Phytophthora cinnamomi is a highly virulent root rot pathogen of highbush blueberry and is present in most growing regions worldwide (Strik and Yarborough, 2005; Zentmyer, 1980). Symptoms of infection include poor shoot growth, root necrosis and dieback, yellowing or reddening leaves, marginal leaf necrosis, early leaf senescence, and, in the most severe cases, dead branches and canes and plant death (Caruso and Ramsdell, 1995). Root infection is more prevalent when plants are irrigated by drip than by sprinklers and occurs most commonly in heavy soils and poorly drained sites (Bryla and Linderman, 2007; de Silva et al., 1999).
Mefenoxam and phosphite (phosphonate) fungicides and certain production practices such as raised planting beds, tile drains, and proper irrigation management can help prevent phytophthora root rot (Brannen et al., 2009; Bryla and Linderman, 2007; Sterne, 1982). However, genetic resistance is currently the most effective means to control the disease (Bryla et al., 2008). The level of resistance to P. cinnamomi is known to vary among cultivars, but most studies have focused on rabbiteye (Vaccinium ashei Reade) or southern highbush blueberry (V. corymbosum L. interspecific hybrids) (Larach et al., 2009; Smith, 2002). Only a limited number of studies have examined differences in root rot among northern highbush cultivars (V. corymbosum) (Bryla et al., 2008; Erb et al., 1987). Milholland and Galletta (1967) found that northern highbush blueberry was generally more susceptible to phytophthora root rot than rabbiteye blueberry.
The objective of this study was to evaluate the response of highbush blueberry cultivars and advanced selections to P. cinnamomi and identify the most resistant genotypes to the pathogen. By choosing cultivars with more resistance to P. cinnamomi, growers may reduce economic losses related to the disease.
Allardyce, J.A., Rookes, J.E. & Cahill, D.M. 2012 Defining plant resistance to Phytophthora cinnamomi: A standardized approach to assessment J. Phytopathol. 160 269 276
Brannen, P.M., Harmon, P. & NeSmith, D.S. 2009 Utility of phosphonate fungicides for management of phytophthora root rot of blueberry Acta Hort. 810 331 340
Bryla, D.R. & Linderman, R.G. 2007 Implications of irrigation method and amount of water application on Phytophthora and Pythium infection and severity of root rot in highbush blueberry HortScience 42 1463 1467
Bryla, D.R., Linderman, R.G. & Wang, W.Q. 2008 Incidence of Phytophthora and Pythium infection and the relation to cultural conditions in commercial blueberry fields HortScience 43 260 263
Caruso, F.L. & Ramsdell, D.C. 1995 Compendium of blueberry and cranberry diseases. APS Press, St. Paul, MN
de Silva, A., Patterson, K., Rothrock, C. & McNew, R. 1999 Phytophthora root rot of blueberry increases with frequency of flooding HortScience 34 693 695
Erb, W.A., Moore, J.N. & Sterne, R.E. 1987 Response of blueberry cultivars to inoculation with Phytophthora cinnamomi Rands zoospores HortScience 22 298 300
Kannwischer, M.E. & Mitchell, D.J. 1978 The influence of a fungicide on the epidemiology of black shank of tobacco Phytopathology 68 1760 1765
Larach, A., Besoain, X. & Salgado, E. 2009 Crown and root rot of highbush blueberry caused by Phytophthora cinnamomi and P. citrophthora and cultivar susceptibility Cienc. Investig. Agrar. 36 433 442
Milholland, R.D. 1975 Pathogenicity and histopathology of Phytophthora cinnamomi on highbush and rabbiteye blueberry Phytopathology 65 789 793
Milholland, R.D. & Galletta, G.J. 1967 Relative susceptibility of blueberry cultivars to Phytophthora cinnamomi Plant Dis. Rptr. 51 999 1001
Strik, B.C. & Yarborough, D. 2005 Blueberry production trends in North America, 1992 to 2003, and predictions for growth HortTechnology 15 391 398
Tsao, P.H. & Guy, S.O. 1977 Inhibition of Mortierella and Pythium in a Phytophthora isolation medium containing hymexazol Phytopathology 67 796 801
Vargas, O.L., Bryla, D.R., Weiland, J.E., Strik, B.C. & Sun, L. 2015 Irrigation and fertigation with drip and alternative micro irrigation sprinklers in northern highbush blueberry HortScience 50 897 903
Zentmyer, G.A. 1980 Phytophthora cinnamomi and the diseases it causes. Monogr no. 10. APS Press, St. Paul, MN