Selection of Potato Haploid Parents for Use in Crosses with 2x (2 Endosperm Balance Number) Wild Species
Haploids (2n = 2x = 24) of Solanum tuberosum L. may be used to tap the genetic diversity present in the related wild species by producing haploid ✕ species hybrids (2n = 2x = 24). The purpose of this study was to identify elite haploids for use in crosses to wild species based on percentage tuberization of their progeny, number of fruit per pollination and seeds per fruit, and their genotype for parallel spindles (ps), a meiotic mutant causing 2n pollen formation. A group of 73 haploids were selected for good flowering and cultivartype haulms. To determine their respective ps-locus genotypes, the haploids were testcrossed as females to four plants of S. chacoense BITT. (psps). All 21 of the haploids that were successfully crossed to S. chacoense BITT. produced families with a high percent tuberization. Only one of the 39 families tested had percentage tuberization that was significantly lower than the average family performance. Eighteen of the 21 haploids were Psps, one was psps, and two gave families that deviated significantly (P < 0.05) from a 1:1 ratio. Six haploids had average seed set of greater than 40 seeds per fruit in all combinations for which twenty or more pollinations were made. Selection of elite haploids should increase the potential of the 4x ✕ 2x breeding scheme by: (i) increasing the amount species germplasm that may be selected among, (ii) making production of haploid ✕ wild species hybrids morefficient, and (iii) increasing the amount of the germplasm pool that can be transferred to the tetraploid level using 2n pollen.
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