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Senescence is the last developmental process in plant, which has an important impact on crop yield and quality. In this study, a stable hereditary early-senescence line BC64 was isolated from the high-generation recombinant inbred lines of 93-11 and Wuyunjing7 (W7). Genetic analysis showed that the premature aging phenotype was controlled by a dominant gene derived from 93-11. By linkage analysis, the gene was primarily mapped in the region between marker B4 and B5 near the centromere of chromosome 4, described as ES(4). Through multiple backcrossing with W7, the near-isogenic line of ES(4) (NIL-ES(4)) was obtained. Compared with wild-type W7, NIL-ES(4) plants showed more sever senescence phenotype in both nature and dark conditions. In NIL plants, leaves turned yellow at the fully tillering stage; photosynthetic rate, pollen fertility and seed setting rate were decreased. Moreover, the malondialdehyde, proline content and relative conductivity in NIL-ES(4) were significantly higher than those in W7; both transcript level and activities of reactive oxygen species scavenging enzymes were repressed; H2O2 and O2- were significantly accumulated. This study provides a basis for further cloning and function identification of ES(4). [ABSTRACT FROM AUTHOR]

Semi-dwarfing improves the lodging resistance and yield of rice, and the vast majority of modern rice varieties harbor the sd1 allele to decrease plant height, resulting in reduced genetic diversity and negative agronomic traits. Thus, exploring alternative sources of dwarfism is imperative for rice breeding. Here, we identified a novel RGA1 allele, d1-w , from a local indica variety Xiaolixiang (XLX) using a map-based cloning approach. Compared with other rice varieties, RGA1 in XLX contained a unique single nucleotide polymorphism that resulted in an additional transcript and reduced functional RGA1 transcript level. The RGA1 from Nipponbare was introduced into XLX to estimate the value of d1-w in rice breeding. Compared with transgenic XLX plants (XLX D1 ), XLX exhibited reduced plant height, increased stem strength, lower reactive oxygen species accumulation, delayed senescence, stronger photosynthesis, higher grain yield and quality (including external, milling and nutritional qualities), and enhanced resistance to drought and Rhizoctonia solani. Therefore, we proposed that the d1-w allele has potential as an excellent dwarfism resource for rice breeding. [ABSTRACT FROM AUTHOR]