胶孢炭疽菌侵染芒果的过程及寄主的组织病理学研究

Process of Mango Infected by Colletotrichum gloeosporioides and Host Histopathology

炭疽菌是一类地理分布广泛、寄主范围广泛的真菌,在作物成熟前和成熟后都能侵染植株和果实,特别对成熟的热带作物危害极大,造成果实腐烂,导致严重的经济损失并影响产品的出口质量。为探讨胶孢炭疽菌侵染芒果的过程及其与寄主的互作关系,揭示该病菌对果实和叶片的侵染方式和扩展途径,以元江本地品种‘三年芒’病果上分离、筛选的强致病菌株CG16接种健康‘三年芒’果实和叶片,通过光学显微镜、扫描电子显微镜和透射电子显微镜对炭疽菌侵染芒果果实和叶片的过程、受炭疽菌侵染后寄主的组织病理学的超微结构进行研究,结果表明,胶胞炭疽菌在侵染芒果12 h后,形成初期侵染菌丝(初生菌丝),在初生菌丝穿透寄主细胞壁的过程中形成一个漏斗状的菌丝锥,在与寄主细胞壁接触的菌丝部位缢缩,并在缢缩处常常形成1个隔膜,穿过细胞壁后迅速膨大成正常菌丝。从接种芒果至出现症状需要1 d左右。随着初生菌丝的侵入和扩展,寄主细胞逐渐消解死亡,初生菌丝先在细胞间扩展,不断建立新的活体营养寄生关系。2.5 d后随着菌丝的侵入,寄主细胞最终坏死消解,在死亡的寄主细胞中扩展的菌丝逐渐变细、分枝增多,即形成次生菌丝,次生菌丝在寄主体内大量繁殖扩展,分散或成菌丝束。4 d后寄主组织和细胞发生了一系列病理变化,包括寄主细胞变形,细胞壁的变薄、畸形、部分消失,原生质体解体,叶绿体等细胞器的崩解、坏死,细胞死亡等。接种5 d后,死体营养阶段的次生菌丝在死亡的寄主细胞中大量繁殖和扩展。接种6 d后分生孢子盘形成,接种8 d后,孢子开始成熟脱落。本研究通过揭示胶孢炭疽菌在芒果果实和叶片中的侵染方式和扩展途径,以及侵染过程中寄主组织发生的一系列病理变化,为芒果生产上防治该病提供理论依据。

Colletotrichum sp.is a kind of fungus with wide geographical distribution and wide host range.It can infect plants and fruits before and after ripening,especially for mature tropical crops,causing serious economic losses and affecting the export quality of products.The infection process of C.gloeosporioides on mango fruit and the interaction between C.gloeosporioides and mango host were studied to reveal the infection mode and expansion pathway of the pathogen on fruit and leaves.After Inoculating the healthy ‘Sannian mango’ fruits and leaves with the strong pathogenic strain CG16 isolated and screened from the diseased fruit of local variety ‘Sannian mango’ in Yuanjiang,the histopathology and ultrastructure of mango fruits and leaves infected by C.gloeosporioides were studied by light microscope,scanning electron microscope and transmission electron microscopy.C.gloeosporioides formed primary hyphae 12 hours after infection,and the primary hyphae penetrating the host cell wall formed a funnel-shaped hyphal cone.It constricted at the hyphae in contact with the host cell wall,often formed a diaphragm,and expanded rapidly into normal hyphae after passing through the host cell wall.It took about one day from the inoculation of mango to the appearance of symptoms.In the process of infecting mango,C.gloeosporioides first formed the primary infection hyphae,and the host cells gradually disappeared and died with the invasion and expansion of the primary hyphae.The primary hyphae first spread between cells and continuously established new nutritional parasitic relationships in vivo.2.5 days after inoculation,with the invasion of hyphae,the host cells finally died and dissolved,and the expanded hyphae diffused in the dead host cells gradually became thinner and more branched,and the secondary hyphae was formed.The secondary hyphae propagated and expanded in large numbers dispersing or forming mycelial bundles in the host.Four days after inoculation,a series of pathological changes occurred in host tissues and cells,including deformation of host cells,thinning of cell walls,deformity and partial disappearance of cells,disintegration of protoplasts and other organelles,necrosis and cell death.Five days after inoculation,the secondary hyphae in the vegetative stage of dead body proliferated and expanded in the dead host cells.Six days after inoculation,the conidiophores formed,and the spores began to mature and fall off 8 days after inoculation.In this study,the way of infection and expansion of C.gloeosporioides in fruits and leaves,as well as a series of pathological changes in host tissues in the process of infection were revealed,which would provide a theoretical basis for the prevention and control of the disease in production.