Advances in Research on Rape Sclerotia and Resistance Breeding

Rapeseed is an important oil crop with high economic value.It can be used not only as edible oil and livestock feed,but also in medicine,industry and tourism.Sclerotium sclerotiorum is a necrotrophic fungal pathogen that harms the yield and quality of rape.This article mainly summarizes the research status of S.sclerotiorum from three aspects:the biological characteristics,infection mode,process and disease resistance breeding of S.sclerotiorum,and summarizes the future research directions of antibacterial sclerotium on rape,to provide reference for future research on sclerotinia.

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.

Identification of Fusarium wilt resistance gene SiRLK1 in Sesamum indicum L.

Sesame Fusarium wilt(SFW),caused by Fusarium oxysporum f.sp.sesami(Fos),is one of the most devastating diseases affecting sesame cultivation.Deciphering the genetic control of SFW resistance is pivotal for effective disease management in sesame.An inheritance study on a cross between the highly resistant variety Yuzhi 11 and the highly susceptible accession Sp1 using a Fos pathogenicity group 1 isolate indicated that resistance was conferred by a single dominant allele.The target locus was located in a 1.24 Mb interval on chromosome 3 using a combination of cross-population association mapping and bulked segregant analysis.Fine genetic mapping further narrowed the interval between 21,350 and 21,401 kb.The locus Sindi_0812400 was identified as the SFW resistance gene and officially designated SiRLK1.This gene encodes a specific malectin/receptor-like protein kinase with three putative tandem kinase domains and is considered a kinase fusion protein.Sequence analysis revealed that a high proportion(49.44%)of variants within the locus was located within the kinase domainⅢ,and several of which were evidently associated with the diversity in SFW response,indicating the critical role of kinase domainⅢin expression of disease resistance.These findings provide valuable information for further functional analysis of SFW resistance genes and marker-assisted resistance breeding in sesame.

Advance of Rice Drought Resistance,Water Saving Cultivation and Genetic Breeding

The water shortage faced with rice production in China was comprehensively analyzed,and the seasonal as well as spatial and temporal differences were the factors limiting rice production,which would be a severe test for grain production safety.Therefore,solving strategies had been proposed from the following aspects：the improvement of irrigation practices was of significant effect on improving the high efficient utilization of water;the screening of drought resistance cultivars and upland rice cultivation could also greatly improve the ability of drought resistance;the combination of traditional breeding techniques with modern transgenic technology as well as the QTL analysis had made considerable progress on improving the soil moisture productive potential of rice from the perspective of genetics.The development of China＇s rice industry would face greater water scarcity in the future,but the conventional water-saving technologies could only reduce water consume to a certain extent,while the exploration and improvement of the water saving potential of wetland rice to give full play to the biological water-saving function would become the goal of agricultural development in China.

Marker-assisted selection to pyramid Fusarium head blight resistance loci Fhb1 and Fhb2 in the high-quality soft wheat cultivar Yangmai 15

Fusarium head blight(FHB)is one of the most detrimental wheat diseases which greatly decreases the yield and grain quality,especially in the middle and lower reaches of the Yangtze River of China.Fhb1 and Fhb2 are two major resistance loci against Fusarium graminearum.Yangmai 15(YM15)is one of the most popular varieties in the middle and lower reaches of the Yangtze River,and it has good weak gluten characters but poor resistance to FHB.Here we used Fhb1 and Fhb2 to improve the FHB resistance of YM15 by a molecular marker-assisted selection(MAS)backcrossing strategy.The selection of agronomic traits was performed for each generation.We successfully selected seven introgressed lines which carry homozygous Fhb1 and Fhb2 with significantly higher FHB resistance than the recurrent parent YM15.Three of the introgressed lines had agronomic and quality characters that were similar to YM15.This study demonstrates that the pyramiding of Fhb1 and Fhb2 could significantly improve the FHB resistance in wheat using the MAS approach.

Advances on genetic and genomic studies of ALV resistance

Avian leukosis(AL)is a general term for a variety of neoplastic diseases in avian caused by avian leukosis virus(ALV).No vaccine or drug is currently available for the disease.Therefore,the disease can result in severe economic losses in poultry flocks.Increasing the resistance of poultry to ALV may be one effective strategy.In this review,we provide an overview of the roles of genes associated with ALV infection in the poultry genome,including endogenous retroviruses,virus receptors,interferon-stimulated genes,and other immune-related genes.Furthermore,some methods and techniques that can improve ALV resistance in poultry are discussed.The objectives are willing to provide some valuable references for disease resistance breeding in poultry.

Knock-out of BnHva22c reduces the susceptibility of Brassica napus to infection with the fungal pathogen Verticillium longisporum

Verticillium longisporum(Vl43)is a soilborne hemibiotrophic fungal pathogen causing stem striping on oilseed rape(OSR)and severe yield losses.Breeding for resistant varieties is the most promising approach to control this disease.Here,we report the identification of Hva22c as a novel susceptibility factor and its potential for improving OSR resistance.Hva22c is a member of the Hva22 gene family,originally described for barley(Hordeum vulgare).Several Hva22 members have been located at the endoplasmic reticulum.Hva22c is up-regulated in response to Vl43 in both Arabidopsis and OSR.We demonstrate that knock-out of Hva22c in OSR by CRISPR/Cas9 and its homolog in Arabidopsis by T-DNA insertion reduced plants’susceptibility to Vl43 infection and impaired the development of disease symptoms.To understand the underlying mechanism,we analysed transcriptomic data from infected and non-infected roots of hva22c knock-out and wild type plants.We identified a homozygous mutant with frame-shifts in all four BnHva22c loci displaying a vastly altered transcriptional landscape at 6 dpi.Significantly,a large set of genes was suppressed under mock conditions including genes related to the endomembrane systems.Among the up-regulated genes we found several defense-related and phytohormone-responsive genes when comparing mutant to the wild type.These results demonstrate that Hva22c is functionally required for a fully compatible plant-fungus interaction.Its loss of function reduces plant susceptibility,most likely due to endoplasmatic reticulum and Golgi dysfunction accompanied by additionally activated defense responses.These findings can help improve OSR resistance to V.longisporum infection.

Genetics and Improvement of Bacterial Blight Resistance of Hybrid Rice in China

Since 1980s, rice breeding for resistance to bacterial blight has been rapidly progressing in China. The gene Xa4 was mainly used in three-line indica hybrid and two-line hybrid rice. The disease has been ＇quiet＇ for 20 years in China, yet in recent years it has gradually emerged and been prevalent in fields planted with newly released rice varieties in the Changjiang River valley. Under the circumstances, scientists inevitably raised several questions： what causes the resurgence and what should we do next？ And/or is resistance breeding still one of the main objectives in rice improvement？ Which approach do we take on resistance breeding so that the resistance will be more durable, and the resistance gene will be used more efficiently？ A combined strategy involving traditional method, molecular marker-assisted selection, and transgenic technology should bring a new era to the bacterial blight resistance hybrid rice breeding program. This review also briefly discusses and deliberates on issues related to the broadening of bacterial blight resistance, and suitable utilization of resistance genes, alternate planting of available resistance genes; and understands the virulent populations of the bacterial pathogen in China even in Asia.

Immunogenomics for identification of disease resistance genes in pigs: a review focusing on Gram-negative bacilli

Over the past years, infectious disease has caused enormous economic loss in pig industry. Among the pathogens, gram negative bacteria not only cause inflammation, but also cause different diseases and make the pigs more susceptible to virus infection. Vaccination, medication and elimination of sick pigs are major strategies of controlling disease. Genetic methods, such as selection of disease resistance in the pig, have not been widely used. Recently, the completion of the porcine whole genome sequencing has provided powerful tools to identify the genome regions that harboring genes controlling disease or immunity. Immunogenornics, which combines DNA variations, transcriptorne, immune response, and QTL mapping data to illustrate the interactions between pathogen and host immune system, will be an effective genomics tool for identification of disease resistance genes in pigs. These genes will be potential targets for disease resistance in breeding programs. This paper reviewed the progress of disease resistance study in the pig focusing on Gram-negative bacilli. Major porcine Gram-negative bacilli and diseases, suggested candidate genes/pathways against porcine Gram-negative bacilli, and distributions of QTLs for immune capacity on pig chromosomes were summarized. Some tools for immunogenomics research were described. We conclude that integration of sequencing, whole genome associations, functional genomics studies, and immune response information is necessary to illustrate molecular mechanisms and key genes in disease resistance.

Development of high yield and tomato yellow leaf curl virus(TYLCV)resistance using conventional and molecular approaches:A review

Tomato(Solanum lycopersicum L.)belonging to the family Solanaceae is the second most consumed and cultivated vegetable globally.Since the ancient time of its domestication,thousands of cultivated tomato varieties have been developed targeting an array of aspects.Among which breeding for yield and yield-related traits are mostly focused.Cultivated tomato is extremely genetically poor and hence it is a victim for several biotic and abiotic stresses.Among the biotic stresses,the impact of viral diseases is critical all over tomato cultivating areas.Improvement of tomato still largely rely on conventional methods worldwide while molecular approaches,particularly Marker Assisted Selection(MAS)has become popular across the globe as a fast,low cost and precise tool which is essential in present day plant breeding.In this review paper,breeding tomato for high yield and viral disease resistance,particularly to tomato yellow leaf curl virus disease(TYLCVD)using conventional and molecular approaches will be discussed.Lining up of this set of information will be useful to those who are interested in tomato variety development with high yielding and TYLCVD resistance.

Research Progresses of Sugarcane Brown Rust Resistance Gene and Molecular Markers

Brown rust is a main sugarcane disease in China, affecting stable development of sugarcane industry. Resistance breeding is an effective measure to control sugarcane rust, and looking for diverse sugarcane rust resistance alternative resources is another important way to improve rust resistance level. This article reviewed from the aspects of construction of sugarcane genetic map, research progress of rust resistance gene, development of rust resistance molecular markers, and research strategies of rust resistance gene, in order to provide scientific guidance and reference for rust resistance breeding.

Evaluation of cotton germplasm for morphological and biochemical host plant UPdates resistance traits against sucking insect pests complex

Background:Sucking insect pests cause severe damage to cotton crop production.The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses.Considering the role of morphological and biochemical host plant resista nee(HPR)traits in plant defense,12 cotton genotypes/varieties were evaluated for leaf area,leaf glanding,total soluble sugars,total soluble proteins,total phenolics,tannin and total flavonoids against fluctuating populations of whitefly,thrips and jassid under field conditions.Results:The population of these insects fluctuated during the growing seas on and remained above threshold level(whitefly>5,thrips>(8-10)f or jassid>1 per leaf)during late June and early July.Strong and negative association of whitefly(r=-0.825)and jassid(r=-0.929)with seed cotton yield was observed.Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30.NIAB-Kiran followed by NI AB-878 and Sadori were the most resistant,with the mean population of 1.41,1.60,1.66(whitefly);2.24,232,2.53(thrips)and 037,0.31,036(jassid),respectively.The resistant variety NIAB-Kiran showed less soluble sugars(8.54 mg.g^(-1)),soluble proteins(27.11 mg.g^(-1))and more phenolic(36.56 mg.g^(-1))and flavonoids(13.10mg.g^(-1))as compared with the susceptible check Glandless-1.Moreover,all insect populations were positively correlated with total soluble sugars and proteins.Whitefly populations exhibited negative response to leaf gossypol glands,total phenolics,tannins and flavonoids.The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits.Conclusion:The ide ntified resistant resources and HPR traits can be deployed against sucking in sect pests'complex in future breeding programs of developing insect resistant cotton varieties.

Development of Hybrid Rice Variety FY7206 with Blast Resistance Gene Pid3 and Cold Tolerance Gene Ctb1

Hybrid rice Fanyou 7206（FY7206）, derived from the cross between a sterile line Fanyuan A and a restorer line Fuhui 7206, was bred by the Rice Research Institute, Fujian Academy of Agricultural Sciences, China. FY7206 was characterized by moderate blast resistance, cold tolerance, as well as wide adaptability, and high yields. The blast resistance results indicated that the frequencies of blast races in race B, race C and the total resistance frequency for FY7206 were 95.5%, 100.0% and 97.2%, respectively. The disease resistance results showed that the leaf blast grade for FY7206 was level 1 and panicle blast was level 5. The indoor spray results indicated that FY7206 was resistant to 11 isolates of Magnorpathe oryzae. The blast resistance of FY7206 might be derived from the high expression of blast resistance gene Pid3. The results for simulated cold resistance in an artificial climate chamber indicated that the cold tolerance for FY7206 was moderate at the booting and flowering stages. The cold tolerance results also indicated that FY7206 could be tolerant to temperatures as low as 10 °C at the seedling stage. The q RT-PCR results showed that the expression of cold tolerance gene Ctb1 in FY7206 was relatively high. These results suggested that FY7206 is a hybrid indica rice variety with good comprehensive characteristics, including blast resistance and cold tolerance.

Can effectoromics and loss-of-susceptibility be exploited for improving Fusarium head blight resistance in wheat?

Bread wheat(Triticum aestiuum L.),which provides about 20%of daily calorie intake,is the most widely cultivated crop in the world,in terms of total area devoted to its cultivation.Therefore,even small increases in wheat yield can translate into large gains.Reducing the gap between actual and potential grain yield in wheat is a crucial task to feed the increasing world population.Fusarium head blight(FHB)caused by the pathogenic fungus Fusaium graminearum and related Fusarium species is one of the most devastating wheat diseases throughout the world.This disease reduces not only the yield but also the quality by contaminating the grain with mycotoxins harmful for humans,animals and the environment.In recent years,remarkable achievements attained in omics"technologies have not only provided new insights into understanding of processes involved in pathogenesis but also helped develop effective new tools for practical plant breeding.Sequencing of the genomes of various wheat patho gens,including F.graminearum,as well as those of bread and durum wheat and their wild relatives,together with advances made in transcriptomics and bioinformatics,has allowed the identification of candidate pathogen effectors and corresponding host resistance(R)and susceptibility(S)genes.However,so far,FHB effectors and wheat susceptibility genes/factors have been poorly studied.In this paper,we first briefly highlighted recent examples of improving resistance against pathogens via new techniques in different host species.We then propose effective strategies towards developing wheat cultivars with improved resistance to FHB.We hope that the article will spur discussions and interest among researchers about novel approaches with great potential for improving wheat against FHB.

Studies on Cotton Breeding Resistant to Fusarium and Verticillium wilt Diseases

Both Fusarium and Verticillium wilts are important soil-borne diseases,which can not be effectively controlled by chemical fungicides.The two diseases,especially Verticillium wilt,have

Utilization and Inheritance of Watermelon Resistance to Fusarium oxysporum f.sp.niveum Introduced from Bottle Gourd

Sugar Baby susceptible to Fusarium oxysporum f.sp.niveum was crossed with high resistant male parents D3-1 and D3-2,respectively.F1 hybrids showed high resistance.The segregation ratios of resistance to susceptibility of F2 and of BC1 hybrid population from Sugar Baby tallied with 3:1 and 1:1,respectively.The results indicated that the resistance to Fusarium wilt was a kind of dominant inheritance controlled by mono-gene or mono-segment DNA.Furthermore,5 hybrid combinations with fine character were bred.Among them,3 were high resistant to Fusarium wilt,and 2 were medium resistant.

Research Advances in New Race Ug99 of Puccinia graminis f.sp. tritici

This paper reviewed the research advances of Ug99 and its resistance breeding from the aspects of its discovery, race variation, pathogenicity, distribution, spread, exploration of relative resistant genes, linked molecular marker selection and resistance breeding strategies, to provide basis for comprehensive understanding of the new Puccinia graminis f. sp. tritici race Ug99 and its potential threat to wheat production. Ug99 is a new Puccinia grarninis f. sp. tritici race with high variability, strong pathogenicity and rapid spread speed, which is likely to cause global damages to world wheat production. We should strengthen the exploration and utilization of new resistance genes in wheat and relative species and breeding of new wheat varieties with durable resistance, to control and prevent damages caused by Ug99 and its variants.

Antixenosis and Tolerance of Rice Genotypes Against Brown Planthopper

Nine genotypes were evaluated under greenhouse conditions for antixenosis and tolerance against brown planthopper （BPH, Nilaparvata lugens Stal）. In antixenosis studies, proportion of insects settled on a test genotype in relation to the susceptible control TN1 was recorded, with significantly lower proportion of nymphs （55.22%-59.18%）, adult males （60.33%-60.75%）, and adult females （80.56%- 79.26%） settled on RP2068-18-3-5 and Ptb33 in relation to those on TN1. Based on number of feeding sites, the test genotypes were ranked in order from the highest to the lowest as RP2068-18-3-5, Ptb33, MR1523, Rathu Heenati, Sinnasivappu, ARC10550, MO1, INRC3021 and TNI. The order was exactly reverse in terms of fecundity expressed as number of eggs laid per female. In tolerance studies, days to wilt, functional plant loss index and plant dry weight loss to BPH dry weight produced were recorded. RP2068-18-3-5, Rathu Heenati and Ptb33 performed better than the other test genotypes. These results helped in relative quantification of BPH resistance levels in the genotypes. RP2068-18-3-5, a new effective source of BPH resistance, can be used in resistance breeding after tagging of resistant genes/QTLs linked to different parameters of antixenosis and tolerance with selectable molecular markers.

Pathogen-informed breeding for crop disease resistance

The development of durable and broad-spectrum resistance is an economical and eco-friendly approach to control crop diseases for sustainable agricultural production. Emerging knowledge of the molecular basis of pathogenesis and plant–pathogen interactions has contributed to the development of novel pathogen-informed breeding strategies beyond the limits imposed by conventional breeding. Here,we review the current status of pathogen-assisted resistance-related gene cloning. We also describe how pathogen effector proteins can be used to identify resistance resources and to inform cultivar deployment. Finally, we summarize the main approaches for pathogen-directed plant improvement,including transgenesis and genome editing. Thus, we describe the emerging role of pathogen-related studies in the breeding of disease-resistant varieties, and propose innovative pathogen-informed strategies for future applications.

Wheat Yield Response to Foliar Fungicide Application against Leaf Rust Caused by Puccinia triticina

A study was conducted on reducing the yield loss of wheat due to leaf rust caused by Puccinia triticina with foliar application of fungicides during the 2014-2015 and 2015-2016 growing seasons at the Wheat Research Institute in Faisalabad, Pakistan. Three fungicides： Folicur （tebuconazole） at 300 mL/ha, Nativo （tebuconazole ＋ trifloxystrobin） at 300 g/ha and Tilt （propiconazole） at 500 mL/ha were applied single or two times to Morocco and Sehar-06 wheat varieties used in the trial. The trial plots were first sprayed at the Zadok＇s scale （ZS） 3 stage and second sprayed between ZS 4.3 and 5.4 stages. The greenness of the trial crop was measured using GreenSeeker. Foliar application of fungicides significantly reduced the loss of grain yield and 1,000-grain weight （TGW） of wheat due to leaf rust in comparison to the control without fungicides application. Of the three fungicides, two times spray of Nativo reduced the grain yield loss of leaf rust susceptible mega wheat variety Sehar-06 by 45%-56% and the loss of TGW by 42%, also giving the highest marginal return in the trial. Single application of Nativo was equally effective as two times spray of Folicur in reducing the loss of wheat grain yield. Two times spray of Folicur was found to be the second choice of fungicide for reducing the yield loss of wheat. The research identified suitable fungicides for reducing the yield loss of wheat due to leaf rust and also generated important scientific knowledge required to manage a sudden outbreak of leaf rust to ensure food security.