Development of phenotyping assays for resistance screening of blueberry plants against Neofusicoccum spp.

Botryosphaeria disease is a common problem on a large range of hosts, including blueberry, causing dieback and cankers. Methods for phenotyping assays were developed in this project to facilitate blueberry resistance breeding. Detached shoots were used to test effects of wound size (needle, scalpel), inoculum type (mycelium, conidia), stem hardness (soft, semi-soft) and incubation temperatures on lesion development. Experiments were carried out on various blueberry cultivars with four Neofusicoccum strains, two each of N. parvum and N. ribis. Lesions of similar lengths developed on both scalpel and needle wounded shoots indicating no wound size effects. Mycelium plugs produced lesions faster than conidial suspension. Similarly, lesions on soft wood progressed faster than those on semi-soft cuttings. Incubation temperature had a significant effect on lesion development, with 26°C showing faster disease development than 19 or 22°C. This information will inform assays for blueberry plant breeding for improved disease resistance.