Occurrence and development of Colletotrichum acutatum on symptomless blueberry bushes

Abstract

The anthracnose fungus Colletotrichum acutatum was detected in symptomless blueberry bushes (Vaccinium spp.) in a Japanese blueberry field. Naturally diseased bushes and their apparently healthy neighbours were selected, and C. acutatum was isolated from the symptomless tissues of each bush from February 2000 to January 2002. Analysis of the diseased bushes during the dormant period revealed that the fungus was able to survive on symptomless tissues, such as shoot bark and bud scales. Furthermore, C. acutatum was consistently isolated from symptomless leaves and shoots of several surrounding symptomless bushes. Arbitrarily primed PCR (ap-PCR) analyses of the fungal isolates obtained from the diseased and symptomless bushes revealed that most C. acutatum isolates were genotypically identical, regardless of their origins. Inoculation tests using leaves of various blueberry cultivars suggested that the presence or absence of symptoms on each bush can not always be explained by differences in cultivar susceptibility, and other factors may be associated with the appearance of symptoms.