Genetic characterization of resistance to wilt disease caused by Fusarium oxysporum f. sp. ricini in castor (Ricinus communis L.)

Abstract

Castor is an industrially important oilseed crop. Vascular wilt caused by the soil borne fungus Fusarium oxysporum f. sp. ricini is a serious disease of castor. Use of resistant cultivars is the only viable option for management of wilt disease problem in castor production. Excellent sources of resistance to wilt have been found in castor germplasm. In this study, a set of four castor inbred lines (48–1, CI-1, AP42 and AP48) was characterized for inheritance of resistance to wilt by studying segregating populations generated by crossing these inbred lines with eight different susceptible genotypes. An artificial screening method (sick pot) with a new scoring system (days to wilt) was used for evaluation of plant progenies for reaction to the pathogen infection. The reaction of F1s indicated that the nature of resistance in 48–1, CI-1 and AP48 is recessive whereas it was dominant in AP42. Inheritance results from eight F2 populations showed that resistance to wilt is conferred by a single locus in one population and at least two loci, which interact in complementary way, in other seven populations. Different modes of inheritance were also observed when the same resistant source was crossed with different susceptible parents, indicating the possible role of genetic backgrounds in determining resistance. Overall, the results suggested that Mendelian resistance to wilt is predominant in the castor genotypes, which can be exploited for breeding cultivars. Particularly, AP42 with dominant nature of resistance will be of great interest to hybrid breeding.