Abstract:
Effective screening of thirteen commonly culti vated rice (Oryza sativa L.) varieties was carried out to
evaluate the varietal-specific differences in morphological,
physiological and biochemical responses to various doses
of UV-B irradiation (7, 14, 21 and 28 kJ m-2
d-1
). Deter mination of UV-B tolerant rice varieties would be helpful
in selecting a suitable variety for the areas experiencing
higher influx of UV-B radiation. Based on the initial
screening of thirteen rice varieties, carried out by analyzing
shoot length, fresh weight, photosynthetic pigments and the
rate of lipid peroxidation under various doses of UV-B, it
was found that Mangalamahsuri, Aathira, Kanchana, Jyothi
and Annapoorna were tolerant lines and Neeraja, Swetha,
Swarnaprabha and Aiswarya were the sensitive ones. Fur ther screening of these nine varieties was done by ana lyzing primary metabolites (total protein, soluble sugar and
proline content) and non enzymatic antioxidants (ascorbate
and glutathione) involved in free radical scavenging
mechanism to mitigate the negative effects of UV-B irra diation. Based on the cumulative stress response index
(CSRI), the sum of relative individual component respon ses (total protein, soluble sugar, proline, ascorbate and
glutathione content) at each UV-B treatment and total
stress response index (TSRI), the sum of CSRI of all the
four UV-B treatments for each variety, nine rice varieties
selected after primary screening were classified as tolerant
(Mangalamahsuri, Aathira and Kanchana), intermediate
(Jyothi, Annapoorna, Neeraja and Swetha) and sensitive
(Swarnaprabha and Aiswarya)
