Mango leaf-spots in Minia Governorate.
Hussein N. E. A.
Author Affiliation: Dept. of Plant Pathology, Fac. of Agric., Minia Univ., Minia, Egypt.
Annals of Agricultural Science, Moshtohor 35 : 2029-2042
Abstract : Leaf spot of mango was studied during 1994-95 in El-Minia Governorate, Egypt. Isolation, identification and pathogenicity tests identified Alternaria alternata, Cladosporium sphaerospermum and Epicoccum nigrum as the causal agents of the disease. Leaf spot severity increased with increasing period after artificial inoculation of these pathogens. Evaluation of the response of 7 mango cultivars (Balady, Tymour, Zepdia, Pairi, Hindy, Alfonse and Dabsha) to leaf spot diseases showed that Balady is the most susceptible while Hindy is the most resistant. Examination of the response of 5 potential hosts (sweet orange, lime, apricot, guava and grape) showed that apricot, grape, guava and lemon were the most susceptible to A. alternata; apricots, guava and lemon were the most susceptible to C. sphaerospermum; and guava was the most susceptible to E. nigrum. Infection by the three test fungi significantly decreased the chlorophyll a and b and carotenoid contents of mango leaves. Such reduction was more pronounced in the susceptible cultivar Balady than in the resistant cultivar Hindy. Culture filtrates of the three fungi induced symptoms typical of each pathogen. A. alternata and C. sphaerospermum produced thermostable toxins, while E. nigrum produced thermolabile toxins in vitro. Phytotoxicity of culture filtrates increased with increasing culture age, especially in the susceptible mango cultivar.