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

Abstract

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°) 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°C d) and PSTINS (1587°C d) in the rainy season than in the post‐rainy season (866°C d in PTINS, 905°C d in PSTINS) but were similar in both the seasons for PTS (∼1040°C d). Insensitive landraces were found in higher proportions at 0.00 to 25.00° N and 15.00 to 35.00° 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.

Variation for Photoperiod and Temperature Sensitivity in the Global Mini Core Collection of Sorghum

“…In the entire collection of sorghum (Upadhyaya et al, 2018), and also in the mini core collection in this study, the mean and range of DGL and CGDD requirements for flowering decreased with the increase in latitude in both the hemisphere. The magnitude of the relationship between DFL and latitude differed between groups (PTINS, PSTINS, and PTS groups and two subgroups of the PSTINS separately) indicating that it varied with the constitution of the group.…”

“…This group was therefore further categorized into three sub-groups. The accessions that took fewer days and fewer CGDD for flowering in the rainy season than in the post-rainy season were grouped into subgroup 1 following ( Upadhyaya et al, 2018 ). None of the mini core accessions fell into this subgroup.…”

“…The magnitude of the relationship between DFL and latitude differed between groups (PTINS, PSTINS, and PTS groups and two subgroups of the PSTINS separately) indicating that it varied with the constitution of the group. The differences in the relationship between northern and southern hemispheres in the mini core could be attributed to the differences in hemispheres in terms of the proportion of land and water and associated climatic parameters ( Upadhyaya et al, 2018 ). The northern hemisphere has four times land portion (80%) than the ocean (20%), and land surfaces conduct the heat poorly, therefore, most of the absorbed radiation heats the land surface and associated vegetation in the northern hemisphere.…”