Genotype-by-environment interaction in grain sorghum. II. effects of temperature and photoperiod on ontogeny

Abstract

In sorghum [Sorghum bicolor (L.) Moench], genotype-by-environment interaction effects on ontogeny can be caused by differing responses to temperature and photoperiod. We conducted glasshouse and field experiments to develop predictive models of ontogeny for old and new sorghum genotypes. New genotypes are considered better adapted to more tropical environments. In the glasshouse studies, 10 genotypes were grown at two temperatures (20 and 25 °C) and six planting dates (photoperiod 10 to 15 h). At photoperiods greater than about 13 h, duration of emergence to floral initiation (GS1) was lengthened about 5 d for all genotypes at both temperatures. Genotypes differed in duration of GS1 by up to 10 d at both temperatures. Hybrids responded like their earlier parent, indicating earliness to show some form of dominance. Photoperiod had little or no effect on duration of floral initiation to anthesis (GS2), and hybrids differed by about 3 d. Field experiments with 12 hybrids were conducted at sites in Australia and USA covering latitudes from 16 to 39 °C. Durations of GS1 and GS2 ranged from 17 to 128 d and 24 to 85 d, respectively. Daily rate of development was modeled using functions of air temperature and photoperiod. Development rate of all hybrids exhibited a curvilinear response to temperature in both phases. Old and new hybrids differed in their temperature responses in GS1 but were similar in GS2. New hybrids had slower rates of development at all temperatures, but the difference was greater at higher temperatures (>25 °C). All hybrids had similar short-day photoperiodic response in GS1, with a critical photoperiod 13.2 h. The models were tested on a separate data set covering a similar broad range of environments and performed well.