Study On The Infection Process On Walnut Of Walnutassociated Colletotrichum Gloeosporioides

Walnut(Juglans regia)is an important "woody grain" ecological species,diploid plants(2n = 32),genome 667 Mb.As the "21st century super food",the nutritional components of walnut are extremely suitable for human health which can effectively prevent cardiovascular diseases and as the preferred food for type 2 diabetes.In recent years,with the expansion of intensive cultivation of walnut,the disease is becoming increasingly serious.Walnut anthracnose,caused by Colletotrichum gloeosporioides,causes fruit gangrene,leaf blade dry and also infects the young shoots.In severe cases,walnut anthracnose can cause 30% to 50% of the green fruit off,resulting in loss of production,and thus considered catastrophic disease in walnut production.In this paper,the germination conditions of conidia were studied,and the life process of Colletotrichum gloeosporioides was observed under suitable conditions.The walnut resistant cultivars ’Ruijia’,and clones 4-23,B26 and B29,which are preserved in Shandong Agricultural University the Forestry Experimental Station,were used to study anatomical observation of the process of infection of walnut tissues and walnut tissue morphological changes after infection by Colletotrichum gloeosporioides;and the effects of conidia germination by different environmental factors were studied,and the life process of conidia under suitable conditions was observed.The main results are as follows:1.The conditions that affect the conidial germination of Colletotrichum gloeosporioides.The optimal germination temperature of conidial germination was 28℃-30℃,the optimum pH was 6.0,the optimum illumination condition was dark culture condition and the optimum humidity was 100% humidity.The optimum carbon source was glucose and maltose,and t he optimum nitrogen source was yeast extract.2.Identification of resistance to Colletotrichum gloeosporioides.The fruit of 4-23 was susceptible,the incidences of leaf and fruit which were inoculation in indoors were higher than in fields.The average incidences of fruit were 84.44% and 84%,respectively,which were significantly higher than that of others.However,the average incidence of leaf in indoors and fields were 2.00% and 1.33%,respectively,which was significantly lower than that of others and showed the relative resistance to walnut anthracnose.The incidence of ?Ruijia‘ fruit was the lowest,the average incidence in indoor and fields were 51.11% and 50%,which were significantly lower than the others,showing the relative resistance to disease.3.Process of Colletotrichum gloeosporioides conidial germination.With glucose as the carbon source and the yeast extract as the nitrogen source,the germination of some conidia was carried out for 10 hours.After incubation for 18 h,the majority of conidia germinated.After 24 hours of culture,the top of the conidiophoreal tube was enlarged to form appressorium.After 36 h of culture,the growth of penetration peg was observed.The infected nail was enlarged to form primary hyphae after 48 hours of culture.After 60 hours o f culture,primary hyphae continued to grow to form expanded primary hyphae.After 72 hours of culture,hyphae continued to grow to form secondary hyphae.4.Infection process of Colletotrichum gloeosporioides on walnut.Infection of walnut clones B29 with conidial suspension,the results showed that the conidia were germinated on the leaf surface,the appressoriums were formed and attached to the leaf surface.Anatomical observation showed that the epidermal cells of the leaf infestation site were slightly depressed.After inoculation for 48 h,there was an infestation nail in the center of the attached cell,at the same time,the morphology of the conidia changed slightly;anatomical observation showed that the epidermal cells of the leaf infection site were significantly depressed.After 60 hours of inoculation,the infected filaments were inserted into the stomatal cavity of the leaf,and a small amount of the primary hyphae appeared in the outer layer of the stomatal chamber.Anatomical observation showed that the epidermal cells were damaged,and the internal tissue cell of leaf depression was significant.After 72 hours of inoculation,the primary hyphae grew and produced secondary hyphae,resulting in programmed cell death;anatomical observation showed that the lesion site epidermal cell damage,the internal tissue cells partially digested.After 96 hours of inoculation,the brown spot was found in the leaves of the infested part,the conidiophores were used to produce new conidia,thus completing an infection cycle;anatomical observation showed that the epidermal cells of leaf infestation site were damaged,a large number of internal tissue cel s digestion.