Genetic Analysis And Gene Mapping Of Two Early Senescence Mutants In Rice

Senescence is the last stage of plant life cycle, which also can be considered as the adaptation during the long evolution with great biological significance. However, in the agriculture production, early senescence means the declination of yield, even none yield. As to rice, which is annual crop, senescence has enormously impact on the yield and quality. So it have significant meaning to find out the mechanism of rice senescence.In this study, two mutants of premature senescence of foliage D101and D343has been selected out of late-ripening Japonica Rice Variety Nipponbare treated by chemical mutagen EMS, then we have scrutinized and analyzed the morphologic characters of the two mutants, subsequently target the location of the premature-senescence gene respectively through F2population of D101/ZF802、D343/Zao63. The main results show as follows:1. the phenotype of the mutants D101and D343:Under the natural conditions of Wenjiang Sichuan, there are no obvious difference between D101or D343with wild type until the8-foliages stage, when light brown mottles appear on the oldest leaf of the mutants, increasing with the time. During tillering stage, mutants show littler tillers and less vigorous than wild type10079; at jointing stage, the tips of new leaves become yellow, curled and withered with the whole oldest leaves turning yellow; plant senescence is getting more serious as heading stage comes; when ripe, overwhelming majority parts of the leaf withered except from the curled and yellow tips of leaves, in the whole, mutants is senescent earlier than wild type, and always begins from curling of leaf edge, then withers to death.2. Contents of chlorophylls and carotenoid of D101、D343mutants leaves:The content of total chlorophyll、chlorophyll a、chlorophyll b and carotenoids of flag leaf from D101relevantly decrease19.9%,21.0%,14.0%,9.68%; at the same time, the content of total chlorophyll、chlorophyll a、chlorophyll b and carotenoids of flag leaf from D343 relevantly decrease15.6%、18.3%、1.73%、1.61%. These results indicate that the content of total chlorophyll、chlorophyll a of the mutants is lower than the wild type significantly, the content of chlorophyll b and carotenoids is no significant with wild type.3. Genetic analysis of characters of D101and D343:F1generation from the hybridization between D101and ZF802shows normal phenotype, however F2generation can be divided into normal and premature senescent phenotype; the generations of hybridization of D343and Z63perform same phenotype with hybridization of D101and ZF802. After chi-square test, the separation of two phenotype complies with3:1, indicates that the phenotype of the mutants is controlled by one recessive gene.4. the gene location of D101, D343mutations:We exploit300pairs of SSR marks (evenly distribution through12chromosomes) to find out the position of the target gene through F2population of D101/ZF802and D343/Z63respectively. At the same time, we develop InDel mark to zoom out the gap between marks, and successfully locate the premature senescent gene from D101at the long arm of the fourth chromosome, the gene from D343at the Centromere of third chromosome.