Análise histológica temporal de folhas de laranjeira azeda inoculadas com Phytophthora parasítica.

Abstract

Histological plant-pathogen interaction studies have been achieved through bioassays, by putting the pathogen in contact with the plant tissues and subsequent observations by microscopy. These macroscopically observations of infection or penetration can be studied through accompaniments at different time intervals after inoculation as well as monitored over the course of the infection. In this context, the aim of this work was to analyze sour orange leaves inoculated with Phytophthora parasitica, causal agent of the citrus gummosis disease, by using of light microscopy at different times after inoculation and the modified traps method. Mycelium of the P. parasitica IAC095 isolate, from the Center APTA Sylvio Moreira, was inoculated in water with citrus leaf discs and plant-pathogen interaction was monitored in eight different times, at 0 , 12 , 24 , 36 , 48 , 60 , 72 and 96 hours after inoculation. As results, it was observed that the pathogen is attracted by the sour orange leaf discs, immediately. The site of greatest immediate attraction of the pathogen is the primary and secondary drivers injured vessels. After inoculation, hyphae fixed on conductor 12 hours vessels and not at 0 hours; an increase in the proliferation of hyphae is between 36 and 48 hours; the loss of green staining of leaf discs to tint green slime occurred at 60 hours; and at 96 hours it were observed necrosis and the presence of the pathogen in the intercellular environment. The visualization of sporangia reproduction structures of the pathogen has occurred at 12 hours, while the appearance of chlamydospores was at 60 hours. Therefore, the modified trap method is practical to study citrus-Phytophthora parasitica interaction at histological level.