The sugarcane pathogen Leifsonia xyli subsp. xyli reduces plant growth by interfering in the development of the shoot apex 
M. CICARELLI CIA (1), J. Rodrigues Marques (1), R. Cunha Antunes de Faria (1), L. Aranha Camargo (1) (1) University of São Paulo, Brazil

The bacterium Leifsonia xyli subsp. xyli (Lxx) causes stunting when present in high titers in the xylem of sugarcane plants, resulting in considerable losses in biomass. In previous studies, we showed that the expression of genes involved in the control of the cell cycle and in the metabolism of DNA were down regulated in plants infected with higher bacterial titers compared to plants with lower titers, suggesting that the stunting symptom results from an interference in the cell cycle. In this study, histological analysis of asymptomatic (low Lxx titers) and symptomatic (high Lxx titer) plants were carried out using standard light stereomicroscopy techniques. We analyzed the shoot apex of the plants and observed that the intercalary meristem (IM) was continuous in both asymptomatic and symptomatic plants, but in the latter ones the zone of dividing cells was thinner and as a consequence the internode was shorter forming smaller phytomeric units. It was also observed that symptomatic plants presented fewer and more elongated cells derived from the IM. The data indicate lower mitotic activity in the meristematic regions of symptomatic plants and explain the major symptom of this important disease of sugarcane. 

Abstract Number: P7-163
Session Type: Poster