稻瘟病菌不同小种菌株间无性重组的研究

 将分别携带抗稻瘟灵对多菌灵敏感(MBC^sIPT^r)标记与携带抗多菌灵对稻瘟灵敏感(MBC^rIPT^s)标记的稻瘟病菌营养体亲和的不同小种菌株在白米玫瑰红培养基上,25℃、黑暗中对峙培养18d,配对菌株菌落交界处出现肉眼可见的菌丝融合带。4个小种间营养体可亲和菌株配对组合是:PO21-MBC^r-27(ZA₄₉)×PO3-IPT^r-54(ZF₁)、PO21-MBC^r-27(ZA₄₉)×PO2-IPT^r-51(ZF₁)、PO21-MBC^r-27(ZA₄₉)×PO33-IPT^r-69(ZD₁)和PO21-MBC^r-41(ZA₄₉)×PO3-IPT^r-54(ZF₁)。分别切取各配对组合产生的菌丝融合带,分别建立单菌丝片段群体,测定其对稻瘟灵、多菌灵的抗药性。结果是,从4个配对组合的单菌丝片段后代中,均检测到分别携带MBC^sIPT^r、MBC^rIPT^s标记和同时携带双亲抗性标记(MBC^rIPT^r)3种个体,其中MBC^rIPT^r个体的检出率为1.0%~3.6%。无性重组体的MBC^r和IPT^r性状在其菌丝块移植继代培养和单菌丝片段株后代发生分离。以配对组合PO21-MBC^r-27×PO3-IPT^r-54产生的菌丝融合带建立单孢无性系,从3178个单孢株中筛选到4株MBC^rIPT^r个体,其MBC^rIPT^r性状在单孢后代和单芽管分离株后代均能稳定遗传。结果表明,营养体亲和的稻瘟病菌不同小种菌株之间可通过菌丝融合产生无性重组体,同时提示无性重组体内可能发生了准性生殖。

INTER RACIAL ASEXUAL RECOMBINATION IN Magnaporthe grisea

Four wild type isolates of Magnaporthe grisea from three vegetative compatible pai rings, PO21(race ZA₄₉)×PO2(race ZF₁),PO21(race ZA₄₉)×PO3(race ZF₁) and PO21(race ZA₄₉)×PO33(race ZD₁) which formed a solid hyphal fusion line between the colonies when paired on polished rice rose bengal medium, were induced fungicide resistance in vitro. The chemical resistance in the isoprothiolane resistance (IPT^r) mutant PO3 IPT^r, PO2 IPT^r, PO33 IPT^r, and carbendazin resistance (MBC^r) mutant PO21 MBC^r inherited stably in two successive conidium progenies. On the contrary, the IPT^r mutants selected were sensitive to MBC (MBC s) and the MBC^r mutant was sensitive to IPT (IPT^s) in the successive conidial progenies. Four vegetative compatible monoconidial isolate pairings with different chemical resistant markers,PO21 MBC^rIPT^s 27(race ZA₄₉)×PO3 MBC sIPT^r 54(race ZF₁),PO21 MBC^rIPT^s 41(race ZA₄₉)×PO3 MBC sIPT^r 54(race ZF₁),PO21 MBC^rIPT^s 27(race ZA₄₉)×PO2 MBC sIPT^r 51(race ZF₁) and PO21 MBC^rIPT^s 27(race ZA₄₉)×PO33 MBC sIPT^r 69(race ZD₁) were selected. The asexual recombinants with marker MBC^rIPT^r were detected in all of the four pairings in their single hyphal fragment progenies established respectively from the hyphal fusion lines presented between the paired inoculated isolates opposite on polished rice rose bengal medium and incubated at 25±1℃ in darkness for 18 days. The percentage of recombinants detected was about 1.0%-3.6% (in about 200 single hyphal fragment isolates tested for each pairing). However, the marker MBC^rIPT^r in recombinants separated obviously in further hyphal fragment progenies even in the subcultures by mass transfers. In this study, four monoconidial isolates carried MBC^rIPT^r marker were also selected out from 3178 monoconidium isolates from hyphal fusion line presented in the pairing PO21 MBC^rIPT^s 27(race ZA₄₉)×PO3 MBC sIPT^r 54(race ZF₁), but the marker MBC^rIPT^r was stably inherited in their monospore and single germ tube progenies. The results indicated that asexual recombination by anastomosis between races and parasexuality occurred in M. grisea. It suggested that asexual recombination may be an important mechanism for M. grisea to produce and maintain genetic diversity in wild population.