The Use of Stress Tolerance Indices for the Selection of Tolerant Inbred Lines and their Correspondent Hybrids under Normal and Water-stress Conditions

Abstract

Drought is a major cause of yield loss for many important crops including maize. Therefore, the development and release of drought tolerant varieties that will yield well under a broad range of environmental conditions is an important breeding goal. Several stress indices have been developed, aiming to assist identification and selection of stable, high-yielding, drought tolerant genotypes. A novel equation (B value) that predicts crop yield potential of a genotype at normal farming densities has been also suggested1. The estimation of B value relies on plant yield potential at ultra-low densities and on the coefficient of variation (CV) of individual plants. The present study aimed to investigate the tolerance of inbred lines and their correspondent hybrids using stress tolerant indices and compare them with the B values. Therefore, we used thirty one maize inbred lines and their correspondent hybrids under ultra-spaced and highly dense and under two different water regimes (normal and drought conditions) in three different areas in Greece during the 2012 and 2013 growing season, respectively. The inbred lines and the hybrids were evaluated using grain yield and for each genotype, B value and nine other stress indices based on their yield under normal and water stress conditions were calculated, including stress susceptibility index (SSI), mean relative performance (MRP), stress tolerance (TOL), mean productivity2 (MP), relative efficiency index (REI), stress tolerant index3 (STI), geometric mean of productivity (GMP), yield index (YI) and harmonic mean4 (HM). It was found a strong and positive correlation (P<0.001) of B values with all indices, except SSI, for all experimental locations. These results suggest that B value matches the ability of the other stress indices to identify drought sensitive and tolerant genotypes and is an effective selection criterion for high yielding genotypes with stable performance under variable environmental conditions.