TIME TO FLOWERING OF MUNG BEAN (VIGNA-RADIATA) GENOTYPES AND THEIR HYBRIDS IN RESPONSE TO PHOTOPERIOD AND TEMPERATURE

Time to flowering of mung bean crops varies appreciably depending on the genotype, and the daylengths and temperatures prevailing during the period after sowing. Relatively little is known about the precise nature and inheritance of flowering responses to photoperiod and temperature. The combined effects of variations in these two factors on time to flowering were therefore evaluated in controlled environment studies on six genotypes and four F1 hybrids. The responses were examined for conformity with hypothesized linear models from which inferences might be made of the genetic control of flowering. The analyses suggest that all the genotypes and F1s tested were quantitative short day plants, with the possible exception of one line which may be day neutral. The analyses further suggest that time to flowering was influenced by four genotype-specific attributes: minimum time to flowering, critical photoperiod (Pc), responsiveness to photoperiod longer than Pc, and responsiveness to temperature. Among the genotypes tested, different values were observed for each attribute. In most instances, the values for the F1s were closer to one or other parent, indicating dominance rather than additive genetic effects. We conclude that, with several levels each, the four attributes provide the potential for a diversity of flowering response types within mung bean. Further, it should prove possible to manipulate the mung bean germplasm to obtain novel combinations of attributes, and thus to breed genotypes adapted to photothermal regimes not previously considered suitable for the crop. © 1990, Cambridge University Press. All rights reserved.