EVALUATION OF RESISTANCE TO VERTICILLIUM WILT IN DIPLOID, WILD POTATO INTERSPECIFIC HYBRIDS

Verticillium wilt (V. albo-atrum Reinke and Berthold or V. dahliae Kleb) threatens potato (Solanum tuberosum L.) production in most growing areas of the world. Genetic resistance offers the most cost-effective and environmentally sound control measure. However, there is a dearth of genetic and breeding information on resistance to verticillium wilt in potato, because of obscure parentage of some standard cultivars and the complex segregation at the tetraploid level. The wide range of genetic variability in wild relatives of potatoes can be potentially useful as a source of disease resistance, such as verticillium wilt resistance. Six diploid, wild, interspecific Solanum hybrids involving resistant x resistant and susceptible x resistant crosses, were assayed for verticillium wilt resistance under greenhouse conditions to evaluate their potential as sources of verticillium wilt resistance. The cross between S. gourlayi Oka. and S. chacoense Bitt. and its reciprocal had the most resistant progenies based on mean colony counts. No simple mode of inheritance can be proposed based on the observed segregation ratios. However, the continuous distributions observed on verticillium wilt disease response among hybrid families indicate that inheritance of resistance may be polygenic and complex. In addition, skewness of colony count distributions toward the resistance parents were characteristic of all resistant x susceptible crosses suggesting that resistance may be dominant. By contrast, the susceptible x susceptible cross showed a more normal distribution. Overall, the cross between S. gourlayi and S. chacoense showed the most potential as a source of verticillium wilt resistance.