ARS | Publication request: Various mutants derived from 'Khao Dawk Mali 105' using gamma radiation

Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 27, 2012
Publication Date: N/A

Technical Abstract: Mutations induced by radiation and chemicals have been widely used for genetic studies and cultivar improvement. Khao Dawk Mali 105 (KDM105), an aromatic cultivar from Thailand, is globally known for its premium quality. Seeds of KDM105 were obtained from the International Rice Research Institute (IRRI) in 1995. Each seed was given an identification number and grown out in quarantine. Seed harvested from each individual plant was grown in panicle rows to verify uniformity and purity and panicle rows were bulk harvested. One hundred grams of seed derived from a single seed identified as KDM 95-14 were irradiated using gamma radiation generated from Cs-137 inside a gamma cell 1000 at 30 kilorads (KR). After growing an M1 population in the spring 2000 in Puerto Rico nursery, two thousand panicles were harvested and the M2 generation was planted in panicle rows in July 2000 at the University of Florida. Numerous mutants were identified and selfed for three generations for seed increase and characterization in this study. Mutant lines exhibited variation that included changes in plant architecture (height, leaf angle), glume size, and leaf anomalies such as necrotic tips, rolled leaves, white variegation, and extreme stunting. This paper describes the inheritance and characterization of some of these traits. 1). Plant architecture. The mutant exhibits an altered architecture with shorter height, and leaves and panicles that are more erect than the KDM105 wild type. Notably, all characteristics seem to be influenced by a simple, single mutation at a single locus. Crosses between the wild type and the mutant line segregated 3:1 in the F2 generation (132:46, Chi-square 0.067, p=0.795). The flag leaf on mutant plants was much more erect, such that the angle between the flag leaf and culm was reduced by 104 degrees compared to the wild type. The leaf below the flag leaf was 46 degrees more erect in the mutant than the wild type. The lengths of the flag, 2nd, and 3rd leaves were 22, 24, and 16 cm shorter than the wild type, respectively. Plant height as measured from soil surface to flag leaf tip was reduced by 44 cm, while plant height measured from soil to panicle tip was reduced by 29 cm in comparison with the wild type. 2).Enlarged glume: Glumes of rice are very reduced and located at the base of the lemma and palea (the hull). The mutant line had greatly enlarged glumes, such that they extended roughly the length of the grain and were lighter in color. In crosses with the wild type, segregation in the F2 was 3:1 (244:69, Chi-square 0.329, p= 0.566), indicating monogenic inheritance of the recessive mutant type. 3). Necrotic leaves: At about the five-leaf stage, the distal 1/3 of leaves became necrotic. Mutant plants grew more slowly and less vigorously than the wild type. This trait segregated 3:1 in the F2, again indication monogenic inheritance of a recessive trait (129:42, Chi-square 0.018, p=0.895). 4). Rolled leaves: Commencing at the three-leaf stage, all leaves rolled inwardly all the way to maturity. The F2 segregation was 114:37, wild type: mutant, with a Chi-square 0.020 and p=0.888. These mutants were identically monomorphic to the wild type and F1 hybrid for all of 11 SSR markers covering 7 chromosomes, indicating true mutations. The simple inheritance and easily recognized morphology of these mutant lines, in the background of one of the world’s most popular commercial rice types, may have utility in genetic studies or breeding line development.