Comparison of haploid Tuberosum-Solanum chacoense versus Solanum phureja-haploid Tuberosum hybrids as staminate parents of 4x-2x progenies evaluated under distinct crop management systems

The relative value of haploid Tuberosum-Solanum chacoense (TCH) vs. Solanum phureja-haploid Tuberosum (PTH) hybrids as male parents in 4x-2x crosses w as estimated under two distinct crop management systems. The first experime nt (E#1) was carried out with supplementary irrigation (three times a week) at Hancock-Wisconsin (WI) with 27 families derived from a sub-set of cross es involving 11 tetraploid (4x) cultivars and 10 diploid (2x) clones (3 TCH ; 6 PTH; and one TCH-PTH hybrid clone). A second experiment (E#2) was condu cted at Rhinelander-WI with the same group of families but it was only rain fed with no supplementary irrigation being provided during the entire cours e of the assay. For comparison, a complete set of 4x and 2x clones (used as parents) was also planted in each location. Three traits were evaluated in both locations: total tuber yield (TTY), haulm maturity (HM), and plant vi gor (PV). Altogether, 18 out of 27 and 10 out of 27 families outyielded the corresponding 4x parents at E#1 and E#2, respectively. Significant differe nces among all 4x-2x families and among families of the TCH group were obse rved for TTY at both locations. No difference was found for TTY among famil ies of PTH and [TCH-PTH] groups at each location. A total of 75% and 50% of the TCH families outyielded their 4x parents at E#1 and E#2, respectively. The percentage of families from the PTH group that outyielded their 4x par ents at E#1 and E#2 was 83.3% and 25%, respectively. The TCH group had on a verage lower HM scores than PTH (at both locations) indicating some segrega tion for earliness. However, the HM values of the 4x-2x families were, in g eneral, higher than those observed for the 4x parents. For PV, the PTH grou p mean was significantly higher than TCH group only in E#1. The PV values o f the 4x-2x families were higher than the 4x-parent group at both locations . Our results indicated that TCH hybrids might be as good parents as PTH to increase the TTY of 4x-2x progenies. In addition, the TCH families display ed a slight higher level of performance under more stressful growing condit ions than PTH hybrids as indicated by the assay at Rhinelander. Therefore, selection of genetic materials with potential broad range of adaptation see ms to be feasible with both hybrids via the 4x-2x breeding scheme.