Evaluating stress tolerance indices for their comparative validity to access terminal heat stress and heat drought tolerance of winter wheat (Triticum aestivum L.) genotypes

Abstract

Stress tolerance indices have been used to evaluate the performance and stability of elite wheat genotypes under non-stress and stress environments. From 1978 to present, many stress tolerance indices have been proposed but only few studies have been conducted so far for the comparative validity of those indices based on stress levels. The study focuses to address the comparative validity of those stress tolerance indices at two distinct stress level under mild stress-heat stress environment (∼20–25 % yield reduction) and high stress-heat drought environment (∼45–50 % yield reduction). Statistical tool such as correlation, linear regression, coefficient of determination (R2), slope of regression line and principal component analysis were performed for the study. Correlation and principal component analysis revealed that, indices such as modified stress tolerance indices (MSTI1), mean productivity (MP), geometric mean productivity (GMP), harmonic mean productivity (HMP), relative efficiency index (REI), mean relative performance (MRP) and modified stress indices 2 (MSTI2) were found to have strong positive association with wheat yield under non stress and stress environments at both levels. The coefficient of determination (R2) and slope of regression line revealed, MP and MSTI1 are the most predictive and explanatory indices under irrigated environment. While indices such as MRP, REI, yield index (YI) are most predictive and explanatory under mild stress-heat stress environment and GMP, HMP, mean stable yield (MSY), tolerance index (TOL), yield stability index (YSI), stress tolerance index (STI), MSTI2, stress susceptibility index (SSI), percentage yield loss (PYL), relative stress index (RSI) are appropriate under high stress-heat drought environment.

Keywords

• Abiotic stress
• regression slope
• stress tolerant genotypes
• wheat improvement program
• variable stress levels