Mutagenesis in Gynomonoecious Spinach (Spinacia oleracea L.) Plants and Selection of Low Oxalate Variants

This study was conducted to evalute mutagenesis in gynomonoecious spinach (Spinacia oleracea L.) plants for inducing low oxalate variants.Gamma-ray and ion beams of 220 MeV12C5+ and 50MeV 4He2+ ware used as mutagen in seed irradiation. Optimum dosages for irradiation were determined to be about 100Gy, 15-20Gy and 150-200Gy in gamma-ray, 12C5+ and 4He2+, respectively. In M2 generation, there was one line segregating albino seedlings, one line segregating xantha seedlings and two lines segregating dioesious spinach. To save on labor and time for analysis, selection of low oxalate variants in M2generation was conducted by a two-step selebtion which consisted of the first snalysis of bulked leaves from 2 plants as one specimen followed by the second analysis of selected individual plants. In the first analysis of 813 specimens, we selected 13 specimens as low and 9 specimens as high in oxalate content. In the second analysus, there was consistency in the distribution of low and high oxalate content corresponding to the first screening, indicating that selebtion of low oxalate variants could be achived by this two-step selebtion with half the labor and time for analysis as compares to non-bulked method. There were no clear differences in distribution of oxalate content between M3progenies of plants selected as low or high oxalate content, suggesting that the low oxalate content in plants isolated in M2generation was not of a genetic origin. From these results, it seems to be necessary to explore a variant with obvious deviation from the bontinuous variation of oxalate content in the M 2 generation.