Author
|
Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 1/14/2004 Publication Date: 1/14/2004 Citation: Polashock, J.J. 2004. Stem blight and phomopsis resistance in blueberry. Meeting Proceedings. p. 138 Interpretive Summary: Stem diseases of blueberry are difficult to control with fungicides and can cause significant crop loss as well as loss of entire bushes. Incorporation of resistance to fungal diseases into horticulturally superior crops offers an attractive alternative to chemical control. The first step in any such program is the identification of genotypes exhibiting resistance to important diseases. A program was initiated to screen 52 blueberry cultivars for resistance to two important stem diseases namely Botryosphaeria stem blight (Botryosphaeria dothidea) and Phomopsis twig blight (Phomopsis vaccinii). For stem blight, the half-high (V. corymbosum x V. angustifolium) cultivars Chippewa and Northblue were the most resistant and the highbush cultivars Bluecrop, Brigitta Blue and Duke were the most susceptible. For twig blight, lowbush cultivars were the most resistant including Chignecto and Blomidon. The most resistant highbush cultivars were Bluechip and Rubel. The most susceptible cultivars were the highbush Legacy and the southern highbush Emerald. Those that were more resistant to one of the pathogens tested, were not necessarily resistant to the other, suggesting that different mechanisms might be associated with resistance to any given pathogen. This work will benefit breeders, growers and extension agents through identification of currently available resistant cultivars. Technical Abstract: Stem diseases of blueberry can cause significant crop loss as well as loss of entire bushes. Stem diseases also tend to be more difficult to control with fungicides than foliar or fruit diseases. A program was initiated to screen blueberry cultivars for resistance to two important stem diseases namely Botryosphaeria stem blight (Botryosphaeria dothidea) and Phomopsis twig blight (Phomopsis vaccinii). An attached stem assay was used for both pathogens in which the tips of selected branches were pruned off and the cut surface was inoculated with an agar plug containing the pathogen. The inoculated branches were then covered with Parafilm to retain moisture. Controls were treated similarly except that the agar plugs did not contain the pathogen. Lesion lengths were recorded every two weeks. Final measurements were taken at four weeks (B. dothidea) or at six weeks (P. vaccinii) after inoculation. Whole potted plants representing 52 cultivars were used for the study. Three different isolates of B. dothidea and two different isolates of P. Vaccinii were used. Controls for all cultivars had 0-2 mm lesions. Stem blight lesions varied from about 10 mm in the most resistant cultivars to around 140 mm in highly susceptible varieties. The half-high (V. corymbosum x V. angustifolium) cultivars Chippewa and Northblue were the most resistant with average lesion lengths of about 10 mm. Of the highbush type (V. corymbosum), the foreign cultivars Reka and Gila '1876' were the most resistant with average lesion lengths of 17 and 20 mm respectively. The highbush cultivars Bluecrop, Brigitta Blue and Duke were the most susceptible with average lesion lengths between 140 and 144 mm. Phomopsis twig blight lesions ranged from 18 mm to 98 mm. Lowbush cultivars were the most resistant including 'Chignecto and 'Blomidon'. The most resistant highbush cultivars, Bluechip and Rubel averaged lesion lengths of 26 mm. Those varieties that were more resistant to one of the pathogens tested, were not necessarily resistant to the other, suggesting that different mechanisms might be associated with resistance to any given pathogen. This work will be repeated next year and information gained from this study will be incorporated into the USDA-ARS breeding program. |
