High levels of heritable resistance to Potato leafroll virus (PLRV) in Solanum tuberosum subsp, andigena

Phenotypic characterization and genetic studies were performed to provide fundamental information for the exploitation of the native cultivated potato species Solarium tuberosum subsp, andigena (Juz. and Bukasov.) Hawkes (andigena) as a source of resistance to Potato leafroll virus (PLRV). Analysis of a diallel mating design among andigena cultivars revealed the importance of additive gene effects. Phenotypic assessment of components of PLRV resistance showed that andigena cultivars with high levels of resistance to infection were also resistant to the accumulation of PLRV and able to restrict translocation of the virus to their tubers. Three andigena cultivars (LOP-868, HUA-332, and OCH-7643) identified with these features also showed high positive general combining ability (GCA) for PLRV resistance. High frequencies of individuals in progenies from crosses between these cultivars and both resistant and susceptible commercial varieties were also resistant. No interaction in the expression of resistance from andigena in tuberosum backgrounds was observed indicating that breeding advances for this trait should proceed well using this new resistance source. Our results support the previous hypothesis that multiple components of resistance in a single genotype could be the result of a common mechanism controlled by several genes. The remarkably high frequency (>70%) of uninfected individuals in all progenies derived from the highly resistant andigena cultivar LOP-868 and the occurrence of highly resistant clones selected from this parent suggest the presence of an allele with large effects.