Field variation in a tetraploid progeny derived by selfing a Solanum commersonii (+) S. Tuberosum somatic hybrid: a multivariate analysis

The practical utilization of interspecific somatic hybridization in plant breeding depends on intergenomic interactions and their effects on agronomically important traits. In order to characterize the variation that could be recovered by selfing a tetraploid somatic hybrid between a dihaploid clone of Solanum tuberosum (tbr) and the sexually incongruent diploid wild species S. commersonii (cmm), an F2 progeny was analyzed in the field for a number of vegetative, reproductive and productive traits. Variation for such traits was summarized by principal component analysis, and genotypes were clustered on the basis of the most important derived variables. Ten main principal components (PC) explaining 98.9% of total variance for 12 epigeous traits were extracted and used in cluster analysis. They were mainly correlated to leaflet number, size, and shape, degree of pigmentation, pubescence, and flowering, flower shape, and no. of primary stems. Genotypes were clustered in two groups, one including the tbr clone, the somatic hybrid, and the vast majority of selfed progenies, another the cmm clone and the remaining progenies. The analysis of principal components carried out with the four hypogeous traits identified three main derived variables correlated to tuber production, to the mean weight of the tuber, and to stolon length. Genotypes were grouped again in two clusters: the first included the two parental genotypes, the somatic hybrid and about two thirds of the F2 plants, the second the remaining F2 progenies. A large variability and the reassortment of parental traits were seen in the F2 population, suggesting the possibility to recover useful characteristics from the wild species into the genetic background of the cultivated one