| Genetic studies of time to flowering are complicated by genotype x environment interaction. For short day plants, photoperiod genes delay days to flowering (DTF) as daylength increases, and synergistically so if temperature also increases. Rising temperature accelerates vegetative development, simultaneously tending to cause earlier DTF. The goal was to elucidate genetic-environmental controls over DTF of tropical Phaseolus vulgaris, and to separate DTF differences caused by photoperiod vs. non-photoperiod genes.; Heterozygous genotypes may respond differently than homozygotes, so DTF of homozygous F8 progenies from all six possible crosses among four Guatemalan indeterminate cultivars were compared in Guatemalan fields at (1) high and (2) low elevation, plus (3) summer- and (4) winter-time greenhouses in New York. Respective environments were 19{dollar}spcirc{dollar}C/13.5 h, 29{dollar}spcirc{dollar}/13.5 h, 25.5{dollar}spcirc{dollar}/16 h and 20{dollar}spcirc{dollar}/12 h.; The environments caused a larger part of the GxE interaction than genotypes. Frequency distribution of DTF, and a combined ANOVA/PCA analysis, agreed that DTF differences were largely controlled by only one or two photoperiod genes plus one or two non-photoperiod genes. Crosses to an early and a late New York cultivar indicated control by the same photoperiod gene that causes early and late DTF, respectively, of tropical cultivars Rabia de Gato and San Martin.; A non-photoperiod gene caused later DTF of Ju-80 than Rabia. A non-photoperiod gene also caused later DTF of Quetzal than San Martin, in non-photoperiod delaying environments (19{dollar}spcirc{dollar}/13.5 h and 12 h/20{dollar}spcirc{dollar}). The early non-photoperiod allele caused earlier DTF for Quetzal than San Martin in the photoperiod delaying environments (16 h/25.5{dollar}spcirc{dollar} and 29{dollar}spcirc{dollar}/13.5 h). The insensitive photoperiod gene of Rabia plus the early allele of its non-photoperiod gene caused Rabia and segregants like it to flower earlier than Quetzal.; Control of flowering by a few genes in contrast to control over biomass by virtually all genes explains why yield improvements arise through earlier maturity and higher harvest index without concomitant gain in biomass. |
