亲和性组合中拮抗细菌菌株Pf7-14和P13-R在稻株上的种群动态研究

Population Dynamics of Antagonistic Bacterial Strains Pf7-14 and P13,a Compatible Combination,in Rice Plants

拈抗细菌菌株（Pseudomonas fluorescens）Pf7—14，（Pseudomonas sp．）P13，均显著地抑制水稻纹枯病。离体测定表明，两菌株并不相互抑制，其为一个亲和性的组合。在温室条件下（菲律宾国际水稻研究所），通过分批播种，接种纹枯病菌（Rhizoctonia solani），在水稻分孽盛期喷雾拈抗细菌，并采用定期取样，平板稀释分离法在含不同抗生素的培养基中回收细菌，测定该组合Pf7—14＋P13-R（Pf7—14是天然的抗萘啶酮酸菌株；P13-R是P13的利福平抗性突变体）中菌株Pf7—14和P13-R以及单剂菌株pf7／-14和P13-R在水稻健株及纹枯病株上的种群数量。2批试验结果均表明，混剂中菌株Pf7—14和P13-R的种群动态的变化是不一致的。在健株上，在相同的时间内单、混剂中菌株Pf7—14的种群数量基本保持相等；但在病株上，混剂中菌株Pf7—14的种群数量在应用后的一段时间内却显著地高于单剂的群体数量，第1批试验中，显著性差异发生在拈抗细菌应用后1～4d，单、混剂中菌株Pf7—14群体数量相差可高达3．99倍，第2批试验中，显著性差异发生在应用后4～7d，群体相差可高达3．17倍。相比，无论是在健株还是在病株上，在相同的时间内单、混剂中菌株P13的种群数量基本保持大致相等，没有显著性差异。这些结果表明混剂中菌株Pf7—14比P13在病斑上具有更强的营养竞争力。同时表明，理论上这个亲和性的拈抗细菌组合是一个增效的组合。

Pseudomonas fluorescens strain Pf7 -14 and Pseudomonads strain P13 were antagonistic to Rhizoctonia solani, the causal of rice sheath blight. The strains Pf7 - 14 and P13 - R did not inhibit each other in measurement in vitro. The population sizes of Pf7 -14 （natural resistant to nalidixic acid） and P13 -R （spontaneous rifampicin- resistant mutants of strain P13 ）, in a compatible combination, as well as single strains Pf7 - 14 and P13 - R to colonize healthy and Rhizoctonia solani - inoculated rice plants were monitored under greenhouse conditions （International Rice Research Institute, Philippines） by sowing rice at batches,inoculation of R. solani, spraying bacterial suspension at rice full tillering stage, as well as periodical sam- piing and recovering the bacteria by the medium with different antibiotics. At the compatible combination, the fluctuation of population sizes of Pf7 - 14 was inconsistent with those of P13 - R over the two batches of trials. On healthy rice plants, the population sizes of Pf 7 - 14 in mixture was approximately equal to those individu- ally,while on diseased rice plants, those in mixture was significantly higher than those individually during a given time. The significant differences in the first batch appeared on the 1 st to 4th days after its application, and the population of 7 - 14 in mixture was as high as 3.99 times of that individually; the significant differences in the second batch appeared on the 4th to 7th days after its application, and the population of 7 - 14 in mixture was as high as 3.17 times of that individually. In contrast, whatever on healthy or diseased rice plants, the fluctuation of population sizes of P13 - R in mixture was consistent with those individually. It revealed that strain Pf7 - 14 in mixture has a stronger ability to compete nutrient on lesion than P13 - R, also that the compatible combination is synergic combination theoretically.