Midday photoinhibition of two newly developed super-rice hybrids

Abstract

Super-rice hybrids are two-line hybrid rice cultivars with 15 to 20 % higher yields than the traditional three-line hybrid rice cultivars. Response of photosynthetic functions to midday photoinhibition was compared between seedlings of the traditional hybrid rice (Oryza sativa L.) Shanyou63 and two super-rice hybrids, Hua-an3 and Liangyoupeijiu. Under strong midday sunlight, in comparison with Shanyou63, the two super-rice hybrids were less photoinhibited, as indicated by the lower loss of the net photosynthetic rate (P N ), the quantum yield of photosystem 2 (Φ PS2 ), and the maximum and effective quantum yield of PS2 photochemistry (F v /F m and F v '/F m '). They also had a much higher transpiration rate. Hence the super-rice hybrids could protect themselves against midday photoinhibition at the cost of water. The photoprotective de-epoxidized xanthophyll cycle components, antheraxanthin (A) and zeaxanthin (Z), were accumulated more in Hua-an3 and Liangyoupeijiu than in Shanyou63, but the size of xanthophyll cycle pool of the seedlings was not affected by midday photoinhibition. Compared to Shanyou63, the super-rice hybrids were better photoprotected under natural high irradiance stress and the accumulation of Z and A, not the size of the xanthophyll pool protected the rice hybrids against photoinhibition.

Characterization and Use of Male Sterility in Hybrid Rice Breeding

“…Improvement of morphological characters is focused on the longer, narrower, thicker and erecter top leaves. Physiologically, it pays more attention to the harmony between the larger sink and enough carbon sources (Wang et al 2005;Wang et al 2006a Additionally, the grain quality and resistance improvement of super rice by incorporating genes for disease and insect resistance have been another important goal of breeders. To develop the new varieties with high yield potential, good quality, higher resistance to diseases and broad adaptability for adverse ecologies will be the next wave of hybrid rice breeding programs.…”

The Long-Term Changes in Midday Photoinhibition in Rice (Oryza sativaL.) Growing under Fluctuating Soil Water Conditions

“…Some highly productive rice genotypes exhibit less photoinhibition (Wang et al, 2005;Kumagai et al, 2009), resulting in a high photosynthetic rate under favorable environmental conditions. In contrast, there is no evidence of the advantage of increased photoinhibition for higher productivity under field conditions.…”

Genotypic Diversity of Cross-Tolerance to Oxidative and Drought Stresses in Rice Seedlings Evaluated by the Maximum Quantum Yield of Photosystem II and Membrane Stability

“…IR72158-16-3-3-1 is a second-generation new plant type line developed by crossing elite indica with improved tropical japonica. Liangyoupeijiu is an indica-japonica hybrid rice with a higher yield than traditional hybrid rice (Wang et al, 2005). B6144-MR-6-0-0 and IR55423-01 are also indica HYVs that are well adapted to upland and aerobic cultivation (Atlin et al, 2006).…”

“…A more severe oxidative damage in the landraces as compared with the improved cultivars was also reported by Kumagai et al (2009), who concluded that the higher photoinhibition of PSII in the traditional variety affected the low sustainability of photosynthesis under nitrogendeficient conditions. Wang et al (2005) compared higheryield super-rice hybrids with traditional hybrid rice cultivars and reported that the super-rice hybrids were well protected against midday photoinhibition. These results suggest that physiological traits related to oxidative stress tolerance have been unintentionally selected during rice breeding aimed at improving the grain yield.…”