Host: The Japan Radiation Research Society
We previously investigated that the supplementary UVB radiation on the growth and yield of Japanese rice cultivar in paddy field in Japan, and found that the supplementary UVB radiation inhibited growth, yield and grain development. One of principal causes of such UVB-induced damage is UVB-induced cyclobutane pyrimidine dimer (CPD), and increasing CPD photolyase activity can significantly alleviate UVB-caused growth inhibition. By the way, how degree of growth inhibition was caused by UVB radiation in natural sunlight? In this work, effects of solar UVB radiation on growth and yield of rice under outdoor conditions were investigated. For this study, UV-resistant Koshihikari (japonica) and the UV-sensitive chromosomal segment substitution line (SL-229) were used as experimental plant; chromosomal 10 region, on which CPD photolyase gene located, in SL-229 was homozygous for Kasalath (indica) allele, whereas all other chromosomal regions were homozygous for Koshihikari alleles. CPD photolyase activity of Kasalath was lower than that of Koshihikari, resulting from the alteration of a single amino acid in the photolyase sequence. The grain size and weight of SL-229 under current outdoor conditions in 2006 were reduced. These results mean that growth and yield of rice grown under current environmental conditions would be inhibited by UVB radiation in natural sunlight.
