Reaction and colonization of common bean genotypes by Curtobacterium flaccumfaciens pv. Flaccumfaciens

Bacterial wilt is one of the main diseases of common beans and the use of cultivars with some level of resistance is fundamental for an adequate disease management. The reaction of 54 common bean genotypes to Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) was evaluated, and the colonization of cultivars and obstruction of primary xylem vessels at the petiole base were assessed. In greenhouse and laboratory tests, resistance was detected in the cultivars IAC Diplomata, IAC Alvorada, IAC Imperador, IPR Corujinha, and IPR Tangará, and in the lines P5-4-4-1 and C4-5-4-1-2. The Cff colonization rate was also slower in the resistant cultivars (IAC Diplomata, IAC Carioca Tybatã, and IAC Carioca Pyatã) and the percentage of obstruction of primary xylem vessels at the petiole base lower than in the susceptible cultivars (IAC Carioca and Pérola).A murcha-de-curtobacterium é umas principais doenças do feijoeiro e o uso de cultivares com níveis de resistência é fundamental para o manejo adequado da doença. A reação de 54 genótipos de feijoeiro comum a um isolado de Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) foi avaliada, assim como a colonização de cultivares e a obstrução de vasos de xilema primário da base de pecíolos de plantas inoculadas foram quantificadas. Ensaios conduzidos em casa-de-vegetação e laboratório evidenciaram resistência nas cultivares IAC Diplomata, IAC Alvorada, IAC Imperador, IPR Corujinha e IPR Tangará e nas linhagens P5-4-4-1 e C4-5-4-1-2. Uma menor velocidade de colonização por Cff também foi evidenciada nas cultivares resistentes (IAC Diplomata, IAC Carioca Tybatã e IAC Carioca Pyatã), assim como uma menor porcentagem de obstrução dos vasos de xilema primários na base de pecíolos, em comparação às cultivares suscetíveis (IAC Carioca e Pérola).Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Instituto Agronômico de CampinasInstituto Agronômico do ParanáUNESP Faculdade de Ciências Agronômicas Departamento de Proteção Vegeta

Analysis of expressed sequence tags from Citrus sinensis L. Osbeck infected with Xylella fastidiosa

In order to understand the genetic responses resulting from physiological changes that occur in plants displaying citrus variegated chlorosis (CVC) symptoms, we adopted a strategy of comparing two EST libraries from sweet orange [Citrus sinensis (L.) Osbeck]. One of them was prepared with plants showing typical CVC symptoms caused by Xylella fastidiosa and the other with non-inoculated plants. We obtained 15,944 ESTs by sequencing the two cDNA libraries. Using an in silico hybridization strategy, 37 genes were found to have significant variation at the transcriptional level. Within this subset, 21 were up-regulated and 16 were down-regulated in plants with CVC. The main functional categories of the down-regulated transcripts in plants with CVC were associated with metabolism, protein modification, energy and transport facilitation. The majority of the up-regulated transcripts were associated with metabolism and defense response. Some transcripts associated with adaptation to stress conditions were up-regulated in plants with CVC and could explain why plants remain alive even under severe water and nutritional stress. Others of the up-regulated transcripts are related to defense response suggesting that sweet orange plants activate their defense machinery. The genes associated with stress response might be expressed as part of a secondary response related to physiological alterations caused by the infection