Molecular Mapping Of Two New Leaf-color Mutant Genes In Rice And Its Application In Breeding

Rice is one of the most important grain crops in the world, providing staple food for more than half population of the world. 90-95% dry matter accumulation in rice is resulted from photosynthetic of rice leaves. So it is significantlyt to map and clone the genes associated with photosynthesis of rice, study the function of these genes and develop the breeding for high photosynthetic efficiency. Leaf color mutant is common in rice mutant. The mutant genes always affect directly or indirectly the synthesis and decomposition of the chlorophyll, which result in the change of chlorophyll content, so leaf color mutant is also called chlorophyll mutant. Chlorophyll mutant havs unique advantages in photosynthesis studies.Meanwhile, it also can be applied to identifying the seed purity of hybrid rice as morphological marker.A white stripe leaf mutant and a yellow leaf mutant were found in rice breeding materials. The objective of this study is to analyze the morphological structure, chlorophyll components, chloroplast ultrastruture and map genes underlying the two novel leaf color mutants in rice.The mainly results are as follows:1. The main characters of WG206 were summerized: White stripe along the veins appeared at seeding stage, but the manifestation of this character was remarkably clear in the tillering stage and throughout the whole growing period. The comparison of the major agronomic characters between WG206 and G206 showed that: there were no remarkable differences except for the number of tillers and growth duration. The number of tillers of WG206 was decreased 61.43%, and its growth duration was prolonged 11.27%. The main characters of YZ138 were summerized: yellow leaf trait was throughout the whole growing period. The comparison of the major agronomic characters between YZ138 and Z138 showed that there were no remarkable differences except for the plant height, 1000-grain weight and growth duration. The plant height of YZ138 was decreased 31.08%, its 1000-grain weight was decreased 14.55%, and its growth duration was prolonged 17.86%.2. The pigment content between the two mutants and their wild-type parent was compared in Tillering date, the result indicated the contents of chlorophyll a, chlorophyll b, and carotenoids in both mutants obviously decreased. Compared to its wild-type parent G206, the chlorophyll a, chlorophyll b, and carotenoid of WG206 was decreased by 22.90%, 37.56 %, 12.20%, respectively. Compared to its wild-type parent Z138, the chlorophyll a, chlorophyll b, and carotenoid of YZ138 was decreased by 84.63 %, 78.50 %, 79.12%, respectively.3. The observation result of chloroplast ultrastructure showed that grana structures were normal and the grana lamellas were very clear in the normal chloroplasts. But comparing with the normal chloroplasts, the granal stacks in the WG206 appeared less dense and lacked granal membranes, and the grana lamella were almost disappeared in the YZ138.4. The genetic analysis indicated that both mutants were controlled by recessive nuclear gene. They were considered as new mutant gene in rice and named tentatively st9(t)(stripe) and chl12(t) (Chlorophyll-deficit).Genetic mapping of the mutant genes was conducted by using SSR(Simple sequence repeat) markers and F2 mapping population developed from the cross between the two mutant lines, the mutant gene st9(t) was located on the tip of the short arm of rice chromosome 1,the genetic distances from st9(t) to the marker RM1331 was 9.6 cM; chl12 (t) was mapped on the short arm of rice chromosome 3, the genetic distances from chl12 (t) to the markers RM411, RM8202 were 1.2 and 5.1 cM, respectively.5. A new male sterile line and maintainer line named WG206A and WG206B with white stripe leaf were created from the offsprings of WG206 and 99B. It has comprehensive application foreground and spread value.