西瓜枯萎病内生拮抗细菌YGRE24的分离鉴定及其特性研究

采用稀释涂布平板法结合平板对峙法，从表面消毒的西瓜根中筛选到一株能够高效抑制尖孢镰刀菌西瓜专化型3种生理小种的内生细菌YGRE24。菌株YGRE24对尖孢镰刀菌西瓜专化型3种生理小种的抑制率分别为54.76%、55.95%和55.24%，且其除菌后的培养液也具有明显的抑菌效果。该菌株对小麦赤霉病菌、水稻纹枯病菌等也具有很强的拮抗作用。此外，菌株YGRE24还具有溶磷、产吲哚乙酸、产铁载体的促生特性。盆栽试验表明，该菌株能够在接种病原菌的情况下促进西瓜苗的生长，使地上部分的鲜重和干重分别增加44.75%和30.32%，可以缓解病害对西瓜苗生长的影响。经形态特征、生理生化特性及16S rDNA序列分析初步确定菌株YGRE24为枯草芽孢杆菌（Bacillus subtilis）。

Screening and identification of endophytic antagonistic bacteria strain YGRE24 against watermelon Fusarium Wilt and its characteristics

An endophytic bacterium, YGRE24, isolated from surface sterilized root of watermelon by dilution plate method and flat confrontation method, could inhibit mycelial growth of three physiological races of Fusarium oxysporum f.sp.niveum with inhibition rates of 54.76%, 55.95% and 55.24%, respectively. The antagonistic activity was detected in the fermentation broth of YGRE24 as well. The strain YGRE24 displayed a broad-spectrum antagonistic activity to five pathogens, like Fusarium graminearum and Rhizoctonia solani and so on. Furthermore, the strain had the capacity of phosphate-solubilizing, indole acetic acid-producing and siderophore-producing. The results of pot culture experiments showed that the fresh weight and dry weight of shoot were increased by 44.75% and 30.32% after incubated with strain YGRE24. The lesions caused by watermelon Fusarium wilt were obviously reduced by inoculating the strain. According to morphology, bio-physiological and biochemical characteristics and 16S rDNA sequence, the strain YGRE24 was identified as Bacillus subtilis.