Evaluation of French bean genotypes for high temperature tolerance using Temperature Induction Response (TIR) technique

Abstract

French bean, being a cool season legume crop, with a requirement of 17-28°C optimum temperature requirement, is grown mainly during Kharif and Rabi seasons. But its cultivations is severely constrained during summer months due to prevailing high temperatures. Further, under climate change conditions high temperature episodes are likely increase and considerably affect pod yield. The identification of suitable cultivars is a prerequisite for adaptation to high temperature situations.Thus, the temperature induction response (TIR) technique, which involves exposure ofseedlings to sub lethal temperatures to induce inherent cellular tolerance and consequent exposure to challenging temperatureswas standardized and employed for screening French bean genotypes for high temperature stress tolerance. Two day old French bean seedlingswere subjected to various challenging temperatures from 43 to 50°C for 3 hoursand were allowed to recover at room temperature for 72 hours. Based on the least survival (11%) and highest growth reduction (92%) during recovery, 45°C for 3hours was identified as challenging temperature. Consequently the induction temperature was identified by subjecting French bean seedlings to different induction temperature regimes. The gradual induction temperature from 30 to 40°C for 3 hours at which 60% of the seedlings survival was observed during recovery was identified as the optimum induction temperature. Subsequently, ten French bean genotype were screened by subjecting them to the standardized induction temperature of 30-40°C for 3 hours followed by challenging temperature of 45°C for 3 hours. The genotypes showed differences in percent seedling growth reduction during recovery period over control. The genotypes, (IC-525224 x IC-525239) IPS-1, (IC-525224 x IC-525239) 1-12and Arka Anoop, with 60%, 65.27 %, 66.30% reduction in seedling growth showed tolerance to high temperature stress. In this study we standardized the TIR technique as a screening method to evaluate and identify temperature tolerant French bean genotypes