CYTOLOGICAL AND CHEMICAL EVIDENCE FOR AN ACTIVE RESISTANCE RESPONSE TO INFECTION BY COLLETOTRICHUM ACUTATUM IN ‘ELLIOTT’ BLUEBERRIES

The infection process of Colletotrichum acutatum on ripe fruit of highbush blueberry (V. corymbosum) ‘Elliott’ (resistant) and ‘Jersey’ (susceptible) was studied using differential interference contrast microscopy.
Ripe berries were inoculated with a drop of conidial suspension of C. acutatum and incubated at 100% relative humidity.
Epidermal peels were evaluated at selected times after inoculation.
In both cultivars, C. acutatum had penetrated the cuticle by 48 hpi, but adopted a different infection strategy in the susceptible versus the resistant cultivar.
In ‘Jersey’, intracellular growth of the pathogen led to the formation of numerous acervuli with orange conidial masses.
In ‘Elliott’, the fungus showed restricted, mostly subcuticular growth.
Acervuli were delayed in their development and contained few conidia.
Also, an accumulation of amorphous globules was seen around intracellular hyphae in ‘Elliott’ but not in ‘Jersey’, suggesting an active resistance response to infection in ‘Elliott’. Chemical analysis of blueberry fruit extracts from both cultivars at various time points after inoculation showed elevated levels of anthocyanins in ‘Elliott’ but not in ‘Jersey’ fruit after infection. ‘Elliott’ fruit also had a lower pH and sugar content than ‘Jersey’ fruit, but these variables did not change significantly during the infection process.
Further research is needed to elucidate the role of chemical factors in the resistance response.

IX International Vaccinium Symposium

T.D. Miles, P.S. Wharton, A.C. Schilder

Vaccinium corymbosum, anthracnose fruit rot, anthocyanins, host resistance

https://doi.org/10.17660/ActaHortic.2009.810.47