Genetic Mapping of a loose upper panicle Mutant and Characterization of Some African Cultivars in Rice

Abstract

CHAPTER I. Genetic Mapping of a loose upper panicle Mutant (lup)

ABSTRACT

We identified a loose upper panicle mutant (lup) from a japonica-type rice variety, Hwacheongbyeo, treated by Ethyl Methane Sulfonate (EMS). The lup mutant displayed an increased distance between spikelets particularly in the upper primary branches, and the number of spikelet was reduced. In addition, aborted spikelets in the tip of upper primary branches were observed. Besides these morphological changes in the panicle, the lup mutant also displayed overall reduction in culm length, panicle length, grain weight, and tiller number. On the contrary, the chlorophyll content was relatively high in lup mutant in comparison to wild-type plants, and displayed a stay-green phenotype even after physiological maturity. Genetic analysis (using F2 population of lup/M.23) revealed that a single recessive gene is involved in the above-mentioned morphological changes in the lup mutant. A candidate genomic region was fine-mapped at an interval of 1.04 Mb flanked by two molecular markers, 18170 and D0052, on the long arm of chromosome 8. In this region, we found a total of 348 mutation points using a slightly modified MutMap method. Based on these results, we expect the candidate genomic region containing a putative LUP gene will provide an important clue in developmental regulation of spikelets and panicle in rice. Keywords: loose upper panicle, spikelet distance, spikelet number per panicle, SNPs, and MutMap.

CHAPTER II. Characterization of Some African Cultivars in Rice ABSTRACTS

Cultivated rice consists of two species, Oryza sativa of Asia and Oryza glaberrima of Africa. NERICA (New Rice for Africa) varieties were developed from the interspecific hybridization of Oryza sativa and Oryza glaberrima to increase the rice productivity in Africa. In this study, we characterized 40 rice germplasms including some of rice released in Africa using 11 yield related agronomic traits and 96 SNP markers. Three groups of germplasm were identified in cluster analysis based on agronomic traits. Genotyping of germplasms were conducted with the 96-plex indica/japonica SNP set. 40 germplasms were divided into two subpopulations in STRUCTURE analysis using SNP markers. We identified two distinct cluster, indica-type and japonica-type, in cluster analysis using SNP markers based on genetic distance. The CG14, which belong to Oryza glaberrima, showed admixture type of indica and japonica based on 96 SNP markers. The number of secondary branch was the only agronomic traits found significantly different between two groups divided based on SNP markers. However, groups clustered using 11 agronomic traits, showed more than two significant difference in agronomic traits among each groups. The result of this study could provide basic agronomic and genomic information of 40 rice germplasms, and would be useful for further varietal improvement in rice breeding program.

Key Words: Rice, Africa, Agronomic traits, SNP, Genetic diversity