Fine Mapping Of Fhb4:A Resistance QTL To Fusarium Infection In Wheat

Fhb4,identified in the scab-resistant germplasm Wangshuibai,is a major quantitative trait locus(QTL)against Fusarium graminearum infection.In the previous study,it was mapped to a 1.7-cM interval flanked by Xhbg226 and Xgwm149 on chromosome 4BL.In this study,The Fusarium infection resistance levels of a F2 population developed from crossing the Fhb4 NIL NMAS009 with its recurrent parent PH691 was evaluated to analyze the inheritance of Fhb4.The resistant group and the susceptible group fitted the 3:1 ratio in this population,suggesting that Fhb4 was inherited like a single dominant gene in NMAS009.To fine map Fhb4,157 STS markers were developed and surveyed based on the collinearity of wheat 4BL with Brachypodium distachyon chromosome 1L or based on the genomic sequence information of the positive Wangshuibai BAC clones which identified with the markers of Fhb4 region.Seven of them were found to be polymorphic between the mapping parents.Then,18 Nanda2419-Wangshuibai RIL recombinants obtained in the Fhb4 interval were genotyped with those polymorphic markers.Combined the genotypes with phenotypes of those recombinants,Fhb4 was placed in the Xmag8990-Xmag8894 interval.At the same time,a total of 239 homozygous recombinants of the Xhbg226-Xgwm149 interval were obtained from a F2 population including 3221 individuals developed by crossing the NMAS009 with PH691.These recombinants were genotyped with 19 polymorphic markers mapped in the Xhbg226-Xgwml49 interval,and they represented twenty recombination types.Phenotypes of these recombinants showed that they had significantly different scab resistance performance and could be clearly classified into resistant or susceptible groups.Base on these results,we concluded that Fhb4 falls in a 0.14 cM interval flanked by Xmag8990 and Xmag8894.