2021 Vol. 20 No. 11 Previous Issue    Next Issue

    Crop Science
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Food Science
    Short Communication

      Cover illustration

    For Selected: Toggle Thumbnails
    Crop Science
    Transgenic japonica rice expressing the cry1C gene is resistant to striped stem borers in Northeast China
    JIN Yong-mei, MA Rui, YU Zhi-jing, LIN Xiu-feng
    2021, 20(11): 2837-2848.  DOI: 10.1016/S2095-3119(20)63279-8
    Abstract ( )   PDF in ScienceDirect  
    Rice production and quality are seriously affected by the lepidopteran pest, striped stem borer (SSB), in Northeast China. In this study, a synthetic cry1C gene encoding Bacillus thuringiensis (Bt) δ-endotoxin, which is toxic to lepidopteran pest, was transformed into a japonica rice variety (Jigeng 88) in Northeast China by Agrobacterium-mediated transformation.  Through molecular detection and the Basta resistance germination assay, a total of 16 single-copy homozygous transgenic lines were obtained from 126 independent transformants expressing cry1C.  Finally, four cry1C-transgenic lines (JL16, JL23, JL41, and JL42) were selected by evaluation of the Cry1C protein level, insect-resistance and agronomic traits.  The cry1C-transgenic lines had higher resistance to SSB and higher yield compared with non-transgenic (NT) control plants.  T-DNA flanking sequence analysis of the transgenic line JL42 showed that the cry1C gene was inserted into the intergenic region of chromosome 11, indicating that its insertion may not interfere with the genes near insertion site.  In summary, this study developed four cry1C-transgenic japonica rice lines with high insect resistance and high yield.  They can be used as insect-resistant germplasm materials to overcome the problem of rice yield reduction caused by SSB and reduce the use of pesticides in Northeast China.
    Genetic dissection of wheat uppermost-internode diameter and its association with agronomic traits in five recombinant inbred line populations at various field environments
    LIU Hang, TANG Hua-ping, LUO Wei, MU Yang, JIANG Qian-tao, LIU Ya-xi, CHEN Guo-yue, WANG Ji-rui, ZHENG Zhi, QI Peng-fei, JIANG Yun-feng, CUI Fa, SONG Yin-ming, YAN Gui-jun, WEI Yuming, LAN Xiu-jin, ZHENG You-liang, MA Jian
    2021, 20(11): 2849-2861.  DOI: 10.1016/S2095-3119(20)63412-8
    Abstract ( )   PDF in ScienceDirect  
    Uppermost-internode diameter (UID) is a key morphological trait associated with spike development and yield potential in wheat.  Our understanding of its genetic basis remains largely unknown.  Here, quantitative trait loci (QTLs) for UID with high-density genetic maps were identified in five wheat recombinant inbred line (RIL) populations.  In total, 25 QTLs for UID were detected in five RIL populations, and they were located on chromosomes 1A, 1D (3 QTL), 2B (2), 2D (3), 3B, 3D, 4A, 4B (3), 4D, 5A (5), 5B (2), 6B, and 7D.  Of them, five major and stable QTLs (QUid.sau-2CN-1D.1, QUid.sau-2SY-1D, QUid.sau-QZ-2D, QUid.sau-SC-3D, and QUid.sau-AS-4B) were identified from each of the five RIL populations in multiple environments.  QUid.sau-2CN-1D.1, QUid.sau-2SY-1D and QUid.sau-SC-3D are novel QTLs.  Kompetitive Allele Specific PCR (KASP) markers tightly linked to them were further investigated for developing near-isogenic lines (NILs) carrying the major loci.  Furthermore, candidate genes at these intervals harboring major and stable QTLs were predicted, and they were associated with plant development and water transportation in most cases.  Comparison of physical locations of the identified QTL on the ‘Chinese Spring’ reference genome showed that several QTLs including two major ones, QUid.sau-2CN-1D.1 and QUid.sau-2SY-1D, are likely allelic confirming their validity and effectiveness.  The significant relationships detected between UID and other agronomic traits and a proper UID were discussed.  Collectively, our results dissected the underlying genetic basis for UID in wheat and laid a foundation for further fine mapping and map-based cloning of these QTLs.
    Identification of quantitative trait loci and candidate genes controlling seed pigments of rapeseed
    ZHU Mei-chen, HU Ran, ZHAO Hui-yan, TANG Yun-shan, SHI Xiang-tian, JIANG Hai-yan, ZHANG Zhi-yuan, FU Fu-you, XU Xin-fu, TANG Zhang-lin, LIU Lie-zhao, LU Kun, LI Jia-na, QU Cun-min
    2021, 20(11): 2862-2879.  DOI: 10.1016/S2095-3119(20)63377-9
    Abstract ( )   PDF in ScienceDirect  
    Rapeseed (Brassica napus L.) is an important source of edible vegetable oil and feed protein; however, seed pigments affect the quality of rapeseed oil and the feed value of the residue from oil pressing.  Here, we used a population of rapeseed recombinant inbred lines (RILs) derived from the black-seeded male parent cultivar Zhongyou 821 and the yellow-seeded female parent line GH06 to map candidate genes controlling seed pigments in embryos and the seed coat.  We detected 94 quantitative trait loci (QTLs) for seed pigments (44 for embryos and 50 for seed coat), distributed over 15 of the 19 rapeseed chromosomes.  These included 28 QTLs for anthocyanidin content, explaining 2.41–44.66% of phenotypic variation; 24 QTLs for flavonoid content, explaining 2.41–20.26% of phenotypic variation; 16 QTLs for total phenol content, accounting for 2.74–23.68% of phenotypic variation; and 26 QTLs for melanin content, accounting for 2.37–24.82% of phenotypic variation, indicating that these traits are under multigenic control.  Consensus regions on chromosomes A06, A09 and C08 were associated with multiple seed pigment traits, including 15, 19 and 10 QTLs, respectively, most of which were major QTLs explaining >10% of the phenotypic variation.  Based on the annotation of the B. napus “Darmor-bzh” reference genome, 67 candidate genes were predicted from these consensus QTLs regions, and 12 candidate genes were identified as potentially involved in pigment accumulation by RNA-seq and qRT-PCR analysis.  These preliminary results provide insight into the genetic architecture of pigment biosynthesis and lay a foundation for exploring the molecular mechanisms underlying seed coat color in B. napus.
    Estimating wheat fractional vegetation cover using a density peak k-means algorithm based on hyperspectral image data
    LIU Da-zhong, YANG Fei-fei, LIU Sheng-ping
    2021, 20(11): 2880-2891.  DOI: 10.1016/S2095-3119(20)63556-0
    Abstract ( )   PDF in ScienceDirect  
    Fractional vegetation cover (FVC) is an important parameter to measure crop growth.  In studies of crop growth monitoring, it is very important to extract FVC quickly and accurately.  As the most widely used FVC extraction method, the photographic method has the advantages of simple operation and high extraction accuracy.  However, when soil moisture and acquisition times vary, the extraction results are less accurate.  To accommodate various conditions of FVC extraction, this study proposes a new FVC extraction method that extracts FVC from a normalized difference vegetation index (NDVI) greyscale image of wheat by using a density peak k-means (DPK-means) algorithm.  In this study, Yangfumai 4 (YF4) planted in pots and Yangmai 16 (Y16) planted in the field were used as the research materials.  With a hyperspectral imaging camera mounted on a tripod, ground hyperspectral images of winter wheat under different soil conditions (dry and wet) were collected at 1 m above the potted wheat canopy.  Unmanned aerial vehicle (UAV) hyperspectral images of winter wheat at various stages were collected at 50 m above the field wheat canopy by a UAV equipped with a hyperspectral camera.  The pixel dichotomy method and DPK-means algorithm were used to classify vegetation pixels and non-vegetation pixels in NDVI greyscale images of wheat, and the extraction effects of the two methods were compared and analysed.  The results showed that extraction by pixel dichotomy was influenced by the acquisition conditions and its error distribution was relatively scattered, while the extraction effect of the DPK-means algorithm was less affected by the acquisition conditions and its error distribution was concentrated.  The absolute values of error were 0.042 and 0.044, the root mean square errors (RMSE) were 0.028 and 0.030, and the fitting accuracy R2 of the FVC was 0.87 and 0.93, under dry and wet soil conditions and under various time conditions, respectively.  This study found that the DPK-means algorithm was capable of achieving more accurate results than the pixel dichotomy method in various soil and time conditions and was an accurate and robust method for FVC extraction. 
    Optimizing the application of a novel harvest aid to improve the quality of mechanically harvested cotton in the North China Plain
    MENG Lu, ZHANG Li-zhen, QI Hai-kun, DU Ming-wei, ZUO Yan-li, ZHANG Ming-cai, TIAN Xiao-li, LI Zhao-hu
    2021, 20(11): 2892-2899.  DOI: 10.1016/S2095-3119(20)63280-4
    Abstract ( )   PDF in ScienceDirect  
    Defoliation is an indispensable step in cotton production with mechanical harvesting, especially in the North China Plain (NCP) where mechanical harvesting is limited by a large proportion of green leaves and unopened bolls at harvest time due to insufficient thermal resources.  It is essential to quantify the optimal use of defoliation products while minimizing yield and quality loss in China.  The objective of this study was to test the effect of a new defoliant Xinsaili (XSL, a compound of 10% thidiazuron and 40% ethephon) on the spatial distribution of cotton leaves and bolls, yield and quality in the NCP.  There were four treatments: XSL 1 800 mL ha–1 , XSL 2 700 mL ha–1, XSL splitted into two equal applications (1 350 mL ha–1 for each), and XSL-free (water) control.  Field experiments were conducted in Hebei, China in 2016–2017.  All the defoliant treatments did not significantly affect cotton yield and fiber quality compared with the water control.  At harvest time, the rate of open bolls under XSL 2 700 mL ha–1 was 13.5% higher than that under XSL-free control, while the other two treatments showed no significant difference, across the two years.  Defoliation percentage of the three XSL treatments showed no difference, but they were on average 42.2% higher than that of XSL-free control.  The year-round effect of the defoliant XSL was significant, indicating that climate factors would affect its application.  It was concluded that the optimal dose of XSL in the NCP was 2 700 mL ha–1, and it was unnecessary to split it into two applications.  These results would promote cotton mechanical harvesting and reduce the labor cost of cotton production in China.
    Construction of high-density SNP genetic maps and QTL mapping for dwarf-related traits in Litchi chinensis Sonn
    HU Fu-chu, CHEN Zhe, WANG Xiang-he, WANG Jia-bao, FAN Hong-yan, QIN Yong-hua, ZHAO Jietang, HU Gui-bing
    2021, 20(11): 2900-2913.  DOI: 10.1016/S2095-3119(20)63387-1
    Abstract ( )   PDF in ScienceDirect  
    Litchi chinensis Sonn is widely cultivated in subtropical regions and has an important economic value.  A high-density genetic map is a valuable tool for mapping quantitative trait loci (QTL) and marker-assisted breeding programs.   In this study, a single nucleotide polymorphism (SNP)-based high-density linkage map was constructed by a genotyping-by-sequencing (GBS) protocol using an F1 population of 178 progenies between two commercial litchi cultivars, ‘Ziniangxi’ (dwarf) and ‘Feizixiao’ (vigorous).  The genetic map consisted of 3 027 SNP markers with a total length of 1 711.97 cM in 15 linkage groups (LGs) and an average marker distance of 0.57 cM.  Based on this high-density linkage map and three years of phenotyping, a total of 37 QTLs were detected for eight dwarf-related traits, including length of new branch (LNB), diameter of new branch (DNB), length of common petiole (LCP), diameter of common petiole (DCP), length of internode (LI), length of single leaf (LSL), width of single leaf (WSL), and plant height (PH).  These QTLs could explain 8.0 to 14.7% (mean=9.7%) of the phenotypic variation.  Among them, several QTL clusters were observed, particularly on LG04 and LG11, which might show enrichment for genes regulating the dwarf-related traits in litchi.  There were 126 candidate genes identified within the QTL regions, 55 of which are differentially expressed genes by RNA-seq analysis between ‘Ziniangxi’ and ‘Feizixiao’.  These DEGs were found to participate in the regulation of cell development, material transportation, signal transduction, and plant morphogenesis, so they might play important roles in regulating plant dwarf-related traits.  The high-density genetic map and QTLs identification related to dwarf traits can provide a valuable genetic resource and a basis for marker-assisted selection and genomic studies of litchi.
    Transcriptome analysis reveals effects of red and blue lightemitting diodes (LEDs) on the growth, chlorophyll fluorescence and endogenous plant hormones of potato (Solanum tuberosum L.) plantlets cultured in vitro
    CHEN Li-li, WANG Hao-ying, GONG Xiao-chen, ZENG Zhao-hai, XUE Xu-zhang, HU Yue-gao
    2021, 20(11): 2914-2931.  DOI: 10.1016/S2095-3119(20)63393-7
    Abstract ( )   PDF in ScienceDirect  
    Red and blue light illumination has been reported to significantly affect plantlet growth.  Potato is an important food and feed crop in the world and potato plantlet cultured in vitro plays an important role in potato production.  However, few studies have documented the effects of red and blue light on the growth of potato plantlets revealed at the transcriptome level.  The objective of this study was to determine the growth and physiological responses of potato plantlets cultured in vitro under monochromatic red (RR), monochromatic blue (BB) as well as combined red and blue (RB) LEDs using the RNA-Seq technique.  In total, 3 150 and 814 differentially expressed genes (DEGs) were detected in potato plantlets under RR and BB, respectively, compared to RB (used as control).  Compared to the control, the DEGs enriched in “photosynthesis” and “photosynthesis-antenna proteins” metabolic pathways were up-regulated and down-regulated by BB and RR, respectively, which might be responsible for the increases and decreases of maximum quantum yield (Fv/Fm), photochemical quantum yield (φPSII), photochemical quenching (qP) and electron transfer rate (ETR) in BB and RR, respectively.  Potato plantlets exhibited dwarfed stems and extended leaves under BB, whereas elongated stems and small leaves were induced under RR.  These dramatically altered plantlet phenotypes were associated with variable levels of endogenous plant hormones gibberellin (GAs), indoleacetic acid (IAA) and cytokinins (CKs), as assessed in stems and leaves of potato plantlets.  In addition, monochromatic red and blue LEDs trigged the opposite expression profiles of DEGs identified in the “plant hormone signal transduction” metabolic pathway, which were closely related to the endogenous plant hormone levels in potato plantlets.  Our results provide insights into the responses of potato plantlets cultured in vitro to red and blue LEDs at the transcriptomic level and may contribute to improvements in the micro-propagation of potato plantlets cultured in vitro from the light spectrum aspect.
    Potassium deficiency inhibits steviol glycosides synthesis by limiting leaf sugar metabolism in stevia (Stevia rebaudiana Bertoni) plants
    SUN Yu-ming, HUANG Xiao-lei, ZHANG Ting, YANG Yong-heng, CHENG Xiao-fang, XU Xiao-yang, YUAN Hai-yan
    2021, 20(11): 2932-2943.  DOI: 10.1016/S2095-3119(20)63472-4
    Abstract ( )   PDF in ScienceDirect  
    The steviol glycosides (SGs) in stevia (Stevia rebaudiana Bertoni) leaves are becoming increasingly valuable due to its high sweetness but low calorific value, which is driving the development of stevia commercial cultivation.  Optimizing fertilization management can effectively increase SGs productivity, but knowledge on the relationship between potassium (K) fertilization and SGs production is still lacking.  In this study, pot experiments were conducted in order to investigate the effect of K deficiency on SGs synthesis in stevia leaves, as well as the underlying mechanisms.  Our results showed that when compared with standard K fertilization, K deficiency treatment has no significant effect on the biomass of stevia plant grown in a given soil with high K contents.  However, K deficiency critically decreased leaf SGs contents as well as the expression of SGs synthesis-related genes.  The contents of different sugar components decreased and the activities of sugar metabolism-related enzymes were inhibited under the K deficiency condition.  Moreover, spraying sucrose on the leaves of stevia seedlings diminished the inhibitory effect caused by K deficiency.  Our results also revealed the significant positive correlations between sucrose, glucose and SGs contents.  Overall, our results suggest that K deficiency would suppress the synthesis of SGs in stevia leaves, and this effect may be mediated by the leaf sugar metabolism.  Our findings provide new insights into the improvement of SGs production potential. 
    Plant Protection
    The putative elongator complex protein Elp3 is involved in asexual development and pathogenicity by regulating autophagy in the rice blast fungus
    ZHANG Li-mei, CHEN Shu-ting, QI Min, CAO Xue-qi, LIANG Nan, LI Qian, TANG Wei, LU Guo-dong, ZHOU Jie, YU Wen-ying, WANG Zong-hua, ZHENG Hua-kun
    2021, 20(11): 2944-2956.  DOI: 10.1016/S2095-3119(20)63493-1
    Abstract ( )   PDF in ScienceDirect  
    Autophagy is responsible for maintaining fundamental cellular homeostasis and is, therefore, essential for diverse development processes.  This study reported that PoElp3, the putative catalytic subunit of Elongator complex, is involved in the maintenance of autophagy homeostasis to facilitate asexual development and pathogenicity in the rice blast fungus Pyricularia oryzae.  It was found that the ΔPoelp3 strains were defective in vegetative growth, conidiation, stress response, and pathogenicity.  The mutants exhibited hyper-activated autophagy in the vegetative hyphae under both nutrient-rich and nutrient-deficient conditions.  The hyper-activation of autophagy possibly suppressed the production of vegetative hyphae in the ΔPoelp3 strains.  Moreover, the ΔPoelp3 strains were found to be more sensitive to rapamycin during vegetative- and invasive-hyphal growth but have no effect on Target-of-Rapamycin (TOR) signaling inhibition.  Taken together, these results demonstrated that PoElp3 is involved in asexual development and pathogenicity by regulating autophagy in the rice blast fungus. 
    Three Sclerotinia species as the cause of white mold on pea in Chongqing and Sichuan of China
    DENG Dong, SUN Su-li, DU Chen-zhang, XIANG Chao, LONG Jue-chen, CHEN Wei-dong, ZHU Zhen-dong
    2021, 20(11): 2957-2965.  DOI: 10.1016/S2095-3119(21)63629-8
    Abstract ( )   PDF in ScienceDirect  
    White mold of pea caused by Sclerotinia sclerotiorum is a common disease in China.  However, we discovered that the diverse Sclerotinia species could cause white mold on pea plants in Chongqing and Sichuan of China during recent disease surveys.  Thus, the objective of this study was to confirm the causal agents from diseased pea plants.  The obtained isolates of white mold from Chongqing and Sichuan were identified by morphological characters and molecular characterization to determine the pathogen species, and their pathogenicity was confirmed on pea through completing Koch’s postulates.  Fungal isolates of Sclerotinia-like were obtained from diseased plants or sclerotia.  Based on morphological characteristics and molecular characterization, 30 isolates were identified to three species, six isolates as S. minor, seven as S. sclerotiorum, and 17 as S. trifoliorum.  In pathogenicity tests on pea cultivars Zhongwan 4 and Longwan 1, all 30 isolates caused typical symptoms of white mold on the inoculated plants, and the inoculated pathogens were re-isolated from the diseased plants.  This study confirmed that white mold of pea was caused by three Sclerotinia species, S. sclerotiorum, S. minor and S. trifoliorum in Chongqing and Sichuan. It is the first report that S. minor and S. trifoliorum cause white mold of pea in Southwest China.
    Three sensitive and reliable serological assays for detection of potato virus A in potato plants
    WU Jia-yu, ZHANG Yu, ZHOU Xue-ping, QIAN Ya-juan
    2021, 20(11): 2966-2975.  DOI: 10.1016/S2095-3119(20)63492-X
    Abstract ( )   PDF in ScienceDirect  
    Vegetative propagation of seed potato often allows passaging of viruses to seed tubers, resulting in significant yield losses and reduction of potato tuber quality.  Thus, virus detection approach is crucial for effective virus management programs and the production of virus-free seed potatoes.  Among the reported potato-infecting viruses, potato virus A (PVA) is considered as one of the most important viruses in potato-growing regions worldwide.  This study prepared four hybridoma lines secreting PVA-specific monoclonal antibodies (MAbs) (2D4, 8E11, 14A6 and 16H10) using purified PVA virions as an immunogen.  Western blotting results indicated that all the four MAbs reacted strongly and specifically with the putative capsid protein of PVA.  Using these four MAbs, this study developed antigen-coated plate enzyme-linked immunosorbent assay (ACP-ELISA), Dot-ELISA and Tissue print-ELISA for detection of PVA infection in potato plants.  The results indicated that PVA can be detected in crude tissue extracts from infected potato plants diluted up to 1:327 680 (w/v, g mL–1) by ACP-ELISA or up to 1:10 240 by Dot-ELISA.  The Tissue print-ELISA is the quickest and easiest approach among the three serological assays, and is more suitable for onsite large-scale potato screening programs.  Further analyses of field-collected potato samples showed that the sensitivities and specificities of the three serological approaches were similar to those of RT-PCR in PVA detection and confirmed that PVA is currently widespread in Yunnan and Zhejiang provinces of China.  Hence, the results strongly suggest that these highly sensitive serological approaches based on PVA-specific MAbs are useful and powerful for PVA-free seed potato production programs and PVA field surveys. 
    The sex peptide receptor in the Asian gypsy moth, Lymantria dispar, is involved in development and stress resistance
    DU Hui, SUN Li-li, LIU Peng, CAO Chuan-wang
    2021, 20(11): 2976-2985.  DOI: 10.1016/S2095-3119(20)63365-2
    Abstract ( )   PDF in ScienceDirect  
    The G protein-coupled receptor (GPCR) regulates downstream genes by binding to a heterotrimeric G protein.  However, the function of sex peptide receptor (SPR) in lepidopteran species is mostly unknown.  Understanding the physiological functions of SPR in insects is essential for exploring new insecticidal targets.  In the present study, the functions of an SPR in Lymantria dispar (Asian gypsy moth; LdSPR) were investigated.  The expression of LdSPR was the highest in the 6th instar larval stage, and there was a large difference in expression between male and female adults.  After LdSPR gene silencing, L.?dispar larvae showed increased sensitivity to high temperature, starvation, and oxidative stress, indicating that LdSPR enhances stress resistance.  These results enrich our knowledge of the function of the insect SPRs, which will lead to a better understanding of other insect GPCR family members and the identification of new targets for the development of environmentally friendly pesticides.
    Animal Science · Veterinary Medicine
    UBE2I stimulates female gonadal differentiation in chicken (Gallus gallus) embryos
    JIN Kai, ZHOU Jing, ZUO Qi-sheng, LI Jian-cheng, Jiuzhou SONG, ZHANG Ya-ni, CHANG Guo-bing, CHEN Guo-hong, LI Bi-chun
    2021, 20(11): 2986-2994.  DOI: 10.1016/S2095-3119(20)63486-4
    Abstract ( )   PDF in ScienceDirect  
    Without known analogous sex-determining factors like SRY (sex determining region Y) in mammals, the chicken (Gallus gallus) sex determination mechanism still remains unclear, which highly restricts the biological research on chicken development and poultry single-sex reproduction.  Here we not only characterized a new female-biased gene UBE2I and identified the expression pattern by qRT-PCR, but also described the functional role of UBE2I in the gonadal development of chicken embryos.  Results showed that UBE2I exhibited a female-biased expression pattern in the early stage of PGCs (primordial germ cells) in embryonic gonads and robust expression in ovaries of newborn chickens.  Most importantly, we successfully developed an effective method to interfere or overexpress UBE2I in chicken embryos through the intravascular injection.  The qRT-PCR analysis showed that the sex-related genes (FOXL2, CYP19A1 and HINTW) in females were upregulated (P<0.05) under the overexpression of UBE2I and the sex-related genes (SOX9, DMRT1 and WT1) in females were downregulated (P<0.05) after interfering UBE2I.  Furthermore, the change of UBE2I expression was associated with the level of estradiol and its receptors (AR and ESR), which suggests that UBE2I is necessary to initiate the female-specific development in chickens.  In conclusion, this work demonstrates that UBE2I is a crucial sex differentiation-related gene in the embryonic development of chickens, which provides insights for further understanding the mechanism of sex determination in chickens.
    Analysis of DNA methylation of CD79B in MDV-infected chicken spleen
    WANG Lu-lu, ZHAO Chun-fang, LIU Chang-jun, ZHANG Hao, LIAN Ling
    2021, 20(11): 2995-3002.  DOI: 10.1016/S2095-3119(20)63564-X
    Abstract ( )   PDF in ScienceDirect  
    Marek’s disease (MD), an immunosuppressive disease induced by Marek’s disease virus (MDV), provides an ideal model for studying diseases caused by a carcinogenic virus.  CD79B is a B-cell antigen receptor complex-associated protein β-chain precursor which is involved in the activation, proliferation, differentiation of B-cell and the transmission of downstream signals.  This study analyzed CD79B gene mRNA expression and methylation by two schemes #20 (5´ flanking to intron 1) and #27 (intron 2 to intron 3), between MDV-infected tumorous spleens (TS) and non-infected spleens (NS).  Results showed that average methylation levels of CpGs in #20 and #27 were higher in TS than in NS (P<0.05), while, CD79B mRNA expression was lower in TS than in NS (P<0.01).  Six of 40 CpG sites showed significantly (P<0.05) different methylation levels between TS and NS.  Correlation analysis showed that the average methylation level rather than a single site methylation level in #20 affected (P<0.05) mRNA expression.  Collectively, it was found that the change of CD79B gene expression after MDV infection might be partly explained by modification of DNA methylation. 
    Agro-ecosystem & Environment
    Divergent responses of tiller and grain yield to fertilization and fallow precipitation: Insights from a 28-year long-term experiment in a semiarid winter wheat system
    WANG Rui, WANG Ying, HU Ya-xian, DANG Ting-hui, GUO Sheng-li
    2021, 20(11): 3003-3011.  DOI: 10.1016/S2095-3119(20)63296-8
    Abstract ( )   PDF in ScienceDirect  
    Tillering is an important phenological stage, which is strongly related to the yield in spike components and final grain yield during winter wheat growth.  Precipitation during the fallow season (fallow precipitation) influences tillering in winter wheat on the semi-arid Chinese Loess Plateau.  However, little work has been done regarding tiller number changes under various types of fertilization and amounts of fallow precipitation on a long-term scale.  Effects of fallow precipitation and fertilization on tiller were investigated in a winter wheat (Triticum aestivum L.) system in a 28-year field study (1990 to 2017) in a semiarid agro-ecosystem.  Tiller number, spike number and grain yield were measured in four fertilization conditions: control without fertilizer (CK); mineral nitrogen fertilizer alone (N); mineral phosphorus fertilizer alone (P); mineral nitrogen and phosphorus fertilizer together (NP).  Based on the long-term annual fallow precipitation, dry years (<mean annual fallow precipitation) and wet years (>mean annual fallow precipitation) were distinguished.  Phosphorus fertilization alone significantly increased the mean annual tiller number (23%), and the increase in tiller number was higher in wet years (29%) than in the dry years (17%).  However, nitrogen fertilization alone had little effect on mean tiller number, while nitrogen and phosphorus together significantly increased mean annual tiller number (30%), mean tiller number in wet years (45%) and mean tiller number in dry years (17%).  Tiller number was significantly and positively correlated with fallow precipitation in dry years for all fertilizer treatments, whereas it was weakly and either positively or negatively correlated with fallow precipitation in wet years depending on the treatment.  This study found positive correlations between tiller number and fallow precipitation in the CK and NP treatments, and it found negative correlations between tiller number and fallow precipitation in the treatments with nitrogen fertilization alone or phosphorous fertilization alone in wet years.  Understanding the impacts of fallow precipitation and fertilization on tiller development shed light on ways to improve crop production in rain-fed agricultural regions.
    Yield performance and optimal nitrogen and phosphorus application rates in wheat and faba bean intercropping
    XIAO Jing-xiu, ZHU Ying-an, BAI Wen-lian, LIU Zhen-yang, TANG Li, ZHENG Yi
    2021, 20(11): 3012-3025.  DOI: 10.1016/S2095-3119(20)63489-X
    Abstract ( )   PDF in ScienceDirect  
    Yield performance in cereal and legume intercropping is related to nutrient management, however, the yield response of companion crops to nitrogen (N) input is inconclusive and only limited efforts have focused on rationed phosphorous (P) fertilization.  In this study, two multi-year field experiments were implemented from 2014–2019 under identical conditions.  Two factors in a randomized complete block design were adopted in both experiments.  In field experiment 1, the two factors included three planting patterns (mono-cropped wheat (MW), mono-cropped faba bean (MF), and wheat and faba bean intercropping (W//F)) and four N application rates (N0, 0 kg N ha–1; N1, 90 and 45 kg N ha–1 for wheat and faba beans, respectively; N2, 180 and 90 kg N ha–1 for wheat and faba beans, respectively; and N3, 270 and 135 kg N ha–1 for wheat and faba beans, respectively).  In field experiment 2, the two factors included three P application rates (P0, 0 kg P2O5 ha–1; P1, 45 kg P2O5 ha–1; and P2, 90 kg P2O5 ha–1) and the same three planting patterns (MW, MF, and W//F).  The yield performances of inter- and mono-cropped wheat and faba beans under different N and P application rates were analyzed and the optimal N and P rates for intercropped wheat (IW) and MW were estimated.  The results revealed that intercropping favored wheat yield and was adverse to faba bean yield.  Wheat yield increased by 18–26%, but faba bean yield decreased by 5–21% in W//F compared to MW and MF, respectively.  The stimulated IW yield drove the yield advantage in W//F with an average land equivalent ratio (LER) of 1.12.  N and P fertilization benefited IW yield, but reduced intercropped faba bean (IF) yield.  Nevertheless, the partial LER of wheat (pLERwheat) decreased with increasing N application rates, and the partial LER of faba bean (pLERfaba bean) decreased with increasing P application rates.  Thus, LER decreased as N input increased and tended to decline as P rates increased.  IW maintained a similar yield as MW, even under reduced 40–50% N fertilizer and 30–40% P fertilizer conditions.  The estimated optimum N application rates for IW and MW were 150 and 168 kg ha–1, respectively, and 63 and 62 kg ha–1 for P2O5, respectively.  In conclusion, W//F exhibited yield advantages due to stimulated IW yield, but the intercropping yield benefit decreased as N and P inputs increased.  Thus, it was concluded that modulated N and P rates could maximize the economic and ecological functions of intercropping.  Based on the results, rates of 150 kg N ha–1 and 60 kg P2O5 ha–1 are recommended for IW production in southwestern China and places with similar conditions.
    Modification of total and phosphorus mineralizing bacterial communities associated with Zea mays L. through plant development and fertilization regimes
    XIN Yuan-yuan, Anisur RAHMAN, LI Hui-xiu, XU Ting, DING Guo-chun, LI Ji
    2021, 20(11): 3026-3038.  DOI: 10.1016/S2095-3119(20)63413-X
    Abstract ( )   PDF in ScienceDirect  
    Harnessing the rhizospheric microbiome, including phosphorus mineralizing bacteria (PMB), is a promising technique for maintaining sustainability and productivity in intensive agricultural systems.  However, it is unclear as to which beneficial taxonomic group populations in the rhizosphere are potentially associated with the changes in soil microbiomes shifted by fertilization regimes.  Herein, we analyzed the diversity and community structure of total bacteria and PMB in the rhizosphere of maize (Zea mays L.) grown in soils under 25 years of four fertilization regimes (compost, biocompost, chemical, or non-fertilized) via selective culture and Illumina sequencing of the 16S rRNA genes.  Plant development explained more variations (29 and 13%, respectively) in the composition of total bacteria and PMB in the rhizosphere of maize than the different fertilization regimes.  Among those genera enriched in the rhizosphere of maize, the relative abundances of Oceanobacillus, Bacillus, Achromobacter, Ensifer, Paracoccus, Ramlibacter, and Luteimonas were positively correlated with those in the bulk soil.  The relative abundance of Paracoccus was significantly higher in soils fertilized by compost or biocompost than the other soils.  Similar results were also observed for PMB affiliated with Ensifer, Bacillus, and Streptomyces.  Although plant development was the major factor in shaping the rhizospheric microbiome of maize, fertilization regimes might have modified beneficial rhizospheric microbial taxa such as Bacillus and Ensifer
    Linking changes in the soil microbial community to C and N dynamics during crop residue decomposition
    2021, 20(11): 3039-3059.  DOI: 10.1016/S2095-3119(20)63567-5
    Abstract ( )   PDF in ScienceDirect  
    Crop residues are among the main inputs that allow the organic carbon (C) and nutrients to be maintained in agricultural soil.  It is an important management strategy that can improve soil fertility and enhance agricultural productivity.  This work aims to evaluate the extent of the changes that may occur in the soil heterotrophic microbial communities involved in organic matter decomposition and C and nitrogen (N) mineralization after the addition of crop residues.  Soil microcosm experiments were performed at 28°C for 90 days with the addition of three crop residues with contrasting biochemical qualities: pea (Pisum sativum L.), rapeseed (Brassica napus L.), and wheat (Triticum aestivum L.).  Enzyme activities, C and N mineralization, and bacterial and fungal biomasses were monitored, along with the bacterial and fungal community composition, by the high-throughput sequencing of 16S rRNA and ITS genes.  The addition of crop residues caused decreases in β-glucosidase and arylamidase activities and simultaneous enhancement of the C mineralization and net N immobilization, which were linked to changes in the soil microbial communities.  The addition of crop residues decreased the bacterial and fungal biomasses 90 days after treatment and there were shifts in bacterial and fungal diversity at the phyla, order, and genera levels.  Some specific orders and genera were dependent on crop residue type.  For example, Chloroflexales, Inquilinus, Rubricoccus, Clitocybe, and Verticillium were identified in soils with pea residues; whereas Thermoanaerobacterales, Thermacetogenum, and Hypoxylon were enriched in soils with rapeseed residues, and Halanaerobiales, Rubrobacter, and Volutella were only present in soils with wheat residues.  The findings of this study suggest that soil C and N dynamics in the presence of the crop residues were driven by the selection of specific bacterial and fungal decomposers linked to the biochemical qualities of the crop residues.  If crop residue decomposition processes showed specific bacterial and fungal operational taxonomic unit (OTU) signatures, this study also suggests a strong functional redundancy that exists among soil microbial communities.
    Food Science
    Melatonin treatment induces chilling tolerance by regulating the contents of polyamine, γ-aminobutyric acid, and proline in cucumber fruit
    Miilion P MADEBO, LUO Si-ming, WANG Li, ZHENG Yong-hua, JIN Peng
    2021, 20(11): 3060-3074.  DOI: 10.1016/S2095-3119(20)63485-2
    Abstract ( )   PDF in ScienceDirect  
    The mechanism of melatonin (MT) induced chilling tolerance in harvested cucumber fruit was investigated at commercial maturity.  In this study, cucumber fruits were treated with 100 μmol L–1 MT at 4°C and 90% relative humidity for 15 d of storage.  In comparison with the control, cucumber treatment with MT resulted in reduced chilling injury (CI), decreased electrolyte leakage and enhanced firmness.  The fruits treated with MT showed higher chlorophyll contents in storage conditions with suppressed chlorophyllase enzyme activity.  MT treatment increased arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) enzyme activities.  Moreover, enhanced expression of the Cucumis sativus ADC (CsADC) and C. sativus ODC (CsODC) genes resulted in the accumulation of polyamine contents.  Similarly, proline levels exhibited higher levels among treated fruits.  Meanwhile, the proline synthesizing enzymes △1-pyrroline-5-carboxylate syntheses (P5CS) and ornithine aminotransferase (OAT) were significantly increased, while a catabolic enzyme of proline dehydrogenase (PDH) activity was inhibited by treatment.  In addition, MT induced expression of C. sativus OAT (CsOAT) and C. sativus P5CS (CsP5CS) genes.  Cucumber fruits treated with MT also exhibited higher γ-aminobutyric acid (GABA) content by enhanced GABA transaminase (GABA-T) and glutamate decarboxylase (GAD) enzyme activities and a higher C. sativus GAD (CsGAD) gene expression.  To sum up, the results show that MT treatment enhanced chilling tolerance, which was associated with the regulation of polyamines, as well as proline and γ-aminobutyric acid.
    Application of methyl jasmonate postharvest maintains the quality of Nanguo pears by regulating mitochondrial energy metabolism
    LI Can-ying, CHENG Yuan, HOU Jia-bao, ZHU Jie, SUN Lei, GE Yong-hong
    2021, 20(11): 3075-3083.  DOI: 10.1016/S2095-3119(21)63611-0
    Abstract ( )   PDF in ScienceDirect  
    The present study was conducted to investigate the effects of methyl jasmonate (MeJA) dipping treatment on mitochondrial energy metabolism and quality parameters of Nanguo pears during room temperature storage.  The results showed that MeJA treatment suppressed the respiration rate and weight loss, and maintained the flesh firmness of Nanguo pears.  MeJA also effectively maintained the content of ascorbic acid and titratable acidity in the fruit.  Furthermore, the activities of H+-ATPase, Ca2+-ATPase, succinate dehydrogenase (SDH) and cytochrome C oxidase (CCO) of the MeJA-treated fruit were significantly higher than those of the untreated fruit.  The contents of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) and the energy charge were also enhanced by MeJA treatment.  These results suggest that postharvest MeJA treatment could maintain the quality of Nanguo pears, in part by modulating mitochondrial energy metabolism during room temperature storage.
    Short Communication
    Viricidal activity of several disinfectants against African swine fever virus
    JIANG Cheng-gang, SUN Ying, ZHANG Fan, AI Xin, FENG Xiao-ning, HU Wei, ZHANG Xian-feng, ZHAO Dong-ming, BU Zhi-gao, HE Xi-jun
    2021, 20(11): 3084-3088.  DOI: 10.1016/S2095-3119(21)63631-6
    Abstract ( )   PDF in ScienceDirect  
    Prevention of African swine fever, a disease caused by African swine fever virus (ASFV), requires maintenance of high biosecurity standards, which principally relies on disinfection.  Finding the perfect disinfectant against ASFV is difficult because of the lack of relevant data.  Therefore, we aimed to find the most effective disinfectant and to optimise its concentration as well as contact time to confirm the viricidal effect against ASFV in vitro.  We evaluated the viricidal activity of three concentrations each of six common disinfectants against ASFV using immersion disinfection assay (IDA) and spray disinfection assay (SDA); the concentrations of these disinfectants at which complete viral inactivation occurred were almost same as the manufacturer-recommended concentrations, but the exposure times for viral inactivation are different.  The following disinfectants (assay: concentration, exposure time) showed complete inactivation: iodine and acid mixed solution (IDA/SDA: 0.5%, 10 min); compound potassium peroxymonosulfate (IDA: 0.25%, 30 min; SDA: 0.25%, 60 min); citric acid (IDA: 0.25%, 60 min; SDA: 0.5%, 60 min); sodium dichloroisocyanurate (IDA: 0.125%, 60 min; SDA: 0.25%, 60 min); and glutaral ang deciquam (IDA/SDA: 0.2%, 60 min); and deciquam (IDA/SDA: 0.5%, 60 min).  However, in the presence of organic material contamination, disinfectants did not show a marked inactivation effect.  Therefore, disinfection procedures should be performed in two steps: thorough mechanical cleaning followed by application of disinfectant.  In conclusion, all the tested disinfectants can inactivate ASFV; these can be used as alternative disinfectants to enhance biosecurity.