STRUCTURAL MODIFICATION OF Quercus eduardii Trel. LEAF CAUSED BY Taphrina caerulescens (Desm. & Mont.) Tul.

Abstract

In the temperate forests of the Sierra Fria, Aguascalientes, Mexico, Taphrina caerulescens (Desm. & Mont.) Tul. was observed affecting leaves of Quercus eduardii Trel. This was the first report of the pathogen in Mexico and Central America. In addition to the typical symptom, the plant-pathogen interaction also results in the appearance of chlorotic lesions on the upper surface of some infected leaves. This was the first report of these atypical symptoms, which do not result in the formation of blisters. The main objective of this study was to describe the histopathological changes that occur in Q. eduardii leaves infected with T. caerulescens. Of the 25 species of oak present in the Sierra Fria, the disease incidence and severity was highest in Q. eduardii. For histopathological studies, sections of healthy and infected leaf tissue were fixed, dehydrated, embedded in paraffin, cut with a microtome and stained with fast green and safranin. The differences in the healthy and infected leaf sections were observed with a Leica DME microscope and a Carl Zeiss microscope. Leaf samples were also processed for scanning electron microscopy. The following changes were observed in the affected blister tissue: hyperplasia and hypertrophy of cells of the upper and lower epidermis and of the palisade layer cells; destruction of the cells of the spongy mesophyll layer, and destruction of the nucleus and other organelles of the palisade cells. The differences in the cell sizes between the infected and healthy leaf tissue were supported by morphometric and statistical analysis. No noticeable changes in the leaves which displayed atypical symptoms were observed.