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    Creating large EMS populations for functional genomics and breeding in wheat

    Wenqiang Wang, Xizhen Guan, Yong Gan, Guojun Liu, Chunhao Zou, Weikang Wang, Jifa Zhang, Huifei Zhang, Qunqun Hao, Fei Ni, Jiajie Wu, Lynn Epstein, Daolin Fu
    2024, 23 (2): 484-493.   DOI: 10.1016/j.jia.2023.05.039
    Abstract480)      PDF in ScienceDirect      

    Wheat germplasm is a fundamental resource for basic research, applied studies, and wheat breeding, which can be enriched normally by several paths, such as collecting natural lines, accumulating breeding lines, and introducing mutagenesis materials.  Ethyl methane sulfonate (EMS) is an alkylating agent that can effectively introduce genetic variations in a wide variety of plant species.  In this study, we created a million-scale EMS population (MEP) that started with the Chinese wheat cultivars ‘Luyan 128’, ‘Jimai 38’, ‘Jimai 44’, and ‘Shannong 30’.  In the M1 generation, the MEP had numerous phenotypical variations, such as >3,000 chlorophyll-deficient mutants, 2,519 compact spikes, and 1,692 male sterile spikes.  There were also rare mutations, including 30 independent tillers each with double heads.  Some M1 variations of chlorophyll-deficiency and compact spikes were inheritable, appearing in the M2 or M3 generations.  To advance the entire MEP to higher generations, we adopted a single-seed descendent (SSD) approach.  All other seed composites of M2 were used to screen other agronomically important traits, such as the tolerance to herbicide quizalofop-P-methyl.  The MEP is available for collaborative projects, and provides a valuable toolbox for wheat genetics and breeding for sustainable agriculture.

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    OsNPF3.1, a nitrate, abscisic acid and gibberellin transporter gene, is essential for rice tillering and nitrogen utilization efficiency

    Junnan Hang, Bowen Wu, Diyang Qiu, Guo Yang, Zhongming Fang, Mingyong Zhang
    2024, 23 (4): 1087-1104.   DOI: 10.1016/j.jia.2023.04.024
    Abstract369)      PDF in ScienceDirect      

    Low-affinity nitrate transporter genes have been identified in subfamilies 4–8 of the rice nitrate transporter 1 (NRT1)/peptide transporter family (NPF), but the OsNPF3 subfamily responsible for nitrate and phytohormone transport and rice growth and development remains unknown.  In this study, we described OsNPF3.1 as an essential nitrate and phytohormone transporter gene for rice tillering and nitrogen utilization efficiency (NUtE).  OsNPF3.1 possesses four major haplotypes of its promoter sequence in 517 cultivars, and its expression is positively associated with tiller number.  Its expression was higher in the basal part, culm, and leaf blade than in other parts of the plant, and was strongly induced by nitrate, abscisic acid (ABA) and gibberellin 3 (GA3) in the root and shoot of rice.  Electrophysiological experiments demonstrated that OsNPF3.1 is a pH-dependent low-affinity nitrate transporter, with rice protoplast uptake assays showing it to be an ABA and GA3 transporter.  OsNPF3.1 overexpression significantly promoted ABA accumulation in the roots and GA accumulation in the basal part of the plant which inhibited axillary bud outgrowth and rice tillering, especially at high nitrate concentrations.  The NUtE of OsNPF3.1-overexpressing plants was enhanced under low and medium nitrate concentrations, whereas the NUtE of OsNPF3.1 clustered regularly interspaced short palindromic repeats (CRISPR) plants was increased under high nitrate concentrations.  The results indicate that OsNPF3.1 transports nitrate and phytohormones in different rice tissues under different nitrate concentrations.  The altered OsNPF3.1 expression improves NUtE in the OsNPF3.1-overexpressing and CRISPR lines at low and high nitrate concentrations, respectively.

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    FgGyp8 as a putative FgRab1 GAP is required for growth and pathogenesis by regulating FgSnc1-mediated secretory vesicles fusion in Fusarium graminearum
    ZHANG Xing-zhi, CHEN Shuang, Yakubu Saddeeq ABUBAKAR, MAO Xu-zhao, MIAO Peng-fei, WANG Zong-hua, ZHOU Jie, ZHENG Hua-wei
    2023, 22 (11): 3444-3457.   DOI: 10.1016/j.jia.2023.04.005
    Abstract353)      PDF in ScienceDirect      

    Fusarium graminearum is an important plant pathogenic fungus that causes disease and yield reduction in many cereal crops, such as wheat and barley.  Gyp8 stimulates GTP hydrolysis on Ypt1 in yeast.  However, the functions of Gyp8 in plant pathogenic fungi are still unknown.  In this study, we investigated the roles of FgGyp8 in Fgraminearum by genetic and pathological analyses.  Through gene knockout and phenotypic analyses, we found that FgGyp8 is required for vegetative growth in Fgraminearum.  The conidiation, conidial size and number of septa per conidium of ΔFggyp8 mutant are significantly reduced when compared to the wild type PH-1.  Furthermore, FgGyp8 is crucial for pathogenicity on wheat coleoptiles and wheat heads.  FgGyp8 contains a conserved TBC domain.  Domain deletion analysis showed that the TBC domain, C- and N-terminal regions of FgGyp8 are all important for its biological functions in Fgraminearum.  Moreover, we showed that FgGyp8 catalyzes the hydrolysis of the GTP on FgRab1 to GDP in vitro, indicating that FgGyp8 is a GTPase-activating protein (GAP) for FgRab1.  In addition, we demonstrated that FgGyp8 is required for FgSnc1-mediated fusion of secretory vesicles with the plasma membrane in Fgraminearum.  Finally, we showed that FgGyp8 has functional redundancy with another FgRab1 GAP, FgGyp1, in Fgraminearum.  Taken together, we conclude that FgGyp8 is required for vegetative growth, conidiogenesis, pathogenicity and acts as a GAP for FgRab1 in Fgraminearum.

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    Exploring the nano-fungicidal efficacy of green synthesized magnesium oxide nanoparticles (MgO NPs) on the development, physiology, and infection of carrot (Daucus carota L.) with Alternaria leaf blight (ALB): Molecular docking
    Lukman AHAMAD, Azmat ALI KHAN, Masudulla KHAN, Orudzhev FARID, Mahboob ALAM
    2023, 22 (10): 3069-3080.   DOI: 10.1016/j.jia.2023.02.034
    Abstract343)      PDF in ScienceDirect      

    In this research, green synthesized magnesium oxide nanoparticles (MgO NPs) from lemon fruit extracts and their fungicidal potential was evaluated against Alternaria dauci infection on carrot (Daucus carota L.) under greenhouse conditions.  The scanning and transmission electron microscopy (SEM and TEM) and ultra-violet (UV) visible spectroscopy were used to validate and characterize MgO NPs.  The crystalline nature of MgONPs was determined using selected area electron diffraction (SAED).  MgO NPs triggered substantial antifungal activity against Adauci when exposed to 50 and 100 mg L–1 concentrations but the higher antifungal potential was noticed in 100 mg L–1 under in-vitro conditions.  In fungal inoculated plants, a marked decrease in growth, photosynthetic pigments, and an increase in phenol, proline contents, and defense-related enzymes of carrot were seen over control (distilled water).  However, foliar application of MgO NPs at 50 and 100 mg L–1 resulted in significant improvement of plant growth, photosynthetic pigments, phenol and proline contents, and defense enzymes activity of carrots with and without Adauci infection.  Spraying of MgO NPs at 100 mg L–1 had more plant length (17.11%), shoot dry weight (34.38%), plant fresh weight (20.46%), and root dry weight (49.09%) in carrots when challenged with A. dauci over inoculated control.  The leaf blight indices and percent disease severity were also reduced in Adauci inoculated plants when sprayed with MgO NPs.  The non-bonding interactions of Alternaria genus protein with nanoparticles were studied using molecular docking.

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    Identification and characterization of the chalkiness endosperm gene CHALK-H in rice (Oryza sativa L.)
    PIAO Ri-hua, CHEN Mo-jun, MENG Fan-mei, QI Chun-yan, KOH Hee-Jong, GAO Meng-meng, SONG An-qi, JIN Yong-mei, YAN Yong-feng
    2023, 22 (10): 2921-2933.   DOI: 10.1016/j.jia.2023.04.020
    Abstract337)      PDF in ScienceDirect      

    Chalkiness is one of the most important agronomic traits in rice breeding, which directly affects the quality of rice seed.  In this study, we identified a chalkiness endosperm mutant, chalk-h, from N-methyl-N-nitrosourea (MNU)-induced japonica rice cultivar Hwacheong (HC).  Compared with wild type (WT)-HC, chalk-h showed severe chalkiness in the endosperm, yellowish green leaves, as well as reduced plant height.  Scanning electron microscopy (SEM) analysis showed that starch grains in the chalk-h mutant were irregular in size and loosely arranged, with large gaps between granules, forming ovoid or orbicular shapes.  MutMap analysis revealed that the phenotype of chalk-h is controlled by a single recessive gene LOC_Os11g39670 encoding seryl-tRNA synthetase, which is renamed as CHALK-H.  A point mutation occurs in chalk-h on the sixth exon (at nucleotide 791) of CHALK-H, in which adenine (A) is replaced by thymidine (T), resulting in an amino acid codon change from glutamine (Glu) to valine (Val).  The chalk-h mutant exhibited a heat-sensitive phenotype from the 3-leaf stage, including yellow-green leaves and reduced pigment content.  The transcriptional expression of starch synthesis-related genes was down-regulated in the chalk-h mutants compared to WT-HC at different grain-filling stages.  With an increase in temperature, the expression of photosynthesis-related genes was down-regulated in the chalk-h mutant compared to WT-HC.  Overexpression of CHALK-H rescued the phenotype of chalk-h, with endosperm and leaf color similar to those of WT-HC.  Our findings reveal that CHALK-H is a causative gene controlling chalkiness and leaf color of the chalk-h mutant.  CHALK-H is the same gene locus as TSCD11, which was reported to be involved in chloroplast development under high temperature.  We suggest that CHALK-H/TSCD11 plays important roles not only in chloroplast development, but also in photosynthesis and starch synthesis during rice growth and development, so it has great application potential in rice breeding for high quality and yield.

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    Seedling Petri-dish inoculation method: A robust, easy-to-use and reliable assay for studying plant–Ralstonia solanacearum interactions
    CAO Peng, CHEN Jia-lan, LI Ning-ning, ZHANG Shuang-xi, WANG Rong-bo, LI Ben-jin, LIU Pei-qing, AN Yu-yan, ZHANG Mei-xiang
    2023, 22 (12): 3709-3719.   DOI: 10.1016/j.jia.2023.05.020
    Abstract337)      PDF in ScienceDirect      

    Ralstonia solanacearum causes a lethal bacterial wilt disease in many crops, leading to huge losses in crop production every year.  Understanding of plant–Rsolanacearum interactions will aid to develop efficient strategies to control the disease.  As a soilborne pathogen, Rsolanacearum naturally infects plants via roots.  A huge limitation in studying plant–Rsolanacearum interactions is the large variation of Rsolanacearum infection assay due to the variable soil conditions and uneven inoculum exposure.  Here, we developed a robust and reliable Petri-dish inoculation method which allows consistent and stable infection in young plant seedlings.  This method is easy to use, takes about only 10 days from seed germination to the completion of inoculation assay, and requires less inoculum of bacteria as well as growth chamber space.  We proved the efficacy of the seedling Petri-dish inoculation method by analyzing plant defense primed by molecular patterns, resistance of defense-related plant mutants, and virulence of Rsolanacearum mutants.  Furthermore, we demonstrated that the seedling Petri-dish inoculation method can be applied to other host plants such as tobacco and has great potential for high-throughput screening of resistant plant germplasms to bacterial wilt in the future.

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    Dek219 encodes the DICER-LIKE1 protein that affects chromatin accessibility and kernel development in maize
    XIE Si-di, TIAN Ran, ZHANG Jun-jie, LIU Han-mei, LI Yang-ping, HU Yu-feng, YU Guo-wu, HUANG Yu-bi, LIU Ying-hong
    2023, 22 (10): 2961-2980.   DOI: 10.1016/j.jia.2023.02.024
    Abstract333)      PDF in ScienceDirect      

    Chromatin accessibility plays a vital role in gene transcriptional regulation.  However, the regulatory mechanism of chromatin accessibility, as well as its role in regulating crucial gene expression and kernel development in maize (Zea mays) are poorly understood.  In this study, we isolated a maize kernel mutant designated as defective kernel219 (dek219), which displays opaque endosperm and embryo abortion.  Dek219 encodes the DICER-LIKE1 (DCL1) protein, an essential enzyme in miRNA biogenesis.  Loss of function of Dek219 results in significant reductions in the expression levels of most miRNAs and histone genes.  Further research showed that the Heat shock transcription factor17 (Hsf17)-Zm00001d016571 module may be one of the factors affecting the expression of histone genes.  Assay results for transposase-accessible chromatin sequencing (ATAC-seq) indicated that the chromatin accessibility of dek219 is altered compared with that of wild type (WT), which may regulate the expression of crucial genes in kernel development.  By analyzing differentially expressed genes (DEGs) and differentially accessible chromatin regions (ACRs) between WT and dek219, we identified 119 candidate genes that are regulated by chromatin accessibility, including some reported to be crucial genes for kernel development.  Taken together, these results suggest that Dek219 affects chromatin accessibility and the expression of crucial genes that are required for maize kernel development

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    Establishment of a system for screening and identification of novel bactericide targets in the plant pathogenic bacterium Xanthomonas oryzae pv. oryzae using Tn-seq and SPR
    Chaoyue Pang, Ling Jin, Haoyu Zang, Damalk Saint-Claire S. Koklannou, Jiazhi Sun, Jiawei Yang, Yongxing Wang, Liang Xu, Chunyan Gu, Yang Sun, Xing Chen, Yu Chen
    2024, 23 (5): 1580-1592.   DOI: 10.1016/j.jia.2023.04.043
    Abstract328)      PDF in ScienceDirect      

    Xanthomonas spp. cause severe bacterial diseases.  However, effective strategies for prevention and management of these diseases are scarce.  Thus, it is necessary to improve the efficiency of control of diseases caused by Xanthomonas.  In this study, Xanthomonas oryzae pv. oryzae (Xoo), which causes rice bacterial leaf blight, has been studied as a representative.  A transposon insertion library of Xoo, comprising approximately 200,000 individual insertion mutants, was generated.  Transposon sequencing data indicated that the mariner C9 transposase mapped at 35.7–36.4% of all potential insertion sites, revealing 491 essential genes required for the growth of Xoo in rich media.  The results show that, compared to the functions of essential genes of other bacteria, the functions of some essential genes of Xoo are unknown, 25 genes might be dangerous for the Xanthomonas group, and 3 are specific to Xanthomonas.  High-priority candidates for developing broad-spectrum, Xanthomonas-specific, and environment-friendly bactericides were identified in this study.  In addition, this study revealed the possible targets of dioctyldiethylenetriamine using surface plasmon resonance (SPR) in combination with high performance liquid chromatography–mass spectrometry (HPLC–MS).  The study also provided references for the research of some certain bactericides with unknown anti-bacterial mode of action.  In conclusion, this study urged a better understanding of Xanthomonas, provided meaningful data for the management of bacterial leaf blight, and disclosed selected targets of a novel bactericide.

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    Identification, pathogenicity, and fungicide sensitivity of Eutiarosporella dactylidis associated with leaf blight on maize in China

    Cheng Guo, Xiaojie Zhang, Baobao Wang, Zhihuan Yang, Jiping Li, Shengjun Xu, Chunming Wang, Zhijie Guo, Tianwang Zhou, Liu Hong, Xiaoming Wang, Canxing Duan
    2024, 23 (3): 888-900.   DOI: 10.1016/j.jia.2023.09.032
    Abstract326)      PDF in ScienceDirect      

    Maize (Zea mays L.) is an economically vital grain crop that is cultivated worldwide.  In 2011, a maize foliar disease was detected in Lingtai and Lintao counties in Gansu Province, China.  The characteristic signs and symptoms of this disease include irregular chlorotic lesions on the tips and edges of infected leaves and black punctate fruiting bodies in dead leaf tissues.  Given favourable environmental conditions, this disease spread to areas surrounding Gansu.  In this study, infected leaves were collected from Gansu and Ningxia Hui Autonomous Region between 2018 and 2020 to identify the disease-causing pathogen.  Based on morphological features, pathogenicity tests, and multi-locus phylogenetic analysis involving internal transcribed spacer (ITS), 18S small subunit rDNA (SSU), 28S large subunit rDNA (LSU), translation elongation factor 1-alpha (TEF), and β-tubulin (TUB) sequences, Eutiarosporella dactylidis was identified as the causative pathogen of this newly discovered leaf blight.  Furthermore, an in vitro bioassay was conducted on representative strains using six fungicides, and both fludioxonil and carbendazim were found to significantly inhibit the mycelial growth of E. dactylidis.  The results of this study provide a reference for the detection and management of Eutiarosporella leaf blight.

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    Differential metabolites and their transcriptional regulation in seven major tea cultivars (Camellia sinensis) in China
    GAO Ting, HOU Bing-hao, SHAO Shu-xian, XU Meng-ting, ZHENG Yu-cheng, JIN Shan, WANG Peng-jie, YE Nai-xing
    2023, 22 (11): 3346-3363.   DOI: 10.1016/j.jia.2023.02.009
    Abstract323)      PDF in ScienceDirect      

    Various genetic and biochemical characteristics exist in tea plant cultivars, and they largely determine production suitability and tea quality.  Here, we performed transcriptomic and metabolomic analyses of young shoots of seven tea cultivars and identified major regulatory transcription factors (TFs) for the characteristic metabolites in different cultivars based on weighted gene co-expression network analysis (WGCNA).  Phenotypically, we found that ‘Tieguanyin’ (TGY) and ‘Fujian Shuixian’ (FJSX), which are suitable for oolong tea, had higher catechin contents.  The metabolites of ‘Jinxuan’ (JX) were more prominent, especially the contents of phenolic acids, flavonoids, terpenes, and tannins, which were higher than those of the other six cultivars.  Moreover, ‘Fudingdabai’ (FDDB), which is suitable for white tea, was rich in amino acids, linolenic acid, and saccharides.  At the molecular level, hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (HCT) (CsTGY12G0001876, and CsTGY06G0003042) led to the accumulation of chlorogenic acid in TGY.  The main reason for the higher l-ascorbic acid content in FJSX was the high expression levels of L-galactono-1,4-lactone hydrogenase (GalLDH) (CsTGY13G0000389) and Myo-inositol oxygenase (MIOX) (CsTGY14G0001769, and CsTGY14G0001770), which were regulated by WRKY (CsTGY11G0001197).  Furthermore, FDDB, ‘Longjing 43’ (LJ43), ‘Shuchazao’ (SCZ)  and ‘Baihaozao’ (BHZ) had higher free fatty acid contents, among which MYB (CsTGY14G0002344) may be a hub gene for the regulation of palmitoleic acid accumulation.  More importantly, we found that the shoots of TGY were green with purple, mainly due to the accumulation of anthocyanins and the downregulation of the Mg-protoporphyrin IX nonomethyl ester cyclase (MPEC) (CsTGY10G0001989) gene that affects chlorophyll synthesis.  These results will provide a theoretical reference for tea cultivar breeding and suitability.

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    A single nucleotide substitution in the MATE transporter gene regulates plastochron and many noded dwarf phenotype in barley (Hordeum vulgare L.)
    GUO Bao-jian, SUN Hong-wei, QI Jiang, HUANG Xin-yu, HONG Yi, HOU Jian, LÜ Chao, WANG Yu-lin, WANG Fei-fei, ZHU Juan, GUO Gang-gang, XU Ru-gen
    2023, 22 (8): 2295-2305.   DOI: 10.1016/j.jia.2023.02.006
    Abstract314)      PDF in ScienceDirect      
    In higher plants, the shoot apical meristem produces lateral organs in a regular spacing (phyllotaxy) and timing (plastochron).  The molecular analysis of mutants associated with phyllotaxy and plastochron would increase our understanding of the mechanism of shoot architecture formation.  In this study, we identified mutant mnd8ynp5 that shows an increased rate of leaf emergence and a larger number of nodes in combination with a dwarfed growth habit from an EMS-treated population of the elite barley cultivar Yangnongpi 5.  Using a map-based cloning strategy, the mnd8 gene was narrowed down to a 6.7-kb genomic interval on the long arm of chromosome 5H.  Sequence analysis revealed that a C to T single-nucleotide mutation occurred at the first exon (position 953) of HORVU5Hr1G118820, leading to an alanine (Ala) to valine (Val) substitution at the 318th amino acid site.  Next, HORVU5Hr1G118820 was defined as the candidate gene of MND8 encoding 514 amino acids and containing two multidrug and toxic compound extrusion (MATE) domains.  It is highly homologous to maize Bige1 and has a conserved function in the regulation of plant development by controlling the leaf initiation rate.  Examination of modern barely varieties showed that Hap-1 was the dominant haplotype and was selected in barley breeding around the world.  Collectively, our results indicated that mnd8ynp5 is a novel allele of the HORVU5Hr1G118820 gene that is possibly responsible for the shortened plastochron and many noded dwarf phenotype in barley.
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    Estimation of the potential geographical distribution of a new potato pest (Schrankia costaestrigalis) in China under climate change
    XIAN Xiao-qing, ZHAO Hao-xiang, GUO Jian-yang, ZHANG Gui-fen, LIU Hui, LIU Wan-xue, WAN Fang-hao
    2023, 22 (8): 2441-2455.   DOI: 10.1016/j.jia.2022.08.023
    Abstract293)      PDF in ScienceDirect      

    Global food security is threatened by the impacts of the spread of crop pests and changes in the complex interactions between crops and pests under climate change.  Schrankia costaestrigalis is a newly-reported potato pest in southern China.  Early-warning monitoring of this insect pest could protect domestic agriculture as it has already caused regional yield reduction and/or quality decline in potato production.  Our research aimed to confirm the potential geographical distributions (PGDs) of Scostaestrigalis in China under different climate scenarios using an optimal MaxEnt model, and to provide baseline data for preventing agricultural damage by Scostaestrigalis.  Our findings indicated that the accuracy of the optimal MaxEnt model was better than the default-setting model, and the minimum temperature of the coldest month, precipitation of the driest month, precipitation of the coldest quarter, and the human influence index were the variables significantly affecting the PGDs of Scostaestrigalis.  The highly- and moderately-suitable habitats of Scostaestrigalis were mainly located in eastern and southern China.  The PGDs of Scostaestrigalis in China will decrease under climate change.  The conversion of the highly- to moderately-suitable habitat will also be significant under climate change.  The centroid of the suitable habitat area of Scostaestrigalis under the current climate showed a general tendency to move northeast and to the middle-high latitudes in the 2030s.  The agricultural practice of plastic film mulching in potato fields will provide a favorable microclimate for Scostaestrigalis in the suitable areas.  More attention should be paid to the early warning and monitoring of Scostaestrigalis in order to prevent its further spread in the main areas in China’s winter potato planting regions.

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    Physiological and biochemical characteristics of boscalid resistant isolates of Sclerotinia sclerotiorum from asparagus lettuce
    SHI Dong-ya, LI Feng-jie, ZHANG Zhi-hui, XU Qiao-nan, CAO Ying-ying, Jane Ifunanya MBADIANYA, LI Xin, WANG Jin, CHEN Chang-jun
    2023, 22 (12): 3694-3708.   DOI: 10.1016/j.jia.2023.09.024
    Abstract286)      PDF in ScienceDirect      

    Laboratory mutants of Sclerotinia sclerotiorum (Lib) de Bary, resistant to boscalid, have been extensively characterized.  However, the resistance situation in the lettuce field remains largely elusive.  In this study, among the 172 Ssclerotiorum isolates collected from asparagus lettuce field in Jiangsu Province, China, 132 isolates (76.74%) exhibited low-level resistance to boscalid (BosLR), with a discriminatory dose of 5 μg mL–1.  In comparison to the boscalid-sensitive (BosS) isolates, most BosLR isolates demonstrated a slightly superior biological fitness, as evidenced by data on mycelial growth, sclerotium production and pathogenicity.  Moreover, most BosLR isolates showed comparable levels of oxalic acid (OA) accumulation, increased exopolysaccharide (EPS) content and reduced membrane permeability when compared to the BosS isolates.  Nevertheless, their responses to distinct stress factors diverged significantly.  Furthermore, the effectiveness of boscalid in controlling BosLR isolates on radish was diminished compared to its efficacy on BosS isolates.  Genetic mutations were identified in the SDH genes of BosLR isolates, revealing the existence of three resistant genotypes: I (A11V at SDHB, SDHBA11V), II (Q38R at SDHC, SDHCQ38R) and III (SDHBA11V+SDHCQ38R).  Importantly, no cross-resistance was observed between boscalid and other fungicides such as thifluzamide, pydiflumetofen, fluazinam, or tebuconazole.  Our molecular docking analysis indicated that the docking total score (DTS) of the type I resistant isolates (1.3993) was lower than that of the sensitive isolates (1.7499), implying a reduced affinity between SDHB and boscalid as a potential mechanism underlying the boscalid resistance in Ssclerotiorum.  These findings contribute to an enhanced comprehension of boscalid’s mode of action and furnish valuable insights into the management of boscalid resistance.

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    A stable and major QTL region on chromosome 2 conditions pod shape in cultivated peanut (Arachis hyopgaea L.)
    ZHANG Sheng-zhong, HU Xiao-hui, WANG Fei-fei, CHU Ye, YANG Wei-qiang, XU Sheng, WANG Song, WU Lan-rong, YU Hao-liang, MIAO Hua-rong, FU Chun, CHEN Jing
    2023, 22 (8): 2323-2334.   DOI: 10.1016/j.jia.2023.02.005
    Abstract260)      PDF in ScienceDirect      
    Peanut pod shape is a heritable trait which affects the market acceptance of in-shell peanut products.  In order to determine the genetic control of pod shape, six component traits of pod shape (pod length, pod width, pod length/width ratio, pod roundness, beak degree and constriction degree) were measured using an image-based phenotyping method.  A recombinant inbred line (RIL) population consisting of 181 lines was phenotyped across three environments.  Continuous distributions and transgressive segregations were demonstrated in all measured traits and environments.   Significant correlations were found among most component traits with broad-sense heritability ranging from 0.87 to 0.95.  Quantitative trait locus (QTL) analysis yielded 26 additive QTLs explaining 3.79 to 52.37% phenotypic variations.  A novel, stable and major QTL region conditioning multiple shape features was detected on chromosome 2, which spans a 10.81-Mb genomic region with 543 putative genes.  Bioinformatics analysis revealed several candidate genes in this region.  In addition, 73 pairs of epistatic interactions involving 92 loci were identified for six component traits explaining 0.94–6.45% phenotypic variations.  These results provide new genetic loci to facilitate genomics-assisted breeding of peanut pod shape.
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    Dissecting the key genomic regions underlying high yield potential in common wheat variety ‘Kenong 9204’
    ZHAO Chun-hua, ZHANG Na, FAN Xiao-li, JI Jun, SHI Xiao-li, CUI Fa, LING Hong-qing, LI Jun-ming
    2023, 22 (9): 2603-2616.   DOI: 10.1016/j.jia.2023.02.013
    Abstract250)      PDF in ScienceDirect      
    The foundation parents play key roles in the genetic improvement of both yield potential and end-use quality in wheat.  Characterizing the genetic basis that underlies certain beneficial traits in the foundation parents will provide theoretical reference for molecular breeding by a design approach.  ‘Kenong 9204’ (KN9204) is a candidate foundation parent characterized by ideotype, high yield potential, and particularly high nitrogen fertilizer utilization.  To better understand the genetic basis of its high yield potential, high throughput whole-genome re-sequencing (10×) was performed on KN9204, its parental lines and its derivatives.  A high-resolution genetic composition map of KN9204 was constructed, which showed the parental origin of the favorable genomic segments based on the identification of excellent yield-related quantitative trait loci (QTL) from a bi-parental mapping population.  Xiaoyan 693 (XY693), a wheat–Thinopyrum ponticum partial amphidiploid, contributed a great deal to the high yield potential of KN9204, and three major stable QTLs from XY693 were fine mapped.  The transmissibility of key genomic segments from KN9204 to its derivatives were delineated, indicating that haplotype blocks containing beneficial gene combinations were conserved along with directional selection by breeders.  Evidence for selection sweeps in the breeding programs was identified.  This study provides a theoretical reference for the breeding of high-yield wheat varieties by a molecular design approach.
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    Host niche, genotype, and field location shape the diversity and composition of the soybean microbiome
    YANG Hong-jun, YE Wen-wu, YU Ze, SHEN Wei-liang, LI Su-zhen, WANG Xing, CHEN Jia-jia, WANG Yuan-chao, ZHENG Xiao-bo
    2023, 22 (8): 2412-2425.   DOI: 10.1016/j.jia.2023.01.006
    Abstract249)      PDF in ScienceDirect      
    Plant-associated microbes represent a key determinant of plant fitness through acquiring nutrients, promoting growth, and resisting to abiotic and biotic stresses.  However, an extensive characterization of the bacterial and fungal microbiomes present in different plant compartments of soybean in field conditions has remained elusive.  In this study, we investigated the effects of four niches (roots, stems, leaves, and pods), four genotypes (Andou 203, Hedou 12, Sanning 16, and Zhonghuang 13), and three field locations (Jining, Suzhou, and Xuzhou) on the diversity and composition of bacterial and fungal communities in soybean using 16S and internal transcribed spacer rRNA amplicon sequencing, respectively.  The soybean microbiome significantly differed across organs.  Host genotypes explained more variation in stem bacterial community composition and leaf fungal community composition.  Field location significantly affected the composition of bacterial communities in all compartments and the effects were stronger in the root and stem than in the leaf and pod, whereas field location explained more variation in stem and leaf fungal community composition than in the root and pod.  The relative abundances of potential soybean fungal pathogens also differed among host organs and genotypes, reflecting the niches of these microbes in the host and probably their compatibility to the host genotypes.  Systematic profiling of the microbiome composition and diversity will aid the development of plant protection technologies to benefit soybean health.  
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    Physiological and transcriptome analyses provide new insights into the mechanism mediating the enhanced tolerance of melatonin-treated rhododendron plants to heat stress
    XU Yan-xia, ZHANG Jing, WAN Zi-yun, HUANG Shan-xia, DI Hao-chen, HE Ying, JIN Song-heng
    2023, 22 (8): 2397-2411.   DOI: 10.1016/j.jia.2023.07.005
    Abstract245)      PDF in ScienceDirect      

    Rhododendron is a well-known genus consisting of commercially valuable ornamental woody plant species.  Heat stress is a major environmental factor that affects rhododendron growth.  Melatonin was recently reported to alleviate the effects of abiotic stress on plants.  However, the role of melatonin in rhododendron plants is unknown.  In this study, the effect of melatonin on rhododendron plants exposed to heat stress and the potential underlying mechanism were investigated.  Analyses of morphological characteristics and chlorophyll a fluorescence indicated 200 µmol L–1 was the optimal melatonin concentration for protecting rhododendron plants from heat stress.  To elucidate how melatonin limits the adverse effects of high temperatures, melatonin contents, photosynthetic indices, Rubisco activity, and adenosine triphosphate (ATP) contents were analyzed at 25, 35, and 40°C, respectively.  Compared with the control, exogenous application of melatonin improved the melatonin contents, electron transport rate, photosystem II and I activities, Rubisco activity, and ATP contents under heat stress.  The transcriptome analysis revealed many of the heat-induced differentially expressed genes were associated with the photosynthetic pathway; the expression of most of these genes was down-regulated by heat stress more in the melatonin-free plants than in the melatonin-treated plants.  We identified RhPGR5A, RhATPB, RhLHCB3, and RhRbsA as key genes.  Thus, we speculate that melatonin promotes photosynthetic electron transport, improves Calvin cycle enzyme activities, and increases ATP production.  These changes lead to increased photosynthetic efficiency and CO2 assimilation under heat stress conditions via the regulated expression of specific genes, including RhRbsA.  Therefore, the application of exogenous melatonin may increase the tolerance of rhododendron to heat stress.

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    CRISPR/Cas9-mediated knockout of SLC15A4 gene involved in the immune response in bovine rumen epithelial cells
    JIANG Mao-cheng, HU Zi-xuan, WANG Ke-xin, YANG Tian-yu, LIN Miao, ZHAN Kang, ZHAO Guo-qi
    2023, 22 (10): 3148-3158.   DOI: 10.1016/j.jia.2023.06.016
    Abstract235)      PDF in ScienceDirect      

    The objective of this study was to determine the role of SLC15A4 in the muramyl dipeptide (MDP)-mediated inflammatory response of bovine rumen epithelial cells (BRECs).  First, changes in the mRNA expression of pro-inflammatory factor genes in BRECs following 10 μg mL–1 MDP treatments were examined.  RT-qPCR results showed that the expression of pro-inflammatory factor (IL-1β, IL-6, and TNF-α) mRNAs were significantly increased under MDP stimulation (P<0.001).  Moreover, SLC15A4-Knockout (SLC15A4-KO) cells were obtained through lentivirus packaging, transfection, screening, and cell monoclonal culture.  In order to gain further insight into the potential function of SLC15A4, we utilized transcriptome data, which revealed a change in the genes between WT-BRECs and SLC15A4-KO.  Five down-regulated pro-inflammatory genes and 13 down-regulated chemokine genes related to the inflammatory response were identified.  Meanwhile, the down-regulated genes were mostly enriched in the nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways.  The results of RT-qPCR also verified these detected changes.  To further determine the mechanism of how WT and SLC15A4-KO BRECs are involved in inflammatory responses, we investigated the inflammatory responses of cells exposed to MDP.  WT-BRECs and SLC15A4-KO were treated with a culture medium containing 10 μg mL–1 MDP, in comparison to a control without MDP.  Our results show that SLC15A4-KO BRECs had reduced the expression of genes (IL-6, TNF-α, CXCL2, CXCL3, CXCL9, and CCL2) and proteins (p-p65 and p-p44/42) from the MDP-mediated inflammatory response compared to WT-BRECs (P<0.05).  In this experiment, CRISPR-Cas9 was used to KO the di/tripeptide transporter SLC15A4, and its role was confirmed via the MDP-induced inflammatory response in BRECs.  This work will provide a theoretical basis for studying the pro-inflammatory mechanism of MDP and its application in the prevention and treatment of subacute rumen acidosis in dairy cows.

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    SNP-based identification of QTLs for thousand-grain weight and related traits in wheat 8762/Keyi 5214 DH lines
    HUANG Feng, LI Xuan-shuang, DU Xiao-yu, LI Shun-cheng, LI Nan-nan, LÜ Yong-jun, ZOU Shao-kui, ZHANG Qian, WANG Li-na, NI Zhong-fu, HAN Yu-lin, XING Jie-wen
    2023, 22 (10): 2949-2960.   DOI: 10.1016/j.jia.2023.03.004
    Abstract227)      PDF in ScienceDirect      

    As important yield-related traits, thousand-grain weight (TGW), grain number per spike (GNS) and grain weight per spike (GWS) are crucial components of wheat production.  To dissect their underlying genetic basis, a double haploid (DH) population comprised of 198 lines derived from 8762/Keyi 5214 was constructed.  We then used genechip to genotype the DH population and integrated the yield-related traits TGW, GNS and GWS for QTL mapping.  Finally, we obtained a total of 18 942 polymorphic SNP markers and identified 41 crucial QTLs for these traits.  Three stable QTLs for TGW were identified on chromosomes 2D (QTgw-2D.3 and QTgw-2D.4) and 6A (QTgw-6A.1), with additive alleles all from the parent 8762, explaining 4.81–18.67% of the phenotypic variations.  Five stable QTLs for GNS on chromosomes 3D, 5B, 5D and 6A were identified.  QGns-5D.1 was from parent 8762, while the other four QTLs were from parent Keyi 5214, explaining 5.89–7.08% of the GNS phenotypic variations.  In addition, a stable GWS genetic locus QGws-4A.3 was detected from the parent 8762, which explained 6.08–6.14% of the phenotypic variations.  To utilize the identified QTLs, we developed STARP markers for four important QTLs, Tgw2D.3-2, Tgw2D.4-1, Tgw6A.1 and Gns3D.1.  Our results provide important basic resources and references for the identification and cloning of genes related to TGW, GNS and GWS in wheat.

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    Effect of delayed sowing on grain number, grain weight, and protein concentration of wheat grains at specific positions within spikes
    CHU Jin-peng, GUO Xin-hu, ZHENG Fei-na, ZHANG Xiu, DAI Xing-long, HE Ming-rong
    2023, 22 (8): 2359-2369.   DOI: 10.1016/j.jia.2023.02.002
    Abstract220)      PDF in ScienceDirect      

    Delays in sowing have significant effects on the grain yield, yield components, and grain protein concentrations of winter wheat.  However, little is known about how delayed sowing affects these characteristics at different positions in the wheat spikes.  In this study, the effects of sowing date were investigated in a winter wheat cultivar, Shannong 30, which was sown in 2019 and 2020 on October 8 (normal sowing) and October 22 (late sowing) under field conditions.  Delayed sowing increased the partitioning of 13C-assimilates to spikes, particularly to florets at the apical section of a spike and those occupying distal positions on the same spikelet.  Consequently, the increase in grain number was the greatest for the apical sections, followed by the basal and central sections.  No significant differences were observed between sowing dates in the superior grain number in the basal and central sections, while the number in apical sections was significantly different.  The number of inferior grains in each section also increased substantially in response to delayed sowing.  The average grain weights in all sections remained unchanged under delayed sowing because there were parallel increases in grain number and 13C-assimilate partitioning to grains at specific positions in the spikes.  Increases in grain number m–2 resulted in reduced grain protein concentrations as the limited nitrogen supply was diluted into more grains.  Delayed sowing caused the greatest reduction in grain protein concentration in the basal sections, followed by the central and apical sections.  No significant differences in the reduction of the grain protein concentration were observed between the inferior and superior grains under delayed sowing.  In conclusion, a 2-week delay in sowing improved grain yield through increased grain number per spike, which originated principally from an increased grain number in the apical sections of spikes and in distal positions on the same spikelet.  However, grain protein concentrations declined in each section because of the increased grain number and reduced N uptake.

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