内生真菌Epichloëguerinii对宿主德兰臭草抗病性的影响

Effects of endophytic fungus Epichloë guerinii on disease resistance of the host Melica transsilvanica

摘要:

【背景】前期研究表明，从国内仅在天山北坡分布的德兰臭草(Melica transsilvanica)中分离得到内生真菌Epichloë guerinii SC012，是一种与禾草共生的香柱菌(Epichloë)。【目的】研究内生真菌Epichloëguerinii与宿主德兰臭草抗病性的相互关系。【方法】体外纯培养条件下内生真菌与4种常见植物病原菌的对峙试验和病原菌侵染宿主的盆栽试验。【结果】平板对峙试验中，分离自德兰臭草的一株内生真菌Epichloëguerinii对立枯丝核菌(Rhizoctonia solani)、链格孢菌(Alternaria tenuis)和禾谷炭疽菌(Colletotrichum cereale)均有抑制作用，抑制率分别为57.39%、26.30%和20.92%，且内生真菌发酵液也可有效抑制这3种病原菌的生长，抑制率分别为64.94%、32.93%和15.61%，2种体外培养试验中内生真菌对镰刀菌(Fusarium sp.)生长无影响；盆栽试验中，与Epichloëguerinii共生可以有效降低宿主德兰臭草在立枯丝核菌、链格孢菌和禾谷炭疽菌侵染下的病情指数，相对防效分别为36.61%、16.01%和21.87%，除可降低立枯丝核菌发病率外，对降低其余病原菌侵染下的发病率并无显著作用。带内生真菌(E+)与不带内生真菌(E‒)的德兰臭草植株除在镰刀菌侵染下苯丙氨酸解氨酶(phenylalnine ammonialyase,PAL)活性无显著差异外，E+植株的多酚氧化酶(polyphenol oxidase,PPO)与PAL活性在各组试验中均显著高于E‒植株(P<0.05)。【结论】内生真菌Epichloëguerinii能提高宿主德兰臭草对一些特定病原菌的抗性，但对不同病原菌的抗性存在差异，这为利用禾草内生真菌进行生物防治或是抗性育种提供了依据。

关键词:内生真菌;德兰臭草;生防作用;对峙试验;防御酶

Abstract:

[Background] Epichloë guerinii SC012 isolated from Melica transsilvanica, a plant only growing in the northern slope of the Tianshan Mountains in China, is a type of endophytic fungus of grasses. [Objective] To investigate the relationship between E. guerinii and the disease resistance of its host M. transsilvanica. [Methods] Dual-culture tests were conducted to assess the interactions between the endophytic fungus and four common plant pathogenic fungi. A pot experiment was performed to evaluate the resistance of M. transsilvanica with E. guerinii to pathogen invasion. [Results] In the dual-culture tests, E. guerinii isolated from M. transsilvanica exhibited inhibitory effects on Rhizoctonia solani, Alternaria tenuis, and Colletotrichum cereale, with the inhibition rates of 57.39%, 26.30%, and 20.92%, respectively. The fermentation broth of E. guerinii also inhibited the growth of the three pathogens, with the inhibition rates of 64.94%, 32.93%, and 15.61%, respectively. The endophytic fungus and its fermentation broth had no impact on the growth of Fusarium sp. The results of the pot experiment showed that E. guerinii reduced the disease indexes of M. transsilvanica exposed to the invasion of R. solani, A. tenuis, and C. cereale, with the relative protective effects of 36.61%, 16.01%, and 21.87%, respectively. Apart from reducing the incidence caused by R. solani, E. guerinii showed no significant effect on the incidence caused by other pathogens. M. transsilvanica plants with the endophytic fungus (E+) had higher polyphenol oxidase (PPO) and phenylalnine ammonialyase (PAL) activities than the plants without the endophytic fungus (E‒) (P<0.05), except that the PAL activity had no significant difference in the case of Fusarium sp. infection. [Conclusion] The endophytic fungus E. guerinii can enhance the resistance of M. transsilvanica to specific pathogens, while the resistance varies depending on the pathogens. The findings provide a basis for the use of endophytic fungi of grasses in the biocontrol and breeding of disease resistant crops.

Key words:endophytic fungus;Melica transsilvanica;biocontrol;dual-culture test;defense enzymes