Direct estimation of the effects of meiotic recombination on potato traitsvia analysis of 4x-2x progenies from synaptic mutants with 2n-pollen formation by FDR without crossing-over

Diploid potato clones with 2n-pollen formation by first-division restitutio n without crossing-over (FDR-NCO) are ideal testers to estimate the breedin g value of elite 4x cultivars by virtue of transmitting their genotypes pra ctically intact to their progenies. This characteristic facilitates genetic analysis, since meiotic recombination would take place only in the 4x pare nt and not in the diploid parent. We evaluated (under shortday conditions) families from complete factorial crosses between four 4x cultivars and five 2x(FDR-NCO) clones. Families were compared with two standard 4x cultivars ('Bintje' and 'Delta') for total tuber yield (TTY), commercial yield (CY), haulm maturity (HM), plant vigor (PV), plant-top uniformity (PU), eye depth (ED), number of tubers per hill (NTH), and the CY/TTY index (CTI). For TTY , the contrasts family group (310 g/ hill) vs 'Delta' (430 g/hill) and the family group vs 'Bintje' (210 g/hill) were significant. Only 25% of the fam ilies were different from 'Delta' and 20% of them outyielded 'Bintje'. For CY, differences were observed between families (240 g/hill) vs 'Delta' (340 g/hill) and families vs 'Bintje' (150 g/hill). The two best families had 5 3% CY over 'Bintje'. Surprisingly, only one family had a higher NTH than 'B intje'. No differences were observed for HM. Seventy five and 30% of the fa milies had an ED similar to 'Delta' (ED = 2) and 'Bintje' (ED = 1), respect ively. A multivariate analysis indicated that 63% of the data variability c ould be explained by two factors. TTY, CY, and PV had high loading on the f irst factor, whereas ED, PU and HM had high loading on the second factor; C n and NTH had equal sizes on both factors. High TTY and PV were associated with high NTH and CTI. Deep eye, PU, and late maturity were associated with high NTH and reduced CTI. The distributions of factor scores of the entrie s indicated that some 2x parents had strong influences (irrespective of the direction of their effects) on the crosses. Six crosses due to two 2x male s were in the 'Bintje' quarter with negative scores for both factors (imply ing low TTY, poor vigor, and low NTH). Also three crosses due to another 2x clone were distributed in the quarter of positive factor 1 and negative fa ctor 2. These crosses plus another one were in the same quarter of 'Delta' (implying high yields, low ED, low PU, and early maturity). The FDR-NCO clo nes provide a homogeneous sample of heterozygous 2n-gametes allowing the un ique opportunity to estimate the relative contribution of the random meioti c products (from the 4x parents) and the 'somatic' 2x genome for the phenot ypic expression of quantitative traits. The interesting result was that mea surable effects (favorable or not) on the data variability were mainly dete rmined by the genomic contribution of the haploid-species hybrids. Three ou t of five 2x-male parents showed rather strong effects on progenies. No suc h effects were observed on the four 4x-female parents.