Mutation breeding is characterized by its merit, creation of new mutant characters and addition of very few traits without disturbing other characters of variety. Gamma ray is generally used to induce mutation in various crops. Heading dat is one of the key factors in the regional and seasonal adaptation of rice verity. This study was carried out to evaluate agronomic characteristics, genetic variation and grain quality of early heading rice (Oryza sativa L. cv. Dongjin 1) lines derived from gamma-ray (Co60, 300 Gy) irradiation. The average heading date of the early heading lines in M7 and M8 generation was faster than that of mother verity as 11 (line γ-2), 10 Aug (line γ-5), 6 Aug (γ-1 line), 5 Aug (γ-3 and X-1), 4 (line γ-4) days, respectively. The selected lines showed shorter culm length and ear length compared with the control. Total spikelets per panicle, percent ripened grain and thousand grain weight of the lines were also mostly shorter or lower than those of the control except total spikelets per panicle of γ-4 and γ-5 lines. When genetic variations of rps16-trnK region were evaluated by nucleotide analysis, nucleotide length of the rps16-trnK region was 664 bp in all the early-heading lines and control. Out of 5 sites of nucleotide transposition detected in the region, however, 2 sites were appeared only in the early-heading lines. Amylose content of the early heading lines ranged from 18.3% to 18.4% and the content was included in high eating quality. Protein content of the lines ranged from 6.6% to 7.0%. The content belonged to Top-rice showing under 7% of protein content. Toyo taste value of the lines ranged from 76.3% to 84.8%.

Genetic diversity of 45 tea accessions from Korea, Japan, China and Taiwan was investigated by using RAPD analysis. Out of the eighty primers screened, twenty primers generated 99 polymorphic bands with a polymorphic rate 87.0%. The size of the amplified fragments ranged from about 3,138 bp to 520 bp. By cluster analysis, all of the 45 accessions can be grouped into five groups. Over 90% of the 32 Korean accessions belonged to group II, III, IV and V. Moreover, newly developed Korean cultivars (accession no. 13, 14 and 15) belonged to very different group compared with any other Korean accessions. Among the Korean accessions, the minimum genetic similarity 0.500 was obtained between accession no. 17 and 37 and the largest genetic similarity 0.912 between no. 20 and 21.