Spatial distribution of soybean bacterial leaf pustule in Benin and identification of Xanthomonas axonopodis pv. glycines host plants

Abstract

Soybean bacterial leaf pustule (SBLP) caused by Xanthomonas axonopodis pv. glycines (Xag) is one of the most economically significant soybean’ diseases. This study aims to determine the spatial distribution of SBLP in Benin and identify other potential host plants. Two surveys were carried  out during the flowering and pod maturation periods in 175 fields across 24 districts belonging to six agroecological zones (AEZ) in Benin in 2019  and 2020. The disease incidence and severity were randomly assessed on 30 and 20 plants, respectively, selected on the diagonals of each field.  Soybean and weeds leaves were sampled based on symptomatology. The disease occurred in 115 out of 175 fields within the prospected AEZs  except the Zone of Depression. The average incidence ranged from 5 to 47.25% and from 17.22 to 44.87% in 2019 and 2020, respectively. The  severity was 2.23 - 37.88% and 6.52 - 34.95% in 2019 and 2020 , respectively. The Cotton Zone of North Benin is the most affected by the disease with  Kandi, Parakou, Gogounou and Segbana the most vulnerable districts contrary to the West Atacora Zone and the Zone of «terre de barre». The  disease-free districts of Kouande and Zogbodomey could be regraded for healthy soybean seeds production. Finally, Acalypha ciliata; Combretum  molle; Christiana africana; Stylochaeton hypogeum and Amorphophalus dracontioides are identified as Xag hosts. Better management of these  host plants would contribute to more effective disease control and, as result, improve soybean output in Benin.