Latitudinal Adaptation of Flowering Response to Photoperiod and Temperature in the World Collection of Sorghum Landraces

Knowledge of photoperiod and temperature sensitivity of landraces is required to understand their latitudinal pattern of adaptation and to identify insensitive germplasm for crop improvement. Photoperiod and temperature sensitivity of 20,710 sorghum [Sorghum bicolor (L.) Moench] landraces was assessed under long-day rainy and short-day post-rainy seasons. The results revealed 1697 landraces to be photoperiod and temperature insensitive (PTINS), 18,766 to be photoperiod sensitive and temperature insensitive (PSTINS), and 247 to be photoperiod and temperature sensitive (PTS). Lower latitudes (0.00-25.00 degrees) were important regions for sorghum landraces. The mean number of days to 50% flowering (DFL) was equal in both the seasons for PTINS landraces. The mean DFL was high (98 d) for PSTINS and low (63 d) for PTS in the rainy season in the entire set of landraces. The DFL in all three groups-PTINS, PSTINS, and PTS-decreased with increase in latitude. The mean cumulative growing degree days were higher for PTINS (1153 degrees C d) and PSTINS (1587 degrees C d) in the rainy season than in the post-rainy season (866 degrees C d in PTINS, 905 degrees C d in PSTINS) but were similar in both the seasons for PTS (similar to 1040 degrees C d). Insensitive landraces were found in higher proportions at 0.00 to 25.00 degrees N and 15.00 to 35.00 degrees S than at other latitudes. Evaluation of these insensitive sources for stress tolerance, and for agronomic and seed quality traits is suggested to identify parents to develop high-yielding, nutrient-dense, and climate-resilient sorghum cultivars.