Blueberry flower infection by Monilinia vacinii-corymbosi: systemic activity of fungicides and development of a cDNA synthesis protocol from inoculated and pollinated pistils

The fungus Monilinia vaccinii-corymbosi infects open blueberry flowers through the gynoecial pathway, causing mummy berry disease. The activity of the fungicides fenbuconazole and azoxystrobin sprayed at different flower developmental stages was investigated. In the greenhouse, the two fungicides performed similarly: only flowers sprayed at anthesis were protected from infection, while those treated between 1and 15 days before anthesis were not. In the field, azoxystrobin failed to decrease the incidence of fruit mummification regardless of flower stage, while fenbuconazole significantly decreased disease incidence at all stages. Thus, while neither fungicide is able to prevent hyphal ingress into styles of flowers treated before anthesis, other factors such as reduction of inoculum or residual activity in the ovary may explain the pre-anthesis activity of fenbuconazole in the field. To lay the groundwork for comparing gene expression patterns in pollinated vs. infected styles, mRNA extraction and cDNA synthesis procedures were developed.