To identify biochemical markers for salt tolerance, two contrasting cultivars of rice (Oryza sativa L.) differing in salt tolerance were analyzed for various parameters. Pokkali, a salt-tolerant cultivar, showed considerably lower level of H(2)O(2) as compared to IR64, a sensitive cultivar, and such a physiology may be ascribed to the higher activity of enzymes in Pokkali, which either directly or indirectly are involved in the detoxification of H(2)O(2). Enzyme activities and the isoenzyme pattern of antioxidant enzymes also showed higher activity of different types and forms in Pokkali as compared to IR64, suggesting that Pokkali possesses a more efficient antioxidant defense system to cope up with salt-induced oxidative stress. Further, Pokkali exhibited a higher GSH/GSSG ratio along with a higher ratio of reduced ascorbate/oxidized ascorbate as compared to IR64 under NaCl stress. In addition, the activity of methylglyoxal detoxification system (glyoxalase I and II) was significantly higher in Pokkali as compared to IR64. As reduced glutathione is involved in the ascorbate-glutathione pathway as well as in the methylglyoxal detoxification pathway, it may be a point of interaction between these two. Our results suggest that both ascorbate and glutathione homeostasis, modulated also via glyoxalase enzymes, can be considered as biomarkers for salt tolerance in Pokkali rice. In addition, status of reactive oxygen species and oxidative DNA damage can serve as a quick and sensitive biomarker for screening against salt and other abiotic stresses in crop plants.
Weedy rice, a menace in rice growing areas globally, is biosimilar having attributes similar to cultivated and wild rice, and therefore is difficult to manage. A study was initiated to characterize the functional traits of 76 weedy rice populations and commonly grown rice cultivars from different agro-climatic zones for nine morphological, five physiological, and three phenological parameters in a field experiment under an augmented block design. Comparison between weedy and cultivated rice revealed a difference in duration (days) from panicle emergence to heading as the most variable trait and awn length as the least variable one, as evidenced from their coefficients of variation. The results of principal component analysis revealed the first three principal components to represent 47.3% of the total variation, which indicates an important role of transpiration, conductance, leaf-air temperature difference, days to panicle emergence, days to heading, flag leaf length, SPAD (soil-plant analysis development), grain weight, plant height, and panicle length to the diversity in weedy rice populations. The variations existing in weedy rice population are a major reason for its wider adaptability to varied environmental conditions and also a problem while trying to manage it.
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