Mapping of watermelon(Citrullus lanatus)Fusarium wilt-resistance gene Fon-1 based on BSA-Sequencing technology
Watermelon Fusarium wilt,a worldwide soil borne fungal disease,is caused by Fusarium oxysporum f.sp.niveum and can dramatically reduce the watermelon yield.In this study,the resistant watermelon germplasm"V13-9-3"and the susceptible germplasm"W16-1"were used as parents to construct F1 and F2 populations.The F1 population showed resistance to Fusarium wilt,while the F2 population had a 3∶1 segregation ratio of resistance and susceptibility.It demonstrated that the resistance against F.oxysporum f.sp.niveum race 1 was controlled by a single dominant gene.Fon-1 was found to be localized to 2.20 Mb and 2.32 Mb on chromosome 1 by single nucleotide polymorphism(SNP)and insertion deletion(InDel)index methods.After accounting for overlapping regions,the target region narrowed down to 2.20 Mb.Reverse-transcription quantitative polymerase chain reaction analysis further confirmed the relative expression of genes,whereby the expression of 7 genes in"V13-9-3"was significantly higher than that in"W16-1"at 5 dpi or 10 dpi.This study proposed a novel combinatorial strategy by combining the SNP and InDel index analyses.This approach allowed rapid mapping of the genes responsible for specific traits and provides a robust base for cloning the Fon-1 gene.