Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2008
Publication Date: 10/1/2008
Publication URL: http://hdl.handle.net/10113/25641
Citation: Espinoza, J.G., Briceno, E.X., Keith, L.M., Latorre, B.A. 2008. Canker and twig dieback of blueberry caused by Pestalotiopsis spp. and a Truncatella sp. in Chile. Plant Dis. 92:1407-1414. Interpretive Summary: Blueberry is an economically important crop in Chile. Canker and dieback symptoms have recently been observed along the productive blueberry zone. The fungus Pestalotiopsis was consistently isolated from diseased samples and was characterized by physiological and molecular techniques. Pathogenicity tests revealed that fungal isolates were pathogenic on apple, kiwifruit and blueberry fruits. The fungi were highly sensitive to the fungicides fludioxonil and pyraclostrobin.
Technical Abstract: Blueberry (Vaccinium spp.) has great economic importance in Chile, currently with about 8,500 ha being cultivated. Recently, the presence of canker and dieback symptoms has been observed along the productive blueberry zone of Chile extending from the V Region (32º49´ South lat.) in the north to the X Region (40º45´ South lat.) in the south, approximately. Species of Pestalotiopsis (sin. Pestalotia) were consistently isolated from diseased samples in 12 plantings in 22 different locations. Therefore, the objective of this study was to identify and characterize the species of Pestalotiopsis associated with canker and twig dieback symptoms on blueberry. Forty nine isolates were obtained on potato dextrose agar acidified with 96% lactic acid (0.5 mL'L-1) in 2006 and 2007. These isolates were morphologically identified as P. clavispora (40 isolates), P. neglecta (four isolates) and Truncatella (= Pestalotia) angustata (five isolates) on the basis of colony characteristics and conidial morphology. This identification was verified by molecular analysis of the ITS region of DNA obtaining >98% of homology with reference sequences of each of these species deposited in GenBank (accession numbers EU342211 through EU 342217). Pathogenicity tests revealed that isolates of P. clavispora, P. neglecta and T. angustata were pathogenic on apple, kiwifruit and blueberry fruits. Similarly, isolates of P. clavispora, were pathogenic on detached blueberry twigs (cv. O´Neal). Additionally, three selected isolates of P. clavispora induced light brown canker lesions, surrounded by a reddish halo, and shoot dieback after twig inoculations on two-yr-old twigs of blueberry cvs. O´Neal, Bluecrop, Brightwell, Brigitta, Duke, Elliot and Misty. Among blueberry cultivars, Brightwell and O’Neal were the most susceptible and Bluecrop and Misty the least susceptible, while Elliot, Brigitta, and Duke were moderately susceptible to P. clavispora. These pathogens were isolated consistently from inoculated plants, confirming Koch’s postulates. P. clavispora was highly sensitive to fludioxonil and pyraclostrobin with ED50 of 0.06 to 0.08 and 0.04 to 0.8 mg'L-1, respectively. Therefore, the results of this study indicate that P. clavispora, P. neglecta and T. angustata are primary pathogens that can cause canker lesions and dieback symptoms on blueberry not previously described in Chile. However, these results do not exclude the possibility that other species of these genera or other plant pathogenic fungi, e.g. Botryosphaeria spp., Pestalotia spp., and Phomopis spp., may eventually be involved in this syndrome of blueberry.