| Common wheat(Triticum aestivum L.,AABBDD)is the grain crop with the largest cultivation acreage in the world,and has great influence to food security.The production of wheat is threatened by multiple diseases.Fusarium head blight(FHB)is one of the major fungal diseases affecting wheat production in many countries.FHB leads to multifold damage such as reduced yields and contaminated seeds with mycotoxins that are seriously harmful to human and livestock.Host resistance constitutes a favorable strategy to manage FHB,it is very effective,economical,and environmentally-friendly.No immunity to FHB has yet been found,and in all cases identified thus far,resistance is conferred by quantitative trait loci(QTLs).Therefore,it is essential to search for additional FHB resistance QTLs,particularly QTLs with major effect and high stability.Our previous observations indicate that the wheat line AQ24788-83(AQ),derived from a double cross involving four of Chinese landraces,possesses FHB resistance.The American wheat cultivar Luke is FHB susceptible.The author completed the following major works:(1)A Luke x AQ population was developed,consisting of 1652 advanced recombinant inbred lines(RILs),from which 272 RILs were randomly sampled for constructing a linkage map.Another 154 RILs were selected with homogeneity in the plant height(PH)and flowering date(FD).Such a selection was done to reduce possible confounding effects on the FHB assessment due to variation in the PH and FD.The 272 and 154 RILs were genotyped applying the markers of SSR(simple sequence repeat),DArT(diversity arrays technology),and SNP(single nucleotide polymorphism).The linkage map consisted of 601 SSR markers with "gaps"(>25.6 cM)being bridged with 38 DArT and SNP markers.(2)Evaluation of FHB resistance was conducted in eight field and greenhouse independent test environments using point inoculation in the greenhouses for both the 272 RILs and the 154 RILs,and also was conducted using spray inoculation in the fields for the 154 RILs.(3)A novel FHB resistance QTL,designated as QFhb.cau-7DL,was detected on the chromosome arm 7DL,being closely linked with the SSR marker gwm428(http://www.wheat.pw.usda.gov/ggpages/SSR/).It explained 20.5%—33.5%phenotypic variation.(4)QFhb.cau-7DL was significantly effective(α = 0.01)in each of the eight trials,and it was validated using three additional wheat crosses.Sumai 3(donor wheat of the FHB resistance gene Fhb1)was used in one of these crosses.(5)QFhb.cau-7DL was comparable to Fhbl in effect magnitude.The marker gwm428 could be applicable to selection for QFhb.cau-7DL if it is polymorphic in a given population.QFhb.cau-7DL provides a great potential for increasing genetic diversity of improving FHB resistance.(6)We identified a RIL from the 1652 RILs of LukexAQ based on marker-assisted selection(MAS).This RIL pyramided QFhb.cau-7DL and several other QTLs for resistance to stripe rust and leaf rust.It also has some favorable agronomic traits including plant height,flowering time,kernel weight,and protein content.In conclusion,we found a new Fusarium head blight QTL(QFhb.cau-7DL),being closely linked with the SSR marker gwm428.QFhb.cau-7DL was comparable to Fhb1 in effect magnitude.QFhb.cau-7DL was significantly effective in different genetic backgrounds and diverse environmental conditions.We have pyramided QFhb.cau-7DL with several QTLs for resistance to other diseases and better agronomic traits,providing a great potential for improving FHB resistance. |
