The Rice Eui2 Gene Discovery, Genetic Molecular Markers And Positioning

Elongated uppermost internode gene is a very useful element for seed production of hybrid rice. It could be used to develop a taller restorer line and a sterile line without the enclosure of the panicle within the sheath of the flagleaf so as to increase yield of seed production, improve seed quality and decrease seed cost. Two types of mutants possessing elongated uppermost internode (eui) was identified from M2 population of Xieqingzao B-line(XQZB) treated with 憏-ray, named Xieqingzao eB-1 (XQZeB-1) and Xieqingzao eB-2 (XQZeB-2) respectively. Both of them showed tall status due to much longer culm length than that of origin XQZB. The increased culm length of XQZeB-2 was mainly due to the elongation of the uppermost internode by 90.2%. But the increased culm length of XQZeB-1 was due to not only the elongation of uppermost internode but also the elongation of the lower intemodes, which come to 53.3% and 46.7% of total increased culm length respectively. The studies on their hybridization progency showed that a recessive gene governed the character of elongated uppermost internode of the two mutants respectively. The two pairs of recessive genes were non-allelic. The 4 allelic test among XQZeB-1, XQZeB-2, and other elongated- uppermost-internode stocks reported by now, such as 76:4512, lRSOeui, Gric, 02428h, showed that the eui gene among XQZeB-1, 76:4512, lRSOeui, 02428h was allelic, but the eui gene of XQZeB-2 was non- allelic to that of them. Based on above results, it could be concluded that the eui gene of XQZeB-2 is a new gene, designated as eui2. A F3 population was developed from the cross of XQZeB-2 and AJNT to identify molecular markers linked with euI2 gene. With the aid of SSR marker analyses, four SSR markers RM271, RM269, RM258 and RM304 with genetic distance to eui2 were 33.1cM, 12.9cM, 12.0cM, and 1.4cM respectively were screened. Using the technique of AFLP analysis and bulked segregant pools, approximately 8960 AFLP loci were screened with 128 primer combinations. Four polymorphic AFLP products were identified, designated as El, E2, E3 and E4, respectively. El was subsequently mapped on the middle of the long arm of chromosome 10 by using doubled-haploid mapping population derived from the crosses ZYQIJXi 17 and their corresponding molecular linkage maps developed in Prof.ZhuLihuang抯 laboratory Institute of Genetics, Chinese Academy of Science. The genetic distance of El to the markers G291 and G2l55 located on it both side is 4.7cM and 13.1cM respectively. The local linkage map of the eui2 gene was constructed with SSR markers and El. It showed that eui2 gene was located between RM304 with 1.4cM and El with 0.6cM. The identification of markers RM304 and El flanking the gene eui2 at 1.4cM and 0.6cM, respectively, will 5 facilitate the selecttion of this character in breeding programs and provide the foundation for map-based cloning of this gene. The identification of eui2 gene makes it possible to develop hybrid rice with sterile lines (A lines) and restorer lines ( R lines) possessing different eui genes simultaneously, which would result in no or less application of GA3 for both of parental lines.