Short and erect rice (ser) mutant from ‘Khao Dawk Mali 105’ improves plant architecture

Plant architecture includes branching (tillering) pattern, plant height, leaf shape and angle, and the structure of reproductive organs. These attributes are of major agronomic importance as they determine the adaptability of a plant to various methods of cultivation, which in turn influence harvest index and grain yield. We detected a recessive mutant from the aromatic cultivar Khao Dawk Mali 105 (KDM105), which exhibits a plant architecture with shorter height, shorter and more erect leaves and panicle than the wild type. The mutant line was named ser for short and erect rice. The ser mutation was induced by 30 kilorads of gamma radiation. Averaged from 10 mature plants grown in the greenhouse, the ser had 104.6 degrees smaller angle between the flag leaf and culm, compared with the KDM105 wild type. For the leaf below the flag leaf, the ser mutant was 46.2 degrees more erect than the wild type. The length of the flag, 2nd and 3rd leaf of the ser was 21.8, 24.4 and 16.3 cm shorter than the wild type, respectively. Plant height as measured from soil surface to flag leaf tip was reduced by 43.5 cm, while plant height measured from soil to panicle tip was reduced by 28.5 cm in the ser in comparison with the wild type. Characterization of 10 booting plants each of the ser, wild and their reciprocal F1 populations confirmed the shortening mutation with no cytoplasmic effect. The ser was identically monomorphic to its wild type and F1 hybrid for all 11 SSR markers covering seven chromosomes, indicating a true mutation. In the F2 generation, a ratio of three wild type to one ser was observed, resulting in a chi(2) of 0.067 (P = 0.795) for a single gene segregation and demonstrating a recessive mutation. The ser will be an ideal material for the study on gene pleiotropy and metabolism functions. Further, the pleiotropic gene in such a premium quality cultivar globally known will be valuable for improving plant architecture in rice cultivars.