棉花内生细菌数量动态及其对棉花黄、枯萎病菌的拮抗作用

Population dynamics and antagonism toward Fusarium oxysporium f.sp. Vasinfectum. and Verticillium dahliae Kleb of endophytic bacteria from cotton

摘要:

摘要：【目的】了解棉花内生细菌数量动态，从棉花中获得拮抗黄、枯萎病菌的内生细菌资源【方法】对棉花根、茎、叶表面灭菌，采用稀释平板法分离棉花内生细菌；通过对峙培养法体外鉴定分离的棉花内生细菌对棉花黄、枯萎病菌的拮抗作用，并对拮抗棉花黄、枯萎病菌的内生细菌16S rDNA序列进行了分析【结果】棉花根中内生细菌的数量显著高于茎、叶；根的苗期总体内生细菌数量低于开花期、吐絮期，茎、叶中的内生细菌数量在不同生育期呈现一定的波动性，但趋势性不明显；6个棉花品种根中内生细菌平均数量差异并不显著，但茎、叶中内生细菌数量不同品种间呈现一定程度差异。平板对峙鉴定显示:棉花根中具有较高比例的拮抗棉花黄、枯萎病菌的内生细菌，拮抗强致病落叶型黄萎病菌（V107）的内生细菌比例不仅低于枯萎病菌（F108），而且低于非落叶型黄萎病菌（V396）。同时拮抗棉花黄、枯萎病菌的内生细菌有44株，16S rDNA分子序列分析表明：这些拮抗内生细菌的类群包括了两个门(变形杆菌门、拟杆菌门)8个属，其中10个菌株与已报道菌株相似性<97%，可能是新的种（属），优势种群为肠杆菌属（18株）、泛菌属（15株）。【结论】棉花的品种、生育期与器官影响棉花内生细菌数量；棉花拮抗黄、枯萎病菌的内生细菌具有优势种群，且具多样性。

Abstract:

Abstract: ［objective］To explore population dynamics of endophytic bacteria and obtain antagonistic endophytic bacteria toward Verticillium dahliae Kleb (Vd), Fusarium oxysporium f.sp. Vasinfectum (Fov) from cotton.［methods］Root, stem and leaf samples were surface-disinfested, and subsequently used to isolate endophytic bacteria by diluting plate counting method. We assayed antagonism of the isolated endophytic bacteria toward three pathogens: Vd (V107, which is a highly virulent defoliating isolate and V396, which is a mildly virulent non-defoliating isolate), Fov (F108) by dual culture method, and analyzed the 16S rDNA sequence of doubly antagonistic endophytic bacteria (DAEB) isolates toward both Vd and Fov.［results］The population size of endophytic bacteria in root was significantly larger than that in leaf and stem. The populations at seedling stage were generally lower than those at the flowering/maturing stage in root, the populations in stem and leaf were fluctuant at different development stages, but variation law was not observed obviously. Furthermore, although no significant differences of the population densities in root were found among 6 cotton cultivars, the population densities in stem and leaf showed cultivar differences. The proportion of endophytic bacteria antagonizing Vd and Fov in root was higher than that in stem/leaf, moreover, the amount of endophytic bacteria antagonizing toward V107 was less than that toward V396/F108. Based on 16S rDNA sequence analysis, all 44 DAEB isolates consisted of two phyla, i.e., Bacteroidetes (1 out of 44) and Proteobacteria (43 out of 44), and fell into 8 genera. The genus enterobacter (18 out of 44) and Pantoea (15 out of 44) were predominant. Notably, ten DAEB isolates demonstrated <97% sequence similarity with the most similar sequences of strain deposited in the Ribosomal Database, these DAEB isolates might be potential novel species.［conclusion］This article suggested that plant genotype, development stage, and tissue influenced the population of endophytic bacteria. We discovered that DAEB with predominant and various genus existed in cotton. Endophytic bacteria in cotton could serve as a pool for discovering biocontrol agent toward cotton pathogens.