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

Fusarium oxysporum Schlechtend,: Fr, f. sp, ciceris (Padwick) causes a vasc ular wilt of chickpea (Cicer arietinum L.) and significantly limits product ion worldwide. The objectives of this study were (i) to determine the inher itance 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 relationsh ips between these two genes and other known wilt resistance genes in chickp ea. Seedlings of 131 F-6-derived recombinant inbred lines (RILs) were teste d for reaction to races 0 and 5, A 1 resistant:1 susceptible segregation ra tio 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 separa ted by 11.2 centiMorgans (cM), The gene for resistance to race 0 was not li nked 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 f rom 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 l inked to the genes for resistance to races 1 and 4 support the hypothesis t hat wilt resistance genes are flustered on the same chromosome. Since the g ene conferring resistance to race 0 is found in a different region of the g enome, other genomic regions may be responsible for resistance to wilt path ogens. 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. Identifi cation and further evaluation of disease resistance gene clusters would imp rove our understanding of wilt resistance in chickpea and facilitate the tr ansfer of resistance genes to new cultivars.