内生枯草芽胞杆菌Itb57对烟草疫霉的抑制及生理生化影响

The physiological and biochemical understanding of the inhibitory effect of endophyte Itb57 on Phytophthora parasitica var. nicotianae

为明确内生枯草芽胞杆菌Itb57菌株抑制烟草疫霉生长的机理,分别采用电镜扫描法、生化测定法和电导法研究了其对烟草疫霉菌丝形态及生理生化指标的影响。结果显示,经Itb57菌株发酵滤液处理的疫霉菌丝畸形膨大、分枝短粗,孢子囊的形成及萌发受到显著抑制,当发酵滤液浓度为50%时,抑制率分别为79.69%和70.85%;且与对照相比,处理组疫霉菌细胞壁主要成分碱溶性、碱不溶性和水溶性的β-1,3-葡聚糖含量分别降低了51.18%、42.56%和39.42%,β-1,3-葡聚糖合成酶活性降低了72.45%,DNA含量降低了14.64%;线粒体复合酶活性显著低于对照,其中复合酶II活性降低了79.25%,菌丝处理液电导率升高。表明枯草芽胞杆菌Itb57菌株发酵滤液能减少疫霉细胞壁主要成分β-1,3-葡聚糖含量,破坏细胞膜的完整性,导致菌丝生长受阻或产生畸形,对烟草黑胫病的控制具有潜在的生防价值。

To understand how the Itb57,an endophytic strain of Bacillus subtilis,inhibite the growth of the tobacco Phytophthora parasitica, the impact of the bacterial fermentation filtrate on mycelium morphology,physiological and biochemical changes of Phytophthora parasitica var. nicotianae were studied with scanning electron microscopy and an array of biochemical and physiological assays. The results showed that treatment with 50% fermentation filtrate caused malformation of the mycelium with short branches,and significantly inhibited the formation and germination of sporangium by 79. 69% and70. 85%,respectively. Main components of the pathogen cell walls,such as alkali soluble β-1,3-glucan,alkali insoluble β-1,3-glucan, and water-soluble β-1,3-glucan content were reduced by51. 18%,42. 56% and 39. 42%,respectively,compared to the control treatment. The activities of β-1,3-glucan synthase was reduced by 72. 45%,and the DNA content was also reduced by 14. 64% in the pathogen. The enzyme activities of mitochondrial complexes were significantly lower than those of the control,and especially that the complex II enzyme activity dramatically reduced by 79. 25%. Moreover,the conductivity of the P. parasitica mycelia increased upon treatment with the fermentation filtrate. The results suggested that the fermentation filtrate of strain Itb57 could reduce β-1,3-glucan as the maincontent in the cell walls of P. parasitica,destroy the integrity of the cell membrane,repress the hyphal growth,and finally lead to malformation of hyphae. Therefore,it can be concluded that the endophytic Itb57 has the potential to be used as a bio-control agent in the control of tobacco black shank disease.