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    Crop Science
    TaMIR1119, a miRNA family member of wheat (Triticum aestivum), is essential in the regulation of plant drought tolerance
    SHI Gui-qing, FU Jing-ying, RONG Ling-jie, ZHANG Pei-yue, GUO Cheng-jin, XIAO Kai
    2018, 17(11): 2369-2378.  DOI: 10.1016/S2095-3119(17)61879-3
    Abstract ( )   PDF in ScienceDirect  
    Through regulating target genes via the mechanisms of posttranscriptional cleavage or translational repression, plant miRNAs involve diverse biological processes associating with plant growth, development, and abiotic stress responses.  In this study, we functionally characterized TaMIR1119, a miRNA family member of wheat (Triticum aestivum), in regulating the drought adaptive response of plants.  TaMIR1119 putatively targets six genes categorized into the functional classes of transcriptional regulation, RNA and biochemical metabolism, trafficking, and oxidative stress defense.  Upon simulated drought stress, the TaMIR1119 transcripts abundance in roots was drastically altered, showing to be upregulated gradually within a 48-h drought regime and that the drought-induced transcripts were gradually restored along with a 48-h recovery treatment.  In contrast, most miRNA target genes displayed reverse expression patterns to TaMIR1119, exhibiting a downregulated expression pattern upon drought and whose reduced transcripts were re-elevated along with a normal recovery treatment. These expression analysis results indicated that TaMIR1119 responds to drought and regulates the target genes mainly through a cleavage mechanism.  Under drought stress, the tobacco lines with TaMIR1119 overexpression behaved improved phenotypes, showing increased plant biomass, photosynthetic parameters, osmolyte accumulation, and enhanced antioxidant enzyme (AE) activities relative to wild type.  Three AE genes, NtFeSOD, NtCAT1;3, and NtSOD2;1, encoding superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) proteins, respectively, showed upregulated expression in TaMIR1119 overexpression lines, suggesting that they are involved in the regulation of AE activities and contribution to the improved cellular reactive oxygen species (ROS) homeostasis in drought-challenged transgenic lines.  Our results indicate that TaMIR1119 plays critical roles in regulating plant drought tolerance through transcriptionally regulating the target genes that modulate osmolyte accumulation, photosynthetic function, and improve cellular ROS homeostasis of plants.
     
    Maize ABP2 enhances tolerance to drought and salt stress in transgenic Arabidopsis
    ZONG Na, LI Xing-juan, WANG Lei, WANG Ying, WEN Hong-tao, LI Ling, ZHANG Xia, FAN Yun-liu, ZHAO Jun
    2018, 17(11): 2379-2393.  DOI: 10.1016/S2095-3119(18)61947-1
    Abstract ( )   PDF (35768KB) ( )  
    Abiotic stresses, especially drought and salt, severely affect maize production, which is one of the most important cereal crops in the world.  Breeding stress-tolerant maize through biotechnology is urgently needed to maintain maize production.  Therefore, it is important to identify new genes that can enhance both drought and salt stress tolerance for molecular breeding. In this study, we identified a maize ABA (abscisic acid)-responsive element (ABRE) binding protein from a 17-day post-pollination (dpp) maize embryo cDNA library by yeast one-hybrid screen using the ABRE2 sequence of the maize Cat1 gene as bait.  This protein, designated, ABRE binding protein 2 (ABP2), belongs to the bZIP transcription factor family.  Endogenous expression of ABP2 in maize can be detected in different tissues at various development stages, and can be induced by drought, salt, reactive oxygen species (ROS)-generating agents, and ABA treatment.  Constitutive expression of ABP2 in transgenic Arabidopsis plants enhanced tolerance to drought and salt stress, and increased sensitivity to ABA.  In exploring the mechanism by which ABP2 can stimulate abiotic stress tolerance, we found that ROS levels were reduced and expression of stress-responsive and carbon metabolism-related genes was enhanced by constitutive ABP2 expression in transgenic plants.  In short, we identified a maize bZIP transcription factor which can enhance both drought and salt tolerance of plants.
     
    Genetic variation in LBL1 contributes to depth of leaf blades lobes between cotton subspecies, Gossypium barbadense and Gossypium hirsutum
    HE Dao-fang, ZHAO Xiang, LIANG Cheng-zhen, ZHU Tao, Muhammad Ali Abid, CAI Yong-ping, HE Jin-ling, ZHANG Rui
    2018, 17(11): 2394-2404.  DOI: 10.1016/S2095-3119(18)61954-9
    Abstract ( )   PDF in ScienceDirect  
    Leaf is a essential part of the plants for photosynthetic activities which mainly economize the resources for boll heath.  Significant variations of leaf shapes across the Gossypium sp. considerably influence the infiltration of sunlight for photosynthesis.  To understand the genetic variants and molecular processes underlying for cotton leaf shape, we used F2 population derived from upland cotton genotype P30A (shallow-lobed leaf) and sea-island cotton genotype ISR (deep-lobed leaf) to map leaf deep lobed phenotype controlling genes LBL1 and LBL2.  Genetic analysis and localization results have unmasked the position and interaction between both loci of LBL1 and LBL2, and revealed the co-dominance impact of the genes in regulating depth of leaf blades lobes in cotton.  LBL1 had been described as a main gene and member of transcription factor family leucine zipper (HD-ZIPI) from a class I homologous domain factor Gorai.002G244000.  The qRT-PCR results elaborated the continuous change in expression level of LBL1 at different growth stages and leaf parts of cotton.  Higher expression level was observed in mature large leaves followed by medium and young leaves respectively.  For further confirmation, plants were tested from hormonal induction treatments, which explained that LBL1 expression was influenced by hormonal signaling.  Moreover, the highest expression level was detected in brassinolides (BR) treatment as compared to other hormones, and this hormone plays an important role in the process of leaf blade lobed formation.
    Combined effect of shading time and nitrogen level on grain filling and grain quality in japonica super rice
    WEI Hai-yan, ZHU Ying, QIU Shi, HAN Chao, HU Lei, XU Dong, ZHOU Nian-bing, XING Zhi-peng, HU Ya-jie, CUI Pei-yuan, DAI Qi-gen, ZHANG Hong-cheng
    2018, 17(11): 2405-2417.  DOI: 10.1016/S2095-3119(18)62025-8
    Abstract ( )   PDF (1180KB) ( )  
    There is limited information about the combined effect of shading time and nitrogen (N) on grain filling and quality of rice.  Therefore, two japonica super rice cultivars, Nanjing 44 and Ningjing 3, were used to study the effect of shading time and N level on the characteristics of rice panicle and grain filling as well as the corresponding yield and quality.  At a low N level (150 kg N ha–1, 150N), grain yield decreased (by 21.07–26.07%) under the treatment of 20 days of shading before heading (BH) compared with the no shading (NS) treatment.  These decreases occurred because of shortened panicle length, decreased number of primary and secondary branches, as well as the grain number and weight per panicle.  At 150N, in the treatment of 20 days of shading after heading (AH), grain yield also decreased (by 9.46–10.60%) due to the lower grain weight per panicle.  The interaction of shading and N level had a significant effect on the number of primary and secondary branches.  A high level of N (300 kg N ha–1, 300N) could offset the negative effect of shading on the number of secondary branches and grain weight per panicle, and consequently increased the grain yield in both shading treatments.  In superior grains, compared with 150N NS, the time to reach 99% of the grain weight (T99) was shortened by 1.6 to 1.7 days, and the grain weight was decreased by 4.18–5.91% in 150N BH.  In 150N AH, the grain weight was 13.39–13.92% lower than that in 150N NS due to the slow mean and the maximum grain-filling rate (GRmean and GRmax).  In inferior grains, grain weight and GRmean had a tendency of 150N NS>150N BH>150N AH.  Under shaded conditions, 300N decreased the grain weight due to lower GRmean both in superior and inferior grains.  Compared with 150N NS, the milling and appearance qualities as well as eating and cooking quality were all decreased in 150N BH and 150N AH.  Shading with the high level of 300N improved the milling quality and decreased the number of chalky rice kernels, but the eating and cooking quality was reduced with increased chalky area and overall chalkiness.  Therefore, in the case of short term shading, appropriate N fertilizer could be used to improve the yield and milling quality of rice, but limited application of N fertilizer is recommended to achieve good eating and cooking quality of rice.
     
    Potato yield gaps across the rainfed Yin-mountain Hilly Area of China
    JIA Li-guo, CHEN Yang, QIN Yong-lin, LIANG Rui-fang, CUI Shi-xin, MA Zhong, FAN Ming-shou
    2018, 17(11): 2418-2425.  DOI: 10.1016/S2095-3119(18)62034-9
    Abstract ( )   PDF in ScienceDirect  
    Yin-mountain Hilly Area is one of the ideal regions for potato (Solanum tuberosum) production in China.  However, potato yield is severely limited as a result of rain-fed crop mode due to water deficiency, as well as an inadequate farming practices.  In this study, yield gaps were determined by using attainable yield (Ya) as a benchmark under optimized management practices, i.e., micro-ridge and side planting with plastic-mulching (MS), and flat planting with plastic-mulching (PM).  The yields under MS and PM modes are defined as Ya1 and Ya2, respectively.  Under the same field with MS and PM modes but different densities and fertilizer usages and so on, it was defined as simulated farmers’ practices.  The yield of simulated farmers’ practices (Yf1) reached 57.3 and 69.6% of Ya1 and Ya2, respectively, while the average yield of 298 randomly surveyed farmers (Yf2) reached only 37.0 and 47.8% of Ya1 and Ya2 for rain-fed potato, respectively.  The gaps of water use efficiency exhibited similar pattern.  Further analysis shows that improper measures in rainwater conservation and accumulation, and other management practices contributed to 18.5, 18.2, and 42.6% of yield gap between Ya1 and Yf2.  Improper nutrition management, including overuse of nitrogen and the deficiency of phosphorus and potassium supplication, was one of the important reasons of yield gap.  The results indicate the possibilities of increasing rain-fed potato yields by optimized water and fertilizer managements in the Yin-mountain Hilly Area.
    Evaluation of photosynthesis, physiological, and biochemical responses of chickpea (Cicer arietinum L. cv. Pirouz) under water deficit stress and use of vermicompost fertilizer
    Saeed Reza Hosseinzadeh, Hamzeh Amiri, Ahmad Ismaili
    2018, 17(11): 2426-2437.  DOI: 10.1016/S2095-3119(17)61874-4
    Abstract ( )   PDF (841KB) ( )  
    One goal in the face of drought stress conditions is to increase growth and yield through the reduction of negative effects of stress.  Vermicompost can play an effective role in plant growth and development and in reducing harmful effects of various environmental stresses on plants due to its porous structure, high water storage capacity, having hormone-like substances, plant growth regulators, and high levels of macro and micro nutrients.  This study considered the physiological, biochemical, and photosynthetic responses of the chickpea to different combinations of vermicompost and water stress in a greenhouse environment.  Two factors were involved, addition of vermicompost to soil at four ratios: control (100 wt%  (weight percentage) soil); 10 wt% vermicompost+90% soil; 20 wt% vermicompost+80 wt% soil; 30 wt% vermicompost+70 wt% soil weight percentage, and treatment of water stress at three levels including 75, 50, and 25% of field capacity.  The results showed that vermicompost had a significant effect on all traits under stress and non-stress conditions.  Application of vermicompost in soil, especially at the levels of 20 and 30 wt% significantly increased all studied traits under non-stress conditions.  Under moderate stress conditions, vermicompost at 30 wt% treatment resulted in a significant increase in the photosynthetic pigments, CO2 assimilation rate, internal leaf CO2 concentration, transpiration, the maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm), concentrations of Ca and K in root and leaf tissues, proline and soluble protein contents in root tissues.  Peroxidase (POX) and catalase (CAT) enzyme activities decreased significantly with increasing proportions of vermicompost, but the activity of superoxide dismutase was not significantly different.  In conclusion, the above results showed that vermicompost fertilizer had a positive effect on physiological, biochemical, and photosynthetic responses of chickpea under non-stress and moderate stress conditions, but no positive effect was determined under severe water stress.
    Horticulture
    Interactive effects of elevated carbon dioxide and nitrogen availability on fruit quality of cucumber (Cucumis sativus L.)
    DONG Jin-long, LI Xun, Nazim Gruda, DUAN Zeng-qiang
    2018, 17(11): 2438-2446.  DOI: 10.1016/S2095-3119(18)62005-2
    Abstract ( )   PDF (777KB) ( )  
    Elevated CO2 and high N promote the yield of vegetables interactively, whilst their interactive effects on fruit quality of cucumber (Cucumis sativus L.) are unclear.  We studied the effects of three CO2 concentrations (400 μmol mol–1 (ambient), 625 μmol mol–1 (moderate) and 1 200 μmol mol–1 (high)) and nitrate levels (2 mmol L–1 (low), 7 mmol L–1 (moderate) and 14 mmol L–1 (high)) on fruit quality of cucumber in open top chambers.  Compared with ambient CO2 , high CO2 increased the concentrations of fructose and glucose in fruits and maintained the titratable acidity, resulting in the greater ratio of sugar to acid in moderate N, whilst it had no significant effects on these parameters in high N.  Moderate and high CO2 had no significant effect on starch concentration and decreased dietary fiber concentration by 13 and 18%, nitrate by 31 and 84% and crude protein by 19 and 20% averagely, without interactions with N levels.  The decreases in amino acids under high CO2 were similar, ranging from 10–18%, except for tyrosine (50%).  High CO2 also increased the concentrations of P, K, Ca and Mg but decreased the concentrations of Fe and Zn in low N, whilst high CO2 maintained the concentrations of P, K, Ca, Mg, Fe, Mn, Cu and Zn in moderate and high N.  In conclusion, high CO2 and moderate N availability can be the best combination for improving the fruit quality of cucumber.  The fruit enlargement, carbon transformation and N assimilation are probably the main processes affecting fruit quality under CO2 enrichment. 
    Variety-specific responses of lettuce grown in a gravel-film technique closed hydroponic system to N supply on yield, morphology, phytochemicals, mineral content and safety
    Bevly M. Mampholo, Martin M. Maboko, Puffy Soundy, Dharini Sivakumar
    2018, 17(11): 2447-2457.  DOI: 10.1016/S2095-3119(18)62007-6
    Abstract ( )   PDF (1029KB) ( )  
    Utilization of nitrogen (N) element is a common practice used to reach profitable yields in horticultural crops and N supply can be used as a tool to manipulate the enhancement of phytochemicals and minerals in vegetable crops to address consumer-oriented quality production.  Hence the study was aimed to investigate the effect of N application on leaf morphology, ascorbic acid content, phenolic acids, flavonoids, mineral content, and nitrate residues in three lettuce varieties (two green leafy lettuce, Multigreen 1 and Multigreen 3; one red leafy lettuce, Multired 4) grown in a closed hydroponic system (gravel-film) at harvest.  Nitrogen was applied as ammonium nitrate (NH4NO3) at six different concentrations of 0, 60, 90, 120, 150 and 180 mg L–1.  The results obtained during 2015 and 2016 seasons were similar and demonstrated variety dependent responses with respect to different N application rates.  Multigreen 3 was more sensitive to N supply and showed higher amount of nitrate residue at harvest.  Variety Multired 4 was less sensitive to N supply followed by Multigreen 1.  Although N supply at 120 mg L–1 improved the yield and the number of leaves in Multigreen 3, overall 90 mg L–1 can be recommended for these lettuce varieties to improve the yield and the accumulation of ascorbic acid content, phenolic acids mainly caffeic, caftaric acids, quercetin (the important flavonoid in lettuce), and Fe and Mn contents.  Furthermore, the concentration of 90 mg L–1 improved the antioxidant property (FRAP and ABTS+) and reduced the nitrate accumulation, ensuring safe food for consumers. 
     
    Intergenic spacer 1 (IGS1) polymorphism map: A marker for the initial classification of cultivated Lentinula edodes strains in China
    SONG Xiao-xia, ZHAO Yan, SONG Chun-yan, LI Chuan-hua, CHEN Ming-jie, HUANG Jian-chun, TAN Qi
    2018, 17(11): 2458-2466.  DOI: 10.1016/S2095-3119(18)61967-7
    Abstract ( )   PDF in ScienceDirect  
    China is currently the world’s leading producer of Lentinula edodes and owns many cultivated strains of this species.  This study was performed in order to investigate intergenic spacer 1 (IGS1) polymorphism and classification among 49 popular cultivated strains.  The great majority of the 49 strains possessed two different IGS1 sequences, with distinct lengths and homologies.  Based on the length and homology of the IGS1 sequences of the 49 strains, the strains were classified into two groups: A and B.  Group A was subdivided into six subgroups.  Forty-seven strains were homozygous or heterozygous among these six subgroups in group A, Cr01 was heterozygous between A and B, and Guangxiang 9 was homozygous in group B.  An IGS1 polymorphism map of each cultivated L. edodes strain is reported for the first time and could be used as a marker for the initial classification and management of cultivated L. edodes strains in China. 
     
    Plant Protection
    Editorial- Response and resistance of cereal crops to pathogens
    KANG Zhen-sheng
    2018, 17(11): 2467-2467.  DOI: 10.1016/S2095-3119(18)62106-9
    Abstract ( )   PDF in ScienceDirect  
    The special topic of the two papers is the systemic acquired resistance (SAR) and pathogenesis-related protein genes (PR).  SAR is an enhanced resistance against further potential parasite beyond the initial infection site, which can be induced by either pathogen infection or exogenous inducer, including synthetic chemicals and natural products.  As a “whole-plant” resistance defense, SAR confers broad-spectrum immunity to widely diverse pathogenic microorganisms, such as viruses, bacteria and fungi for a relatively long lasting period.  Convincingly, it is a promising way to prevent crop diseases by activating the plants’ own natural defenses via application of chemical inducers or creating resistant wheat cultivars.  

    The first article from Wang et al. (2018) reviewed SAR in wheat and barley, the possible involvement of the master regulator Non-expresser of PR genes 1 (NPR1) and PR genes in the SAR processes.  The author summarized to our current knowledge of the three different types of SAR-like responses in wheat and barley in comparison to Arabidopsis and rice.  Research updates on the wheat and barley NPR1 homologs in SAR, downstream genes of SAR, including PR genes and BTH-induced genes were highlighted, which provided initial clue for understanding the SAR mechanism in these two plant species.  The review is informative in the research advances of SAR in wheat and barley, which would help the readers to obtain an overall understanding of SAR in the resistance of wheat and barley to different pathogens.  

    The second article from Farrakh et al. (2018) investigated the roles of different PR protein genes in race-specific resistance and non-race specific high-temperature adult-plant (HTAP) resistance of wheat to wheat stripe rust fungus by profiling the expression of eight different PR genes.  The authors elucidated that different PR genes are involved in different types of resistance and resistance controlled by different Yr genes, owing to the varied expression level of PR genes at different stages of infection and among different Yr gene lines.  The research provides useful and needed information of the function of PR genes in wheat all-stage resistance and HTAP, which greatly improves the understanding of the molecular mechanism underlying race specificity and durability of stripe rust resistance.   

    At the molecular level, the findings of the papers deepen our knowledge on the response of crop plant to pathogen invasion.  More importantly, the information obtained give clues for improving plant resistance in novel ways.  I genuinely believe that the findings will inspire the readers of the Journal of Integrative Agriculture for developing future research on the given topics.
    Systemic acquired resistance, NPR1, and pathogenesis-related genes in wheat and barley
    WANG Xiao-dong, BI Wei-shuai, GAO Jing, YU Xiu-mei, WANG Hai-yan, LIU Da-qun
    2018, 17(11): 2468-2476.  DOI: 10.1016/S2095-3119(17)61852-5
    Abstract ( )   PDF (2791KB) ( )  
    In Arabidopsis, systemic acquired resistance (SAR) is established beyond the initial infection by a pathogen or is directly induced by treatment with salicylic acid (SA) or its functional analogs, 2,6-dichloroisonicotinic acid (INA) and benzothiadiazole (BTH).  NPR1 protein is considered the master regulator of SAR in both SA signal sensing and transduction.  In wheat (Triticum aestivum) and barley (Hordeum vulgare), both pathogen infection and BTH treatment can induce broad-spectrum resistance to various diseases, including powdery mildew, leaf rust, Fusarium head blight, etc.  However, three different types of SAR-like responses including acquired resistance (AR), systemic immunity (SI), and BTH-induced resistance (BIR) seem to be achieved by activating different gene pathways.  Recent research on wheat and barley NPR1 homologs in AR and SI has provided the initial clue for understanding the mechanism of SAR in these two plant species.  In this review, the specific features of AR, SI, and BIR in wheat and barley were summarized and compared with that of SAR in model plants of Arabidopsis and rice.  Research updates on downstream genes of SAR, including pathogenesis-related (PR) and BTH-induced genes, were highlighted.
     
    Special Focus: Response and resistance of cereal crops to pathogens
    Pathogenesis-related protein genes involved in race-specific allstage resistance and non-race specific high-temperature adult-plant resistance to Puccinia striiformis f. sp. tritici in wheat
    Sumaira Farrakh, Meinan Wang, Xianming Chen
    2018, 17(11): 2478-2491.  DOI: 10.1016/S2095-3119(17)61853-7
    Abstract ( )   PDF (1008KB) ( )  
    Interactions of the stripe rust pathogen (Puccinia striiformis f. sp. tritici) with wheat plants activate a wide range of host responses.  Among various genes involved in the plant-pathogen interactions, the expressions of particular pathogenesis-related (PR) protein genes determine different defense responses.  Different types of resistance have been recognized and utilized for developing wheat cultivars for resistance to stripe rust.  All-stage resistance can be detected in seedling stage and remains at high levels throughout the plant growth stages.  This type of resistance is race-specific and not durable.  In contrast, plants with only high-temperature adult-plant (HTAP) resistance are susceptible in seedling stage, but become resistant when plants grow older and the weather becomes warmer.  HTAP resistance controlled by a single gene is partial, but usually non-race specific and durable.  The objective of this study was to analyze the expression of PR protein genes involved in different types of wheat resistance to stripe rust.  The expression levels of 8 PR protein genes (PR1, PR1.2, PR2, PR3, PR4, PR5, PR9 and PR10) were quantitatively evaluated at 0, 1, 2, 7 and 14 days after inoculation in single resistance gene lines of wheat with all-stage resistance genes YrTr1, Yr76, YrSP and YrExp2 and lines carrying HTAP resistance genes Yr52, Yr59, Yr62 and Yr7B.  Races PSTv-4 and PSTv-37 for compatible and incompatible interactions were used in evaluation of PR protein gene expression in wheat lines carrying all-stage resistance genes in the seedling-stage experiment while PSTv-37 was used in the HTAP experiment.  Analysis of quantitative real-time polymerase chain reaction (qRT-PCR) revealed that all of the PR protein genes were involved in the different types of resistance controlled by different Yr genes.  However, these genes were upregulated at different time points and at different levels during the infection process among the wheat lines with different Yr genes for either all-stage resistance or HTAP resistance.  Some of the genes were also induced in compatible interactions, but the levels were almost always higher in the incompatible interaction than in the compatible interaction at the same time point for each Yr gene.  These results indicate that both salicylic acid and jasmonate signaling pathways are involved in both race-specific all-stage resistance and non-race specific HTAP resistance.  Although expressing at different stages of infection and at different levels, these PR protein genes work in concert for contribution to different types of resistance controlled by different Yr genes. 
     
    Plant Protection
    Two mutations in the truncated Rep gene RBR domain delayed the Wheat dwarf virus infection in transgenic barley plants
    Pavel Cejnar, Ludmila Ohnoutková, Jan Ripl, Tomá? Vl?ko, Jiban Kumar Kundu
    2018, 17(11): 2492-2500.  DOI: 10.1016/S2095-3119(18)62000-3
    Abstract ( )   PDF (20567KB) ( )  
    Wheat dwarf virus (WDV), an important cereal pathogen, is closely related to Maize streak virus (MSV), a model virus of the Mastrevirus genus.  Based on its similarity to known MSV resistance strategies, a truncated part of the WDV replication-associated (RepA) gene (WDVRepA215) and the WDV RepA gene with a mutated retinoblastoma-related protein (RBR) interaction domain (WDVRepA215RBRmut) were cloned into the pIPKb002 expression vector and transformed into immature embryos of spring barley cv. Golden Promise plants through Agrobacterium-mediated transformation.  A detailed study of T1-generation plants infected by leafhoppers (Psammotettix alienus) fed on infection sources of variable strength was performed over a 5-week period encompassing the initial stages of virus infection.  A DNA WDV TaqMan qPCR assay normalized using the DNA puroindoline-b SYBR Green qPCR assay for samples on a per week basis revealed an approximately 2-week delay in WDVRepA215RBRmut plants to WDVRepA215 plants before significant increases in the WDV viral levels occurred.  Both WDVRepA215 and WDVRepA215RBRmut plants showed similar levels of transgenic transcripts over the screened period; however, the transgenic plants also showed increased numbers of infected plants compared to the control plants. 
     
    Distribution pattern and titer of Candidatus Liberibacter asiaticus in periwinkle (Catharanthus roseus)
    LI Ya, XU Mei-rong, DAI Ze-han, DENG Xiao-ling
    2018, 17(11): 2501-2508.  DOI: 10.1016/S2095-3119(18)61918-5
    Abstract ( )   PDF in ScienceDirect  
    Candidatus Liberibacter asiaticus (CaLas), an uncultured Gram-negative alphaproteobacterium, is the causal agent of Huanglongbing (HLB) in citrus.  CaLas resides in phloem sieve tubes and has been shown to be unequally distributed in different tissues.  Although HLB is a disease of citrus plants, it has been demonstrated that periwinkle can serve as an experimental host of CaLas, which can be transmitted from citrus to periwinkle via the parasitic plant dodder (Cuscuta spp.).  To investigate the distribution of CaLas in various periwinkle tissues, the bacteria were transmitted from an infected periwinkle plant to healthy periwinkles by top-grafting.  The movement of the inoculum and associated titer changes were observed over time in various tissues.  CaLas could be detected in the leaves, main stems, and roots of infected periwinkle by conventional PCR, and in all three tissues a clear time-dependent change in CaLas titer was observed, with titer increasing soon after inoculation and then decreasing as disease symptoms became severe.  The highest titer was found at 25, 35 and 35 days after inoculation in leaves, main stems and roots, respectively.  The titer in leaves was much higher than in the main stems and roots at the same time point, and the spatial distribution of CaLas in the leaves, main stems and roots of infected periwinkle was uneven, similar to what has been shown in citrus.  The results provide guidance for selecting the proper periwinkle tissues and sampling times for early detection of CaLas.
     
    Species diversity of thrips (Thysanoptera) in selected avocado orchards from Mexico based on morphology and molecular data
    Daniel Bravo-Pérez, Ma. Teresa Santillán-Galicia, Roberto M. Johansen-Naime, Héctor González- Hernández, Obdulia L. Segura-León, Daniel L. Ochoa-Martínez, Stephanie Guzman-Valencia
    2018, 17(11): 2509-2517.  DOI: 10.1016/S2095-3119(18)62044-1
    Abstract ( )   PDF (851KB) ( )  
    Avocado is one of the most important crops in the world, and Mexico is the largest producer of this fruit.  Several insect pests affect its production, and thrips are amongst the most important.  A key step in the design of control methods is accurate species identification.  Despite this, formal reports on species diversity of thrips in Mexico are very scarce.  Morphological identification can sometimes be time-consuming and inconclusive.  Therefore, we explored the species diversity of thrips in Mexican avocado orchards (Michoacan state) based on partial sequences of the mitochondrial gene cytochrome oxidase subunit I (COI).  Forty-four specimens were analysed, which represented approximately 8% of all individuals collected from five localities distributed in three Municipalities.  All specimens were analysed using the COI marker, and specimens within the genera Frankliniella were also analysed using a marker within the D2 domain of the 28S (28SD2) nuclear ribosomal DNA.  Molecular identifications were confirmed using morphological taxonomy.  Overall, six genera were found (Neohydatothrips, Scirtothrips, Frankliniella, Arorathrips, Caliothrips and Leptothrips).  All genera contained only one species, except Frankliniella, for which there were six species.  Data from the two molecular markers suggest the existence of cryptic species within Mexican F. occidentalis populations.
    Transcriptome approach to understand the potential mechanisms of resistant and susceptible alfalfa (Medicago sativa L.) cultivars in response to aphid feeding
    TU Xiong-bing, ZHAO Hai-long, ZHANG Ze-hua
    2018, 17(11): 2518-2527.  DOI: 10.1016/S2095-3119(17)61843-4
    Abstract ( )   PDF in ScienceDirect  
    Plant breeding for resistance to agricultural pests is an essential element in the development of integrated crop management systems, however, the molecular and genetic mechanisms underlying resistance are poorly understood.  In this pilot study, we conducted a transcriptomic analysis of a resistant (R) and susceptible (S) variety of alfalfa, with (+A) or without (–A) aphids (totally four treatments).  We used the resistant cultivar Zhongmu 1 and the susceptible cultivar Soca.  A total of 3 549 mRNAs were differentially expressed, of which 1 738 up-regulated and 1 307 down-regulated genes were identified in S+A/S–A plants, while 543 up-regulated and 331 down-regulated genes were identified in the R+A/R–A plants.  KEGG analysis mapped 112 and 546 differentially expressed genes to 8 and 17 substantially enriched pathways for Zhongmu 1 and Soca, respectively.  Six shared pathways were linked to plant resistance traits, including phenylpropanoid biosynthesis associated with salicylic acid synthesis, and linoleic acid metabolism associated with both jasmonic acid and flavonoid biosynthesis.  Ultimately, we proposed a preliminary regulatory mechanism of alfalfa cultivar resistance response to aphids feeding based on transcriptome analyses and published documents.
     
    Animal Science · Veterinary Medicine
    Genome-wide detection of selective signatures in a Duroc pig population
    DIAO Shu-qi, LUO Yuan-yu, MA Yun-long, DENG Xi, HE Ying-ting, GAO Ning, ZHANG Hao, LI Jia-qi, CHEN Zan-mou, ZHANG Zhe
    2018, 17(11): 2528-2535.  DOI: 10.1016/S2095-3119(18)61984-7
    Abstract ( )   PDF in ScienceDirect  
    The Duroc pig has high adaptability and feeding efficiency, making it one of the most popular pig breeds worldwide.  Over long periods of natural and artificial selection, genetic footprints, i.e., selective signatures, were left in the genome.  In this study, a Duroc pig population (n=715) was genotyped with the Porcine SNP60K Bead Chip and the GeneSeek Genomic Profiler (GGP) Porcine Chip.  The relative extended haplotype homozygosity (REHH) method was used for selective signature detection in a subset of the population (n=368), selected to represent a balanced family structure.  In total, 154 significant core regions were detected as selective signatures (P<0.01), some of which overlap with previously reported quantitative trait loci associated with several economically important traits, including average daily gain and backfat thickness.  Genome annotation for these significant core regions revealed a variety of interesting candidate genes including GATA3, TAF3, ATP5C1, and FGF1.  These genes were functionally related to anterior/posterior pattern specification, phosphatidylinositol 3-kinase signaling, embryonic skeletal system morphogenesis, and oxidation-reduction processes.  This research provides knowledge for the study of selection mechanisms and breeding practices in Duroc and other pigs.
     
    Mycoplasma leachii causes polyarthritis in calves via the blood route but is not associated with pneumonia
    CHANG Ji-tao, WANG Guan-bo, ZHANG Yue, WANG Fang, JIANG Zhi-gang, YU Li
    2018, 17(11): 2536-2545.  DOI: 10.1016/S2095-3119(18)62050-7
    Abstract ( )   PDF (4124KB) ( )  
    Mycoplasma leachii was initially isolated from arthritic calves in South Queensland, Australia, and its ability to cause clinical polyarthritis in calves was demonstrated by experimental infection.  However, the source of M. leachii infection in calves and its means of spreading are not well known.  In this study, one-month-old calves were inoculated with cultures of M. leachii or joint fluid (collected from M. leachii-infected calves) through the intraarticular, intravenous, intratracheal, intranasal or oral routes.  Multidisciplinary procedures, including clinical assessment, etiology assessment, pathology and immunohistochemistry (IHC), were used to evaluate the pathogenicity of M. leachii in calves and to elucidate the transmission route of M. leachii infection in calves.  The results showed that all calves inoculated intraarticularly with cultured GN407 or joint fluid and two-thirds of the calves inoculated intravenously with joint fluid developed severe polyarthritis, and the M. leachii antigen was detected in the joints of all infected calves by IHC and PCR.  In contrast, calves inoculated with cultured M. leachii or joint fluid through the intratracheal, intranasal or oral routes did not show any M. leachii infection in the clinical assessment, etiology assessment, or pathology and IHC results.  These results indicated that polyarthritis caused by M. leachii in calves is transmitted via the blood route; however, this disease is not transmitted through the respiratory or digestive routes.  In addition, the M. leachii antigen was not detected in the lungs of all the inoculated calves using IHC and PCR, indicating that M. leachii is not associated with pneumonia, even in the calves inoculated through the respiratory duct.  These findings are important information for the prevention and control of calf polyarthritis caused by M. leachii.
     
    Agro-ecosystem & Environment
    Inter-annual changes in the aggregate-size distribution and associated carbon of soil and their effects on the straw-derived carbon incorporation under long-term no-tillage
    YIN Tao, ZHAO Cai-xia, YAN Chang-rong, DU Zhang-liu, HE Wen-qing
    2018, 17(11): 2546-2557.  DOI: 10.1016/S2095-3119(18)61925-2
    Abstract ( )   PDF (1055KB) ( )  
    Converting from conventional tillage to no-tillage influences the soil aggregate-size distribution and thus soil organic carbon (SOC) stabilization.  However, the dynamics of soil aggregation and the straw-derived carbon (C) incorporation within aggregate fractions are not well understood.  An experiment was established in 2004 to test the effects of two treatments, no-tillage with residue (NT) and conventional tillage without residue (CT), on the soil aggregate-size distribution and SOC stabilization in a continuous maize (Zea mays L.) cropping system located in the semiarid region of northern China.  Soil samples were collected from the 0–10 cm layer in 2008, 2010 and 2015, and were separated into four aggregate-size classes (>2, 0.25–2, 0.053–0.25, and <0.053 mm) by wet-sieving.  In each year, NT soil had a higher proportion of macroaggregates (i.e., >2 and 0.25–2 mm) and associated SOC concentration compared with CT.  Additionally, to compare straw-derived C incorporation within NT and CT aggregate fractions, 13C-labeled straw was incubated with intact NT and CT soils.  After 90 days, the highest proportion of 13C-labeled straw-derived C was observed in the >2 mm fraction, and this proportion was lower in NT than that in CT soil.  Overall, we conclude that long-term continuous NT increased the proportion of macroaggregates and the C concentration within macroaggregates, and the physical protection provided by NT is beneficial for soil C sequestration in the continuous maize cropping system in semiarid regions of northern China.
     
    Alternate row mulching optimizes soil temperature and water conditions and improves wheat yield in dryland farming
    YAN Qiu-yan, DONG Fei, LOU Ge, YANG Feng, LU Jin-xiu, LI Feng, ZHANG Jian-cheng, LI Jun-hui, DUAN Zeng-qiang
    2018, 17(11): 2558-2569.  DOI: 10.1016/S2095-3119(18)61986-0
    Abstract ( )   PDF (1844KB) ( )  
    Straw mulching allows for effective water storage in dryland wheat production.  Finding a suitable straw mulching model that facilitates wheat growth was the objective of this study.  A 2-year field experiment was conducted to investigate the effects of two straw mulching patterns (FM, full coverage within all the rows; HM, half coverage within alternate rows) and two mulching rates (4.5 and 9.0 t ha–1) on soil moisture, soil temperature, grain yield, and water use efficiency (WUE) of winter wheat in northern China, with no mulching (M0) as the control.  Results showed that mulching increased the soil water storage in all growth stages under high mulching rates, with a stronger effect in later growth stages.  Water storage under the HM model was greater in later stages than under the FM model.  Soil water content of HM groups was higher than that of FM groups, especially in surface soil layers.  Evapotranspiration decreased in mulched groups and was higher under high mulching rates.  Aboveground biomass during each growth stage under the HM model was higher than that under M0 and FM models with the same mulched rate, leading to a relatively higher grain yield under the HM model.  Mulching increased WUE, a trend that was more obvious under HM9.0 treatment.  Warming effect of soil temperature under the HM pattern persisted longer than under the FM model with the same mulching rates.  Accumulated soil temperature under mulched treatments increased, and the period of negative soil temperature decreased by 9–12 days under FM and by 10–20 days under HM.  Thus, the HM pattern with 9.0 t ha–1 mulching rate is beneficial for both soil temperature and water content management and can contribute to high yields and high WUE for wheat production in China. 
     
    Effect of long-term continuous cropping of strawberry on soil bacterial community structure and diversity
    LI Wei-hua, LIU Qi-zhi, CHEN Peng
    2018, 17(11): 2570-2582.  DOI: 10.1016/S2095-3119(18)61944-6
    Abstract ( )   PDF in ScienceDirect  
    Long-term monoculture leads to continuous cropping (CC) problems, which complicate agricultural production, both locally and abroad.  This study contrasted the different bacterial community compositions, physicochemical properties and enzyme activities of strawberry soil subjected to CC, CC rhizosphere (CCR), non-CC (NCC) and non-CC rhizosphere (NCCR) treatments.  The soil physicochemical properties and enzyme activities were significantly reduced after long-term CC.  In addition, five variation trends were observed for the 11 major bacterial genera in the soil.  Sphingomonas was the only stable group among all treatments.  The proportions of Novosphingobium, Rhodoplanes, Povalibacter, Cellvibrio and Stenotrophobacter decreased after CC.  The relative abundances of Pelagibius, Thioprofundum and Allokutzneria increased only in the CC treatment.  Nitrospira were more abundant in rhizosphere soil than in non-rhizosphere soil.  The relative abundance of Bacillus increased after CC.  Redundancy analysis revealed that Bacillus, Pelagibius and Allokutzneria had significant negative correlations with the soil physicochemical properties and enzyme activities.  Therefore, these genera may be the key bacteria influenced by the physicochemical properties and enzyme activities altered by replanting.  These results indicate that long-term CC of strawberry leads to less favourable rhizosphere soil conditions, which can be understood as a stress-induced response of the bacterial community diversity.  Further research is needed to determine how the quality of soil is reduced by the shift in the diversity of the soil bacterial community.
    Sustainability assessment of potato fields using the DEXi decision support system in Hamadan Province, Iran
    Mohammed Ebrahim Rezaei, Morteza Barmaki, Hadi Veisi
    2018, 17(11): 2583-2595.  DOI: 10.1016/S2095-3119(18)62107-0
    Abstract ( )   PDF (1225KB) ( )  
    Potato is a staple food crop and the most important agricultural commodity, which critically affects food security and economic stability in Hamadan Province, Iran.  Ex-ante sustainability appraisal of new cropping systems and their comparisons with conventional systems can increase the efficiencies of innovations and changes within the production process.  This study aimed to explore the sustainability levels of potato cropping systems in Hamadan Province, Iran.  To this end, DEXi methodology was developed for the sustainability assessment of the cropping systems.  For assessing the three dimensions of environmental, economic, and social sustainability in the four systems of traditional potato system (TPS), Quasi-industrial potato system (QIPS), industrial potato system (IPS), and government-promoted potato system (GPPS), five groups of features were utilized: (1) irrigation method; (2) seed placement; (3) farm machinery use; (4) agrochemical use; and (5) rotation.  The impact assessments of the cropping systems were based on two, three, and two groups of ecological, social, and economic indicators, respectively.  Employment, supply chain, protection, operational difficulty, productivity, profitability, input use, and biodiversity resulted in 21 basic indicators and 13 aggregated indicators, by which the cropping systems were described.  The results revealed that GPPS with distinctive economic and social profiles could have a better overall sustainability despite the fact that some indicators like biodiversity could be negatively affected.  Finally, three strategies were recommended for the sustainability of GPPS as follows: biodiversity enhancement, input substitution, and integrated water management.
     
    Short Communication
    First report of Athelia bombacina causing postharvest fruit rot on pear
    JIA Xiao-hui, FU Jun-fan, WANG Wen-hui, CUI Jian-chao, DU Yan-min, ZHOU Ru-jun, SUN Pingping
    2018, 17(11): 2596-2599.  DOI: 10.1016/S2095-3119(18)62091-X
    Abstract ( )   PDF (2222KB) ( )  
    Pear is an important fruit crop in the world. An uncharacterized disease has been observed on pear fruits during cold storage in Suning, Shenzhou, Xinji and other locations in Hebei Province, China. The incidence rate of the disease has reached 10%, and sometimes up to 20%. A particular fungus was consistently isolated from the infected pear fruit and cultured. Based on its morphology, molecular characteristics, pathogenicity and ITS sequence, the fungus was identified as Athelia bombacina. To our knowledge, this is the first report of Athelia bombacina causing postharvest fruit rot on pear.