Methods for evaluating eggplant resistance to bacterial wilt caused by Pseudomonas solanacearum

Abstract

Four methods of inoculation combined with four plant development stages were used in order to define one reliable method to screen eggplant (Solanum melongena) germplasm for resistance to bacterial wilt caused by Pseudomonas solanacearum. Resistant and susceptible genotypes were best differentiated upon inoculation of plants with one pair of expanded leaves, by wounding the stem with an entomological needle which passed through a 10 microlitre drop of a bacterial suspension containing 10⁷ to 10⁸ cfu/ml. When plants of 16 genotypes at the same growth stage were inoculated with stem wounding and without wounding (root inoculation), there was a correlation of 74 and 87% when disease was assessed at six and ten days after inoculation, respectively, indicating that the recommended wounding method is not so severe that could promote resistance breakdown, what would result in elimination of resistant genotypes.