Pre‐infection processes of Botryosphaeriaceae spp.: adhesion of conidia to different substrata

Abstract

Species of Botryosphaeriaceae are important wound pathogens of grapevines as causal agents of botryosphaeria dieback, but the behaviour of their conidia pre‐infection is unknown and may be important for disease development. Adhesion properties of conidia were investigated for Botryosphaeria dothidea, Neofusicoccum luteum and N. parvum on substrata with different affinities for water. Greatest adhesion on any surface was reached after 5 min for isolates N. luteum MM558, B. dothidea 007 and N. parvum G652 (53·1, 54·0 and 50·6%, respectively) and for N. luteum isolate CC445 after 20 min (61·4%). As conidia adhered well to all artificial substrata, it appeared as if the attachment process was nonspecific. Overall, surface wettability did not play a major role in the adhesion of conidia. Spore surface proteins appeared to play a role in the adhesion process because treatment of conidia of N. luteum MM558 with a protease completely prevented adhesion. Histochemical labelling of conidia and germlings with Coomassie brilliant blue (specific for proteins) was positive for all isolates, with a blue ‘halo’ often seen surrounding conidia or near the germ tube emergence point after incubation times conducive to germination. Alcian blue also stained material surrounding conidia after longer incubation times, which indicated that mucopolysaccharide and protein production may be involved in a second phase of adhesion.