Investigation into physiology and genetic infrastructure regarding the impact of heat stress on commercially cultivated chickpea

Abstract

This thesis is the culmination of a multi-faceted investigation into the impacts, physiological management, and genetic architecture of heat stress and tolerance in chickpea (Cicer arietinum). Previous research in stress tolerance of this crop has had a predominant focus on disease, with heat stress research increasing in the last 10 years. Such research has typically focused on stress escape via accelerated development, primarily in the reproductive phase when the plant is the most vulnerable. Twelve field trials were conducted across two Australian growing regions, Narrabri (New South Wales) and Kununurra (Western Australia), in which a delayed sowing approach was used to create differentiated heat treatments. These were then paired with glasshouse trials in which heat stress was induced at different developmental stages. These experiments were collectively done to identify differences in physiology and trait performance when heat is induced at flowering versus podding.

SNP sequencing was completed for all genotypes and combined with data from the field trials to complete a genome-wide association study. 14 QTLs were identified for 5 physiological traits under either commercially typical, or heat stressed conditions. These were aligned with genes and QTLs related to heat stress in chickpea identified in previous studies. This is the first study to identify genomic regions linked with final canopy closure in chickpea, therefore the 3 QTLs linked to final canopy closure are novel. In addition, a flowering QTL was identified that is likely linked to earliness of flowering under heat stress. This is due to its co-location with a known heat stress transcription factor (HSF) under heat stressed conditions. This HSF is known to be linked to acceleration of flower and shoot growth under heat stress, and the co-location suggests that the QTL may be involved in the up-regulation of this HSF.

This thesis provides a great deal of value to the chickpea breeding community.