Physiological responses and molecular mechanism of rice (Oryza sativa) exposed to enhanced UV-B radiation

In this paper, the genetic physiology and defense mechanism to enhanced UV-B radiation were reviewed at cellular, individual and population levels of rice. Analysis and achievements of recent researches in this field under combined agro-ecosystem approach and research observations were explained. Significant differences in the responses of rice germplasms to enhanced UV-B radiation had been reported. Since ambient UV-B radiation level at lower latitudes was greater than that at higher latitudes, rice cultivars originated near the equator had been generally assumed to be more tolerant to UV-B radiation. However, no results had existed to substantiate the hypothesis that there was association between rice cultivars sensitivity to UV-B radiation and geographic origin of rice germplasms. This required researches to explore differences in sensitivity of rice germplasms (including the indica and japonica types) to UV-B radiation. Studies had shown that differences in rice response to enhanced UV-B radiation were inheritable quantative traits. Result of QTL location analysis had suggested that most additive QTL of rice tolerance to enhanced UV-B radiation were mainly located on chromosomes 1, 2, 3 and 6. Epistasis effects of additive QTL and additive × additive QTL were also detected and appeared significantly interacted with the environment. The author also analyzed molecular physiology and regulation mechanism of rice in defense to enhanced UV-B radiation. It was determined as an effective way of increasing rice tolerance to enhanced UV-B radiation to improve silicon nutrition in rice plant. Finally, it was suggested that investigations and assessments regarding ecological risks of enhanced UV-B radiation at farmland ecosystem level be a key component of future research programs to enable us cope with the challenges of global change. It was emphasized that integrated effects of the interaction of other ecological factors with enhanced UV-B radiation on growth and development of crop be studied under field conditions. Based on the results, crop genetic improvement and cultivation regulation technology for disaster alleviation and hazard prevention was recommended to be set up so as to provide the theoretical knowledge and information for establishment of related protection strategies.