GENETIC-MAPPING OF A WIDE SPECTRUM NEMATODE RESISTANCE GENE (HERO) AGAINST GLOBODERA-ROSTOCHIENSIS IN TOMATO

The Hero gene confers resistance to a wide spectrum of pathotypes of t he potato cyst nematode Globodera rostochiensis, This gene has been in trogressed from the wild tomato species Lycopersicon pimpinellifolium into the cultivated tomato, We have used RFLP and RAPD analysis for th e targeted search of the L. pimpinellifolium segment, The resistant li ne LA 1792 contains a single introgressed segment on chromosome 4, whi ch is characterized by three RFLP markers from the high-density RFLP m ap of tomato. The map position of the Hero gene is not equivalent to a ny of the previously mapped G. rostochiensis resistance genes in potat o. For the fine mapping of the Hero gene in large populations, four ad ditional markers were identified in the introgressed region, After ana lyzing more than 800 gametes for recombination, we found that one mark er is only 0.4 cM away from the Hero gene, YAC clones isolated from a region near the Hero gene indicate that in this area of the genome, th e kb/cM ratio is relatively low (<450 kb/cM) and chromosome walking sh ould be feasible in order to isolate this gene.