离体条件下外源茉莉酸甲酯对人参锈腐病菌的影响(英文)

Influence of exogenously applied methyl jasmonate on soilborne pathogen, Cylindrocarpon destructans in vitro

关键词:  茉莉酸甲酯, 生物量, 人参锈腐病菌, 致病酶

Key words:  methyl jasmonate, biomass, Cylindrocarpon destructans, pathogenic enzyme

摘要:

人参(Panax ginseng)是我国传统的名贵药材,由毁灭柱孢(Cylindrocarpon destructans)引起的人参锈腐病是严重影响人参产量和品质的重要根部病害之一,在人参生产中会造成严重的经济损失。茉莉酸甲酯(methyl jasmonate, MeJA)是一类新型的生长调节物质,既可以参与植物对病原菌及其他逆境胁迫做出的应答并进行信号传递,又可用来诱导植物的抗病反应。为了明确MeJA对人参锈腐病菌的影响并解析MeJA与病原菌致病因子之间的相互关系,该文研究了外源MeJA在不同浓度下对C. destructans的直接影响,包括对菌落生长、孢子萌发、菌丝生长量、病菌分泌水解酶的影响。结果表明:MeJA能够强烈抑制病原菌的生长和孢子萌发,而对病原菌致病酶的活性则表现出促进作用; 人参锈腐病菌在PDA平板上的菌落直径从(8.23±0.15)cm(对照)减少到(0.71±0.00)cm(800 μg·mL^-1 MeJA),在MeJA浓度达到最高时,菌落生长几乎完全被抑制; MeJA的浓度大于400 μg·mL^-1时,病原菌的生物量减少了65.3%～100%,孢子萌发率和芽管长度减少了100%; MeJA在浓度大于200 μg·mL^-1时,果胶酶、纤维素酶和淀粉酶活性升高而蛋白酶的活性却没有变化。综上表明,MeJA对病原菌产生抑制作用的临界浓度为200 μg·mL^-1。该研究结果为后续使用MeJA处理人参植株进行诱导抗病性的研究奠定了基础,同时也有助于进一步了解人参锈腐病的致病机理,并为病害防控提供了理论参考。

Abstract:

Ginseng(Panax ginseng)is a traditional medicinal plant in China, and the dried root is highly valued for its medicinal properties and is widely used in Chinese traditional medicine. Cylindrocarpon root rot of ginseng caused by Cylindrocarpon destructans is the main disease, which is difficult to be eliminated from soil, leading to serious crop yield losses and limited the re-use of fields for successive ginseng crops. Methyl jasmonate(MeJA), which is one of the plant lipid derivatives, considered as a signaling substance during plant-microbe interactions. It is related to plant resistance to biotic and abiotic stress, can be involved in plant response to pathogens and other adversity stress and signal transmission, and can be used to induce plant disease resistance reaction. The objective of this study was to test the effects of MeJA on C. destructans and to find the possible relationships between MeJA and pathogenic factors of C. destructans. To assess the influence of MeJA on soil pathogens, the direct effects of artificially applied MeJA on C. destructans were evaluated, including the effects on colony growth, spore germination, biomass and phytopathogenic enzyme activities of this pathogen. The results showed that MeJA strongly inhibited its growth and spore germination, whereas it stimulated phytopathogenic enzyme activities. The colony diameter of C. destructans on PDA decreased from(8.23±0.15)cm(control)to(0.71±0.00)cm(800 μg·mL^-1). At the highest concentration(800 μg·mL^-1)of MeJA, the colony diameter of C. destructans had almost totally inhibited, but the diameter had no difference compared with the untreated control at lower concentrations(1-50 μg·mL^-1 MeJA). The biomass reduced by 65.3%-100% and the percent of spore germination decreased by 100% at concentrations higher than 400 μg·mL^-1. Potent suppression of the growth of germ-tubes was observed at different concentrations, especially at(400-800)μg·mL^-1, where the growth of germ-tubes was inhibited completely. However, activities of phytopathogenic enzymes(pectinase, cellulase, amylase, and protease)were greatly stimulated by MeJA at higher concentrations(MeJA>200 μg·mL^-1), while the activity of protease was little changed. The activity of pectinase was high up to(0.61±0.05)U·mL^-1·min^-1 at the concentration of 800 μg·mL^-1. The activity of cellulase was stimulated at high concentrations of MeJA in liquid culture, while it was suppressed at low concentrations(1-50 μg·mL^-1). The activity of cellulase was(0.31±0.02)μmol·min^-1 at 800 μg·mL^-1 of MeJA. Amylase activity substantial increased at concentrations of(200-800)μg·mL^-1, which was(0.45±0.02)μmol·min^-1 at the concentration of 800 μg·mL^-1. It was concluded that MeJA greatly inhibited C. destructans growth and spore germination, but stimulated activities of hydrolytic enzymes of C. destructans at higher doses. There might be different mechanisms presented for the effects of MeJA on hyphal growth and virulence factors of C. destructans. The critical concentration of MeJA inhibitory effects on C. destructans was 200 μg·mL^-1. The research lays a foundation for the subsequent experiment using MeJA to induct disease resistance. This is of help to understand the mechanism of Cylindrocarpon root rot of ginseng and to control pathogen in practice.