掘氏疫霉遗传学研究——Ⅱ.交配型遗传与变异的研究

GENETICS OF PHYTOPHTHORA DRECHSLERI——Ⅱ. THE INHERITANCE OF MATING TYPES

本研究以掘氏疫霉Phytophthora drechsleri Tucker野生型菌株的单游动孢子无性系为亲本,测定了自交、杂交后代交配型的遗传,经KMnO_4处理引起的交配型变异以及F_1代可自孕单卵孢株有性生殖后代交配型的遗传与变异。聚碳膜间隔配对诱导A_1和A_2菌株自交产生的卵孢子经H_2O_2处理刺激萌发(萌发率12～16％)获得单卵孢株。交配型测定结果表明,A_1和A_2亲本自交S_1代单卵孢株均保持与亲本一致的交配型。用KMnO_4处理上述卵孢子导致A_1和A_2亲本的部分S_1代单卵孢株出现自孕现象,少数A_1亲本自交后代改变为A_2交配型;从A_1交配型亲本的S_1代可自孕菌株产生的卵孢子萌发所建立的单卵孢株中,同时获得A_1和A_2交配型菌株。上述结果不支持Sansome关于疫霉菌A_1、A_2交配型分别由纯合、杂合基因控制的假说,进一步证明了Ko关于交配型抑制因子控制交配型表达的假说的合理性。掘氏疫霉种内菌株直接配对产生的卵孢子用H_O_2刺激萌发获得F_1代单卵孢株。测定结果表明,在F_1代出现A_1、A_2、A_1A_2、A^04种交配型的单卵孢株,其比例因不同亲本组合而有较大差异。 F_1代出现的A_1A_2菌株自孕产生的卵孢子经H_2O_2处理刺激萌发建立自交系,观察到A_1A_2交配型在有性生殖后代发生分离,各交配型比例因亲本不同而异。A_1A_2菌株的自孕能力在单游动孢子无性系后代可稳定遗传,认为F_1代出现的A_1A_2个体来自亲本的杂交。A_1A_2单卵孢株保藏4～6个月后大多仍具自孕能力,少数改变为A_2交配型。

The inheritance of mating types of Phytophthora drechsleri Tucker in S_1 and F_1 progenies, the separation of mating type of self-fertile single-oospore cultures (A_1 A_2) in sexual progeny from F_1 progeny, and the variation of mating types resulting from oospore treatment with KMnO_4 were studied. Three single-zoospore isolates of wild type (one A_1 and two A_2) were induced to self fertile by the membrane technique. Oospores were treated with 0.3% H_2O_2 for 2 min. after 210 day storage and germinated on S+L medium (with germination rates 12—16%). The mating types of S_1 progeny were the same types as their parents, while those oospores treated with KMnO_4 may be different mating types in S_1 progeny from both A_1 and A_2 parents. Some of the cultures become self-fertile (A_1A_2), and one culture from A_1 parent converted to A_2. Among single-oospore cultures from a A_1A_2 culture of S_1 progeny from A_1 parent, nearly a half of cultures converted to mating type A_2. Results from this experiment do not support the hypothesis that mating type A_1 is homozygous, while mating type A_2 is heterozygous. Oospores from two crosses of P. drechsleri were treated with H_2O_2 after 45, 60 day storage, 128 and 79 single-oospore cultures of F_1 progeny were obtained respectively (with germination rates 76% and 50%). Four mating types (A_1, A_2, A_1A_2, A^0) were presented in F_1 progeny, the proportion of the mating types varied between two crosses. Oospores produced by two self-fertile single-oospore cultures (type A_1 A_2) of F_1 progeny (Phy 607×Phy 115) after 30 day storage treated with H_2O_2 (with germination rate 30—40%), 100 and 112 single-oospore cultures wtre obtained. Type A_1A_2 might be separated into two to four mating types in its sexual progeny, the proportion of mating types were obviously different. However, the selffertility was stably inherited in single zoospore clones from the two type A_1A_2 parents. Self-fertility of type A_1A_2 cultures usually remained unchangel after 4—6 month storage, only one culture converted to self-sterile A_2.