In the rice inflorescence development, timing of inflorescent meristem abortion, conversion of the rachis branch meristem to the terminal spikelet meristem and shift to lateral meristem identity determine the overall architecture of the rice panicle (keda-Kawakatsu et al. 2009). Cheng et al. (2011) reported that quantitative trait loci (QTLs) have major effects on panicle apical abortion in rice. However, there have been very few reports about panicle tip mutants. Therefore, this research is conducted to fine map mutant gene and perform functional analysis of mutant gen. Hwacheongbyeo (japonica rice) seed was treated with ethyl methane sulfonate (EMS) for inducing mutation. Two F2 population (Japanica mutant crossed with wild type and Japanica mutant crossed with Milyang 23, Indica type) were established for Phenotyping and genomic analysis. STS markers in crop molecular Breeding laboratory. Additional STS markers for fine mapping were developed based on the Nipponbare genome sequence (http://rgp.dna.affrc.go.jp/blast/runblast.html). All F2 generations showed the segregation of normal plants and mutant following a ratio of 3:1 suggesting the mutant phenotype is caused by a single recessive gene. Initial BSA test made using STS markers confirmed the mutant gene is found in the long arm of chromosome 8. Panicle tip mutant gene, pnt has pleotropic effect which has been manifested in significant reduction of tiller development starting from late stage of vegetative growth and pronounced effect on possession of stay green nature of the rice during the vegetative stage of development. The only significant difference observed within panicle traits is the number of spikelet on primary branch and spikelet fertility. The first primary branch which contain aborted spikelet and elongated distance between spikelet is the most affected structure in the panicle.

The early senescence mutant was isolated from the japonica rice Koshihikari through Ethyl-methane-sulfonate (EMS) mutagenesis. The early senescence phenotype was controlled by a single recessive gene, tentatively symbolized as es-k. Using an F2 population derived from a cross between the mutant and Milyang23 and molecular markers, we mapped the es-k locus to the long arm of chromosome 7 between STS markers 147-1 and 147-2 with a physical distance of 66-kb. The symptom of early senescence appeared even before heading, while appeared during ripening in wild-type. Physiological characteristics of the es-k mutant before initiation of senescence was similar to the wild-type. However, after heading, es-k mutants started to exhibit a significant decrease in chlorophyll and soluble protein content compared to the wild-type. The wild-type leaf color appeared normal irrespective of temperature treatment, while the leaf of es-k mutant appeared pale-green at the low temperature and dark-green at the high temperature. During dark-induced senescence, mutant did not show significant differences compared to normal type. The results show that es-k is sensitive to temperature but not to light.

The early senescence mutant was isolated from the japonica rice Koshihikari through Ethyl-methane-sulfonate(EMS) mutagenesis. The early senescence phenotype was controlled by a single recessive nuclear gene, tentatively symbolized as es-k. Using phenotypic and molecular markers, we mapped the es-k locus to the long arm of chromosome 7 between STS markers 147-1 and 150-1, a physical region of 370-kb. The symptom of early senescence appeared even before heading, while appeared after heading in those of the wild-type rice during senescence. Early stage physiological characteristics of the es-k mutant was similar to that of the wild-type. However, after heading, es-k mutants started to exhibit a significant decrease in chlorophyll content, soluble protein content 10 days earlier compared to normal type. To characterize the interaction with the environment factors, experiments were carried out under controlled temperature and light conditions, respectively. The wild-type leaf color appeared normal irrespective of temperature treatment, while the leaf of es-k mutant appeared pale-green at the low temperature and dark-green at the high temperature. During dark-induced senescence, mutant did not show significant differences compared to normal type. The results show that es-k is sensitive to temperature but not to light.