Large genetic variation for heat tolerance in the reference collection of chickpea (Cicer arietinum L.) germplasm

Chickpea is the third most important pulse crop worldwide. Changes in cropping system that necessitate late planting, scope for expansion in rice fallows and the global warming are pushing chickpeas to relatively warmer growing environment. Such changes demand identification of varieties resilient to warmer temperature. Therefore, the reference collection of chickpea germplasm, defined based on molecular characterization of global composite collection, was screened for high temperature tolerance at two locations in India (Patancheru and Kanpur) by delayed sowing and synchronizing the reproductive phase of the crop with the occurrence of higher temperatures ($358C). A heat tolerance index (HTI) was calculated using a multiple regression approach where grain yield under heat stress is considered as a function of yield potential and time to 50% flowering. There were large and significant variations for HTI, phenology, yield and yield components at both the locations. There were highly significant genotypic effects and equally significant G £ E interactions for all the traits studied. A cluster analysis of the HTI of the two locations yielded five cluster groups as stable tolerant (n ¼ 18), tolerant only at Patancheru (n ¼ 34), tolerant only at Kanpur (n ¼ 23), moderately tolerant (n ¼ 120) and stable sensitive (n ¼ 82). The pod number per plant and the harvest index explained $60% of the variation in seed yield and $49% of HTI at Kanpur and $80% of the seed yield and $35% of HTI at Patancheru, indicating that partitioning as a consequence of poor pod set is the most affected trait under heat stress. A large number of heat-tolerant genotypes also happened to be drought tolerant