Evaluation of potential morpho-physiological and biochemical indicators in selecting heat-tolerant tomato (Solanum lycopersicum Mill.) genotypes

A few degrees in temperature above the optimum can cause a considerable yield loss in tomatoes. A research experiment was conducted in which three tomato genotypes of (Solanum lycopersicum Mill.), 'Suncherry Extra Sweet' (Suncherry), 'Walter', and 'CLN-2498d', were evaluated for response to moderate high temperature at the reproductive stage. High temperature reduced the total number of fruits per plant, fruit size, number of seeds per fruit, seed setting, and relative ovule viability. However, high temperature increased proline accumulation and membrane thermo-stability in plant parts of the investigated genotypes. Fruit size and the number of seeds per fruit were reduced in all the genotypes, with the greatest reduction occurring in Suncherry. Similarly, viability of male and female gametes was also reduced in all of the investigated genotypes due to high temperature injury. The reduction in seed setting due to high temperature was greatest in 'Suncherry' and 'Walter', and least in 'CLN-2498d'. Likewise, ovule viability was least reduced in 'CLN-2498d'. The genotypes accumulating higher proline concentrations in reproductive parts and with enhanced membrane thermo-stability under high temperature likewise produced the highest fruit yield, and hence, exhibited high temperature tolerance.