우량수도품종육성(優良水稻品種育成)을 위(爲)한 기초자료(基礎資料)를 얻고자 입(粒)의 크기가 서로 다른 벼 7개품종(個品種)을 이면교잡(二面交雜)하여 미립(米粒)의 크기와 모양에 대(對)해 잡종강세(雜種强勢), 조합능력(組合能力) 및 유전분석(遺傳分析)을 실시(實施)하여 얻어진 결과(結果)를 요약(要約)하면 다음과 같다. 1. 평균(平均) heterosis는 입장(粒長)과 장/폭비(長/幅比)에서 부(負)의 방향(方向)으로 유의(有意)하였고, 입폭(粒幅), 입후(粒厚), 입중(粒重)에서는 유의성(有意性)이 없었다. 2. 전형질(全形質)에서 일반조합능력(一般組合能力), 특정조합능력(特定組合能力) 및 정역교잡효과(正逆交雜效果)가 유의(有意)하였고, 입장(粒長), 입폭(粒幅), 입후(粒厚), 입중(粒重)에서는 상가적(相加的) 유전분산(遺傳分散)이 비상가적(非相加的) 유전분산(遺傳分散)보다 컸다. 3. 일반조합능력효과(一般組合能力效果)는 입(粒)의 크기와 입중(粒重)에서 Arborio와 BG2 등(等) 대립종(大粒種)이 정(正)의 방향(方向)으로, 장/폭비(長/幅比)에서는 BG2와 낙동(洛東)벼가 단원방향(短圓方向)으로 유의(有意)한 효과(效果)를 나타내었다. 4. 전형질(全形質)에서 부분우성(部分優性)을 나타내었으며, 우성(優性)의 방향(方向)은 입장(粒長), 입폭(粒幅), 장/폭비(長/幅比)에서 부(負)의 우성(優性)이었고 입후(粒厚)와 입중(粒重)에서는 일정(一定)하지 않았다. 5. 유효유전자수(有效遺傳子數)는 입장(粒長)과 장/폭비(長/幅比)에서 2개정도(個程度)로 추정(推定)되었고 협의(狹義)와 광의(廣義)의 유전력(遺傳力)은 전형질(全形質)에서 매우 높게 나타났다.

To diversify the grain size and shape of japonica rice, we developed the Breeding Materials with Diverse Grain Size and Shape (BM_DGS) and characterized the grain and yield-related traits. We used the donor parents Jizi1560 and Jizi1581, japonica germplasm with extremely large grain size. Four cross combinations between the each donor parents and Korean high yielding japonica rice cultivars, Deuraechan and Boramchan, were constructed and anther culture method was applied. Among 290 doubled haploid lines, we selected 91 elite lines with diverse grain size and shape and designated to the BM_DGS. The grain size and shape of BM_DGS exhibited beyond the characteristics of previously developed Korean rice cultivars. The alleles of major grain-related genes, GW2, GS3, and qSW5, in BM_DGS showed two types, wild type or loss-of-function mutant type. The loss-of-function mutant alleles, gw2, gs3, and qsw5, had an effect on increasing grain size. The phenotypic variation of grain length was mostly controlled by GS3 alleles, and grain width and thickness were influenced by the combinations of GW2 and qSW5 alleles. 1,000-grain weight was determined by the combinations of GW2, GS3, and qSW5. The grain-related genes influenced the phenotypic variation of yield-related traits. The result of this study could be useful to elucidate the relationship between the grain-related genes and agronomic traits. And the BM_DGS are being utilized in the breeding programs to diversify the grain size and shape in japonica rice.

Increasing demand on cereal grains to meet the population growth requires more production of rice as well as other cereals, which is supposed to rise up to 40% until 2030. Grain size and shape are critical factors determining grain yield. Several genes on grain shape and size have been reported, and of them, seven cloned genes were chosen for haplotype analysis, such as GS3, GW2, qSW5, GS6, GW8, GS5, and TGW6. We genotyped 218 rice varieties which had diverse grain size and shape originating from 25 countries. As for GS3 and qSW5, PCR markers were developed for point mutation and deletion, respectively. For the other five genes in which functional SNPs were reported, we designed primer sets to distinguish a fuctional allele for each gene. GW2 and TGW6 had two alleles, while the other five genes displayed three alleles which were evenly distributed throughout the population. Analysis on the relationship between haplotype of the genes and grain phenotype is in progress. We expect that desirable allelic combination of genes would assure the optimal grain size and shape for higher grain yield and market quality. This work was supported by a grant from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No.PJ009076), Rural Development Administration, Republic of Korea.

An indica rice cultivar, Milyang23 is a semidwarf plant type with long and slender grains, whereas a temperate japonica rice cultivar, Stejaree45 is a japonica cultivar with short and bold grains. Genetic analysis was carried out to determine the number of quantitative trait loci (QTL), chromosome location, gene action, and effects of QTLS controlling grain length, width, thickness, and shape. The grain traits averages in the recombinant inbred lines (RILs) were near the mid-parent value, but the standard deviations in the RILs were more than those of the parents. A linkage map based on 138 simple sequence repeat (SSR) markers from 12 linkage groups was constructed using the 143 RILs as the base population. The map, spanning 1208 cM of the rice genome with an average interval length of 12.9 cM, was used for QTL analysis. A total of 13 QTLS for grain quality traits were identified. The phenotypic variation accounted for by each QTL ranged from 4.2% to 10.4%, with an average of 6.7%. Among the 13 QTLS, only one QTL accounted for more than 10% of the total phenotypic variation. Each of the traits studied was governed by one or two major QTLs that accounted for the large proportion of the total phenotypic variation. Several minor QTLS explain a small proportion of the total phenotypic variance.