Lack of host specificity of strains of Erwinia rhapontici, causal agent of pink seed of pulse and cereal crops

Erwinia rhapontici is the causal agent of pink seed and soft rot diseases of several crops. Laboratory and field experiments were conducted to study the host specificity of strains of E. rhapontici collected from diseased seeds of pea, bean, lentil, chickpea, wheat, and canola or from infested field soil in western Canada. For the growth chamber experiments, plants of pea, bean, lentil and chickpea were inoculated with each strain of E. rhapontici by injection of bacterial suspension (1 x 10(9) cfu/mL) into young pods at 0.1 mL/pod, whereas developing heads of wheat were injured by abrading with a wire brush and inoculated by spraying of bacterial suspension at 20 mL/plant. Results showed that the E. rhapontici strains were not host specific, since all of the strains could infect each of the host crops tested, regardless of the origin of strains. The frequency of infected seeds was high (>50%) for most strain by crop combinations. Field experiments conducted in 2003 and 2004 revealed that the inoculum of E. rhapontici on infected pea seeds was readily transmitted to neighboring crops of durum wheat, spring wheat, and common bean, if the crops were injured by abrading with a wire brush at the early pod formation stage. The impact of the lack of host specificity on management of the pink seed disease caused by E. rhapontici is discussed.