| To effectively explore and exploit the favorable alleles in Oryza longistaminata for rice improvement, especially in breeding for perennial rice or for fixing rice heterosis with perenniality, an F2 population containing 227 individuals derived from an interspecific cross RD23 / O. longistaminata, was raised. RD23 is an indica cultivar from Thailand, the accession of O. longistaminata was collected from Niger and kindly supplied by Dr. Hiroshi Hyakutake, the Institute of Physical and Chemical Research, Japan. This F2 population was utilized for molecular linkage map construction with well distributed microsatellite markers. Several traits associated with perennial growth habit (listed below) were investigated on this population and the data was used for QTL analysis:1, Rhz = rhizome presence or absence2, RN = rhizome number per plant,3, RED = rhizome branching degree,4, RBN = rhizome branching number per plant,5, RL = average rhizome length (in cm),6, RIL = average rhizome internode length (in cm),7, RIN = average rhizome internode number,8, RDW = rhizome dry weight (in g) per plant, and9, TN = tiller number per plant,The main findings of this study are as follows:1, The FI plant from RD23/O. longistaminata cross was obtained by direct hybridization followed by embryo rescue. The FI showed indehiscent anthers with 32.53% pollen fertility. The rhizome expression of O. longistaminata showed incomplete dominance with intermediate number of rhizomes, implying that the genetic linkage between rhizomeexpression and lethal gene was in contrast with earlier findings of other workers.2, An F2 segregating population containing 227 individuals was obtained by enforced self-pollination of the FI plant. The number of F2 plants with and without rhizomes were 121 and 106 (X2 is 0.801177), indicating the action of two dominant complementary genes for rhizome expressed. We tentatively assigned the two dominant complementary genes controlling the rhizome expression in O. longistamina as Rhz2(t) and Rhz3(t), respectively.3, The 71.92% of 456 SSR markers (published or unpublished) showed polymorphism, whereas the rest failed to show amplification or they were monomorphism. Fifty five percent of these polymorphism markers detected heterozygy in the FI interspecific hybrid, indicated that O. longistaminata parent is highly heterozygous. Sometimes it shared one of its alleles with RD23.4, It is the first report that a molecular linkage map constructed using 181 microsatellite and 227 individuals derived from (O. sativa/O. longistaminat) interspecific cross. The genetic map spanned 1758.6 cM and covered all of 12 rice chromosomes with an average distance of 9.72 cM between adjacent markers. Segregation of 40% of the markers fitted the Mendelian expectation with 1:2:1, whereas the remaining markers showed distortion on regions of chromosome 2, 3, 4, 5, 6, 9, 11. On the average, O. longistaminata accounted for 45.5% of the genome. Genetic background for chromosome 3, 9 is mostly skewed to O. longistaminata. The markers (loci) linear order and location is nearly identical with previous genetic map (IR64/Azucena). This map our constructed could provid a useful tool for detecting new alleles and for mapping favorable traits from O. longistaminata.5, The loci, OSR16 and RM119, located on chromosome 3 and 4 respectively, were significantly associated with Rhz2(t) (X2 = 40.28, P<0.0001) and Rhz3(t) (X2 = 64.41, P<0.0001). A subset of population according to this two loci genotype was constructed to test rhizome inheritance model. We tentatively designated it as map-based population, meanwhile, experiment-based population was named according to phenotype. The goodness-fit test also indicated that the predicted rhizome phenotypes of the ? individuals based on the genotypes at the two markers were consistent with the observed rhizomeexpression (X2 = 1.29, P = 0.26). The X2 value from the two-gene model was 113.2 (P < 0.0001), much greater than that obtained from either single-marker models...
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