内生真菌Alternaria sp. GHX-P17代谢产物防治广藿香青枯病及保护酶的变化

广藿香是著名药材,青枯病是威胁广藿香生产和质量的主要病害。针对从广藿香茎叶中分离出的1株有抑菌活性的内生真菌Alternaria sp. GHX-P17,研究其代谢产物对广藿香青枯病的防治作用及耐病机制。在室内通过人工接种Alternaria sp. GHX-P17菌株与喷施粗提物稀释液2种方式,于不同时间调查广藿香青枯病的发病率和严重度,并计算其病情指数(disease index,DI)。同时,对处理后不同时间的广藿香苯丙氨酸解氨酶(phenylalanine ammonia lyase,PAL)、过氧化物酶(peroxidase,POD)和超氧化物歧化酶(superoxide dismutase,SOD)3种保护酶活性进行测定。结果表明:(1)Alternaria sp. GHX-P17处理后青枯病DI显著降低,与对照比较,204 h后DI降低为27.16%,方差分析呈显著性差异(P<0.05)。(2)随着处理时间延长,青枯病严重度升高缓慢,严重度等级降低,到204 h时,处理组的严重度明显低于对照,防治效果达到74.65%。(3)处理后的广藿香3种保护酶PAL、POD和SOD活性增强,但3种酶活性高峰出现时间不同。PAL随时间逐渐升高; POD先升高后降低,然后又升高,出现2个峰值; SOD快速升高后逐渐降低。这表明内生真菌菌株Alternaria sp. GHX-P17可以提高广藿香3种保护酶活性,延缓了青枯菌的侵染过程,降低了青枯病的发病程度。该研究结果为植物内生真菌次级代谢产物活性成分研究及生物农药开发提供了参考。

Control effects of metabolites of endophytic fungus Alternaria sp. GHX-P17 on bacterial wilt and changes of protective enzymes in Pogostemon cablin

There is a long history to cultivate the Pogostemon cablin in Guangdong Province, and it is a famous medicinal material. The bacterial wilt is the important disease that impacts the production and quality of P. cablin. Aiming to the control effects of metabolites of Alternaria sp. GHX-P17 strain that is belonging to an endophytic fungus isolated from the stems and leaves of P. cablin and the mechanism of disease resistance on bacterial wilt, a laboratory experiment had been conducted to investigate the incidence and severity of bacterial wilt in P. cablin at different time after artificial to inoculate the strain of Alternaria sp. GHX-P17 and to spray the crude extracts of the metabolites, and disease index(DI)was calculated. The activity changes of protective enzymes of phenylalanine ammonia lyase(PAL), peroxidase(POD)and superoxide dismutase(SOD)were determined in different time in P. cablin. The results were as follows:(1)The DI was significantly lower in the treatment groups with the crude extracts of Alternaria sp. GHX-P17 at different concentrations than that of control groups, and the DI decreased by 27.16% in the treatment groups at 204 h after inoculation. The variance analysis showed significant differences(P<0.05).(2)The severity of bacterial wilt was reduced with the extension of investigation time in P. cablin, and the severity levels increased slowly in treatment groups. The average severity was significantly lower than that of the control groups at 204 h, and the control effects reached 74.65%.(3)The activities of protective enzymes of PAL, POD and SOD increased observably after to inoculate spore suspension and to spray metabolites in P. cablin, but the activity peak time was different. PAL activities gradually increased after inoculation. POD first increased and then decreased, and then increased again, and there were two the activity peaks. SOD increased rapidly and then decreased gradually. Obviously, the metabolites of Alternaria sp. GHX-P17 can not only increase the activities of protective enzymes in P. cablin, and delay the infection process of Ralstonia solanacearum, but also decrease the severity levels of bacterial wilt. However, the research findings provide a reference for the study of active components of secondary metabolites of endophytic fungi and the development of biopesticides.