MOLECULAR MARKERS LOCATE GENES FOR RESISTANCE TO THE COLORADO POTATO BEETLE, LEPTINOTARSA-DECEMLINEATA, IN HYBRID SOLANUM-TUBEROSUM X SOLANUM-BERTHAULTII POTATO PROGENIES

The wild Bolivian potato, Solanum berthaultii Hawkes, has been used as a source of resistance to the Colorado potato beetle (CPB), Leptinota rsa decemlineata Say, one of the most significant pests of potato. In this study, two reciprocal backcross S. tuberosum x S. berthaultii pot ato progenies, BCB and BCT, were mapped with RFLP markers and screened for resistance to CPB consumption, oviposition and defoliation. The g enotypic and phenotypic data were combined and analysed to locate quan titative trait loci (QTLs) for resistance to CPB. Three QTLs on three chromosomes in BCB, and two QTLs on two chromosomes in BCT influenced resistance. The QTLs were generally additive but one instance of epist asis was noted. Each QTL accounted for 4-12% of the phenotypic variati on observed in resistance. In the more resistant BCB population, a thr ee QTL model explained ca. 20% of the variation in CPB oviposition. Wh en alleles at the three QTLs were homozygous S. berthaultii, ovipositi on was reduced ca. 60% compared to the heterozygotes. The QTLs for res istance to CPB were compared to those previously identified for the ty pe A and B glandular trichomes, which have been implicated in resistan ce in the same progenies. Generally, the QTLs for resistance to CPB co incided with loci associated with the glandular trichomes confirming t he importance of the glandular trichomes in mediating resistance. Howe ver, a relatively strong and consistent QTL for insect resistance in b oth BCB and BCT on chromosome 1 was observed that was not associated w ith any trichome traits, suggesting the trichomes may not account for all of the resistance observed in these progenies.