Mango leaf-spots in Minia Governorate.
Hussein N. A.
Author Affiliation: Department of Plant Pathology, Faculty of Agriculture, Minia University, Minia, Egypt.
Egyptian Journal of Microbiology 33 : 217-231
Abstract : Leaf spot of mango was studied in El-Minia Governorate, Egypt, in 1994-96. Three fungal species, Alternaria alternata, Cladosporium sphaerospermum and Epicoccum nigrum were frequently isolated. Pathogenicity test for these fungi revealed that they were major leaf-spot inducing agents. Leaves of 7 mango varieties differed in their response to infection by the fungi. Leaves of mango cv. Balady were highly susceptible, but mango cv. Hindy was relatively resistant. Disease severity increased with increasing period after artificial inoculation. In a study of host ranges, apricot, grape, guava and lemon were most susceptible to infections by A. alternata, while apricot, followed by guava and lemon, were most susceptible to C. sphaerospermum. Guava was most susceptible to E. nigrum. Infection by the 3 fungi resulted in a decrease in chlorophyll a, chlorophyll b and carotenoid content. The decrease of pigments was more pronounced 9 days after inoculations and was greater in the susceptible mango cv. Balady than in the relatively resistant cultivar Hindy. Culture filtrate of the 3 fungi induced symptoms typical of each pathogen. A. alternata and C. sphaerospermum produced thermostable toxins. Phytotoxicity of A. alternata and C. sphaerospermum culture filtrates increased with increasing culture age (15 days), while E. nigrum culture filtrate induced more symptoms after 10 days incubation.