Breed New Strain Of Agaricus Bisporus By The Technique Of Radioisotope⁶⁰Co Mutagenesis

The objective of this work was to breek new excellent strains of Agaricus bisporus by60Co-gamma ray mutagenensis of Agaricus bisporus spores.Both the parent and the contrast strains were domestic cultivars As2796. Basidiospore of the parent strain was under mutagenensis treatment with different irradiation dose of gamma ray. And the objective was to discover the possibility of creating Agaricus bisporus breeding materials combining with molecular maker experiments (RAPD and ISSR markers), isozyme markers experiments and field fruiting experiments.The results of mutagenic treatment showed that the optimal condition of spore germination included the spore suspension concentration of103spores/ml,10mg/ml of thiamine added and keeping for40min at40℃. A total of100μL spore suspension was pipetted and coated on the dung medium uniformly and spore started to germinate after incubating at25℃for ten days. It concluded that the mortality rate of spores was between50.6%to90.63%when the irradiation doses were between100-1000Gy. And the mortality rate of spores increased with the increasing of irradiation dose. Furthermore, there was significant difference among different mortality rate of spores (P<0.05or P<0.01). The semi-lethal dose was100Gy, which indicated that spores of Agaricus bisporus were sensitive to radiation exposure. The mycelium morphological characteristics of mutant strains and parent ones were basically the same, but it differed from the growth rate of mycelium. Irradiation dose affected mycelial growth rate:the average growth rate of strains was fastest under500Gy irradiation doses and reached2.39cm/10d; the average growth rate of strains was slowest under600Gy irradiation doses, only1.89cm/10d. Based on mycelial morphological characteristics and growth rate, it was difficult to compare mutant strains to parent ones, so molecular marker experiments were needed to distinguish the differences.The resuts of molecular genetic markers and isozyme markers research showed: there was a different genetic relationship between mutant strains and parent ones, which suggested RAPD, ISSR and isozyme markers experiments could provide a good way of discovering better mutant strains with reducing the workload of mutation breeding in the process of cultivation. Moreover, ISSR was more suitable for selecting mutant strains than RAPD. In general, RAPD, ISSR and isozyme markers experiments were able to be applied to select mutant Agaricus bisporus strains and it would be a good way to analyze genetic relationship of Agaricus bisporus strains and identify new mutant strains.The results of field test showed:compared the genetic mapping of ISSR and isozyme, as well as the growth of strains,12strains were selected eventually from the mutant strains to culture.The fruiting result showed:the shape of mushroom was rotundity basically in the12selected strains compared with the parent and there were differences between the12selected strains and parent one in color, size and fruit quality. And there were4high yield strains and8strains of low yield strains.The fruit body of SAU-As6、SAU-As38、SAU-As69strains were white and compact. Their pileus were smooth and circular. Their stipes were short and thick. The yield was increased by16.60%—13.68%compared with As2796.Through comprehensive analysis, ISSR indicated that the genetic similarity coefficient of SAU-As6,SAU-As38,SAU-As69with parent one was0.68,0.64and0.74, respectively. The results of isozyme markers showed that the genetic similarity coefficient of SAU-As6,SAU-As38,SAU-As69with parent one was0.75,0.59and0.76, respectively. The SAU-As6,SAU-As38,SAU-As69strains could be used for subsequent experiments in cultivation and they would become breeding materials for subsequent breeding of new variety.