play key roles in phloem loading, grain filling, pollen nutrition, and plant-pathogen interactions.  To date, the study of SWEET genes in response to abiotic stress is very limited.  In this study, we performed a genome-wide identification of the SWEET gene family in wheat and examined their expression profiles under mutiple abiotic stresses.  We identified a total of 105 wheat SWEET genes, and phylogenic analysis revealed that they fall into five clades, with clade V specific to wheat and its closely related species.  Of the 105 wheat SWEET genes, 59% exhibited significant expression changes after stress treatments, including drought, heat, heat combined with drought, and salt stresses, and more up-regulated genes were found in response to drought and salt stresses.  Further hierarchical clustering analysis revealed that SWEET genes exhibited differential expression patterns in response to different stress treatments or in different wheat cultivars.  Moreover, different phylogenetic clades also showed distinct response to abiotic stress treatments.  Finally, we found that homoeologous SWEET genes from different wheat subgenomes exhibited differential expression patterns in response to different abiotic stress treatments.  The genome-wide analysis revealed the great expansion of SWEET gene family in wheat and their wide participation in abiotic stress response.  The expression partitioning of SWEET homoeologs under abiotic stress conditions may confer greater flexibility for hexaploid wheat to adapt to ever changing environments.
    Genetic analysis and QTL mapping of a novel reduced height gene in common wheat (Triticum aestivum L.)
    ZHOU Chun-yun, XIONG Hong-chun, LI Yu-ting, GUO Hui-jun, XIE Yong-dun, ZHAO Lin-shu, GU Jiayu, ZHAO Shi-rong, DING Yu-ping, SONG Xi-yun, LIU Lu-xiang
    2020, 19(7): 1721-1730.  DOI: 10.1016/S2095-3119(20)63224-5
    Abstract ( )   PDF in ScienceDirect  
    Low stature in wheat is closely associated with lodging resistance, and this impacts harvest index and grain yield.  The discovery of novel dwarfing or semi-dwarfing genes can have great significance for dwarf wheat breeding.  In this study, we identified an EMS-induced dwarf wheat mutant JE0124 from the elite cultivar Jing411.  JE0124 possesses increased stem strength and a 33% reduction in plant height compared with wild type.  Gibberellic acid (GA) treatment analysis suggested that JE0124 was GA-sensitive.  Analysis of the frequency distribution of plant height in four F2 populations derived from crosses between JE0124 and the relatively taller varieties Nongda 5181 and WT indicated that the dwarfism phenotype was quantitatively inherited.  We used two F2 populations and 312 individuals from the reciprocal cross of Nongda 5181 and JE0124 to map the quantitative trait locus (QTL) for reduced height to a 0.85-cM interval on chromosome 2DL.  The mapping was done by using a combination of 660K SNP array-based bulked segregant analysis (BSA) and genetic linkage analysis, with logarithm of odds (LOD) scores of 5.34 and 5.78, respectively.  Additionally, this QTL accounted for 8.27–8.52% of the variation in the phenotype.  The dwarf mutant JE0124 and the newly discovered dwarfing gene on chromosome 2DL in this study will enrich genetic resources for dwarf wheat breeding.
    Differentially expressed miRNAs in anthers may contribute to the fertility of a novel Brassica napus genic male sterile line CN12A
    Dong Yun, Wang Yi, Jin Feng-wei, Xing Li-juan, Fang Yan, Zhang Zheng-ying, ZOU Jun-jie, Wang Lei, Xu Miao-yun
    2020, 19(7): 1731- 1742.  DOI: 10.1016/S2095-3119(19)62780-2
    Abstract ( )   PDF in ScienceDirect  
    In Brassica napus L. (rapeseed), complete genic male sterility (GMS) plays an important role in the utilization of heterosis.  Although microRNAs (miRNAs) play essential regulatory roles during bud development, knowledge of how GMS is regulated by miRNAs in rapeseed is rather limited.  In this study, we obtained a novel recessive GMS system, CN12AB.  The sterile line CN12A has defects in tapetal differentiation and degradation.  Illumina sequencing was employed to examine the expression of miRNAs in the buds of CN12A and the fertile line CN12B.  We identified 85 known miRNAs and 120 novel miRNAs that were expressed during rapeseed anther development.  When comparing the expression levels of miRNAs between CN12A and CN12B, 19 and 18 known miRNAs were found to be differentially expressed in 0.5–1.0 mm buds and in 2.5–3.0 mm buds, respectively.  Among these, the expression levels of 14 miRNAs were higher and the levels of 23 miRNAs were lower in CN12A compared with CN12B.  The predicted target genes of these differentially expressed miRNAs encode protein kinases, F-box domain-containing proteins, MADS-box family proteins, SBP-box gene family members, HD-ZIP proteins, floral homeotic protein APETALA 2 (AP2), and nuclear factor Y, subunit A.  These targets have previously been reported to be involved in pollen development and male sterility, suggesting that miRNAs might act as regulators of GMS in rapeseed anthers.  Furthermore, RT-qPCR data suggest that one of the differentially expressed miRNAs, bna-miR159, plays a role in tapetal differentiation by regulating the expression of transcription factor BnMYB101 and participates in tapetal degradation and influences callose degradation by manipulating the expression of BnA6.  These findings contribute to our understanding of the roles of miRNAs during anther development and the occurrence of GMS in rapeseed.
    Effects of light-emitting diodes on tissue culture plantlets and seedlings of rice (Oryza sativa L.)
    YU Lan-lan, SONG Chang-mei, SUN Lin-jing, LI Li-li, XU Zhi-gang, TANG Can-ming
    2020, 19(7): 1743-1754.  DOI: 10.1016/S2095-3119(19)62793-0
    Abstract ( )   PDF in ScienceDirect  
    Light-emitting diodes (LEDs) are a new light source with low energy consumption and high photoelectric conversion efficiency, and they can satisfy the energy-saving needs of plant culture systems.  However, the effects of LED light sources on rice tissue culture and rice seedling cultivation are poorly understood.  This study aimed to evaluate the effects of LEDs on the growth of tissue culture plantlets and seedlings of the rice (Oryza sativa L.) cultivar Nipponbare.  The best light source for rice tissue culture was different from that for rice seedling cultivation.  Blue (B) LED light was the most appropriate light for rice tissue culture.  Under a B LED light, the time required for callus proliferation, differentiation and regeneration was the shortest, and the frequency of plantlet initiation, differentiation and regeneration was the highest.  A blue:red (B:R)=1:1 LED light facilitated the growth of rice seedlings and produced the highest chlorophyll and carotenoid contents and photosynthetic rates in the rice seedlings.  Abundant photosynthetic products were more effectively generated in the rice seedlings under the B:R=1:1 LED and R LED lights than under the B LED light.  B LED light is the most appropriate light for rice tissue culture plantlets and can be used as an alternative light source for rice tissue culture, and B:R=1:1 LED light facilitated the cultivation of robust rice seedlings and can be used as the primary light source for rice factory seedling cultivation.
    Effects of seedling age on the growth stage and yield formation of hydroponically grown long-mat rice seedlings
    LI Yu-xiang, LIU Yang, WANG Yu-hui, DING Yan-feng, WANG Shao-hua, LIU Zheng-hui, LI Gang-hua
    2020, 19(7): 1755-1767.  DOI: 10.1016/S2095-3119(19)62756-5
    Abstract ( )   PDF in ScienceDirect  
    Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.  However, such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings (HLMS), which constitutes a new method of seedling cultivation.  Field experiments were conducted to evaluate the effects of seedling age on the growth stage, photosynthesis characteristics, dry matter production, and yield of HLMS.  A conventional japonica rice cultivar (Wuyunjing 24) and an indica hybrid rice cultivar (6 Liangyou 9368) were used as test materials.  The results showed that the whole phase was shortened by 13–15 days for young seedlings (13-day-old) compared with old seedlings (27-day-old), which occurred because the growth process accelerated with the transplantation of young seedlings.  As seedling age increased, the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage (MS).  Compared with that of 27-day-old seedlings, the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71% for Wuyunjing 24 and by 3.78% for 6 Liangyou 9368 at the MS.  Moreover, as seedling age increased, the leaf area index and photosynthetic potential decreased for both cultivars, and the photosynthetic rate markedly decreased at the heading stage (HS).  With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014, the crop growth rate was higher for young seedlings than for old seedlings.  Grain yield significantly decreased with seedling age, but no significant difference was detected between the 13- and 20-day-old seedlings for either cultivar.  Therefore, equilibrious and high biological yield formation, vigorous growth in the late stages, and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings (13–20-day-old).
    Integrated agronomic practices management improved grain formation and regulated endogenous hormone balance in summer maize (Zea mays L.)
    YU Ning-ning, ZHANG Ji-wang, LIU Peng, ZHAO Bin, REN Bai-zhao
    2020, 19(7): 1768-1776.  DOI: 10.1016/S2095-3119(19)62757-7
    Abstract ( )   PDF in ScienceDirect  
    Compared with single agronomic practices management during grain formation, knowledge about integrated agronomic practices management on grain-filling characteristics and physiological function of endogenous hormones was limited.  In order to clarify this issue, two field experiments, integrated agronomic practices management (IAPM), T1 (local conventional cultivation practices), T2 (an optimized combination of cropping systems and fertilizer treatment), T3 (treatment based on high-yield studies), and T4 (further optimized combination of cropping systems and fertilizer treatment), and nitrogen rate testing (NAT) (four nitrogen rates, 0, 129.0, 184.5, and 300.0 kg N ha–1) were performed with summer maize hybrid Zhengdan 958 (ZD958). Results showed that with increased nitrogen rate, the endogenous hormone balance was promoted and the grain-filling characteristics were improved sufficiently to resulting in a significant increase in grain yield.  However, the grain-filling characteristics deteriorated and yield was reduced with excessive nitrogen fertilization.  However, IAPM could promote hormone balance and improve grain filling characteristic.  The indole-3-acetic acid (IAA), zeatin riboside (ZR), and gibberellin (GA3) contents under T2 and T4 treatments were higher and the abscisic acid (ABA) content was lower, and the ZR and GA3 contents under T3 were higher than those under T1.  Those resulted in the maximum grain-filling rate (Wmax) and the active grain-filling period (P) under T2, T3 and T4 were significantly increased than those under T1, and hence promoted kernel weight and grain yield.  So IAPM promoted hormone balance by improving tillage model, optimizing fertilizer rate and fertilization period, appropriately increasing planting density and delaying harvest, which promoted grain filling rate and lengthened active grain-filling period, finally increased grain yield.
    Flumetralin and dimethyl piperidinium chloride alter light distribution in cotton canopies by optimizing the spatial configuration of leaves and bolls
    LIANG Fu-bin, YANG Cheng-xun, SUI Long-long, XU Shou-zhen, YAO He-sheng, ZHANG Wang-feng
    2020, 19(7): 1777-1788.  DOI: 10.1016/S2095-3119(19)62792-9
    Abstract ( )   PDF in ScienceDirect  
    Plant growth regulators (PGRs) are frequently used to adjust cotton growth and development.  The objectives of this study were to determine how PGRs affect plant morphology, light distribution and the spatial distribution of leaves and bolls within the cotton canopy.  The field experiments were carried out at Shihezi (Xinjiang Uyghur Autonomous Region, China) in 2014 and 2015.  The experiment included two PGR treatments: (i) flumetralin (active ingredient (a.i.), N-N-ethyl-2,6-dinitro-4-aniline) and (ii) mepiquat chloride (a.i., 1-dimethyl-piperidiniuchloride) plus flumetralin.  No PGR (manual topping) was applied in the control treatment.  The chemically-topped plants were taller and had more main stem internodes than the manually-topped plants.  Furthermore, the PGRs significantly reduced the length of fruiting branches in the upper canopy, resulting in a more compact canopy.  The maximum leaf area index was significantly greater in the chemically-topped treatments than that in the control.  In particular, the PGRs increased leaf area index by 25% in the upper canopy.  The leaf area duration was also longer in the chemically-topped treatments than in the control.  Compared with the control, the chemically-topped treatments increased canopy diffuse non-interceptance by 35.75% in the upper canopy layer, while reducing the fraction of intercepted photosynthetically active radiation by 14.45% in the upper canopy layer.  Light transmittance in the upper and middle canopy layers was greater in the chemically-topped treatments than in the control, which increased boll numbers in both the upper canopy and the middle canopy.  However, the chemically-topped treatments resulted in less light-leakage through the lower canopy layer during the late growth stages, which had a tendency to increase boll numbers in the whole canopy.  In summary, the PGRs optimized canopy shape, light distribution and the spatial distribution of bolls and leaves.
    What are the differences in yield formation among two cucumber (Cucumis sativus L.) cultivars and their F1 hybrid?
    WANG Xiu-juan, KANG Meng-zhen, FAN Xing-rong, YANG Li-li, ZHANG Bao-gui, HUANG San-wen, Philippe DE REFFYE, WANG Fei-yue
    2020, 19(7): 1789-1801.  DOI: 10.1016/S2095-3119(20)63218-X
    Abstract ( )   PDF in ScienceDirect  
    To elucidate the mechanisms underlying the differences in yield formation among two parents (P1 and P2) and their F1 hybrid of cucumber, biomass production and whole source–sink dynamics were analyzed using a functional–structural plant model (FSPM) that simulates both the number and size of individual organs.  Observations of plant development and organ biomass were recorded throughout the growth periods of the plants.  The GreenLab Model was used to analyze the differences in fruit setting, organ expansion, biomass production and biomass allocation.  The source–sink parameters were estimated from the experimental measurements.  Moreover, a particle swarm optimization algorithm (PSO) was applied to analyze whether the fruit setting is related to the source–sink ratio.  The results showed that the internal source–sink ratio increased in the vegetative stage and reached a peak until the first fruit setting.  The high yield of hybrid F1 is the compound result of both fruit setting and the internal source–sink ratio.  The optimization results also revealed that the incremental changes in fruit weight result from the increases in sink strength and proportion of plant biomass allocation for fruits.  The model-aided analysis revealed that heterosis is a result of a delicate compromise between fruit setting and fruit sink strength.  The organ-level model may provide a computational approach to define the target of breeding by combination with a genetic model.
    The effects of rootstocks on performances of three late-ripening navel orange varieties
    ZHU Shi-ping, HUANG Tao-jiang, YU Xin, HONG Qi-bin, XIANG Jin-song, ZENG An-zhong, GONG Gui-zhi, ZHAO Xiao-chun
    2020, 19(7): 1802-1812.  DOI: 10.1016/S2095-3119(20)63212-9
    Abstract ( )   PDF in ScienceDirect  
    Selection of rootstock is very important for citrus production.  Besides its major role on resistance, the rootstock also can affect fruit production and quality.  Currently, the main concerns on selection of rootstock for citrus production are compatibility and resistance, due to less information on the impacts of rootstock to the performance of scion varieties.  This study aims to provide information on performances of navel orange varieties on different rootstocks.  Three late-ripening navel orange varieties (Citrus sinensis var. Powell, Chislett and Banfield) grafted on seven rootstocks (Swingle citrumelo (C. paradisi×P. trifoliata), Carrizo citrange (C. sinensis×P. trifoliata), X639 (C. reticulata×P. trifoliata), MXT (C. sinensis×P. trifoliata), Hongju (C. reticulata), Ziyang Xiangcheng (C. junos) and trifoliate orange (P. trifoliata)) were used as plant materials for comprehensive comparison of the performances on tree growth, fruit yield and quality in 21 scion–stock combinations.  Investigation was carried out in these combinations in field nine years after planting.  Vigorous growth of all the three late-ripening navel orange varieties was observed on Carrizo citrange with the largest canopy volume at 33.34 m3 and the highest yield at 29.43 kg per tree, but a low yield efficiency at 2.87 kg m–3.  On the contrary, those on trifoliate orange had the smallest canopy volume at 10.79 m3 and the lowest fruit yield at 12.51 kg per tree, but the highest yield efficiency at 3.95 kg m–3. Rootstocks did not show significant effects on fruit size, fruit shape index, peel thickness and the edible rate of the fruits, but fruit quality was significantly affected by the rootstocks.  Fruits from the trees grafted on trifoliate orange presented the best quality with significantly higher total soluble solids (TSS) content than those on Ziyang Xiangcheng and Hongju, and also the highest ratio of TSS/titratable acidity (TA).  The TA content was observed from the fruits on X639 at 0.59 g 100 mL–1.  Vitamin C (Vc) content of fruits on Hongju was the highest at 49.25 mg 100 mL–1.  Growth vigor of the trees was positively correlated with fruit yield at an extremely significant level.  The canopy volume was negatively correlated with yield efficiency, but positively correlated with compatibility index.  Results of this study indicated that the rootstock has great impacts on the growth vigor of the tree, yield efficiency and quality of the fruit.  In order to achieve good quality and yield efficiency for navel orange production, less growth vigor rootstock such as trifoliate orange is highly recommended. 
    Plant Protection
    FgHAT2 is involved in regulating vegetative growth, conidiation, DNA damage repair, DON production and virulence in Fusarium graminearum
    Lü Wu-yun, YANG Nan, XU Zhe, DAI Han, TANG Shuai, WANG Zheng-yi
    2020, 19(7): 1813-1824.  DOI: 10.1016/S2095-3119(19)62819-4
    Abstract ( )   PDF in ScienceDirect  
    Histone lysine acetylation is catalyzed by acetyltransferases (HATs), which is important in regulating gene expression and physiological function in eukaryotic cells.  HATs can be classified into two main types: A- and B-type HATs.  Recently, in Fusarium graminearum, it has been reported that A-type HATs are involved in hyphal development, conidiation, sexual reproduction and virulence.  However, the biological roles of B-type HATs are unknown.  Here we report the identification and characterization of two B-type HATs (FgHat1 and FgHat2) in F. graminearum.  Targeted deletion of FgHAT1 did not result in any detectable phenotypes.  However, ΔFghat2 mutants were severely defective in vegetative growth, conidia production and morphogenesis, deoxynivalenol (DON) biosynthesis and virulence.  Interestingly, deletion of FgHAT2 resulted in significantly increased sensitivity to the DNA-damaging agent methyl methanesulfonate (MMS).  Furthermore, double deletion mutants (ΔFghat1ΔFghat2) displayed similar phenotypes to the ΔFghat2 mutants.  Taken together, we conclude that FgHat2 but not FgHat1 plays essential roles in regulating morphogenesis, DNA damage repair, DON production and virulence in F. graminearum.
    Virome identification in wheat in the Czech Republic using small RNA deep sequencing
    Khushwant SINGH, Jana JAROŠOVÁ, Jan FOUSEK, CHEN Huan, Jiban Kumar KUNDU
    2020, 19(7): 1825-1833.  DOI: 10.1016/S2095-3119(19)62805-4
    Abstract ( )   PDF in ScienceDirect  
    High-throughput deep-sequencing technology and bioinformatics analysis of the small RNA (sRNA) population isolated from plants allows universal virus detection and complete virome reconstruction for a given sample.  In the present sRNA deep-sequencing analysis of virus-infected wheat samples in the Czech Republic, samples were firstly tested for barley yellow dwarf viruses (BYDVs), wheat streak mosaic virus (WSMV) and wheat dwarf virus (WDV) using ELISA, RT-PCR and PCR.  Subsequent sRNA sequencing of these samples yielded more than ~60 million single-end 50-bp reads with high confidence for nine field samples of wheat.  Overall, 16.5% of reads were virus-specific and 83.5% were mapped to the host.  More 21-nt reads (~7.7E+06 reads) were found than 24-nt (~6.20E+06 reads) or 22-nt (~4.30E+06 reads) reads.  De novo assembly of the high-quality contigs revealed the presence of three earlier reported viruses in the Czech Republic: BYDVs (31.48%), WSMV (24.23%) and WDV (26.66%).  We also showed the presence of cereal yellow dwarf virus (14.33%; two species CYDV-RPS and CYDV-RPV (family Luteoviridae/Polerovirus) and wheat yellow dwarf virus (WYDV, 3.30%; Luteoviridae).  Phylogenetic analysis showed CYDV and WYDV grouped separately from BYDVs.  Furthermore, several recombination breakpoints were found among the groups of yellow dwarf viruses (BYDVs, CYDV, and WYDV).  Using RNA deep sequencing, we confirmed the presence of the three known viruses (BYDVs, WSMV, and WDV) and the first record of two species of CYDV and WYDV in wheat in the Czech Republic.
    A sensitive SYBR Green RT-qPCR method for grapevine virus E and its application for virus detection in different grapevine sample types
    REN Fang, ZHANG Zun-ping, FAN Xu-dong, HU Guo-jun, ZHANG Meng-yan, DONG Ya-feng
    2020, 19(7): 1834-1841.  DOI: 10.1016/S2095-3119(19)62784-X
    Abstract ( )   PDF in ScienceDirect  
    To develop a rapid and high-sensitivity method for detection of grapevine virus E (GVE), a SYBR Green based real-time fluorescence quantitative RT-PCR method (RT-qPCR) was established.  This method could be used to detect GVE specifically, and the sensitivity was about 100 times greater than conventional RT-PCR.  An excellent linear correlation (R2=0.997) and a high amplification efficiency (E=97.5%) were obtained from the standard curve of this method.  Reproducibility tests revealed that the coefficients of variation in the intra- and inter-assay results were 0.31–1.03% and 0.82–2.62%, respectively, indicating a good reproducibility.  The RT-qPCR method could be used to detect GVE in a wide range of grapevine sample types.  The detection rates of RT-qPCR for nearly all sample types from different positions and seasons were higher than conventional RT-PCR.  The detection rates in spring, summer, autumn and winter increased gradually.  Samples in autumn and winter were best for detection, and the detection rates of most samples were 80–100%, which were 10 to 40% higher than conventional RT-PCR.  In general, old petioles and branches were the best tissues for GVE detection.  The detection rates of these samples in each season were all 100%, which were 20 to 40% higher than conventional RT-PCR.  The second highest rates were in the old leaf, with detection rates for RT-qPCR of 80–100% in all seasons, which were 20 to 40% higher than conventional RT-PCR.  GVE could be difficultly detected in young leaves by conventional RT-PCR, and the detection rates were only 0–50%, while by RT-qPCR the rates could increase to 0–80%.  A total of 33 out of 363 samples (belonging to 68 cultivars) from 20 regions in China were detected to be positive by RT-qPCR (9.1%), which was more than twice the rate of the conventional RT-PCR (3.9%). 
    Effect of three insect-resistant maizes expressing Cry1Ie, Cry1Ab/Cry2Aj and Cry1Ab on the growth and development of armyworm Mythimna separata (Walker)
    SU Hong-hua, JIANG Tao, SUN Yu, GU Hui-jie, WU Jiao-jiao, YANG Yi-zhong
    2020, 19(7): 1842-1849.  DOI: 10.1016/S2095-3119(20)63162-8
    Abstract ( )   PDF in ScienceDirect  
    Three transgenic maize events (IE09S034, Shuangkang 12–5 and C0030.3.5) produced Cry1Ie, Cry1Ab/Cry2Aj and G10-EPSPS, Cry1Ab and EPSPS, respectively, all of which target the Asian corn borer.  The oriental armyworm Mythimna separata (Walker) is the secondary target.  In this study, the effects of the three Bt maizes on the development and survival of armyworm were studied.  The results showed that IE09S034 had insecticidal activity against 1st instar larvae, and the survival rate of armyworm fed with Bt maize for 10 days was 46.2%, significantly lower than that of the control.  The larvae at 3rd–6th instar were more tolerant of the Bt toxin than the early instar larvae.  However, Shuangkang 12-5 had good insecticidal activity against 1st–5th instar larvae.  The mortality was nearly 100% when the larvae were fed with Shuangkang 12-5 before 3rd instar, and the toxin had quick-acting efficacy.  This event significantly inhibited the development of armyworm; that is, the larval duration of the 3rd and 4th instar larvae fed with Shuangkang 12-5 was prolonged by 4.5 and 3.0 days, respectively.  The pupal weight and egg number were also significantly lower than those of the control.  For C0030.3.5, it could control 1st–5th instar larvae effectively.  The mortality rates were all over 50% if 1st–3rd larvae were fed with this event.  The pupal weight of 4th–6th instar larvae fed with Bt maize were only 53.9, 56.8 and 54.6%, respectively, compared to that of the control.  The number of eggs laid was significantly less than the control.  The results indicate that all three transgenic maize events exhibit the potential to provide effective control of early instar larvae of armyworm, which can be commercialized in future to control lepidoptera pests such as Asian corn borer and armyworm.
    Animal Science · Veterinary Medicine
    Effect of dietary supplementation of pyrroloquinoline quinone disodium on growth performance, meat quality and antioxidative ability of broilers
    LIU Guo-qing, SUN Guang-ming, LIAO Xiu-dong, HUANG Jian-zhong, GUO Mei-jin, ZHANG Li-yang, GUO Yan-li, LU Lin, LUO Xu-gang
    2020, 19(7): 1850-1856.  DOI: 10.1016/S2095-3119(19)62851-0
    Abstract ( )   PDF in ScienceDirect  
    This study was conducted to investigate the effect of dietary supplementation with pyrroloquinoline quinone (PQQ) in the form of PQQ disodium (PQQ·Na2) on the growth performance, carcass traits, meat quality and antioxidative ability of broilers.  A total of 720 one-d-old Arbor Acres male broilers were randomly allocated to 1 of 6 treatments with 8 replicates of 15 birds per replicate in a completely randomized design.  Birds were fed a PQQ·Na2-unsupplemented corn-soybean meal basal diet (control) or the basal diet supplemented with 0.1, 0.2, 0.3, 0.4 or 0.5 mg PQQ·Na2 kg–1 for 42 d.  Compared with the control chicks, the chicks fed the diets supplemented with PQQ·Na2 had lower (P<0.05) feed:gain (F/G) during the grower phase and drip losses of breast muscles on day 42.  As supplemental PQQ·Na2 level increased, plasma total antioxidant capacity (T-AOC) on d 42, liver T-AOC on d 21 and heart T-AOC on d 21 and 42 increased linearly (P<0.05), but malondialdehyde concentrations in plasma, liver and heart on d 21 or 42 decreased linearly (P<0.001) or quadratically (P<0.005).  The results from the present study indicate that dietary supplemental PQQ·Na2 can improve antioxidant ability and meat quality  of broilers, and in general, it is implied that the optimal supplemental PQQ·Na2 level is 0.1 mg kg–1 of diet for broilers from 1 to 42 d of age.
    A protective role of resveratrol against the effects of immobilization stress in corpora lutea of mice in early pregnancy
    Saif ULLAH, Sheeraz MUSTAFA, Wael ENNAB, Muhammad JAN, Muhammad SHAFIQ, Ngekure M. X. KAVITA, Lü Zeng-peng, MAO Da-gan, SHI Fang-xiong
    2020, 19(7): 1857-1866.  DOI: 10.1016/S2095-3119(19)62856-X
    Abstract ( )   PDF in ScienceDirect  
    In the present study, we aimed to investigate a protective role for resveratrol against the effects of immobilization stress on corpora lutea (CL) of mice in early pregnancy.  A total of 45 early-pregnant mice were divided into no immobilization stress (NIS) group, immobilization stress (IS) group, and immobilization and resveratrol treatment (IS+RES) group (n=15).  Mice were immobilized in plastic tubes (50 mL) for 3 h per day during day 1 to 7 of pregnancy.  In the IS+RES group, 5 mg kg–1 d–1 of resveratrol was administered just prior to application of stress.  We analyzed apoptotic activity in CL by Western blotting analysis (WB), transmission electron microscopy (TEM), and immunohistochemistry (IHC).  Serum progesterone levels were examined with radioimmunoassay (RIA).  IHC results showed that the intensity of positive staining for Bax was increased, and for Bcl-2 was decreased in CL after IS, while resveratrol treatment reversed the positive staining for Bax and Bcl-2.  WB revealed that immobilization stress up-regulated the expression of Bax and caspase-9, and down-regulated Bcl-2 expression, while resveratrol treatment attenuated the effects of immobilization stress on the expression of Bax, Bcl-2 and caspase-9.  According to our TEM results, apoptosis as defined by chromatin condensation was found in CL after immobilization stress, while resveratrol inhibited the apoptosis.  We also demonstrated that immobilization stress decreased progesterone concentrations and ovarian expression of StAR, while resveratrol restored the concentrations of progesterone and expression of StAR back to normal.  These results indicated that immobilization stress induced luteal regression while resveratrol inhibited luteal regression, suggesting that resveratrol plays a protective role on corpora lutea of mice during early pregnancy.
    The circulation of unique reassortment strains of infectious bursal disease virus in Pakistan
    Altaf HUSSAIN, WU Tian-tian, FAN Lin-jin, WANG Yu-long, Farooq Khalid MUHAMMAD, JIANG Nan, GAO Li, LI Kai, GAO Yu-long, LIU Chang-jun, CUI Hong-yu, PAN Qing, ZHANG Yan-ping, Asim ASLAM, Khan MUTI-UR-REHMAN, Muhammad Imran ARSHAD, Hafiz Muhammad ABDULLAH, WANG Xiao-mei, QI Xiao-le
    2020, 19(7): 1867-1875.  DOI: 10.1016/S2095-3119(20)63183-5
    Abstract ( )   PDF in ScienceDirect  
    Infectious bursal disease (IBD), caused by IBD virus (IBDV), is one of the most devastating and immunosuppressive diseases of the poultry and has been a constraint on the sustainable poultry production around the globe including Pakistan.  While the disease is threatening the poultry industry, the nature of predominant strains of IBDV in Pakistan remained ill-defined.  In this study, an epidemiology survey was conducted in the main chicken-farming regions of Pakistan.  The batch of Pakistan IBDVs genes simultaneously covering both VP1 and VP2 were amplified, sequenced, and analyzed.  The unique segment-reassortant IBDVs (vv-A/Uniq-B), carrying segment A from vvIBDV and segment B from one unique ancestor, were identified as one important type of circulating strains in Pakistan.  The data also discovered the characteristic molecular features of Pakistan IBDVs, which will contribute to scientific vaccine selection and effective prevention of the disease.
    Agro-ecosystem & Environment
    Variation in spectral characteristics of dissolved organic matter derived from rape straw of plants grown in Se-amended soil
    JIA Wei, ZHAO Xiao-hu, ZHAO Yuan-yuan, XU Jia-yang, MING Jia-jia, CAI Miao-miao, HU Cheng-xiao
    2020, 19(7): 1876-1884.  DOI: 10.1016/S2095-3119(19)62867-4
    Abstract ( )   PDF in ScienceDirect  
    Straw return is an effective management practice.  It not only utilizes agricultural waste but also introduces dissolved organic matter (DOM) into the soil.  Selenium (Se) is an essential trace element in the human diet and contributes to the popularity of Se-enriched agricultural products in the Chinese market.  Moreover, there are still some Se-enriched agricultural products that have yet to be utilized.  This study investigated whether Se addition in soil caused component changes in the DOM extracted from rape straw.  DOM extracted from rape straw grown in soil with four Se levels (0, 0.1, 0.5 and 1.0 mg Se kg–1 soil) was characterized by UV-Visible spectroscopy, fluorescence spectroscopy and FTIR spectroscopy.  The UV-visible spectra revealed that 0.1 mg Se kg–1 soil reduced the molecular weight of DOM and caused the presence of more irreplaceable aromatic structures in the substituent groups of the DOM, while 0.5 and 1.0 mg Se kg–1 soil only reduced the DOM molecular weight.  Fluorescence spectroscopy indicated that Se improved the humification degree but reduced the aromaticity of DOM.  FTIR spectra proved that Se altered the contents of carboxylic acids, amino acids, alcohols and aromatic heterocycles in DOM, which were maximized in the 0.5 and 1.0 mg Se kg–1 treatment groups.  We concluded that Se application could change the composition of DOM extracted from rape straw, potentially impacting the nutrient bioavailability in soil.  This study provides basic data on Se-enriched rape straw utilization for eco-agriculture.
    Mapping the fallowed area of paddy fields on Sanjiang Plain of Northeast China to assist water security assessments
    LUO Chong, LIU Huan-jun, FU Qiang, GUAN Hai-xiang, YE Qiang, ZHANG Xin-le, KONG Fan-chang
    2020, 19(7): 1885-1896.  DOI: 10.1016/S2095-3119(19)62871-6
    Abstract ( )   PDF in ScienceDirect  
    Rice growth requires a large amount of water, and planting rice will increase the contradiction between supply and demand of water resources.  Paddy field fallowing is important for the sustainable development of an agricultural region, but it remains a great challenge to accurately and quickly monitor the extent and area of fallowed paddy fields.  Paddy fields have unique physical features associated with paddy rice during the flooding and transplanting phases.  By comparing the differences in phenology before and after paddy field fallowing, we proposed a phenology-based fallowed paddy field mapping algorithm.  We used the Google Earth Engine (GEE) cloud computing platform and Landsat 8 images to extract the fallowed paddy field area on Sanjiang Plain of China in 2018.  The results indicated that the Landsat8, GEE, and phenology-based fallowed paddy field mapping algorithm can effectively support the mapping of fallowed paddy fields on Sanjiang Plain of China.  Based on remote sensing monitoring, the total fallowed paddy field area of Sanjiang Plain is 91 543 ha.  The resultant fallowed paddy field map is of high accuracy, with a producer (user) accuracy of 83% (81%), based on validation using ground-truth samples.  The Landsat-based map also exhibits high consistency with the agricultural statistical data.  We estimated that paddy field fallowing reduced irrigation water by 384–521 million cubic meters on Sanjiang Plain in 2018.  The research results can support subsidization grants for fallowed paddy fields, the evaluation of fallowed paddy field effects and improvement in subsequent fallowed paddy field policy in the future. 
    Early-season crop type mapping using 30-m reference time series
    HAO Peng-yu, TANG Hua-jun, CHEN Zhong-xin, MENG Qing-yan, KANG Yu-peng
    2020, 19(7): 1897-1911.  DOI: 10.1016/S2095-3119(19)62812-1
    Abstract ( )   PDF in ScienceDirect  
    Early-season crop type mapping could provide important information for crop growth monitoring and yield prediction, but the lack of ground-surveyed training samples is the main challenge for crop type identification.  Although reference time series based method (RBM) has been proposed to identify crop types without the use of ground-surveyed training samples, the methods are not suitable for study regions with small field size because the reference time series are mainly generated using data set with low spatial resolution.  As the combination of Landsat data and Sentinel-2 data could increase the temporal resolution of 30-m image time series, we improved the RBM by generating reference normalized difference vegetation index (NDVI)/enhanced vegetation index (EVI) time series at 30-m resolution (30-m RBM) using both Landsat and Sentinel-2 data, then tried to estimate the potential of the reference NDVI/EVI time series for crop identification at early season.  As a test case, we tried to use the 30-m RBM to identify major crop types in Hengshui, China at early season of 2018, the results showed that when the time series of the entire growing season were used for classification, overall classification accuracies of the 30-m RBM were higher than 95%, which were similar to the accuracies acquired using the ground-surveyed training samples.  In addition, cotton, spring maize and summer maize distribution could be accurately generated 8, 6 and 8 weeks before their harvest using the 30-m RBM; but winter wheat can only be accurately identified around the harvest time phase.  Finally, NDVI outperformed EVI for crop type classification as NDVI had better separability for distinguishing crops at the green-up time phases.  Comparing with the previous RBM, advantage of 30-m RBM is that the method could use the samples of the small fields to generate reference time series and process image time series with missing value for early-season crop classification; while, samples collected from multiple years should be further used so that the reference time series could contain more crop growth conditions.
    Short Communication
    First report of the South American tomato leafminer, Tuta absoluta (Meyrick), in China
    ZHANG Gui-fen, MA De-ying, WANG Yu-sheng, GAO You-hua, LIU Wan-xue, ZHANG Rong, FU Wen-jun, XIAN Xiao-qing, WANG Jun, KUANG Meng, WAN Fang-hao
    2020, 19(7): 1912-1917.  DOI: 10.1016/S2095-3119(20)63165-3
    Abstract ( )   PDF in ScienceDirect  
    Tuta absoluta (Meyrick) originated in South America and is one of the most serious pests of tomatoes.  It is also known to attack other solanaceous crops, including potato, eggplant, pepper, tobacco, and weedy species such as black nightshade.  After accidental introduction into Spain in 2006, this pest spread rapidly throughout Afro-Eurasia and has become a major threat to tomato production worldwide.  Here, we report the first record of T. absoluta as an invasive pest in China.  It was found in tomato fields in Ili Kazakg Autonomous Prefecture, Xinjiang Uygur Autonomous Region (Ili, Xinjiang), China, and its occurrence was confirmed by both morphological and molecular approaches.  In Ili, T. absoluta has been found to attack eggplant, potato, and black nightshade.  We found the larvae generally mining and feeding on leaves and boring into tomato fruits, with multiple larvae sometimes observed in a single fruit.  Its infestation levels differ among the tomato fields and host species.  In all of the surveyed tomato fields, T. absoluta infested 100% of plants.  In some of the fields, up to 90% of the eggplant and 100% of the potato plants were infested.  Since no natural enemies were found under field conditions, suitable management practices are urgently needed to stop the further spread of this destructive pest in China.