Biplot analysis of genotype × environment interactions and identification of stable sources of resistance to Ascochyta blight in chickpea (Cicer arietinum L.)

Abstract

Ascochyta blight (AB) caused by Ascochyta rabei (Pass.) Labr. is one of the most important constraints that limits the productivity of chickpea (Cicer arietinum L.). The absence of high levels of stable resistant sources to the pathogen has necessitated the continued search and identification of new sources of resistance. The main aim of this work was to identify new sources of resistance to AB and validate their stability across multi-environments. A collection of 424 elite chickpea genotypes were evaluated for AB resistance under controlled environmental conditions in 2005–2006 at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India. Fifty-one genotypes with AB severity ≤3.0 (based on the 1–9 scale) were selected for a second round of evaluation in 2006–2007 at ICRISAT. Based on the results obtained during both years, an Ascochyta Blight Nursery (ABN) was established to evaluate the selected 29 chickpea genotypes, including 4 germplasm lines, 24 breeding lines and a highly susceptible line. The nursery was evaluated at 3 locations (Almora, Dhaulakuan and Ludhiana) in India over three crop seasons (2007–2008, 2008–2009 and 2009–2010) and under controlled environment conditions at ICRISAT to further confirm the stable performance of these genotypes. Analysis of variance revealed highly significant effects of year, location (year), genotype and genotype × location (year) interaction. The genotype and genotype × environment (GGE) biplot analyses of multi-environment data showed that resistance of five genotypes (EC 516934, ICCV 04537, ICCV 98818, EC 516850 and EC 516971) had mean disease severity ≤3.0 on the 1–9 scale and the reactions were consistent across the environments. Genotype EC 516934 was found resistant to AB at the seedling stage in the controlled environment at ICRISAT. The remaining genotypes showed moderately resistant reaction (3.0–5.0) to AB under controlled environment conditions. A significant positive correlation was found between the performance of the genotypes under controlled environment and field screening conditions (r = 0.70; P < 0.01). The resistant genotypes identified in the present study would be useful in breeding programs as stable resistant donors to evolve agronomically desirable AB resistant varieties.