Evaluation Of Resistance And QTL Mapping Of Powdery Mildew And Yellow Rust In Common Wheat

Wheat powdery mildew and yellow rust,the two serious diseases in China,occur frequently each year and seriously threat to wheat.Contrast to treat seed with fungicide before sowing and spray fungicide at the disease emerged stage,breeding and planting resistance cultivars are the most economic and environmental method.Resistance germplasms discovery and resistance gene/QTL mapping are effective ways to achieve disease resistance,good quality and high yield in wheat.This study evaluated the resistance of 68 wheat cultivars,which are planted at least over 70 thousand hectares each year,to powdery mildew.Adult resistance to powdery mildew and yellow rust were assessed with 411 cultivars and candidate cultivars.Based on the resistance results,the cultivars E07901 and XK0106 with good resistance were seleted to construct a double haploid(DH)population with 388 lines,which was induced by maize pollen haploid technology.QTL resistance to powdery mildew and yellow rust were mapped by SSR and 90K SNP markers and the effect of these QTLs in different enviroments were evaluated.Resistance mechanism of the detected QTLs on powdery mildew were analysised by histological staining method.The main results are as follows:1.Diversity and disease risk assessment of the 68 major cultivars planted in large area in China were carried out.Sixty-eight major wheat cultivars,which are planted at least over 70 thousand hectares each year according to the wheat planting area information released by the National Agricultural Extension Service Center,were collected form different breeding teams.One thousand and nity-four wheat powdery mildew strains collected from 12 provinces(districts)including the southwest,northwest,Yangtze River downstream,Northplain,and Huang-Huai region in the same year(2011)were inoculated on the 68 major wheat cultivars in seedling,respectively.Resistance frequency of each cultivar to different province's isolates groups had been tested and compared.Virulence phenotype data were cluster using UPGAMA(unweighted pair group arithmetic mean analysis)model of the software NTSYSpc2.10e.Powdery mildew resistance genes of all the cultivars were postulated by comparing the virulence spectra of 31 differential isolates on 68 cultivars with that of 30 known Pm gene lines.The resistance diversity analysis showed that anti-spectra between cultivars varied significantly.Resistance frequencies of the three cultivars Mianmai37,Neimai8 and Neimai9 with broad-spectrum resistance were greater than 99%,while the resistance frequencies of the five cultivars Jimai22,Yangmai11,Yangmai12,Yangmail3 and Lunxuan987 were between 70%and 90%.Resistance frequency of six cultivars containing Yanzhan4110,Xingmai208,Yumai18-99,Bainongaikang58,Yangmai 15 and Ningmai13 were from 40 to 70%.There are 54 cultivars's resistance frequencies,79.4%of all the cultivars,were below 40%,which suggested the resistance of these cultivars are less or their resistance had been overcome.In general,the cultivars of Mianmai and Neimai from Sichuan province and Yangmai from Jiangsu province have better resistance to all the isolates groups.The result showed resistance differentiation between cultivars to the different group isolates.Resistance frequency of one cultivar to the isolates groups in where the cultivars has been wildly planted is less than to the isolate group in where the cultivars has not been wildly planted.System cluster analysis categorized 68 cultivars into four groups.Group I included 6 cultivars and 5 out of 6 cultivars,namely Yanzhan4110,Xingmai208,Yumai18-99,Bainongaikan58 and Yangmail5,had the resistance frequency between 40%and 70%.Group ? were comprised by 7 cultivars including Jimai22,Yangmai 12 with resistance frequency higher than 70%.Group III contained 54 cultivars such as Xingmai16,Xingmai18 and Xingmai19,had the resistance frequency lower than 40%.Group IV had only contained cultivar Ningmail3 with resistance frequency of 46.1%.The cultivars come from the same province and the cultivars with the similar resistance frequency had been clustered to the same group,which showed that they had the similar resistant genetic background.Pm gene postulation on the cultivars showed that Neimai8 and Neimai9 contains Pm21,Yanzhan4110 contains Pm4+8 and Pm4b+Mli,Xingmai 208 contains Pm4b+Mli,Jimai 22 holds Pm2+ta.The above results indicated that the cultivars have significant resistance difference on the different geographical powdery mildew isolates.Whereas,the resistance levels on powdery mildew of these cultivars are lower in general.The forecast of epidemic on powdery mildew must be enhanced in order to avoid powdery mildew burst occurance in a large areas as long as the conditions are suit for it's prevelent.2.Adult resistance to powdery mildew and yellow rust were assessed on 411 cultivars or candidate cultivars.Twenty-one and 94 cultivars with the adult resistance were identified.Based on the results,the parents for QTL mapping were selected.The resistance of 411 cultivars or candidate cultivars,which came from the Huang-Huai-Hai as well as the Yangtze River basin,were evaluated by innoculation method to the powdery mildew and yellow rust in the field.Progress of the diseases were systematically observed and scored on the all cultivars during the whole incidence period of disease.The resistance type on powdery mildew had been further divided by three parameters of the final disease index,the area under disease progress curve(AUDPC)and the seedling virulence frequency.There were 20 and 21 cultivars were identified to immune and partial resistance to powdery mildew,respectively.The infection types,the final disease index and the area under disease progress curve had been used to classify the resistance type to yellow rust.There were 3 cultivars and 13 cultivars were identified to immune and nearly immune to yellow rust,respectively.Ninty-three cultivars were identified to be partial resistance to yellow rust.Cultivar E07901 exhibiting adult plant resistannce to powdery mildew and yellow rust and XK0106 showing high level resistance to powdery mildew and yellow rust were selceted for the resistace QTL mapping.3.A much higher density genetic map with SSR and SNP markers had been constructed and 4 QTLs for powdery mildew and 3 QTLs for yellow rust were mapped.The QPm.haas-2A and QYr.haas-lB-2 are new QTLs that have not been previously identified.The combine of different QTL can significantly improve the resistance to powdery mildew and yellow rust.A population of 388 doubled haploid(DH)lines,derived from a cross between cultivar E07901 and XK0106,was constructed.The genetic linkage map were produced with genotype data of 395 SSR markers and large population(388 lines)for frame genetic map.It was also constructed with 90K SNP markers and one subgroup population(91 lines randomly selected from the 388 lines).The QTLs for powdery mildew were mapped by combination with the phenotype data of seedling and adult data of powdery mildew(2011-2013),while the QTLs for yellow rust were mapped with the phenotype data of two year(2011 and 2013)in the field.The results indicated that one QTL for powdery mildew(QPm.haas-6A)and two QTLs(QYr.haas-1B-1 and QYr.haas-2A)for yellow rust were detected by SSR markers and the large population.Whereas,the more QTLs,such as QPm.haas-2A,QPm.haas-3A and QPm.haas-5A for powdery mildew and QYr.haas-2A had been identified by the genetic integrated mapping of SNP and SSR markers and a subpopulation.Among the QTLs detected above,QPm.haas-3A,QPm.haas-6A and QYr.haas-1B-1 were derived from XK0106,QPm.haas-2A,QPm.haas-5A,QYr.haos-1B-2 and QYr,haas-2A were from E07901.QPm.haas-2A and QYr.haas-1B-2 are newly discovered QTLs.QPm.haas-6A is identical to Pm21 and QYr.haas-1B-1 is the same as Yr24/26.The results indicated that one of QPm.haas-2A,QPm.haas-3A,QPm.haas-5A,QYrnhaas-1B-2 and QYr.haas-2A alone has a stronger resistance effect in the weaken disease press condition,while it has a weaken resistance effect in serious disease condition.The QYr.haas-1B-1 had obvious resistance to stripe rust in Wuhan and Xiangyang Hubei province and Kunming,Yunnan province,but it had a weaken resistance in Gangu of Gansu province.QPm.haas-2A combined with QPm.haas-3A,QPm.haas-2A combined with QPm.haas-5A can both significantly enhance the resistance to powdery mildew,while QYm.haas-2A with each of QYr.haas-1B-1 and QYrhaas-2A can significantly enhance resistance to stripe rust.4.Histological staining revealed hypersensitive reaction(HR)also one of mechanism to the non-race resistance of QTL or multiple QTLs combination.We firstly reported that the DH lines with Pm21(QPm.haas-6A)could be infected by Bgt and a few colony can produce conidia.We presumed some of the QTLs has a surpress effect on the Pm21(QPm.haas-6A).Seven lines with the different combination of QTLs detected in the above study by the closed linked marker were selected and the development of powdery mildew on them were analysed by histological staining method.The results showed that there were not difference on the spore germination and the formation of attached cells between lines contain different QTL or QTL combination,but significant differences in the number of pallid(halo),the number of HR,haustrum and colony formed were existed.The DH line contained QPm.haas-2A with QPm.haas-3A,or the DH line contained QPm.Haas-2A,QPm.haas-3A and QPm.haas-5A can both significantly improve the rate of HR.It indicated HR is also one of the mechanisms of no race resistance QTL or QTL combinations against powdery mildew.All of the DH lines containing QPm.haas-6A(Pm21)forms a certain percent of the colonies,and a small number of the colonies have formed the conidia.This is reported by the first time.We speculated that some resistance QTLs have a negative interaction on QPm.haas-6A(Pm21).Up to now,although there is no pathogenic strain for Pm21 has been found,we need to take in mind the negative effects of other genes on Pm21 in the future.