Anthracnose fruit caused by Colletotrichum acutatum is the most important postharvest disease of blueberries (Vaccinium corymbosum). In order to develop a disease forecasting model for anthracnose fruit rot in blueberries, the effects of temperature, wetness duration, relative humidity and wetness interruptions were studied on appressorium formation and infection of green and blue fruit by C. acutatum. Three-dimensional response surfaces were fitted to the data. A model combining all variables was developed. The resistance response in blueberry cultivar ‘Elliott’ was investigated. Using suppression subtraction hybridization, several defense-related genes as well as abiotic stress-related genes were found to be upregulated in ‘Elliott’ but not in ‘Jersey’ fruit within 24 hours after inoculation. Some genes were related to oxidative stress in plant tissues. Higher levels of hydrogen peroxide were also found in inoculated ‘Elliott’ compared to ‘Jersey’ fruit. To investigate the role of antifungal compounds in resistance, a series of fruit extractions was performed with water, methanol, and ethyl acetate, and fractions were tested for antifungal activity in agar plate bioassays. The methanolic extract was the most biologically active; disease incidence was reduced by 88% when ‘Jersey’ fruit was pretreated with a 4% solution prior to inoculation with C. acutatum. Spectrophotometry showed that this fraction mainly contained flavonoids. Anthocyanins and flavonols were then quantified and identified in both cultivars using HPLC-MS. ‘Elliott’ fruit overall contained more anthocyanins than ‘Jersey’ fruit but the same compounds were found in both cultivars. However, two unique flavonols were present in ‘Elliott’.A total of 26 blueberry cultivars was screened for anthracnose resistance using several different techniques. A cut-fruit technique was promising for use as a rapid screening method. A negative linear correlation was observed between resistance and fruit sugar content but not fruit pH. The growth of C. acutatum in culture was restricted at higher sugar and lower pH levels. The inheritance of resistance was also investigated to facilitate future breeding work. Using inoculated fruit from F-1 populations of specific crosses between resistant and susceptible cultivars, resistance ratings based on AUDPC values were compared to resistance ratings predicted from previous studies. Significant correlations were observed, providing strong evidence that anthracnose resistance is highly heritable in highbush blueberries. The results from these studies contribute to the understanding of the biology and management of anthracnose fruit rot in blueberry.
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