Abstract
The early senescence of rice during the reproductive growth period seriously affects rice yield and quality. In this study, ethyl methylsulfonate (EMS) was used to induce the japonica rice variety Hwacheongbyeo to obtain a leaf early senescence mutant during the reproductive growth period of rice, and named as es-h ( early senescence - Hwacheongbyeo ). Phenotypic analysis showed that the mutant began to have rust spots on the leaves after heading, and withered rapidly with the filling process, the whole plant died off by the fifth week of heading. Agronomic trait analysis showed that, compared with the wild type, the es - h mutant had no significant changes in heading date, panicle length, panicle excertion and panicle number, while significantly reduced in plant height, grain number per panicle, seed setting rate and thousand grain weight. Physiological analysis showed that after heading of es - h mutant, the SPAD value, chlorophyll content, Fv/Fm value and soluble protein content of its flag leaf all decreased sharply. Genetic analysis revealed that the premature aging traits of es - h mutants were controlled by recessive single gene. The target gene was located on the 44.2 kb physical segment of the long arm of chromosome 1 through gene mapping. This study provides a basis for Es-h gene cloning and functional analysis, and molecular mechanism of premature aging.
Highlights
Plant senescence is the last link in the process of growth and development and is a process of programmed cell death
1.1 Phenotype identification and agronomic traits of rice early senescence mutant es-h Rice early senescence mutant es-h was screened from japonica rice variety Hwacheongbyeo after ethyl methylsulfonate (EMS) mutagenesis
At heading and maturity stages, compared with the wild type, the es-h mutant plants were shorter, the number of spikelets decreased significantly, the seed setting rate and 1000-grain weight decreased significantly, but there was no significant difference in heading stage, panicle length, panicle excertion and panicle number per plant (Table 1)
Summary
Plant senescence is the last link in the process of growth and development and is a process of programmed cell death. Many leaf early senescence mutants have been identified in rice, and more than 20 rice leaf early senescence genes have completed gene mapping and partial functional analysis. According to the characteristics of senescence phenotype, leaf senescence mutants are divided into two types: leaf etiolation and leaf spots Their wild type varieties (lines), premature aging traits, senescence occurrence period and target gene location are different (Li. Rice Genomics and Genetics 2022, Vol., No.2, 1-8 http://cropscipublisher.com/index.php/rgg et al, 2020). The plant leaf senescence will lead to the decrease of chlorophyll-protein complex and photosynthetic yield because that the photosynthetic carbon cycle in leaves is destroyed, and a variety of free radicals and membrane lipid peroxidation are accumulated in cells, resulting in the stems and leaves wilt, leaves early senescence, and poor grain filling, resulting in the decrease of yield (Tang et al, 2005). Its regulatory gene was located on chromosome 3 (Zhang et al, 2014)
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