Dynamics of conidial adhesion and elicitor uptake in relation to pisatin accumulation in aqueous droplets on the endocarp of pea pods

Abstract

The adhesion of conidia of Monilinia fructicola to, and uptake of a biotic elicitor (pea- M. fructicola diffusate preparation) and two abiotic elicitors (actinomycin-D and CuCl 2) by endocarp tissue of pea pods has been investigated in relation to the elicitation of pisatin. Conidia were found to rapidly adhere to the endocarp surface and were not readily dislodged by washing. The dynamics of elicitor uptake from the bathing solutions varied with the elicitor treatments. In the case of the biotic elicitor, bioassays of the solutions remaining on the endocarp surface for residual elicitor activity indicated there was a gradual loss of elicitor from the bathing solution. By 10 h, approximately 41% of the original elicitor activity had disappeared from the bathing solution. Direct measurement of actinomycin-D in the bathing solution showed that uptake appeared to begin about 6 h after its application. On the other hand, direct measurement of Cu 2+ in the bathing solution showed that approximately 60% of the original concentration of Cu 2+ rapidly disappeared from the bathing solution in the first 30 min. The results highlight the need for sustained contact between plant and fungus or elicitor in the bathing fluid of the infection-droplet or of the elicitor solution for the maximum outcome of the pisatin response.