The Investigation Of Eucalyptus Leaf Diseases And Its Relationship With Native Trees Leaf Diseases In Guangxi

Eucalyptus is an important fast-growing tree species in the world and it’s production has become a mainstay industry on agriculture and forestry in Guangxi. Five hundred and six species of pathogenic microbes of Eucalyptus were reported, most of which were pathogens of leaf diseases. Thirty-seven Eucalyptus diseases have been reported in China, among which 27 diseases are leaf and seedling diseases. In this paper, an investigation on eucalyptus leaf disease and seasonal changing pattern of disease composition, leaf disease and its tendency in two ecological research stations in Guangxi, pathogen identification and regularty of epidemic of eucalyptus dieback,the relationships of Eucalyptus diseases and diseases of Castanopsis hystrix, the interaction effects for eucalyptus diseases and mangrove diseases was carried out. The results were shown as follow:Four new Eucalyptus leaf diseases in China and a new Eucalyptus leaf diseases in Guangxi were firstly recorded. A symstemic survey on eucalyptus leaf disease was done in Guangxi and 17 diseases were identified including 6 main diseases:dieback (Cylindrocladium spp.), purple spot (Phaeoseptoria eucalypti), Cryptosporiopsis leaf spot (Cryptosporiopsis eucalypti), zonate spot (Pilidiella eucalyptorum, Pilidiella diplodiella), anthracnose (Colletotrichum gloeosporioides), grey mould (Botrytis cenerea); and 11 minor diseases: Pestalotiopsis leaf spot(Pestalotiopsis sp.), Alternaria leaf spot (Alternaria altermata), seedling damping-off(Rhizoctonia solani), Chaetomella leaf spot(Chaetomella raphigera), Corynespora leaf spot (Corynespora cassiicola), gray spot (Guignardia mangiferae), round spot (Pseudocercospora sp.), yellow-purple leaf spot (Phaeophleospora destructans), Curvularia leaf spot (Curvularia sp.), Nigrospora leaf spot (Nigrospora sphaerica) and leaf blight spot (Harknessia gibbosa), among which Corynespora leaf spot (Corynespora cassiicola), Curvularia leaf spot (Curvularia sp.), Nigrospora leaf spot (Nigrospora sphaerica) and leaf blight spot (Harknessia gibbosa) were new records in China, and Alternaria leaf spot (Alternaria altermata) was new record in Guangxi.A continuous survey on eucalyptus leaf disease in two eucalyptus ecological research station in Guangxi was carried out,12 and 8 eucalyptus leaf diseases were found in Qipo Research Station and Huangmian Research Station, respectively. Purple spot occurred extensively and seriously in two stations; Cryptosporiopsis leaf spot caused by Cryptosporiopsis eucalypti and anthracnose caused by Colletotrichum gloeosporioides were quite serious; Pestalotiopsis leaf spot caused by Pestalotiopsis sp., zonate spot caused by Pilidiella eucalyptorum, Pilidiella diplodiella caused by, round spot caused by Pseudocercospora sp. and Alternaria leaf spot caused by Alternaria altermata occurred partly and not seriously.Two new pathogens of eucalyptus dieback in China were firstly recorded. After a research on pathogens and regularty of epidemic of eucalyptus dieback, it was found that pathogens of dieback in Guangxi were caused by Cylindrocladium quinqueseptatum, Cylindrocladium floridanum, Cylindrocladium scoparium, Calonectria sulawesiensis and Calonectria hongkongensis, among which Calonectria sulawesiensis and Calonectria hongkongensis were new record in China. Dieback in Guangxi started at the end of April or at the beginning of May, peaked period appeared in July and August, then the disease will stop developing in mid-November or early December. High temperature and frequent rainfall promoted epidemic of dieback. Dieback occurred seriously at seedling stage, slowed down at young tree stage and became light as eucalyptus tree grew up. The resistance of eucalyptus clones mainly cultivated in Guangxi was examined and it showed that Guanglin No.9 was more resistant than DH 32-29.It was firstly verified that there was a little relationship between eucalyptus leaf diseases and leaf disease of Castanopsis hystrix; but the relationship was not tight. Relationship between Eucalyptus leaf disease and leaf disease of Castanopsis hystrix was studied in Longmen town, Pubei County of Qinzhou City. The results that 8 Eucalyptus leaf spots and 8 leaf spots of Castanopsis hystrix were obtained, pathogen of anthracnose (Colletotrichum gloeosporioides) were the same, and four diseases shared pathogenic fungi belonged the same genera (Pestalotiopsis, Curvularia, Nigrospora and Alternaria). After comparison of rDNA-ITS sequences, it was found Pestalotiopsis sp., Curvularia sp., Nigrospora sp. and Alternaria sp. on Eucalyptus and on Castanopsis hystrix were different species. Because the same pathogen of Eucalyptus and Castanopsis hystrix was only one eighth, suggesting that Eucalyptus leaf disease and leaf disease of Castanopsis hystrix existed a little relationship, their relationship was not tight. Eight diseases obtained from Castanopsis hystrix were new records in China.It were firstly confirmed that there was a little relationship between eucalyptus leaf diseases and mangrove(Aegicera corniculatum) leaf disease; but the inter-influence was not obvious. Relationship between Eucalyptus leaf disease and mangrove leaf disease was studied in Shatian town, Hepu County of Beihai City. The results that 12 leaf spots of Eucalyptus and 5 leaf spots of mangrove(Aegicera corniculatum) were obtained, pathogen of anthracnose (Colletotrichum gloeosporioides) were the same, and three diseases shared pathogenic fungi belonged the same genera(Pestalotiopsis, Alternaria and Nigrospora). After comparison of rDNA-ITS sequences, it was found Pestalotiopsis sp., Alternaria sp. and Nigrospora sp. on Eucalyptus and on Aegicera corniculatum were different species. Because the same pathogen of Eucalyptus and Aegicera corniculatum was only Colletotrichum gloeosporioides, it suggesting that Eucalyptus leaf disease and mangrove leaf disease existed a little relationship, their relationship was not tight.