Evaluating sugarcane (Saccharum sp.) cultivars for water deficit tolerance using some key physiological markers

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Seven sugarcane (Saccharum sp.) commercial cultivars, viz., UT-94-2-483, LK92-11, K84-200, K97-32, K95-84, K88-92 and K 92-80, originally derived from meristem cuttings were subjected to simulated osmotic stress (as 200 mM mannitol) under controlled environmental conditions. Proline content in the leaf tissues of all cultivars except K92-80, increased in plants subjected to mannitol-induced osmotic stress. Chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (TC), maximum quantum yield of PSII (Fv/Fm), and photon yield of PSII (ΦPSII) of all seven cultivars decreased under osmotic stress resulting in a reduction in net-photosynthetic rate (Pn). A positive correlation was found between Fv/Fm and ΦPSII, proline content and non-photochemical quenching (NPQ), ΦPSII and Pn, and Pn and plant dry weight in the sugarcane cultivars. Based upon Ward’s multivariate cluster analyses of data for proline content, photosynthetic capacity, chlorophyll fluorescence, and growth inhibition, three cultivars (K88-92, K92-80 and UT-94-2-483) were identified as water deficit sensitive, whereas four (K84-200, K95-84, K97-32 and LK92-11) as water deficit tolerant. These observations on different cultivar’s sensitivity/tolerance were confirmed by growth and yield attributes measured in a field trial. The plant dry weight (in vitro) correlated positively with total stalk weight of sugarcane cultivars