Weeds as A Potential Host of Xanthomonas Oryzae Inoculum in Irrigated Rice Systems in Burkina Faso

Bacterial Leaf blight and bacterial leaf streak caused, respectively, by Xanthomonas oryzae pv. oryzae and X. oryzae pv. oryzicola are two rice diseases that occur in rice-growing areas in Burkina Faso. For better management of both pathogens, it is essential to integrate the use of resistant varieties with good agronomic practices including weed management which plays a role in their survival and dissemination.

This study aims to identify the main weeds that can act as reservoirs of Xanthomonas oryzae strains.

Soil was sampled on three rice-growing sites. In the laboratory, we sifted the soil to collect the seeds of the weeds which were put in pots in the greenhouse for germination. After emergence, all weed species were inventoried and then inoculated to determine their host capacity.

We identified 14 species belonging to dicotyledons against 10 species from the Poaceae and three species from the Cyperaceae genus. This presence is effective in all plots sampled but at a variable level of prevalence. Our results showed that some Poaceae and Cyperaceae species were the main reservoirs of X. oryzae pv. oryzae and X. oryzae pv. oryzicola and behave sometimes like epiphytes. We detected a latent infection of X. oryzae pv. oryzicola from Oryza sativa, Echinochloa colona, Eleusine indica, Digitaria horizontalis, and Rottboellia cochinchinensis. Except Oryza longistaminata, Sacciolepis Africana, Paspalum vaginatum, Paspalum polystachyum, and Echinochloa colona which manifested typical symptoms of bacterial leaf streak, the other species showed yellowing, whitish spots and necrosis at the inoculation site.

The high prevalence of weeds in rice fields, especially Poaceae and Cyperaceae, is one of the main causes of the importance of bacterial leaf streak disease in the irrigated rice system in Burkina Faso.