Genotypic variation for grain and stover yield of dryland (rabi) sorghum in India: 1. Magnitude of genotype x environment interactions

Grain and stover yield are key traits for the improvement of rabi sorghum varieties and hybrids in India. Large genotype-by-environment interactions (GEI) were identified for both grain and stover yield based on 10 years' data available from the All India Coordinated Sorghum Improvement Program (AICSIP) experiments conducted from 1986/87 to 1996/97. From the estimates of the genotypic, GEI and residual components of variance for the four traits, a multi-environment testing strategy based on 15-20 locations, 2-3 years, and two replicates per trial would be required to achieve estimates of repeatability of approximately 0.70 for grain yield, 0.45 for stover yield, 0.70 for flowering time, and 0.85 for plant height. The results of these experiments indicate that over the 10-year period there was little genetic progress demonstrated for both yield traits and greater grain yields were associated with earlier flowering and greater stover yields were associated with greater plant height. Selection for greater grain and stover yield, while holding flowering time and plant height constant will be difficult. Unless the physiological trade-off between grain and stover yield and the causes of the large GEI for both traits can be better understood, conventional selection on phenotypic performance for grain and stover yield in the AICSIP trials is likely to continue to be slow. (C) 2010 Elsevier B.V. All rights reserved.