EVALUATION OF SEED DISSEMINATION STRATEGIES OF XANTHOMONAS AXONOPODIS PV. VIGNICOLA CAUSAL AGENT OF BACTERIAL BLIGHT OF COWPEA

Abstract

Bacterial blight is seed transmitted but the mechanism of pathogen attachment to seed, their colonization of emerging seedling has not been fully studied. The aim of this study was to investigate the seed dissemination strategies of bacterial blight induced by Xanthomonas axonopodis pv. vignicola. Experiment to determine bacteria adhesion to seeds were conducted using twenty seeds each of Ife Brown(cowpea), Maize, Millet and Sorghum. The seeds were surface disinfected by washing in 3 % sodium hypo chlorite solution for 5minutes and was rinsed SDW. Ten seeds each of the grains were put into a sterilized sample bottles containing 10 ml of bacterial suspension adjusted to ca.4.5x107 cfu/ml. Seeds soaked in SDW was used as control. The experiment to determine bacteria seed and seedling colonizing pattern were conducted using one hundred seeds of cowpea which were soaked in 100 ml of SDW containing Xav suspension adjusted to ca. 4.5 x 107cfu/ml-1. Five seeds were placed in a Petri-dish containing SDW and spread filter papers. Seeds soaked in SDW were used as control. At different times after inoculation seeds were collected at random and ground, from which serial dilutions were made to quantify the population of bacterial colonizing the seeds/seedlings (cfu seed-1). The result shows the adhesion of Xav to host’s seed (cowpea) and non-host seeds (millet, sorghum and maize) after 4 h of inoculation. The result shows the population of Xav was correspondingly increasing with the germinating seeds and growing seedling. This shows that distribution of bacterial blight is partly associated with the ability of the pathogens to adhere to seeds of both host cowpea and other seeds surfaces.