Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Creating a test to measure resistance to soybean

Bacterial blight is a foliar disease caused by Pseudomonas savastanoi pv. glycinea. The disease is characterised by angular leaf spots yet with only little impact on the yield. The seeds constitute the primary source of inoculum, and contaminated seeds may affect the diffusion of new varieties. The best approach to preventing the disease is to use resistant varieties. The aim of this study was to develop a resistance test for the greenhouse to determine the resistance of soybean lines to bacterial blight. The test included seven bacterial strains with distinct and specific avirulence genes tested on 91 soybean genotypes. The results exhibit a wide spectrum of interactions. Whilst all genotypes were resistant to part of the bacteria, only four varieties were resistant to all bacterial strains. This test will be used to screen the diversity of avirulence genes present in the populations of Pseudomonas savastanoi pv. glycinea in order to determine which resistance genes are most useful for preventing bacterial blight and the transmission of the seed-borne pathogen.

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