Stem diseases of blueberry (Vaccinium spp.) can cause significant crop loss as well as loss of entire bushes. Stem diseases are also more difficult to control with fungicides than foliar or fruit diseases. A screening program was initiated to test blueberry cultivars for resistance to two pathogenic fungi: botryosphaeria stem blight and phomopsis twig blight. An attached stem assay was developed to compare the host response with both fungi. The relative resistance of 50 blueberry cultivars was assessed using stem lesion lengths, analyzed on a log scale, taken at 4 weeks postinoculation. For Botryosphaeria stem blight, mean lesion length ranged from about 10 mm in resistant cultivars to about 140 mm in susceptible cultivars. The half-high cultivars Northsky, Northblue, and Chippewa, and the lowbush cultivar Putte were among the most resistant. Phomopsis twig blight lesions ranged in mean length from about 18 to 98 mm. Similar to results for Botryosphaeria stem blight, resistance was limited to half-high (`Northsky' and `Chippewa') and lowbush (`Blomidon', `Chignecto', and `Cumberland') cultivars. Individual cultivars resistant to one pathogen were not necessarily resistant to the other; although, overall, the resistances were correlated. Approximate 95% confidence intervals were established for all cultivars to predict mean performance across years. The cultivars tested varied in resistance, but the largest single factor affecting lesion length was the fungal isolate used for inoculations. These data enable us to identify cultivars resistant to both diseases that can be used for planting in problem areas, as well as selection of parental material for breeding cultivars with improved resistance.
James J. Polashock and Matthew Kramer
Liming Chen, Matthew Wallhead, Michael Reding, Leona Horst, and Heping Zhu
berry disease is established in blueberry plants, it can completely destroy the crop ( Anco and Ellis, 2011 ). Thus, an effective fungicide spray program is critical for control of this disease. Phomopsis, caused by the fungus Phomopsis vaccinii , is
Jean Beard Baker, J.F. Hancock, and D.C. Ramsdell
One-year-old rooted microshoots and 2-year-old rooted hardwood blueberry cuttings (Vaccinium corymbosum L.) were inoculated with Phomopsis vaccinii Shear using stem flap, stem freeze, needle pierce, and leaf tear wounding techniques. The needle pierce was the simplest method that produced high infection rates. Nine northern-adapted cultivars were placed in a factorial experiment to measure their infection resistance. Microshoots and hardwood cuttings of `Elliott' and `Bluetta' survived the longest and had the lowest mortality rate. Phomopsis vaccinii was reisolated successfully from inoculated shoots of all cultivars.
Eric Hanson and Annemiek Schilder
Twenty cranberry (Vaccinium macrocarpon) genotypes were evaluated for five seasons in an experimental upland planting in southwest Michigan. Beds were constructed on a silty clay loam soil by excavating to grade, and filled with 30 to 45 cm of sand. Four 2 × 2-m plots of each genotype were planted in 1996. Fruit were harvested with hand scoops from 2000 to 2005. Yield per plot, average berry weight, and percent berries exhibiting decay were determined. Sound fruit were also stored at 2 °C for 4 to 8 weeks and sorted to determine the percentage of fruit developing decay in storage. Fungi were isolated and identified by morphological characteristics. Genotypes producing the highest average yields were `Stevens', `Ben Lear', #35, `LeMunyon', and `Franklin'. Varieties with the highest average berry weight were `Pilgrim', `Stevens', `Baines', `Beckwith', `Searles', and #35. Genotypes with lower rot incidence at harvest were #35, `Early Black', and `Foxboro Howes', whereas `Howes' and #35 developed the least rot during storage. Fungi commonly isolated from decaying fruit were Colletotrichum sp., Coleophoma empetri, Phomopsis vaccinii, Phyllosticta vaccinii, Fusicoccum putrefaciens, Botrytis cinerea, Pestalotia sp., and Allantophomopsis sp. Prevalence of specific fungi differed among cranberry genotypes.
Jennifer Johnson-Cicalese, James J. Polashock, Josh A. Honig, Jennifer Vaiciunas, Daniel L. Ward, and Nicholi Vorsa
order of abundance) Phyllosticta vaccinii , Phomopsis vaccinii , Coleophoma empetri , and C. gloeosporiodes ; at week 14 (corresponding to 7 Sept. 2012) were Physalospora vaccinii , Phyllosticta vaccinii , Phomopsis vaccinii, and C
Charles C. Reilly, Bruce W. Wood, and Katherine L. Stevenson
characterization of Phomopsis vaccinii and additional isolates of Phomopsis from blueberry and cranberry in the eastern United States Mycologia 94 494 504 Farr, D.F. Castlebury, L.A. Rossman, A.Y. Putnam, M
R. Karina Gallardo, Parichat Klingthong, Qi Zhang, James Polashock, Amaya Atucha, Juan Zalapa, Cesar Rodriguez-Saona, Nicholi Vorsa, and Massimo Iorizzo
species), phytophthora ( Phytophthora spp.), storage rots (various fungal species), upright dieback ( Phomopsis vaccinii ), and other diseases. The arthropod pest traits included were blackheaded fireworm ( Rhopobota naevana ), blunt-nosed leafhoppers
R. Karina Gallardo, Qi Zhang, Michael Dossett, James J. Polashock, Cesar Rodriguez-Saona, Nicholi Vorsa, Patrick P. Edger, Hamid Ashrafi, Ebrahiem Babiker, Chad E. Finn, and Massimo Iorizzo
( Phomopsis vaccinii ), Phytophthora root rot ( Phytophthora cinnamomi ), Blueberry shock virus (BlShV), stem blight (incited by multiple species in the Botryosphaeriaceae ), and “other diseases.” Arthropod pest resistance traits included resistance to
Liming Chen, Heping Zhu, Leona Horst, Matthew Wallhead, Michael Reding, and Amy Fulcher
conditions ( Hartman, 2007 ). Mummy berry ( Monilinia vaccinia-corymbosi ) is one of the most serious fruit diseases, and phomopsis ( Phomopsis vaccinii ) is the most common canker disease for blueberry ( Anco and Ellis, 2011 ; Fulcher et al., 2015