Preliminary Study On Ganoderma Australe,a Pathogen Of 14 Species Of Tropical Tree Stem Rot

The fungi of the genus Ganoderma are wood-rot fungi,and some species can still infect the pathogenic fungus of living trees.They exist in various parts of the world and can cause stem rot or root rot in trees,which in turn can cause trees death or decline in growth.Ganoderma has a wide range of hosts.Ganoderma australe is a basidiomycete of the Ganodermatoideae,Ganoderma,and is also a pathogenic wood-rot fungus.It can infect the trunk and stem base of a variety of broad-leaved trees,causing white decay at the base of the trunk,and death of the tree in severe cases.In this study,the Ganoderma australe and suspected samples that cause tropical tree stalk rot were collected,separated,purified,and preserved.The pathogenicity of the isolated pathogens was determined,and the types of pathogens were identified through morphology combined with molecular biology.Intraspecies differentiation and biological characteristics of pathogenic bacteria identified as Ganoderma australe were studied.The results are as follows:1.The investigation found that Ganoderma australe can infect a variety of trees and cause stem rot.From 2018 to 2020,a total of 32 Ganoderma australe and suspected samples were collected from 14 species of tropical trees in 11 cities and counties in Hainan and Yunnan provinces,and 23 strains were successfully isolated.It was identified as Ganoderma australe by morphology and molecular biology.2.The pathogenicity of 9 Ganoderma australe pathogens isolated from 9 kinds of hosts: Hevea brasiliensis,Cocos nucifera,Broussonetia papyrifera,Casuarina equisetifolia,Persea americana,and Acacia mangium.Ganoderma australe which causes stem rot in tropical trees is identified as pathogenic bacteria.3.Through the ITS-SSU-LSU gene joint analysis of Ganoderma australe,study the intraspecific differentiation of Ganoderma australe.The results showed that the 23 Ganoderma australe strains isolated can be divided into two genetic groups.The first group indicates that the cause of genetic differentiation may have nothing to do with geographic origin.Some strains with the same host are closely related,indicating that genetic differentiation may be related to the type of host is related.The second population indicates that the strains of the same host may also have certain genetic differentiation,and may also infect each other with the strains.Combining genetic populations Ⅰ and Ⅱ,it can be seen that the genetic differentiation within the Ganoderma australe species has little relationship with the geographical location of the host,and may be affected by the type of host,but there may also be some genetic differentiation between strains of the same host.The biological characteristics of Ganoderma australe pathogenic bacteria showed that the Ganoderma australe pathogen strains can grow on the tested media.The growth rate is the fastest on the PDA medium,the hyphae are the densest,and the optimal growth range is 25～ 33°C,the optimal growth temperature is 28°C or 30°C,the strain stops growing at40°C,and the optimal growth p H is in the range of 5～7.Full darkness is beneficial to the growth of mycelium,with the fastest growth rate and the thickest hyphal layer.And the hyphae grows the slowest under full light.It can be seen that light can inhibit the growth of Ganoderma australe pathogens.