Effect of NaCl Levels on In-vitro Growth and Hardening Performance of Three Banana Cultivars Grand Naine (G9) Povilachandam (B5) and Nendran (B3)

Salinity is a major abiotic stress that restricts banana growth and yield by disrupting water uptake, ion balance and plant development. The present study assessed the morphological responses of three banana varieties: Grand Naine (G9, AAA), Povilachandam (B5, AAB) and Nendran (B3, AAB), under in vitro NaCl stress and during hardening. Sterilised suckers were cultured on Murashige and Skoog medium supplemented with 0, 2, 4 and 8 g L⁻¹ NaCl. Morphological traits were assessed after 21 days of culture and following hardening. Increasing NaCl concentration reduced regeneration, shoot length, root number, root length, fresh weight and dry weight, whereas mortality, medium browning and electrical conductivity increased. Incubation from 7 to 30 days generally improved regeneration and shoot and root growth at most salinity levels. Regeneration ranged from 55% to 100%, with B3 showing the highest regeneration and lowest mortality under salinity. B5 exhibited superior root growth, biomass accumulation and performance during hardening, whereas G9 showed higher shoot initiation and pseudostem diameter. During hardening, increasing NaCl concentration consistently reduced shoot length, leaf number, root number and root length across all varieties. Overall, B3 performed better during in vitro screening, whereas B5 showed superior performance during hardening. These findings highlight variation in varietal responses to salinity and indicate the potential of B3 and B5 for developing salt-tolerant banana planting material through tissue culture-based selection.