Development of new aromatic rice lines with high eating and cooking qualities

Rice is the staple food for about half of the world’s population.Preferred by consumers,aromatic rice is a special type of rice with great commercial value.Cooking and eating qualities and aroma are the major grain qualities favored by most consumers.Currently,most of the available aromatic varieties have low yields and some undesirable agronomic traits.Thus,there is an urgent need to develop better aromatic rice varieties.This work aims to identify rice germplasm lines that have good grain quality and to develop new varieties with desirable traits.Thirty-six out of 188 germplasm lines were found to have betaine aldehyde dehydrogenase 2 (badh2) controlling the aroma and were analyzed for their 2-acetyl-1-pyrroline (2AP) contents.Then,17 of those lines were found to have alleles for low amylose content and low gelatinization temperature,controlled by waxy and starch synthase Ⅱa (SSⅡa),respectively,suggesting that they are aromatic rice lines with high cooking and eating qualities.A total of 158 F_(7)recombinant inbred lines (RILs) generated from five crosses of the selected germplasm lines were planted for phenotypic and yield observations,resulting in 27 F_(8)RILs selected for yield evaluation and genotyping.Finally,four out of the seven F_(9)aromatic RILs showed high yield,high 2AP production,and low amylose content,in agreement with their genotypes.The other three F9RILs were aromatic rice lines with high amylose content and high yield.Because consumer preferences for grain quality vary depending on regions and ethnic groups,the high-yielding aromatic RILs generated from this study can be used to increase the yield of Thai rice and to raise market value and farm profits.

Molecular Markers and Candidate Genes for Thermo-Sensitive Genic Male Sterile in Rice

The discovery of thermo-sensitive genic male sterility(TGMS) has led to development of a simple and highly efficient two-line breeding system. In this study, genetic analysis was conducted using three F_2 populations derived from crosses between IR68301 S, an indica TGMS rice line, and IR14632(tropical japonica), Supanburi 91062(indica) and IR67966-188-2-2-1(tropical japonica), respectively.Approximately 1:3 ratio between sterile and normal pollen of F_2 plants from the three populations revealed that TGMS is controlled by a single recessive gene. Bulked segregant analysis using simple sequence repeat(SSR) and insertion-deletion(InDel) markers were used to identify markers linked to the tms gene. The linkage analysis based on the three populations indicated that the tms locus was located on chromosome 2 covering the same area. Using IR68301S × IR14632 F_2 population, the results showed that the tms locus was located between SSR marker RM12676 and InDel marker 2gAP0050058. The genetic distance from the tms gene to these two flanking markers were 1.10 and 0.82 cM, respectively.InDel marker 2gAP004045 located between these two markers showed complete co-segregation with the TGMS phenotype. In addition, InDel marker vf0206114052 showed 2.94 cM linked to the tms gene using F_2 populations of IR68301S × Supanburi 91062. These markers are useful tool for developing new TGMS lines by marker-assisted selection. There were ten genes located between the two flanking markers RM12676 and 2gAP0050058. Using quantitative real-time PCR for expression analysis, 7 of the 10 genes showed expression in panicles, and response to temperatures. These genes could be the candidate gene controlling TGMS in IR68301S.