Fine Mapping Fhb2,a Resistance Gene To Fusarium Head Blight In Wangshuibai

Fusarium head blight(FHB)is one of the most important fungal diseases in wheat production,and is most widespread in regions with a warm and humid climate.In the previous study of our laboratory,a major QTL Qfhs.nau-6B for type ? resistance was detected using Nanda 2419 x Wangshuibai RIL population and the chromosomal location of this QTL is almost same as from Sumai 3.With the help of markers-assisted selection,Fhb2 near-isogenic line(NIL)was developed by introgressing Qfhs.nau-6B from resistant landrace Wangshuibai to recurrent parent PH691.Compared with the recurrent parent,the resistance of Fhb2 NIL was significantly improved.To fine map Fhb2 from Wangshuibai,a secondary F2 population of 988 plants was developed by crossing the NIL with its recurrent parent PH691.In addition,a residual heterozygous line(RHL)NW068 that showed heterozygous in Fhb2 region but nearly homologous in other regions was screened from Nanda 2419 x Wangshuibai RIL population,and a 'F2'population of 594 plants from the selfed progenies of NW068 was developed.Out of 108 new markers developed in this study,61 showed polymorphism in one or two populations.These markers were designed based on the collinearity of Fhb2 region between Brachypodium and wheat,the genetic linkage map of Aegilops tauschii and synthetic wheat W7984,and the 90K SNP chip data of wheat.Finally,a high-resolution map of Fhb2 interval was constructed by genotyping the two F2 populations with all polymorphic markers mapped in the target region.In this study,9 homozygous recombinants covered Xwmc398?Xgwm644 region were identified from the Nanda2419 x Wangshuibai RIL population with 552 plants.These recombinants did not carry another FHB resistance gene Fhbl.In addition,116 heterozygous recombinants in Xwmc398?Xgwm644 region were identified from the Fhb2 NIL-derived secondary F2 population comprised of 1132 plants,and 207 homozygous recombinants were further obtained through screening the selfed progenies of the identified plants.Resistance evaluation of these homozygous recombinants was made in 2-4 environments in 2014-2016.These recombinants showed significantly different disease resistance,and could be classified into resistant and susceptible groups clearly.According to the genotypic and phenotypic data of all the recombinants,the Fhb2 was placed in a 0.7 cM interval flanked by Xwgrb682 and Xwgrb737.These results established the basis for map-based cloning of Fhb2 and efficient utilization in FHB resistance breeding.