Survey And Identification Of Fungal Disease For Mango Fruits In Hainan

Mango is perennial plant belonging to the genus of Mangifera, in the family of Anacardiaceae. It mainly distributed in Hainan, Guangdong, Guangxi, Yunnan, Sichuan and Fujian provinces of China. It is known as "the king of tropical fruits" because of its nutritive value, taste, attractive fragrance and health promoting qualities. The postharvest diseases caused by pathogenic fungi resulted in a large number of rot and serious economic loss, and shorten the storage and shelf life, has become an important bottleneck restricting the development of the mango industry. The incidence of postharvest disease and the kinds of postharvest pathogenic fungi and latent infection fungi from4places including Changjiang, Dongfang, Ledong and Sanya of Hainan provinces were investigated in this study from2010to2012. The pathogenic fungi of postharvest disease and the fungi of latent infection were identified by morphological characteristic and molecular biology methods, and the biological characteristics of pathogen whose damage is increasingly serious were studied.12species of fungi were isolated from rotting mango fruits, including Colletotrichum gloeosporioides, Colletotrichum acutatum, Botryodiplodia theobromae, Dothiorella dominicana, Neofusicoccum parvum, Phomopsis mangiferae, Trichothecium roseum, Pestalotiopsis mangiferae, Aspergillus niger, Aspergillus terreus, Guignardia mangiferae and a new fungus not yet identified. All the12fungi are pathogenic organisms by pathogenicity test, the colony morphology in re-isolated strain after inoculation was similar to that of strain isolated from infected tissue of mango fruit. The postharvest diseases caused by N. parvum, G. mangiferae and T. roseum were first report in China.18species of fungi were isolated from health mango fruits, including Botryodiplodia theobromae, Dothiorella dominicana, Neofusicoccum parvum, Phomopsis mangiferae, Colletotrichum gloeosporioides, Colletotrichum acutatum, Trichothecium roseum, Pestalotiopsis mangiferae, Guignardia mangiferae, Alternaria alternate, Corynespora cassiicola, Bipolaris sp., Curvularia lunata, Cladosporium cladosporioides, Fusarium spp., Chaetomium sp. and Nigrospora sp.. Of which forward14fungi were pathogenic by pathogenicity test. So they have the characteristics of latent infection. Corynespora cassiicola, Curvularia lunata, Bipolaris sp. were first report as latent infection fungi in China.The result of biological characteristics of Pestalotiopsis mangiferae showed that optimum temperature for mycelium growth was25-28℃, the optimum temperature for germination of conidia was32℃, and the fatal temperature was60℃for10min. The optimum pH value for the growth of mycelium was4-5, and the optimum pH value for germination of conidia was4. Among the tested carbon souses, mannite was the best carbon source, but maltose was not propitious to mycelium growth. The best nitrogen source for mycelium growth was beef extract or peptone, but carbamide was not propitious to mycelium growth. Complete dark or12h dark/12h light cycles were best for mycelium growth.The result of biological characteristics of Trichothecium roseum showed that the best optimum temperature was25℃for mycelium growth and30℃for conidial production. The optimum pH values were ranged from5-7for mycelium growth and conidial production. Illumination condition had no distinct effects on mycelium growth and conidial production, but continuous illumination was most favorable to conidial production. Glucose was advantageous to mycelium growth, but the effect was not prominent. The best nitrogen sources for mycelium growth were yeast extract, peptone or beef extract.The toxicities of eight fungicides against Trichothecium roseum causing mango fruit rot were tested by mycelia growth rate method. The results showed that the eight fungicides could inhibit pathogen efficiently. All the tested fungicides could be used to control the disease caused by T. roseum except flusilazole. The toxicity result was analyzed according to the EC50value, EC75value and slope coefficient of toxicity regression equation. The toxicity of carbendazim was the strongest to T. roseum with the EC50value of1.30mg/L and EC75value of3.09mg/L, followed by prochloraz-manganese chloride complex, tebuconazole, myclobutanil, kresoxim-methyl. The toxicities of mancozeb and chlorothalonil were lower than these fungicides mentioned above.