Genetic Analysis of Quantitative Resistance Loci (QRL) of Tomato Variety Hawaii 7996 in Taiwan

The interaction between virulence or avirulence of Ralstonia solanacearum and susceptibility or resistance of different tomato lines does not seem to follow a classical gene-for-gene system (Flor, 1971). Until now, dominant single gene resistance to bacterial wilt in tomato has not been found. Instead, resistance is inherited as a polygenic character, with several loci playing a quantitative role in the ability of a plant to withstand pathogen attack. A first indication that one such locus might reside on chromosome 6 came from observations made in a breeding programme, where it was difficult to combine resistance to bacterial wilt with the resistance to nematodes conferred by the gene Mi (Acosta et al. 1964). Subsequent work has confirmed this to be true in other resistant lines of tomato (Prior et al. 1994) and by mapping with molecular markers in quite different host varieties (Aarons et al. 1993, Thoquet et al. 1993, Danesh et al. 1994, Thoquet et al. 1996a, 1996b). QRL on chromosomes 6, 7 and 10 were identified as involved with resistance in a cross between L285, resistant, (L. esculentum var. cerasiforme) and CLN286, susceptible (Danesh et al. 1994).