Inheritance and linkage of two genes that confer resistance to Fusarium wilt in chickpea

Fusarium oxysporum Schlechtend,: Fr, f. sp, ciceris (Padwick) causes a vascular wilt of chickpea (Cicer arietinum L.) and significantly limits production worldwide. The objectives of this study were (i) to determine the inheritance of resistance to races 0 and 5 of fusarium wilt and the genetic map positions of the resistance genes and (ii) to assess the linkage relationships between these two genes and other known wilt resistance genes in chickpea. Seedlings of 131 F(6)-derived recombinant inbred lines (RILs) were tested for reaction to races 0 and 5, A 1 resistant:1 susceptible segregation ratio was observed for both races, indicating that resistance to each race is controlled by a single gene. Linkage analysis indicated that the genes for resistance to races 4 and 5 were in the same linkage group and were separated by 11.2 centiMorgans (cM), The gene for resistance to race 0 was not linked to the race 4 and 5 resistance genes. In addition, an allele-specific associated primer (ASAP) product (CS-27R/CS-27F), developed from the CS-27 primer, was located between the two resistance genes and was 7.2 and 4 cM from the genes for resistance to races 4 and 5, respectively, Map positions of these two race-specific resistance genes and the marker reported to be linked to the genes for resistance to races 1 and 4 support the hypothesis that wilt resistance genes are flustered on the same chromosome. Since the gene conferring resistance to race 0 is found in a different region of the genome, other genomic regions may be responsible for resistance to wilt pathogens. The gene symbols foc-0, foc-4, and foc-5 are proposed for the genes for resistance to rates 0, 4, and 5 of the pathogen, respectively. Identification and further evaluation of disease resistance gene clusters would improve our understanding of wilt resistance in chickpea and facilitate the transfer of resistance genes to new cultivars.