THE MAIN WAYS OF INFECTION OF GRAIN SORGHUM BY BURKHOLDERIA ANDROPOGONIS (BURKHOLDERIACEAE, BURKHOLDERIALES) IN THE FOREST-STEPPE OF THE MIDDLE VOLGA REGION

Abstract

Bacterial leaf stripe, caused by Burkholderia andropogonis, is one of the main sorghum diseases in the forest-steppe of the Middle Volga region. The purpose of the research was to examine the main ways of infection of sorghum by Burkholderia andropogonis. The studies were carried out on experimental fields of the Volga region Scientific Research Institute of Selection and Seed-growing and in the laboratories of Plant Protection and Microbiology of the Samara State Agricultural Academy in 2010-2015. The severity of sorghum leaf stripe in the stage of physiological maturity was 9-60%, with a maximum in high-drought (2010), minimum in wet and cool (2011) years. Losses of grain sorghum yield from B. andropogonis were on average up to 30 %. The main overwintering and primary inoculum sources reported are infested seeds. Up to 97-100 % of the sorghum seeds were infected with B. andropogonis. After sowing infected seeds, bacteria spread through the vascular system in seedlings and developing plants, penetrating into emerging and ripening seeds. The main indirect vector of bacterial leaf stripe is the flea beetle Phyllotreta vittula feeding on sorghum leaves. In the first half of July, adults of the new generation of P. vittula facilitate the penetration of the pathogen from B. andropogonis exudate into the tissues of sorghum through wounds that feeding beetles form on the upper surface of young leaves. The role of flea beetles P. vittula in the spread of the bacteria B andropogonis in crops of sorghum recorded for the first time.