Induction of post-infection ethylene and its role in resistance of bean (Phaseolus vulgaris) against Colletotrichum lindemuthianum

Abstract

The influence of inoculation techniques on induction of post-infection ethylene production in susceptible and resistant genotypes of bean (Phaseolus vulgaris) inoculated with the kappa race of Colletotrichum lindemuthianum was studied. Three inoculation methods (brushing, dipping and spraying) of excised leaves were compared. The brushing technique caused both the highest ethylene production at 120 h after inoculation, and better symptom development than dipping and spraying. It was, therefore, adopted to determine the post-infection ethylene production in four inoculated bean genotypes (GLP406 and Kaboon – resistant, GLP636 – moderately resistant; and MDRK – susceptible). Ethylene production increased slightly 24 h after inoculation in all four genotypes, followed by a rapid decline after 48 h. Ethylene production remained low until 120 h after which a sharp rise was observed in genotype MDRK. Increased production, though to a lesser extent, was observed in GLP636. This trend was repeatable and thus may offer an additional physiological marker to bean breeders to screen for resistance to C. lindemuthianum.