| Summary: | 碩士 === 國立臺灣大學 === 農藝學研究所 === 98 === The Effects of Hd1, Hd6, and Ehd1on Rice Heading Date
TNG 67 was an elite cultivar in Taiwan. This variety carried hd1, hd6 and ehd1 three recessive genes and insensitive to photoperiod. The Japanes elite cultivar, Ko-shihikari, possessing good quality, is very popular not only in Japan but also in Taiwan. However, Koshihikari heads early in Taiwan because of 3 photoperiodic genes Hd1, Hd6 and Ehd1. One of elite cultivar in Taiwan, Tainung 67 is photoperiod insensitive. Through marker assisted selection (MAS), in these three heading date genes of TNG 67 had been introgressed to Koshihikari, and three BC3F2 populations derived from three different BC3F1 individuals, ＃286-85-A4、＃286-14-A23 and ＃286-85-A27. In second crop season in 2009, those BC3F2 populations were planted under natural lightness’ field. The heading dates for each population displayed continuous distribution. After analysis the effect cause by three genes, Ehd1 with the largest effect on heading date. Recessive homozygotes ehd1 could posponed 23.5 days to head, significantly. Hd1 was the second effective gene, Hd6 had the minor effect for heading date delay. Total of 27 genotypes composed by combination of three heading date genes. The earliest heading time was 69.4 days found in A27 population, which genotype was Hd1Hd1 Hd6 hd6 Ehd1Ehd1. The lasted heading time was 109 days. Discovered in A4 population, which genotype were hd1hd1 Hd6Hd6 ehd1ehd1. The heading dates for most of the genotypic combinations in three populations were be-tween 80 to 90 days and transgressive segregants were found. Thus heading date could be adjusit by different genotype combination. By using MAS, near isolation lines of Koshihikari carring different heading date genes could be developed. After evaluation of field trials under different environment, several varieties derived from NILs of Koshihikari possessing different heafing dates could be promoted to growal different location and different crop seasons.
Development of molecular markers of wild rice
Through human domestication and breeding program, people have developed a lots of elite cultivars and received huge economical reward, but it let the genetic di-versity of the rice gene pool much narrower than before. Recovering the land race and wild rice material is one way to improve the genetic diversity of cultivar gene pool searching for polymorphic markers is essential. Through this method, researchers have discoveried lots of genes, which can endow with elite cultivar resistance of biotic and abiotic stress, developed a complete linkage map to posit the genes; breeders can breed by marker assisted selection (MAS) a more efficient way to utilized wild genetic resource to improve better cultivar traits (Gupta et al., 2002). The final goal for this research is to develop a complete chromosome segment substitution (CSSLs), each carry chromosome from O. officinalis (CC genome) and O. australiensis with O. sativa sub-species (AA genome) TCS 10 and TNG 67 background, respectively. This research was trying to figure out a new way to received polymorphic DNA markers between wild and cultivar rice.
249 SSR (simple sequences repeat; rice microsatellite) had been selected, but only 100 (40%) and 67 (27%) of markers could amplify in O. officinalis and O. aus-traliensis successfully. Due to all SSR markers are developed based on sequence of O. sativa, the sequence variation between difference genomes, the regions for primers may lose in the others genome. Few SSR markers can be transferred into others ge-nome. To more effencially acquire the polymorphic markers; we compare the sequence of wild and cultivar rice by bioinformatics software, search for indel regions. Finally 123 markers had been developed. 109 (89%) and103 (84%) markers can amplify in two wild species successfully, and 79 (72%) and 82 (68%) of markers can present polymorphic between O. officinalis . TCS 10 and O. officinalis vs. TNG 67; 64 (62%) and 65 (63%) of markers can present polymorphic between O. australiensis vs. TCS 10 and O. australiensis vs. TNG 67. This is an efficient way to receive polymorphic markers for linkage analysis, develop such as CSSLs for research and breeding program, to improve the use efficiency of wild material.
From the result of genotying BC1F1 and BC2F1 populations, derived from O. of-ficinalis × TNG 67, the ratios of heterozygous change from 86.7% in the (BC1F1) to 18.1% (BC2F1), the chromosome segment of wild rice be eliminated from progenies, rapidly. So it is almost impossible to develop a complete CSSLs population, which carried the chromosome segment from different genome of wild species into O. sativa background.
|
|---|
