Development Of Low Phytic Acid Mutants In Rice (Oryza Sativa L.)

Four mutated rice populations, derived fromM1 materials of which dried seeds (ca 13.5% moisture) were treated with 60Co gamma rays of 300 Gy at 0.8 Gy/min, or with 250 Gy followed by 2 h treatment of germinating seeds in NaN3 solution (10~3 mol/L), were screened for high inorganic phosphorus (HIP) seeds, the frequency and transmission mode of HIP seeds from M2 to Ms were investigated. Several types of low phytic acid mutants (named HIPin, HIPjn) were obtained from Xieqingzao B and Xiushui 110 , and some representative mutants were studied in the experiment. The main results are as follows:1. Less than expected number of HIP M3 plant lines (M2:3) were identified from HIP M2 plants. However, most HIP M3 lines yielded HIP MI progenies. Based on the number of HIP plant lines confirmed in Mi and Mi, it was estimated that HIP mutation frequency was around 0.1% in M2 rice populations.2. Genetic analysis showed that the HIP mutations in mutant line HIPil and HIPi2 derived from different M2 plants of the indica variety Xieqingzao B and HIPjl from japonica Xiushui 110 were controlled by a pair of recessive nuclear genes. Allelic test revealed that mutation loci in HIPil and HIPi2 were allelic to the 1pal in Kaybonnet reported in USA, but the mutation in HIPil was non-allelic to that in HIPjl.3. Analysis of phosphorus showed that the content of inorganic P was higher and phytic acid P was lower in every portion of HIPil and HIPjl seeds than that in corresponding parent, while little was changed for total seed P. The ratio of phytic acid to total P in seed of HIPil decreased from 65.3% of its parent to 35. 1%, while the inorganic P was increased from 7.2% to 20.5%. Therefore, HIPil has the characteristic of 1pal mutation. The mutant of HIPjl was designatedIpa2 because it remained same TP level as its parent, but the ratio of phytic acid was decreased from 62. 1% of its parent to 26. 4% , while inorganic P increased from 9. 3% to 26%, accompanied with the increase of Ins polyps from 9. 7% to 19. 6%, little effect on TP.4. The agronomic performance of HIPil was similar to its parent Xieqingzao B except plant height and grain weight.