Efficiency of yield-based tolerance indices to identify suitable genotypes for stress and non-stress environments

Nikolay Tsenov and Margarita Nankova
Agricultural Academy, Dobrudja Agricultural Institute, General Toshevo, Depertment of Agronomy and Animal Husbandry, 9525 General Toshevo, Bulgaria

Abstract

Tsenov, N. & Nankova, M. (2026). Efficiency of yield-based tolerance indices to identify suitable genotypes for stress and non-stress environments. Bulg. J. Agric. Sci., 32(2), 418–427

The present study investigated the performance of popular crop breeding indices for assessing abiotic stress tolerance in selected wheat cultivars. The working hypothesis was to identify those indices whose application allows the identification of varieties possessing tolerance to drought in combination with the highest possible yield productivity. Three datasets were analyzed, formed from agroecological field trials in which different reported groups of cultivars, locations, and seasons were included. From the grain yield values of each genotype in contrasting environmental conditions, breeding indices were calculated to assess tolerance to abiotic stress. Their effectiveness and applicability for cultivar assessment were evaluated by direct comparison using correlational, principal component, and cluster analyses. Rank correlations between indices and cultivar grain yield varied across the databases. Correlations of indices with yield under favorable conditions showed strong variation among the individual datasets. Only a few indices (GMP, STI, MRP) maintained reliably high and valid correlations with grain yield. A preponderance of the calculated indices (excluding ATI and SSPI) had high positive correlations with yield under stress, maintaining these high levels across all three datasets. The high performance of the GMP, STI, and MSTI indices was confirmed by a specific assessment of cultivar differences in 40 ABC. Almost all of the investigated indices (except TOL, ARI, and SSPI) were significantly more effective and applicable for assessing stress tolerance than for the conditions under which the maximum possible grain yield was formed. Determining the most valuable cultivars exhibiting high yield under both types of conditions was possible by applying the GMP, STI, MSTI, or SNPI indices.

Keywords: breeding indices; stress tolerance; stress and non-stress environments; grain yield; common wheat
Abbreviations: GY – grain yield; (TOL) – Tolerance Index; (MP) – Mean Productivity; (GMP)-Geometric Mean Productivity; (HM) – Harmonic Mean; (YSI)-Yield Stability Index; (SSI) – Stress Susceptibility Index; (STI) – Stress Tolerance Index; (YI) – Yield Index; (RSI) – Relative Stress Index; (MRP) – Mean relative performance; (ATI) – Abiotic Tolerance Index; (SSPI) – Stress Susceptibility Percentage Index; (MSTI) – Modified Stress Tolerance Index; (SNPI) – Stress and Non-stress Production Index; (PCI) – Potential Capacity Index; (RCI) – Resilience Capacity Index

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