Mechanisms of Yield Stability in Sorghum 1

Mechanisms that contribute to yield stability in sorghum [ Sorghum bicolor (L.) Moench] were studied using six hybrids grown in 14 environments in Nebraska and Kansas. The objective was to relate yields and yield components to rainfall and temperature regimes during the growth stages GS 1 , GS 2 , and GS 3 . Potential sink size in each hybrid was evaluated by tiller and/or partial panicle removal in a supplementary experiment. The hybrids produced mean yields from 5410 to 9840 kg ha −1 in the diverse environments. In the regression of hybrid yield on environment mean yield, three hybrids with below average slope (b < 1.0) were designated as “stable,” and three hybrids with above average slope (b > 1.0) were designated as “unstable” or highly responsive. There was no significant correlation of yields or yield components with rainfall during the three growth stages. Length of GS 2 (initiation of panicle to anthesis) was negatively correlated with mean temperature in that period. Fewer days in GS 2 resulted in fewer seeds panicle −1 , fewer seeds m −2 , and lower yields only in unstable cultivars. Neither length of GS 2 nor length of GS 3 (anthesis to physiological maturity) was related to seed weight. Maximum 100‐seed weights over 14 environments were 2.47 to 2.79 g in stable hybrids, and 2.10 to 2.20 g in unstable hybrids. When portions of panicles were removed, all hybrids snowed genetic capacity to expand 100‐seed weight (2.87 to 3.54 g), with no apparent difference in potential between stable and unstable hybrids. Differences in 100‐seed weight between stable and unstable hybrids in low‐yield environments contributed to yield stability, adding credence to the importance of larger seed weight as one objective in a breeding program for low input agriculture.