S11 - Session O1 - Physiological and molecular responses of stress sensitive and tolerant banana genotypes to drought, heat and their combination

Authors: Bal Krishna *, Rakesh S Chaudhari, Bhavesh L Jangale, Prafullachandra V Sane, Aniruddha P Sane

Drought and heat stress affects the crop productivity adversely . Combined (drought + heat) stress to Grand Nain (GN, AAA genome) banana caused 100% yield loss, while the yield loss was only 46% in Hill banana (HB, AAB genome) . We compared physiological and molecular responses of these two contrasting banana genotypes to individual drought, heat and their combination under controlled as well as field conditions. Individual drought and combined stress caused higher reduction in leaf relative water content, increased ion leakage and H 2 O 2 content in GN plants than in HB plants as compared to individual heat stress. Expression of DREB (A-1 and A-2 group) and stress responsive NAC genes revealed higher background levels in leaves of HB plants for individual stresses as compared to GN plants. However, combination of heat and drought suppressed their expression in HB but activated them in GN. Most of these genes were strongly upregulated within 30n60 min upon application of exogenous a bscisic acid (ABA) and the increase was prominent in GN. Interestingly, the expression of the DREB and stress responsive NAC genes was blocked in the drought tolerant HB even when subjected to combined drought and heat stress in field, unlike in GN. This response in HB seems correlated to a better stomatal control over transpiration thus avoiding the need for stress pathway activation unlike in GN. The study suggests that the B genome in the stress-tolerant HB may be responsible for tolerating more drastic combined stresses without taking recourse to the expression of DREB (A-1 and A-2 group) and stress responsive NAC genes .