In tropics, combined stresses of drought and heat often reduce crop productivity in plants like Musa acuminata L. We compared responses of two contrasting banana genotypes, namely the drought-sensitive Grand Nain (GN; AAA genome) and drought tolerant Hill banana (HB; AAB genome) to individual drought, heat and their combination under controlled and field conditions. Drought and combined drought and heat treatments caused greater reduction in leaf relative water content and greater increase in ion leakage and H O content in GN plants, especially in early stages, while the responses were more pronounced in HB at later stages. A combination of drought and heat increased the severity of responses. Real-time expression patterns of the A-1 and A-2 group DEHYDRATION-RESPONSIVE ELEMENT BINDING (DREB) genes revealed greater changes in expression in leaves of HB plants for both the individual stresses under controlled conditions compared to GN plants. A combination of heat and drought, however, activated most DREB genes in GN but surprisingly suppressed their expression in HB in controlled and field conditions. Its response seems correlated to a better stomatal control over transpiration in HB and a DREB-independent pathway for the more severe combined stresses unlike in GN. Most of the DREB genes had abscisic acid (ABA)-responsive elements in their promoters and were also activated by ABA suggesting at least partial dependence on ABA. This study provides valuable information on physiological and molecular responses of the two genotypes to individual and combined drought and heat stresses.

In vitro micropropagation of banana (Musa spp.) cv.virupakshi (Hillbanana) was studied. Suckers were collected from the germ plasm block of Jain R&D (originally established from the suckers from Palani Hills, Tamil Nadu) during summer. The sucker surface sterilized with 1% NaOCl for 30 min gave 100% survival without any contamination. Apical meristems that were isolated and cultured on MS based media supplemented with benzylaminopurine (BAP) 10.0 mg/l and IAA1.0 mg/l gave higher number of shoots (134.3 shoots/explant) within168 days (24 weeks). Kinetin 2.0 mg/l and NAA0.5 mg/l gave early rooting in just five days with 6.6 roots per plant. Observations were recorded after every four weeks up to six sub-culturing. Acclimatization was done in poly house, followed by shade house under 50% light conditions. The hardened plants when shifted to the field showed luxurious growth. The regenerated micro propagated banana plants were tested for genetic uniformity through 13 inter simple sequence repeat (ISSR) markers recommended by NCS-TCP, DBT. Profiles obtained by all the three ISSR primers namely, 834, 840 and 850, respectively exhibited similar banding patterns, which revealed the existence of genetic uniformity in micro-propagated plants.

No abstract

No abstract

No abstract