The Photosynthetic Characteristics of ‘Chaling’ Common Wild Rice (Oryza rufipogon Griff.) under Cold Stress

Abstract

‘Chaling’ common wild rice (CWR, Oryza rufipogon Griff.), found in Chaling county, Hunan province, China, is one of the only two wild rice populations grown northernmost in the world. Although the cold tolerance of ‘Chaling’ CWR is extremely strong, its photosynthetic characteristics under cold stress remain unknown. In this study, the photosynthetic parameters of leaves at tiller stage in ‘Chaling’ CWR were first determined under the conditions of cold stress (15 °C) and normal temperature (28 °C), and then compared with those in the standard rice cultivars including indica ‘Guangluai 4’, indica ‘Y-Liangyou 1’ (a Chinese hybrid rice with super high grain yield), and japonica ‘Nipponbare’ under the same temperature conditions. The results showed that the net photosynthetic rate, the total chlorophyll and total carotenoid contents, the maximum quantum yield of PSII, the apparent quantum yield, and the carboxylation efficiency in ‘Chaling’ CWR were all significantly higher than those in the standard rice cultivars under cold stress (P < 0.05). The ratios of these parameters in ‘Chaling’ CWR under cold stress to those under normal temperature condition were 47.9 ~ 84.9%, much higher than those in the standard rice cultivars, which were 3.1 ~ 73.8%. These results indicate that the photosynthetic characteristics of ‘Chaling’ CWR under cold stress are excellent. Our findings would have an enormous benefit if the trait of the cold stress tolerance of ‘Chaling’ CWR is transferred to the cultivated rice via the traditional breeding or molecular breeding.