Temperature induction response technique: a screening tool for evaluation of banana cultivars for thermotolerance

Abstract

Banana is a succulent tropical fruit crop. Screening and identification of cultivars for high temperature stress conditions is essential under changing environment. Temperature induction response (TIR) technique, is based on the principle of subjecting plantlets to sublethal temperatures and subsequent exposure to challenging temperatures, and further assessing growth and recovery. In this study, 5–6 weeks old micro-propagated banana plantlets were subjected to various temperatures from 55 to 70 °C for a duration of 2 h. Based on least survival (11%) and highest growth reduction (92%) during recovery of plantlets, 55 °C for 2 h was identified as challenging temperature or lethal temperature. The induction temperature, 42 °C for 2 h 30 min, at which more than 50% of the plantlets survived and a lower reduction in growth (20%) during recovery after exposure to lethal temperatures (55 °C for 2 h) were identified as the optimum induction temperature. Twenty banana cultivars were screened using TIR. Using Z distribution analysis the cultivars were grouped into tolerant (cvs. Grand Naine and Rasbale), which clustered in quadrant I, and susceptible (cvs. Red Banana and Kunnan), which clustered in quadrant III. Injury index was lower in cv. Grand Naine (tolerant) compared to cv. Red Banana (susceptible). Hence, we propose this technique as a potential tool to screen and identify temperature-tolerant genotypes in banana.