AMF+PGPR组合提高黄瓜抗枯萎病的作用机制

对黄瓜(Cucumis sativus)品种香翠16接种尖孢镰刀菌黄瓜专化型(Fusarium oxysporum f.sp.cucumerinum,Foc)、丛枝菌根真菌(AMF)Funneliformis mosseae(Fm)+Foc、丛枝菌根真菌Glomus versiforme(Gv)+Foc、根围促生细菌(PGPR)PS2-6+Foc、PS3-2+Foc、Fm+PS3-2+Foc以及Gv+PS2-6+Foc,以不接种处理作为对照。结果表明,接种Foc条件下,Fm+PS3-2和Gv+PS2-6组合处理的抗病效果显著优于单接种AMF或PGPR处理;镜检观测到靠近AMF菌丝的Foc菌丝纤细,生长不良。AMF菌丝能缠绕Foc菌丝,并阻挡其侵入根系;AMF侵染率与其防效均呈正相关(P0.05);Fm+PS3-2+Foc和Gv+PS2-6+Foc处理的根系活力是单接种Foc的4.6倍;与不接种对照相比,Fm+PS3-2+Foc和Gv+PS2-6+Foc处理的黄瓜叶片中吲哚乙酸(IAA)含量分别提高了205%和166%,赤霉素(GA3)提高了33%和22%,玉米素核甘(ZR)提高了100%和80%,JA平均提高了65%,ABA降低23%和17%;而与单接种Foc处理相比,IAA提高了667%和568%,GA3提高了223%和196%,ZR提高了254%和219%,茉莉酸(JA)含量平均提高了215%,而脱落酸(ABA)含量只有单接种Foc处理的53%;Fm+PS3-2+Foc和Gv+PS2-6+Foc处理显著提高了黄瓜叶内苯丙氨酸解氨酶(PAL)防御酶活性和PAL基因表达量。综上推断AMF+PGPR组合是通过拮抗病原物、促进合成抗病信号物质、上调防御基因表达、提高防御酶活性和降低植株体内有毒物质等机制降低病害和改善植物抗病性。

Mechanism of increasing resistance of cucumber plants to Fusarium wilt disease by combined inoculation with arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria

The purpose of this study was to explore the mechanism of antagonizing Fusarium oxysporum and improving resistance to wilt disease on cucumber plants by combined inoculation with arbuscular mycorrhizal fungi (AMF) and growth promoting rhizobacteria (PGPR). “Sweet green 16” cucumber (Cucumis sativus ) was treated with Fusarium oxysporum f. sp. cucumerinum (Foc), AMF Funneliformis mosseae (Fm)+Foc, AMF Glomus versiforme (Gv)+Foc, PGPR PS2 6+Foc, PGPR PS3 2+Foc, Fm+PS3 2+Foc, Gv+PS2 6+Foc, respectively. The results showed that combined inoculation with Fm+PS3 2 and Gv+PS2 6 had a stronger effect on improving disease resistance than inoculation with AMF or PGPR alone when the plants were challenged with Foc. Microscopic examination showed that the hyphae of Foc near AMF hyphae within cucumber roots were slender and grew poorly. AMF hyphae could wrap Foc hyphae and block their invasion into plant roots. The colonization percentage of AMF was positively correlated with the control efficacy (P<0.05). The root activity of cucumber plants treated with Fm+PS3 2+Foc and Gv+PS2 6+Foc was 4.6 times greater than that of inoculation with Foc alone. Compared with non inoculated control, indole acetic acid (IAA) content increased by 205% and 166%, gibberellin (GA3) increased by 33% and 22%, zeatin nucleotide (ZR) content increased by 100% and 80%, the average jasmonic acid (JA) level increased by 65%, and ABA level decreased by 23% and 17% respectively in leaves of cucumber plants inoculated with Fm+PS3 2+Foc and Gv+PS2 6+Foc. Compared with inoculation with Foc alone, IAA content increased by 667% and 568%, GA3 content increased by 223% and 196%, ZR content increased by 254% and 219%, JA content increased by 215%, while abscisic acid (ABA) decreased by 53%. The gene expression and enzymatic activity of phenylalanine ammonia lyase (PAL) increased in leaves of cucumber plants colonized with Fm+PS3 2+Foc and Gv+PS2 6+Foc, compared with both control and inoculation with Foc alone. It was concluded that the AMF+PGPR combination improved plant disease resistance through a variety of mechanisms such as antagonism, promoting synthesis of disease resistance signal molecules, up regulating expression of defense related genes, increasing enzymatic activities of defense related enzymes and reducing accumulation of toxic substances.