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

Abstract

French bean is a cool season legume crop requires a
temperature of 170C-28°C for ideal growth. It is grown mainly
during kharif and rabi seasons. But its cultivation 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 of seedlings to sub lethal
temperatures to induce inherent cellular tolerance and
consequent exposure to challenging temperatures was
standardized and employed for screening French bean
genotypes for high temperature stress tolerance. Two day
old French bean seedlings were subjected to various
challenging temperatures from 43°C to 50°C for 3 hours and
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 3 hours 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°C to 40°C for 3
hours at which 60% of the seedlings survival was observed
during recovery and identified as the optimum induction
temperature. Subsequently, ten French bean genotypes were
screened by subjecting them to the standardized induction
temperature of 30°C-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) 1-12 and Arka
Anoop, with 60%, 65.27 %, 66.30% reduction in seedlinggrowth
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.