Impact of the colonization of Leifsonia xyli subsp. xyli in a susceptible sugarcane genotype on water status and physiological traits

Leifsonia xyli subsp. xyli (Lxx) is a pathogenic bacterium that causes Ratoon Stunting Disease (RSD) in the sugarcane crop. Disease symptoms caused by Lxx have been associated with hormonal imbalance, which may be intensified when plants are under water deficit conditions. However, up to date there are no studies showing that Lxx colonization decreases water status in sugarcane. The objective of this study was to evaluate the effect of water status and physiological traits of sugarcane colonized by Lxx under irrigation and water deficit conditions. We inoculated cuttings of the sugarcane genotype CB 49260 with Lxx using four treatments: i) healthy plants fully irrigated, ii) healthy plants under water deficit, iii) plants inoculated with Lxx fully irrigated, and iv) plants inoculated with Lxx under water deficit. Lxx inoculation in sugarcane did not affect relative water content (RWC) in the leaves, independently of the water conditions tested. For gas exchange and fluorescence traits, we did not identify differences between plants inoculated with Lxx and healthy plants. As expected, plants under water deficit conditions decreased RWC, CO2 assimilation, stomatal conductance, transpiration and fluorescence traits, and increased soluble amino acids and proline contents in the leaves. Lxx inoculation increased amino acids and proline contents in plants under water deficit conditions. Therefore, the results indicated that sugarcane colonized with Lxx did not change plant water status independently of the water conditions during the entire growing season.