Factors affecting Neofusicoccum luteum infection and disease progression in grapevines

Abstract

This study investigated some factors that affect Neofusicoccum luteum infection and disease progression in grapevines, on which it causes cankers and die-back. Inoculation of green shoots with each of the conidial suspensions (20 μL of 102–106 conidia/mL) caused 100 % infection, but significant differences in lesion lengths among concentrations (P < 0.001). Lesion lengths increased with conidial concentrations to a maximum of 41.7 mm, in tissue inoculated with 104/conidial. Lesions then decreased for 105 and 106 conidial/mL (28.6 and 27.8 mm, respectively). The different wetness durations (0–24 h) tested after inoculating trunks of 1-year old vines with conidia did not affect pathogen incidence or lesion lengths, however continued incubation at 95 % RH caused greater pathogen progression (maximum isolation distances from point of inoculation; P < 0.001; 100.6 mm) than at ambient 78 % RH (77.0 mm) within 3 months after inoculation. Inoculation of trunks, canes and green shoots caused different rates of pathogen colonisation (P < 0.001); by 5 months after N. luteum inoculation mean maximum distances were 39.1, 31.6 and 23.2 mm, respectively. Wound age at the time of inoculation significantly affected (P < 0.001) infection incidence by N. luteum, which decreased as wounds aged. Conidial inoculum caused 100-0 % incidence over 0–14 days and mycelial inoculum caused 100-40 % infection over 0–30 days. Soil moistures affected lesion development, with 15 and 100 % soil moisture causing greatest dieback and bud death during winter. This study has shown how some features of the natural infection environment can affect infection by Botryosphaeria spp. inoculum and symptom development, which could underpin improvements in vineyard management.