温郁金内生真菌Chaetomium globosum L18对植物病原菌的抑菌谱及拮抗机理

通过体外培养法,研究了药用植物温郁金内生真菌Chaetomium globosum L18对几种常见的植物病原菌的抑菌谱及其拮抗机理。结果表明,Chaetomium globosum L18对多种植物病原真菌和细菌均有不同程度的抑制作用,具有较广的抑菌谱,但对不同植物病原菌的抑制作用具有显著性差异(P<0.05),抑制率最高可达到92.9%;抑菌机制结果显示,竞争作用和重寄生作用是其主要的拮抗机制之一;发酵产物抑制作用测定发现,内生真菌Chaetomium globosum L18能够分泌产生抗菌物质抑制病原菌菌丝的生长和孢子萌发,可引起病原菌菌丝菌丝膨大成串珠状,分枝增多,分枝顶端膨胀后细胞壁破裂,原生质外溢,产生溶菌作用;使分生孢子萌发畸形,萌发率降低。

Inhibition effects and mechanisms of the endophytic fungus Chaetomium globosum L18 from Curcuma wenyujin

Fungal endophytes are microorganisms that colonize living, internal tissues of plants without causing any immediate, overtly negative effects. Many fungal endophytes produce secondary metabolites and some of these compounds exhibit antifungal and antibacterial activity that strongly inhibits the growth of other microorganisms. Antimicrobial strains are widely distributed among endophytic fungi and do not cause any obvious symptoms on host plants. Infected hosts usually grow quickly, have strong resistance to adverse conditions and diseases, and are immune to herbivory in comparison with uninfected plants. Endophyte-infected plants thus have competitive advantage. Endophytes act as biological control agents by inhibiting pathogen growth by the production of antibiotics, hydrolases, plant growth regulators and alkaloids. They also compete with pathogens for nutrition, enhancing resistance of host plants to diseases and inducing systemic resistance. Endophytic fungi are therefore biological control agents with great potential for applied use. We investigated the antimicrobial properties of an endophytic fungus Chaetomium globosum L18 from a traditional Chinese medicinal plant Curcuma wenyujin Y. H. Chen et C. Ling (Zingiberaceae), on several conventional plant pathogens, using in vitro culturing methods. We thus present a preliminary discussion of the antimicrobial spectrum and antagonistic mechanisms of Chaetomium globosum L18. This fungus had different inhibitory actions on plant pathogenic fungi and bacteria, and wide-ranging inhibitory effects. There was significant difference (P<0.05) on inhibition of different plant pathogenic bacteria; and the inhibition rate was up to 92.9%. Our inhibition experiment showed that competition and mycoparasitism were the main antagonistic mechanisms. When two strains intersected with pathogenic fungi on co-culturing plates, plant pathogens were surrounded, and the margins of colonies gradually collapsed and shriveled. The pathogens stopped growing and began to die; and Chaetomium globosum L18 colonized the nutritious space. Chaetomium globosum L18 parasitized pathogens by parallel intergrowth, intertwining, and even penetrating their mycelia. Our fermented product test showed that Chaetomium globosum L18 was able to strongly inhibit mycelial growth and spore germination. Its presence resulted in mycelia that were twisted and inflated, with increased abnormal branching, broken mycelial walls, and cell contents released. Spores were reduced in number and deformed; germination rate and germination tube length were decreased.