恶疫霉有性生殖交配行为的研究

 对同宗配合疫霉种——恶疫霉(Phytophthora cactorum Schroter)抗甲霜灵突变株和抗地茂散突变株的抗药性在游动孢子和卵孢子后代的遗传分析,筛选到抗性分别由细胞核纯合显性单基因控制的抗甲霜灵突变株和由细胞质可稳定遗传的线粒体基因控制的抗地茂散突变株。将携带抗甲霜灵对地茂散敏感(即Mt^rCn^s)标记的亲本与携带抗地茂散对甲霜灵敏感(即Mt^sCn^r)标记的亲本共同培养,在200个有性生殖单卵孢后代中检测到携带3种不同抗药性标记的单孢株,其中32株携带Mt^rCn^s标记,165株携带Mt^sCn^r标记,另有3株同时携带双亲的标记性状即MtrCnr。结果表明:恶疫霉种内不同菌株共同培养时,有性生殖以配对亲本的各自自交为主,同时配对亲本间也可发生一定频率的杂交。

ON MATING BEHAVIOR OF SEXUAL REPRODUCTION OF PHYTOPHTHORA CACTORUM

Progenies derived from oospores produced by a metalaxyl-resistant (Mt^r) mutant AP14 M-1 of Phytophthora cactorum (a homothallic species) seperated into Mt^r and Mt^s with a ratio of 3:1,this result indicated that metalaxyl-resistance in AP14 M-1 was controlled by a single dominant gene in the heterozygous condition.AP14 M-1-08,a single oospore isolate carrying homozyous dominant-resistant alleles was selected.Chloroneb-resistance (Cn^r) of a Cn^r mutant PK9 Cn-2 (P.cactorum) inherited stably in both zoospore and selfed oospore progenies.This result indicated that chloroneb-resistance was controlled by mitochondrial DNA in cytoplasm.From the selfed oospore progenies of PK9 Cn-2,mono oospore isolate PK9 Cn-2-02 was obtained,carried homozygous-resistance to chloroneb.Progenies from the pairing between AP14 M-1-08 carrying Mt^r Cn^s marker and PK9 Cn-2-02 carrying Mt^s Cn^r marker consisted of selfed oospores from two parents and hybrids (Mt^rCn^r) from the cross of two parents,the percentage of hybrids is about 1.5%~2% (in 200 single oospore cultures).The results indicated that intraspecific hybridization occur within P.cactorum.It was suggested that intraspecific hybridization may be an important mechanism for homothallic Phytophthora spp.to produce and maintain genetic diversity in wild population.