Hatching and development of maize cyst nematode Heterodera zeae infecting different plant hosts

The occurrence, distribution, and rapid molecular detection technology of Heterodera zeae Koshy et al. 1971, have been reported in China. We explored the biological characteristics of H. zeae sampled in Henan Province, China to understand its interaction with plants. Cysts and second-stage juveniles(J2s) were identified under an optical and scanning electron microscope, internal transcribed spacer(ITS) phylogenetic tree, and sequence characterized amplified region(SCAR)-PCR analyses. The optimum hatching temperatures of H. zeae were 30°C and 28°C, with cumulative hatching rates of 16.5 and 16.1%, respectively, at 30 days post-hatching(dph). The hatching rate of H. zeae eggs was improved by 20-and 50-time maize soil leachate and root juice, and 10-time root exudates. The hatching rate in 10-time root exudates was the highest(25.9%). The 10-time root exudates of maize and millet produced the highest hatching rate at 30 dph(25.9 and 22.9%, respectively), followed by wheat(19.9%), barley(18.3%), and rice(17.6%). Heterodera zeae developed faster in maize than in other crops. Fourth-stage juveniles(J4s) were detected in maize roots 8 days post-inoculation(dpi) at 28°C but not in other crops. Combined with hatching tests, the Huang–Huai–Hai summer maize region and the south and central-southwest mountainous maize areas are highly suitable for H. zeae in China. This is the first systematically study of the hatching and infection characteristics on different plant hosts of corn cyst nematode H. zeae in temperate regions. This study laid a theoretical foundation for the rapid spread and high environmental adaptability of corn cyst nematode.

Development of a stable attenuated double-mutant of tobacco mosaic virus for cross-protection

Tobacco(Nicotiana tabacum)and tomato(Solanum lycopersicum)are two major economic crops in China.Tobacco mosaic virus(TMV;genus Tobamovirus)is the most prevalent virus infecting both crops.Currently,some widely cultivated tobacco and tomato cultivars are susceptible to TMV and there is no effective strategy to control this virus.Cross-protection can be a safe and environmentally friendly strategy to prevent viral diseases.However,stable attenuated TMV mutants are scarce.In this study,we found that the substitutions in the replicase p126,arginine at position 196(R^(196))with aspartic acid(D),glutamic acid at position 614(E^(614))with glycine(G),serine at position 643(S^(643))with phenylalanine(F),or D at position 730(D^(730))with S,significantly reduced the virulence and replication of TMV.However,only the mutation of S^(643) to F reduced the RNA silencing suppression activity of TMV p126.A double-mutant TMV-E614G-S643F induced no visible symptom and was genetically stable through six successive passages in tobacco plants.Furthermore,our results showed that TMV-E614G-S643F double-mutant could provide effective protection against the wild-type TMV infection in tobacco and tomato plants.This study reports a promising mild mutant for cross-protection to control TMV in tobacco and tomato plants.

Development of Machine Learning Methods for Accurate Prediction of Plant Disease Resistance

The traditional method of screening plants for disease resistance phenotype is both time-consuming and costly.Genomic selection offers a potential solution to improve efficiency,but accurately predicting plant disease resistance remains a challenge.In this study,we evaluated eight different machine learning(ML)methods,including random forest classification(RFC),support vector classifier(SVC),light gradient boosting machine(lightGBM),random forest classification plus kinship(RFC_K),support vector classification plus kinship(SVC_K),light gradient boosting machine plus kinship(lightGBM_K),deep neural network genomic prediction(DNNGP),and densely connected convolutional networks(DenseNet),for predicting plant disease resistance.Our results demonstrate that the three plus kinship(K)methods developed in this study achieved high prediction accuracy.Specifically,these methods achieved accuracies of up to 95%for rice blast(RB),85%for rice black-streaked dwarf virus(RBSDV),and 85%for rice sheath blight(RSB)when trained and applied to the rice diversity panel I(RDPI).Furthermore,the plus K models performed well in predicting wheat blast(WB)and wheat stripe rust(WSR)diseases,with mean accuracies of up to 90%and 93%,respectively.To assess the generalizability of our models,we applied the trained plus K methods to predict RB disease resistance in an independent population,rice diversity panel II(RDPII).Concurrently,we evaluated the RB resistance of RDPII cultivars using spray inoculation.Comparing the predictions with the spray inoculation results,we found that the accuracy of the plus K methods reached 91%.These findings highlight the effectiveness of the plus K methods(RFC_K,SVC_K,and lightGBM_K)in accurately predicting plant disease resistance for RB,RBSDV,RSB,WB,and WSR.The methods developed in this study not only provide valuable strategies for predicting disease resistance,but also pave the way for using machine learning to streamline genome-based crop breeding.

A glycine-rich nuclear effector VdCE51 of Verticillium dahliae suppresses plant immune responses by inhibiting the accumulation of GhTRXH2

Verticillium dahliae is an important soil-borne fungal pathogen that causes great yield losses in many cash crops.Effectors of this fungus are known to regulate plant immunity but the mechanism much remains unclear.A glycine-rich nuclear effector,VdCE51,was able to suppress immune responses in tobacco against Botrytis cinerea and Sclerotinia sclerotiorum.This effector was a required factor for full virulence of V.dahliae,and its nuclear localization was a requisite for suppressing plant immunity.The thioredoxin GhTRXH2,identified as a positive regulator of plant immunity,was a host target of VdCE51.Our findings show a virulence regulating mechanism whereby the secreted nuclear effector VdCE51 interferes with the transcription of PR genes,and the SA signaling pathway by inhibiting the accumulation of GhTRXH2,thus suppressing plant immunity.

Physiological Response and Resistance of Plants to Disease and Pest Stress

This paper outlines the physiological responses of plants to pathogenic microbial infection and pest feeding stress,as well as the resistance characteristics of plants to diseases and pests,and proposes new directions for future research on crop resistance to diseases and pests.The objective of this paper is to provide a reference framework for the breeding of crops with enhanced resistance to diseases and pests,the utilization of natural immunity in crops,and the efficient prevention and control of diseases and pests.This framework is intended to facilitate the healthy and sustainable development of the agricultural industry.

Antagonistic Activities of Volatiles from Four Strains of Bacillus spp. and Paenibacillus spp. Against Soil-Borne Plant Pathogens

The four effective antagonistic Bacillus strains, isolated from the rhizosphere soil of cucumber in a greenhouse, produced antifungal volatiles. These volatiles strongly inhibited the growth of the most tested pathogenic fungi with wide host plants, induced the mycelial morphological abnormalities, and decreased the sclerotoid production of Sclerotinia sclerotiorum in sealed plates. Spores of Botrytis cinerea exposed to these volatiles for 24-48 h in cavity slides cracked and the sporaceous inclusion became brown and effused to the suspension. An interesting phenomenon observed was that all the bacterial volatiles exhibited intense inhibitory activities against the pigment formation of tested pathogenic fungi, including Ascochyta citrullina, Alternaria solani, Alternaria brassicae, and so on. Interactions mediated by microbial volatiles could be widespread in soils, and volatiles may play an important role in reducing disease levels. A phylogenetic analysis based on 16S rDNA sequence placed the four bacteria in three species Paenibacillus polymyxa （BMP-11）, Bacillus subtilis （BL02）, and Bacillus pumilus （BSH-4 and ZB 13）. Through headspace sampling and GC-MS analysis, a rich profile was found from B. subtilis and overlapping volatile patterns could be found among the different species. Studies are under the way to find the possible action mechanisms and to seek the effective application of bacterial volatiles in greenhouse.

Behavioral responses of potato tuber moth (Phthorimaea operculella) to tobacco plant volatiles

Potato tuber moth(PTM)Phthorimaea operculella,also known as tobacco splitworm,is an important pest of tobacco plants.The knowledge on the interaction of tobacco plant volatiles and PTM behavior is limited.To clarify the effect of tobacco plant volatiles on the orientation and oviposition behaviors of PTM and to identify potential compounds for PTM control,tobacco plant volatiles were collected by headspace collection method,and volatile compounds were identified by gas chromatography-mass spectrometry.Thirteen electrophysiological active compounds were screened by employing coupled gas chromatography-electroantennogram detection and from which nine available compounds were further verified by electroantennogram recording.cis-3-Hexen-1-ol showed significant attractant effect on the orientation behaviors of both male and female moths.Nonanal and decanal could only attract females,while octanal exhibited repellent effect on males.Oviposition selection experiment indicated that nonanal,decanal,decane and methyl hexadecanoate could stimulate the gravid females to lay more eggs,while octanal and 2,6-bis(1,1-dimethylenthyl)-4-methyl phenol inhibited their oviposition.Our study added more compounds to the list that could serve as potential PTM deterrents or attractants.

Ovipositional responses of Spodoptera frugiperda on host plants provide a basis for using Bt-transgenic maize as trap crop in China

Spodoptera frugiperda,the pest fall armyworm(FAW),is widespread in more than 100 countries.To date,planting insectresistant transgenic crops is one of the main control methods in its native countries.In this study we evaluated Bt-transgenic maize(Bt maize)and non-transgenic(conventional)maize and six other host plants in greenhouse pot experiments and field trials for oviposition preference by the Chinese populations of FAW.In laboratory trials,female moths preferred to oviposit on maize with no significant preference between conventional and Bt maize.However,after conventional and transgenic maize were exposed to FAW larvae and damaged,oviposition was significantly higher on transgenic maize than on the conventional one.Field trials showed that for plants less damaged at an early stage(seedling stage),oviposition of FAW on transgenic and conventional maize was significantly higher than that on wheat,sorghum,foxtail millet,peanut and soybean while showing no significant difference between transgenic or conventional maize.FAW adults mainly laid eggs on Bt maize,while the larval density and leaf damage rating or percentage of damaged plants were significantly lower than on conventional maize.Larval density and its damage on conventional maize were significantly higher than that on Bt maize and the other five hosts.Thus,maize is a highly preferred and suitable host for S.frugiperda feeding and ovipositing,and Bt maize can be used as trap crop to protect other crops.

Identification of summer nectar plants contributing to outbreaks of Mythimna separata(Walker)(Lepidoptera: Noctuidae) in North China

The presence of adequate nectar sources along the migratory pathway is a prerequisite for moths of oriental armyworm, Mythimna separata, to reach target habitats and lay eggs. Identification of plant species and assessment of their suitability as wild nectar sources along the summer migration pathway of adult M. separata are critical steps in making effective forecasts of second-and third-generation armyworm outbreaks in North China. We explored five aspects of moth-nectar source relationships：（1） Field investigations in 2014 and 2015 showed that the florescence of chaste tree, Vitex negundo var. heterophylla, a primary nectar plant in apiculture, coincided with the summer migration of oriental armyworm moths. The flowers of chaste tree opened day and night and M. separata moths were found actively flying around and resting on tree.（2） Identification of moth-borne pollen by scanning electronic microscopy（SEM） micrographs in 2015 and 2016 revealed that 15.4% of 369 moths trapped by blacklight traps, 17.1% of 557 moths captured by vertical-pointing searchlight traps and 24.4% of 311 moths caught by pheromone traps were found with pollen attached to their proboscis. A total of 228 pollen-carrying individuals out of 1237 armyworm moths were captured by the three types of traps. The three highest percentages of pollen-bearing armyworm moths were carrying pollen of Toona sp.（59.65%）, Ligustrum sp.（27.19%） and Syringa sp.（4.39%）. In total, 14 types of pollen were detected where three were identified to species, 10 to genus and one as an unknown species.（3） Analysis of geographical distribution, flowering periods and relative abundances of candidate nectar plants suggested that Chinese toon, Toona sinensis, and privet, Ligustrum lucidum, were two important nectar plant species.（4） Analysis on relationship between pollen and ovarian development showed that 14, 15 and 10 females carrying pollen of T. sinensis had ovaries at developmental stages Ⅰ, Ⅱ and Ⅲ, respectively. Many T. sinensis pollen grains were present on the proboscises of female moths.（5） Comparison of trap effectiveness between blacklight and vertical-pointing searchlight traps indicated blacklight traps caught the highest proportion（35.2%） of female in ovarian stage Ⅴ, whereas vertical-pointing searchlight traps caught the highest proportion（43.5%） of female in ovarian stage I with additional proportions of decreasing percentages for stages Ⅱ, Ⅲ and Ⅳ. Integrated analysis on these five aspects suggests that T. sinensis is an important, suitable summer nectar source that potentially influences migration and reproduction of M. separata moths andthus contributes to outbreaks of this pest. The vertical-pointing searchlight trap was the most effective tool for monitoring the migratory flight of adult M. separata. Privet, Ligustrum lucidum, and clove, Syringa sp., are possible suitable summer nectar plants that need further study to elucidate their importance. The reason why field investigation results on chaste tree differed from the results of moth-borne pollen analyses was discussed.

Mapping of QTL conferring leaf rust resistance in Chinese wheat lines W014204 and Fuyu 3 at adult plant stage

Wheat leaf rust is a destructive foliar disease of common wheat （Triticum aestivum L.） worldwide. The most effective, economical s to control the disease is growing resistant cultivars with adult plant resistance （APR）. The Chinese wheat tines W014204 and Fuyu 3 showed high leaf rust resistance in the field. To identify leaf rust APR genes in the two lines, two mapping populations with 215 and 163 F2：3 lines from the crosses W014204/Zhengzhou 5389 and Fuyu 3/Zhengzhou 5389, respectively, were phenotyped for leaf rust severities during the 2010-2011, 2011-2012 and 2012-2013 cropping seasons in the field at Baoding, Hebei Province, China. A total of 1 215 SSR markers were used to identify the quantitative trait loci （QTLs） for leaf rust APR in the two populations. In the W014204/Zhengzhou 5389 population, three QTLs were detected and designated as QLr.hbu-lBL.1, QLr.hbu-2BS.1 and QLr.hbu-7DS, and explained 2.9-8.4, 11.5-38.3 and 8.5-44.5% of the phenotypic variance, respectively; all the resistance alleles at these loci were derived from W014204. In the Fuyu 3/Zhengzhou 5389 population, three QTLs, QLr.hbu-lBL.2, QLr.hbu-2BS.2 and QLr.hbu-7BL, explained 12.0-19.2, 22.3-38.9 and 4.1-4.3% of the phenotypic variance, respectively, and all resistance alleles were contributed by Fuyu 3. Based on chromosome positions of closely linked markers, both QLr.hbu-lBL. 1 and QLr.hbu-lBL.2 are Lr46, and QLr.hbu-7DS is Lr34. QLr.hbu-7BL was mapped on chromosome 7BL near to Lr68 and they are likely the same gene. Based on chromosome positions, pedigree and field reactions, the two 2BS QTLs are different from all the known APR genes and are likely to be newAPR QTL for leaf rust. These QTLs and their closely linked markers are potentially useful for improving leaf rust resistance in wheat breeding.

Attraction of bruchid beetles Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) to host plant volatiles

Host-plant volatiles play an important role as cues for herbivores in search of resources, mates and oviposition sites in complex environments. Plant volatile-based attractants can be developed for pest monitoring and control. Previously, we indicated that mated female adults of Callosobruchus chinensis showed choice preference behavior toward 2-hexenal and benzaldehyde. Our objective here was to investigate the synergistic effect of host-derived attractive volatiles in attracting C. chinensis under laboratory and field conditions in Shanxi Province, China. We hypothesized that the ratio and concentration of volatiles derived from Vigna radiata play critical roles for C. chinensis in locating this host. Therefore, we collected and identified the volatiles of mungbean by using headspace collection and GC-MS. The effectiveness of different ratios and concentrations of two compounds (2-hexenal and benzaldehyde) that elicit C. chinensis searching behavior were examined in Y-tube olfactometer assays. The combination of 300 μg μL^–1 2-hexenal and 180 μg μL^–1 benzaldehyde loadings exhibited a synergistic effect on attracting C. chinensis (82.35%). Compared to control traps, the adults were significantly attracted to traps baited with blends, and more attraction to females than males was found for blend traps in the field experiments. Our results suggest that blends of this specific concentration and ratio of benzaldehyde and 2-hexenal can be used in traps as attractants for C. chinensis monitoring and control in the field.

Phosphate deficiency induced by infection promotes synthesis of anthracnose-resistant anthocyanin-3-O-galactoside phytoalexins in the Camellia sinensis plant

Tea(Camellia sinensis)is a well-known beverage crop rich in polyphenols with health benefits for humans.Understanding how tea polyphenols participate in plant resistance is beneficial to breeding resistant varieties and uncovering the resistance mechanisms.Here,we report that a Colletotrichum infection-induced‘pink ring’symptom appeared outside the lesion,which is highly likely to occur in resistant cultivars.By identifying morphological feature-specific metabolites in the pink ring and their association with disease resistance,and analysis of the association between metabolite and gene expression,the study revealed that the accumulation of anthocyanin-3-O-galactosides,red phytotoxin compounds resistant to anthracnose,plays a pivotal role in the hypersensitive response surrounding infection sites in tea plants.The results of genetic manipulation showed that the expression of CsF3Ha,CsANSa,CsUGT78A15,CsUGT75L43,and CsMYB113,which are involved in anthocyanin biosynthesis,is positively correlated with anthracnose-resistance and the formation of the pink ring.Further phosphorus quantification and fertilization experiments confirmed that phosphate deficiency caused by anthracnose is involved in the occurrence of the pink ring.Genetic manipulation studies indicated that altering the expression levels of Pi transporter proteins(CsPHT2-1,CsPHT4;4)and phosphate deprivation response transcription factors(CsWRKY75-1,CsWRKY75-2,CsMYB62-1)enhances resistance to anthracnose and the formation of the pink ring symptom in tea plants.This article provides the first evidence that anthocyanin-3-O-galactosides are the anthracnose-resistant phytoalexins among various polyphenols in tea plants,and this presents an approach for identifying resistance genes in tea plants,where genetic transformation is challenging.

A recommended rate for application of Chaetomium globosum ND35 fungus fertilizer on poplar plantations in China

Previous studies showed that Chaetomium globosum ND35 fungus fertilizer can improve the microbial community structure and enzyme activities of replanted soil. However, it remains unclear whether can improve the physiological and ecological characteristics of plants under successive rotation. In this study, we investigated the photosynthetic, physiological, and biochemical indexes including photosynthetic parameters, chlorophyll fluorescence, and chlorophyll content of 1-yeax-old poplar seedlings under seven different doses （range from 0 to 1.67 g kg-1） of C. globosum ND35 fungus fertilizer to study the effects of fungus fertilizer on photosynthesis of Poplar. Our results showed that： （1） With increasing application of fungus fertilizer in replanted soil, chlorophyll content of poplar leaves （Chl） increased, while physiological indexes such as electron transport rate （ETR）, net photosynthetic rate （Pn）, quantum efficiency （φ）, nitrate reductase （NR） activity and root vigor initially increased and then declined. Meanwhile, heat dissipation that depended on the xanthophyll cycle declined and nonphotochemical quenching （NPQ） initially increased and then decreased. When the dose of C. globosum ND35 fungus fertilizer was 0.67 g kg-1 （T3） and 1.00 g kg-1 （T4）, excess light energy of photosynthetic apparatus was reduced, and photosynthetic apparatus distributed more light energy to the direction of photochemical reactions, which improved the efficiency of energy use. Plant height and biomass of leaves, stems, and roots were maximum at T3. We conclude that applying appropriate amounts of C. globosum ND35 fungus fertilizer can improve root physiological activity and capacity for use of light by poplar leaves. This can improve the operating states of the photosynthetic apparatus and lead to increased photosynthetic efficiency of poplar leaves and accumulation of dry matter.This suggests a strategy to alleviate the successive rotation obstacle of soil nutrient depletion.

Association of host plant growth and weed occurrence with armyworm(Mythimna separata) damage in corn fields

To clarify association between armyworm（Mythimna separata） damage level and the corn growth and weed occurrence, we investigated corn plant height, stem diameter and vigor as well as weed coverage and biomass. The investigations were conducted at three locations of Shaanxi Province, China which were suffered seriously from armyworm. Significant correlations were found between the parameters analyzed. At stunted corn growth and presence of plenty of weeds, the armyworm damage tended to be heavy; oppositely, when corn grew well and weed density were low, armyworm harm was the minimal. Therefore, corn growing status and weed density can significantly affect armyworm damage level. Our results imply that promoting corn growth and timely removal of weeds are conducive to reducing armyworm occurrence.

Solar thermotherapy reduces the titer of Candidatus Liberibacter asiaticus and enhances canopy growth by altering gene expression profiles in HLB-affected citrus plants

Huanglongbing(HLB),a systemic and destructive disease of citrus,is associated with‘Candidatus Liberibacter asiaticus’(Las)in the United States.Our earlier work has shown that Las bacteria were significantly reduced or eliminated when potted HLB-affected citrus were continuously exposed to high temperatures of 40 to 42°C for a minimum of 48 h.To determine the feasibility and effectiveness of solar thermotherapy in the field,portable plastic enclosures were placed over commercial and residential citrus,exposing trees to high temperatures through solarization.Within 3–6 weeks after treatment,most trees responded with vigorous new growth.Las titer in new growth was greatly reduced for 18–36 months after treatment.Unlike with potted trees,exposure to high heat did not eradicate the Las population under field conditions.This may be attributed to reduced temperatures at night in the field compared to continuous high temperature exposure that can be maintained in growth chambers,and the failure to achieve therapeutic temperatures in the root zone.Despite the presence of Las in heat-treated commercial citrus,many trees produced abundant flush and grew vigorously for 2 to 3 years after treatment.Transcriptome analysis comparing healthy trees to HLB-affected citrus both before and after heat treatment demonstrated that post-treatment transcriptional expression patterns more closely resembled the expression patterns of healthy controls for most differentially expressed genes and that genes involved with plant-bacterium interactions are upregulated after heat treatment.Overall,these results indicate that solar thermotherapy can be an effective component of an integrated control strategy for citrus HLB.

Electrophysiological responses of Plutella xylostella to 9 different plant volatiles

Plutella xylostella is the main pest of cruciferae plants in the worldwide fields.The volatiles released from host plants serve vital roles in host-finding and oviposition behavior.Electroantennograms were recorded from male and female Plutella xylostella to 9 different plant volatiles(cabbage Brassica oleracea L.var.capitata,baby bokchoi Brassica chinensis L.,broccoli Brassica oleracea L.var.botrytis L.,Chinese cabbage Brassica pekinensis Rupr.,Radish Raphanus sativus L.,towel gourd Luffa Cylindrica Roem.,eggplant Solanum melongena L.,tomato Solanum lycopersicum,pepper Capsicum annuum L.) in healthy/injured status.The statistic analysis show there is a significant difference of EAG relative values between cruciferae and non-cruciferae volatiles.The EAG relative values of injured plant volatiles to both male and female changed a lot during the tests.Multiple-ANOVA analysis represents cross factors(sex,host-plant,plant status) showed a great interactive impacts to the EAG-RV.

Identification of Damage on Different Plants Caused by Botrytis cinerea and its Extracellular Macromolecular Toxin

With Bowytis cinerea and its extracellular macromolecular toxins as the test materials, 30 speiees of plants belonging to 29 genera and 21 families were selected as the test plants to observe the infectivity of B. dnerea and damage status of macromolecular toxins secreted by B. cinerea on plants. The resulsts showed that 17 species of plants were beth infected by B. cinerea and damaged by toxins, accounting for 56.7% of the total plants. Two species of plants could be neither infected by B. cinerea nor damaged by toxins. The study provided the reference for further understanding of pathogenic mechanism of plant pathogenic fungi toxins.

QTL mapping of adult plant resistance to stripe rust and leaf rust in a Fuyu 3/Zhengzhou 5389 wheat population

Stripe or yellow rust(YR)and leaf rust(LR)cause large losses in wheat production worldwide.Resistant cultivars curtail the levels of losses.The present study aimed to identify quantitative trait loci(QTL)for YR and LR resistance in 147 F2:6 recombinant inbred lines(RIL)derived from the cross Fuyu 3/Zhengzhou 5389.The RIL population and parents were genotyped with the Wheat55 K single nucleotide polymorphism(SNP)array and simple sequence repeat(SSR)markers.All materials were also phenotyped for YR severity at Mianyang in Sichuan province and Baoding in Hebei province in the 2015/2016,2016/2017,and 2017/2018 cropping seasons,and LR severity at Zhoukou in Henan province and at Baoding in 2017/2018.Eleven QTL for YR resistance and five for LR resistance were detected using inclusive composite interval mapping(Ici Mapping).Four of these QTL on chromosomes 1 BL,2 BS,3 AL,and 5 AL conferred resistance to both YR and LR.The QTL on 1 BL was Lr46/Yr29,and that on 7 BL might be Lr68.The QTL on chromosome 2 BS was detected at a similar position to previously detected loci.QYr.hebau-3 AL/QLr.hebau-3 AL,QYr.hebau-5 AL/QLr.hebau-5 AL,QYr.hebau-7 DL,QYr.hebau-4 BS,QYr.hebau-6 DL,and QYr.hebau-2 AS are likely to be new.An SSR marker for QYr.hebau-7 DL was developed and validated in a diverse wheat panel from China,suggesting effectiveness in different genetic backgrounds.These QTL with closely linked SNP and SSR markers could be useful for marker-assisted selection in wheat breeding programs targeting durable resistance to both diseases.

Genetic analysis of adult plant,quantitative resistance to stripe rust in wheat landrace Wudubaijian in multi-environment trials

Stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most destructive diseases on wheat worldwide.Wudubaijian,a wheat landrace released from Gansu Province in China since 1950,exhibits adult-plant resistance to stripe rust for several decades.To elucidate the genetic basis of stripe rust resistance,Wudubaijian was crossed with the high susceptible cultivar Mingxian 169,and stripe rust tests of both parents and the F2:3 lines were conducted in four environments of Yangling and Tianshui in 2015 and 2016,respectively.The relative area under disease progress curve(rAUDPC)of Mingxian 169/Wudubaijian F_(2:3) lines showed that the resistance of Wudubaijian was controlled by quantitative trait loci(QTL).Combined with phenotypic data and molecular markers,two stable QTLs were identified in Wudubaijian.QYrwdbj.nwafu-5A with the phenotypic variance of 15.02-40.26% was located between 5AS1-0.40-0.75 and 5AS3-0.75-0.98 of chromosome 5AS,and QYrwdbj.nwafu-2B.1 with the phenotypic variance of 9.54-10.40%was located in the bin C-2BS1-0.53 of chromosome 2BS.Through the location of flanking markers and epistasis analysis,QYrwdbj.nwafu-5A may be a new major QTL that can be used in conjunction with other stripe rust resistance genes(QTLs).

Identification of candidate soil microbes responsible for small-scale heterogeneity in strawberry plant vigour

Studies were conducted to identify candidate soil microbes responsible for observed differences in strawberry vigour at a small spatial scale, which was not associated with visual disease symptoms. Samples were obtained from the soils close to the rhizosphere of ‘big＇ and ‘small＇ plants from small plots which exhibited large local heterogeneity in plant vigour. A metabarcoding approach was used to profile bacterial and fungal compositions, using two primer pairs for 16 S ribosomal RNA genes（16S r DNA） and one for the fungal internal transcribed spacer（ITS） region. Of the two 16 S r DNA primer sets, the 341F/805 R resulted in sequences of better quality. A total 28 operational taxonomic units（OTUs） had differential relative abundance between samples from ‘big＇ and ‘small＇ plants. However, plausible biological explanation was only possible for three fungal OTUs. Two were possible phytopathogens： Verticillium spp. and Alternaria alternata although the latter has never been considered as a main pathogen of strawberry in the UK. For samples from ‘small＇ plants, the abundance of these OTUs was much greater than from ‘big＇ plants. The opposite was true for a mycorrhizal OTU. These results suggest that soil microbes related to crop production can be identified using metabarcoding technique. Further research is needed to assess whether A. alternata and Verticillium spp. could affect strawberry growth in the field.