Comparison of Leifsonia xyli subsp. xyli molecular detection in heat-treated sugarcane setts

Abstract

The thermotherapy of sugarcane setts is currently the primary management method for Leifsonia xyli subsp. xyli (Lxx), in Brazil. When they are immersed, the enzymes and proteins of the bacterial cell are denatured without harming the setts buds. Due to possible escapes from detection and consequent bacterium survival to thermotherapy, what may result in asymptomatic seedlings, this study aimed to detect the Leifsonia xyli subsp. xyli bacterium in sugarcane setts using molecular techniques and different time and temperature combinations, with or without the addition of antibiotics. The conventional PCR method detected the Lxx bacterial DNA only in the positive control, consisting of a highly susceptible plant with a high bacterial concentration. Using the nested-PCR, the Lxx DNA was detected in all the treatments used. Thus, none of the treatments adopted in the thermotherapy was able to eliminate the Lxx from the setts, and the use of kasugamicin also did not eliminate the bacterium, but reduced the bacterial population in the tested treatments. These results confirm that the nested-PCR is a useful tool to detect the presence of this phytobacterium in setts that will be used as seedlings.

KEYWORDS: Heat treatment, ratoon stunting disease, polimerase chain reaction.