Stress physiology and metabolism in hybrid rice. IV. Variability in antioxidative enzymes— an aid to metabolic breeding for drought tolerance

ABSTRACT

The state of internal metabolism constitutes the major regulatingfactor for growth sustenance and yield of crops under harsh environments. In this study, we examined the relative significance of certain antioxidative enzymes in rice (Oryza sativa L.) cultivars under water stress to explore the possibility of any relationship of these enzymes with their original habitats. Accordingly, four rice cultivars, belonging to upland (Barani-Deep), lowland (Jal-Lahari), irrigated (NDRH-2) and saline/alkaline (NDURH-3) ecosystems, were grown in a greenhouse for 45 days and then plants were kept under water stress for 12 days by stopping water supply. Observations on antioxidative enzymes– superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX) and lipidperoxidase (LPOX), along with morpho-physiological drought tolerance characteristics of these cultivars were recorded. The findings revealed significant genotypic variability in SOD, CAT, APOX and LPOX among cultivars during drought. Barani-Deep–a drought-tolerant cultivar, exhibited enhanced activities of all the antioxidative enzymes, i.e. SOD (2.4-fold, from 251 to 605 μmol nitroblue tetrazolium), CAT (2.5-fold, 110 to 308 μmol H₂O₂), APOX (2-fold, 44 to 90 μmol ascorbate) and LPOX (2.6-fold, 60 to 155 μmol MDA g−1) on the 12th day of soil drying. The other three cultivars also showed a similar trend of increased enzyme activities, though quantitatively different. However, LPOX in water loving cultivar Jal-Lahari was much higher (3.2-fold) than that of Barani-Deep, indicating a higher degree of metabolic perturbation and membrane damage in Jal-Lahari under drought, i.e. low soil-water potential. Based on these findings, drought-tolerant and water-use-efficient hybrid rice cultivars could be developed. .

KEYWORDS:

• Antioxidative enzymes
• diverse ecosystems— upland
• lowland
• irrigated and saline/alkaline
• habitats
• drought-tolerance
• metabolic variability
• rice cultivars
• water stress

Acknowledgments

We owe our sincere thanks to the departed soul of late Ch. A.K. Singh and Dr. F.D. Yadav, Head, Department of Botany for providing logistics and fruitful suggestions during these investigations and Prof. N.S. Dharamwal of Dr. R.M.L. Avadh University, Faizabad for assisting in the determination of enzyme activities. We also thank Drs. R.S. Verma,S.P. Giri, Plant Breeders and Mr. Ram Akshabar Yadav, Rice Germplasm-Incharge for providing rice seeds for these investigations and Dr. Amarpal Singh for statistical analyses of the data (all the latter four persons belong to N.D. University of Agriculture & Technology, Faizabad, UP, India).We also extend our sincere thanks to the anonymous reviewers and Prof. M.S. Kang (Editor-in-Chief) who have very greatly improved the text of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.