| Camellia oleifera is a unique woody oil plant in China.However,anthracnose is one of the main diseases of C.oleifera that affects its production.The disease can damage the leaves,fruits and other parts of C.oleifera,causing the flowers and fruits to fall,thus,greatly affecting the Chinese C.oleifera industry.Colletotrichum fructicola it is the dominant pathogen that causes anthracnose in C.oleifera,it was widely distributed in all the major production areas of C.oleifera in China including Hunan,Jiangxi,Hubei and additional provinces.There have been no studies on the histopathology and immunocyto chemistry of the infection process of C.fructicola on C.oleifera.And its pathogenic mechanism has not been clear.In this study,frozen sections,whole leaf transparent staining,transmission electron microscopy(TEM)and other methods were used to observe the transformation of nutritional mode and the colonization and expansion of pathogenic fungi in different stages of C.oleifera.Finally,starting with the anti-anthracnose mechanism of C.oleifera,the differences in the physiological and biochemical indicators of C.oleifera when the C.fructicola invaded were found.Then provide theoretical basis for green prevention and control of C.fructicola.The main research results are as follows:(1)The transformation of nutritional mode of pathogenic fungi in different stages of C.oleifera.C.fructicola was cultured for sporulation and then inoculated into C.oleifera leaves,and the whole leaf was observed by transparent staining.Observation indicated that the conidia begin to germinate within 2 hours of inoculation,Appressoria began to form 4 hours after inoculation,but the appressorium at this time was relatively young and lacked a deposit of melanin.After 24 hours of infection,the infected vesicles could be observed producing thicker primary hyphae between them.After 40 hours of infection,the primary hyphae shrank to produce finer secondary hyphae and gradually expanded into the neighboring cells.(2)Histopathology of C.oleifera Infected by C.fructicola.The study was carried out by whole-stain clearing,frozen tissue sections,KOH-aniline blue fluorescent staining and TEM.Optical microscopic observation,indicated that C.fructicola utilizes two methods of invasion when it infects C.oleifera leaves.One is the more common way of intrusion,i.e.,directly penetrating the host stroma to invade the host.Another way of invasion is to have the germ tube that is produced by the conidia or mycelium invade from the host stomata.When pathogenic fungi are in the host tissues,the host cells will have a series of pathological reactions,such as plasmolysis,disintegration and rupture of organelles,etc.,at the same time,the host cells also show a defense response to resist the invasion of pathogens,such as the electron-density materials of the spores are deposited in the intercellular hyphae adjacent to the host cell space.(3)Study on the immunological and biochemical characteristics of C.fructicola infecting the C.oleifera leaves.The contents of POD,CAT,PPO,soluble sugar and soluble protein in the C.oleifera leaves were measured after inoculation with the conidia suspension.The results showed that the POD and CAT activity began to increase after 24 hours of inoculation,the POD activity reached a peak at 60 hours,and the CAT activity reached the highest value at 48 hours.The PPO activity remained almost unchanged in the first 60 hours,and was not much different from the control.The soluble sugar content of the inoculated C.oleifera leaves was similar to that of uninoculated plants.When pathogenic fungi were infected for 24 hours,the soluble protein content increased,and the soluble protein content remained almost stable at 36-72 hours,the soluble protein content was always higher than the control group during the infection process. |
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