Morpho-Physiological Characterization of Cold-and Pre-flowering Drought Tolerance in Grain Sorghum (Sorghum bicolor L. Moench) Inbreds

Aim: The relationships between early-season cold temperature germination and pre-flowering drought stress in eight grain sorghum inbreds were assessed using morpho-physiological traits.
Study Design: Field was laid out in a randomized complete block design.
Place and Duration: The experiment was conducted at Vernon, Texas (34º9'4"N 99°17'26"W) during the month of April to August, 2013.
Methodology: Lines were sown in the field in early April to determine early-season cold temperature germination. At the pre-booting stage, lines were subjected to limited and no irrigation treatments, to establish a correlation between cold temperature germination and pre-flowering drought stress tolerance. Pre-flowering drought tolerance was assessed at five defined phenological phases of the reproductive growth stage, using morpho-physiological traits.
Results: Final germination percent (FGP) differed among lines (range 30-80%) and was positively correlated with leaf area index, plant height (HGT), and harvest index (HI). These three traits and single plant biomass (SPB) also positively correlated with grain yield (SPY) under pre-flowering drought. Most significant correlations among measured traits were observed at the heading to flowering phase. HI explained 75 and 91% variability in SPY for the limited and no irrigation treatments respectively. Other predictors for SPY were; FGP, HGT and SPB under limited irrigation, and FGP and HGT under no irrigation.
Conclusion: The ability to cease growth, maintain LAI, and retain high CLC and high HI, will be important selection traits to develop sorghum cultivars for temperate and highland regions, with possibility of pre-flowering drought occurrence.