Genetic Analysis And Gene Mapping Of Two Plant Height Mutants In Rice

Plant height is one of the important agronomic traits of rice. Over higher plant would easily result in plant lodging and output reducing. On the other hand, the dwarf varieties with proper plant height had higher lodging resistance and a greater harvest index, allowing for the increased use of nitrogen fertilize. Dwarf breeding had made a great breakthough in the rice breeding. The breeding and extension of excellent dwarf varieties remarkably improved the yield potential of rice. Therefore, the plant height is still one of focuses in rice genetic research.So far a great deal of studies have been made on the dwarf trait of rice, and about sixty dwarf and semi dwarf genes have been reported. A small grain dwarf mutant "162d" was identified from a semidwarf variety Shuhuil62. 162d was crossed with four semidwarf varieties. The analysis of plant height in the F1 and F2 populations shows that the dwarf trait of 162d is controlled by one recessive major gene. The allelic analysis between mutant gene harbored in 162d and small grain dwarf gene d1 indicates that they are nonallelic. The local linkage map of the mutant gene was constructed with F2 population of 162d crossed with II-32B and molecular marker technique. The results suggest that the dwarf gene is located on the one side of the microsatellite markers, RM218 and RM157, on the short arm of rice chomosome 3, and the genetic distances from the target gene to the markers, RM218 and RM157, are 3. 5cM and 10. OcM, respectively. At the same time, phenotype effects of the gene were analyzed by using the near isogenic lines, the results indicate that this mutant gene can reduce the plant height and grain size to about a quarter of that of its near isogenic line Shuhui162, shorten and broaden the leaf, and decrease the seed setting rate evidently. This gene, probably being a new dwarf gene in rice, is designated tentatively as d162(t).Until now, some rice recessive long culm mutants from the semidwarf varieties have been reported, but there has been no report on the dominant long culm mutant.A long culm mutant "D111" was identified from progenies of the cross between semidwarf varieties 6442S-7 and Shuhui881. Its culm length extremely increased, being longer 87.06% than that of Shuhui881. D111 was crossed with semidwarf varieties, Shuhui88K 6442S-7, Shuhui527, Xianguo and 02428. The analysis of plant height in the F1 and F2 populations shows that the long culm trait of D111 is controlled by one dominant major gene. D111 is probably the first example of dominant long culm mutant indentified from the semidwarf varieties of rice. The local linkage map of the mutant gene was constructed with F2 population of D111 crossed with Shuhui527 and molecular marker technique. The results suggest that the long culm gene is located on the one side of the microsatellite markers, RM302 and RM212, on the long arm of rice chomosome 1, and the genetic distances from the target gene to the markers, RM302 and RM212, are 21. 9cM and 24. 1cM, respectively. This gene is designated tentatively as LC(t).