Survival niches of Pseudomonas savastanoi pv. glycinea, causal agent of bacterial blight in soybean (Glycine max L.)

Abstract

Bacterial blight caused by Pseudomonas savastanoi pv. glycinea (Psg) is a prevalent disease in soybean crops worldwide, and crop rotation is a potential management strategy. However, the importance of alternative crops and soil as hosts of Psg is not well understood. This study aimed to assess the survival of Psg in four soil types, the phyllosphere and rhizosphere of 12 crops rotated with soybean, and endophytic colonization of crops by Psg. The pathogenic strain Soj. 1462 of Psg, resistant to rifampicin, was used in all experiments, and PCR confirmed bacterial survival. Psg survived for a maximum of two days in all soil types. In the phyllosphere, soybean had the longest Psg survival (70 days), followed by white oat, black oat, ryegrass, sunflower, and sorghum (35 days). In the rhizosphere, the longest Psg survival was obtained for white oat, black oat, ryegrass, barley, corn, soybean, and wheat (28 days), and less than 21 days for all other crops. In endophytic colonization, Psg survived for 70 days in soybean, white oat, black oat, ryegrass, corn, and sorghum, and between 42 to 56 days in other crops, when inoculated in artificially wounded plants. In plants inoculated by spray, the highest Psg survival was in ryegrass and soybean (70 days), and between 14 to 63 days in other crops. Cultivating sunn hemp, common bean, and radish in succession with soybean is recommended to reduce Psg inoculum since the survival periods recorded for these crops were lower.