Identification of Molecular Markers Linked to the Verticillium wilt Resistance Gene Homologue in Potato (Solanum tuberosum L.)

Verticillium wilt is a vascular disease predominantly caused by the soil-borne fungi Verticillium dahliae and Verticillium albo-atrum. Most of the commercial potato cultivars grown in the USA are susceptible to Verticillium, resulting in significant crop losses. Development of new cultivars with resistance gene(s) against the pathogen can be assisted with molecular marker technology that allows identification and tracking of resistance genes. In tomato, resistance to Verticillium dahliae is conferred by two closely linked genes (Ve1, Ve2) that were mapped to chromosome 9. We have employed primers that amplify the leucine-rich repeat (LRR) domain from tomato Ve1 and Ve2 genes. Verticillium resistance gene homologues have been detected in resistant cv. ‘Reddale’ when using these primers and genomic DNA as a template. Deduced amino acid sequence shared high identity with Ve1 (87%-90%) and Ve2 (88%-91%) tomato resistance genes. The StVe1 a potato homologue to the Ve1 gene mapped to the genomic position corresponding to the tomato Ve1 gene. Microsatellite markers linked to the StVe1 have been used to screen 48 (mostly) tetraploid genotypes of various pedigrees. One of the tested markers showed high linkage with Verticillium resistance (p < 0.001). The correlation is mainly based on the complete absence of resistant genotypes that lack the STM1051 marker (~190bp size band). The STM1051 marker has a potential use in the detection of genotypes that are susceptible to Verticillium. Our results suggest that there may be a direct evolutionary relationship between Verticillium resistance genes in potato and tomato. INTRODUCTION Verticillium wilt (also called potato early dying disease) is predominantly caused by two soil-borne fungi, Verticillium dahliae (Kleb) and V. albo-atrum (Reinke and Berthold). This common vascular disease is a limiting factor for production of all commonly grown cultivars of potato, especially in dry climates (Susnoschi et al., 1976). Disease symptoms in potato include wilting and leaf chlorosis and necrosis, while the tubers of infected plants develop necrosis in the vascular tissue, that reduces tuber quality, in particular for the manufacture of french fries and chips (Powelson and Rowe, 1993). Moreover, in heavily infested soils, the yield of susceptible clones can be reduced more than 50% (Goth and Haynes, 2000). Verticillium wilt has received the most attention by breeding programs in areas where it occurs, because of the drastic yield reductions it causes in very susceptible cultivars and because it is difficult to control by chemical means (Pavek and Corsini, 1994). Planting resistant cultivars is ultimately the most practical method for management of potato early dying disease. Potato cultivars that are currently available differ considerably in their susceptibility to Verticillium. Those with the greatest resistance, however, are presently not widely used in commercial production (Powelson et al., 1993). Verticillium wilt resistance in potato has been shown to be heritable (Corsini et al., 1990) and stable over space and time (Corsini et al., 1985). The genetic mechanism of resistance toward Verticillium in potato has been shown to be of a polygenic nature Proc. XXVI IHC – Potatoes Healthy Food for Humanity