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Primary and secondary trisomics as well as telotrisomics have been well characterized in rice morphologically and the transmission rates of extra chromosomes have been investigated. Primary trisomics have been utilized for associating genes and linkage groups with respective chromosomes. Secondary trisomics and telotrisomics were employed to associate genes with respective chromosome arms. As a result the positions of centromeres on the linkage maps could be pinpointed. Monosomic alien addition lines (MAALs) have a complete chromosome complement of Oryza sativa and a single chromosome of a wild species in genus Oryza. All the MAALs of O. officinalis and O. punctata have been produced. A partial set of MAALs of 5 other wild species of rice have also been produced. These aneuploid stocks of rice are useful not only for genetic study such as gene dosage analysis but also for rice breeding. [ABSTRACT FROM AUTHOR]

We have developed near-isogenic introgression lines (NIILs) of an elite indica rice cultivar (IR64) with the genes for β-carotene biosynthesis from dihaploid (DH) derivatives of golden japonica rice (cv. T309). A careful analysis of the DH lines indicated the integration of the genes of interest [phytoene synthase ( psy) and phytoene desaturase ( crtI)] and the selectable marker gene (hygromycin phosphotransferase, hph) in two unlinked loci. During subsequent crossing, progenies could be obtained carrying only the locus with psy and crtI, which was segregated independently from the locus containing the hph gene during meiotic segregation. The NIILs (BC2F2) showed maximum similarity with the recurrent parent cultivar IR64. Further, progenies of two NIILs were devoid of any fragments beyond the left or right border, including the chloramphenicol acetyltransferase ( cat) antibiotic resistance gene of the transformation vector. Spectrophotometric readings showed the accumulation of up to 1.06 µg total carotenoids, including β-carotene, in 1 g of the endosperm. The accumulation of β-carotene was also evident from the clearly visible yellow colour of the polished seeds. [ABSTRACT FROM AUTHOR]

Quantitative trait loci (QTLs) for plant height in rice were mapped on to RFLP maps in five populations, whose sizes varied from 135 to 250. A total of 23 QTLs were located in all 12 rice chromosomes, and eight of these QTLs were shared by at least two populations. The positions of the 23 mapped QTLs were compared to the positions of 13 major dwarfing or semi-dwarfing genes previously linked to RFLP markers. Results indicated that all 13 dwarfing or semidwarfing genes were in close proximity to the QTLs, providing evidence to support the hypothesis that QTLs and major genes were different alleles of the same loci. [ABSTRACT FROM AUTHOR]