Características morfofisiológicas e de crescimento em resposta à inoculação com Hemileia vastatrix Berk & Br. em cafeeiro

Abstract

The rust, caused by the fungus Hemileia vastatrix is the main fungal disease that affects the coffee crops. Resistance mechanisms to disease have been sought, since the fungus presents high genetic variability and its most efficient and sustainable control is through the use of resistant cultivars. This work aim was to identify the coffee genotypes morphophysiological and growth characteristics in response to inoculation with the fungus Hemileia vastatrix. Ten coffee trees genotypes were selected from the Germoplasma Active Bank of Minas Gerais and planted in a greenhouse. The seedlings were inoculated with the fungus Hemileia vastatrix. Physiological, anatomical and growth characteristics were evaluated before and after inoculation. Incidence evaluations and severity of the disease were carried out. Genotypes behaved differently for physiological responses over time of evaluation. The genotype that presented the highest incidence and severity of rust was Topazio MG 1190, confirming its susceptibility, followed by MG 0582 and Catiguá MG 3. Lower values of liquid photosynthesis, stomatal conductance, leaf transpiration and carboxylation efficiency occurred in genotypes with higher incidence of disease. Chlorophyll contents were not altered with the incidence of rust. The genotypes were grouped differently for both anatomical and physiological characteristics, before and after inoculation, suggesting different adaptations of the studied genotypes to the stress caused. Besides that, groups of correlated characteristics involving morphophysiological and growth characteristics were identified. Lower abaxial face cuticle thickness, smaller xylem vessel diameter, less instantaneous water use efficiency, greater number and density of stomata and greater stomatal conductance provided greater severity of the disease. Lower thickness of palisade parenchyma and lower ratio between thickness of the palisade parenchyma and spongy parenchyma may occur in coffee trees that present a greater severity of the disease, depending on the inoculation with the pathogen. According to the observed results, morphophysiological and growth characteristics may be promising for use in selection assisted by conventional and biotechnological breeding programs of coffee in the development of rust cultivars resistant.