Microorganisms asssociated with Withania somnifera leaves

Microorganisms including bacteria, actinomycetes and fungi were recovered f rom the leaves of Withania somnifera, which were collected from two altitud inal ranges (0-300 m and 1700-2000 m) in the Asir region, Saudi Arabia. Typ es and numbers of microorganisms varied according to the altitude and the m onth of collection. The number of microorganisms was higher on old leaves t han that on young ones in most cases. Low altitude exhibited more microorga nisms than high altitude. The relationship between meteorological factors a nd type and number of the recovered microorganisms is discussed. Inoculatio n of detached healthy leaves of Withania by all recovered fungal species re vealed only Alternaria solani as a pathogen of this plant. To confirm patho genicity, scanning and transmission electron microscopic examination reveal ed the colonization of this pathogen inside the leaf tissue. Penetration of Withania leaves by the fungus occurred only through stomata, and the invad ing hyphae were located in the intercellular spaces of leaf tissues. Ultras tructural changes noted in infected cells included changes in chloroplasts and the invagination of the host plasma membrane.