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M.A. Ellis and S.A. Miller

A commercially available serological assay kit (flow-through enzyme-linked immunosorbent assay, Phytophthora F kit) was compared to a culture-plate method for detecting Phytophthora spp. in apparently diseased (phytophthora root rot) and apparently healthy red raspberry (Rubus idaeus subsp. strigosus Michx.) plants. During 4 years of testing, 46 tests were conducted on apparently diseased roots. All diseased plants gave a strong positive reaction, a result indicating that Phytophthora spp. were present. Of the 46 plants that tested positive, Phytophthora spp. were recovered from all but one using a selective medium for Phytophthora and the culture-plate method. When the same test was conducted on 27 apparently healthy plants, all had a negative reaction for the presence of Phytophthora except one sample, which had a slight positive reaction. No Phytophthora spp. were isolated from any apparently healthy plants. Our results indicate that the serological test kit enables rapid, dependable, on-site diagnosis of raspberry phytophthora root rot.

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John A. Menge, Greg W. Douhan, Brandon McKee, Elinor Pond, Gary S. Bender, and Ben Faber

losses of over $40 million ( Coffey, 1992 ). The use of tolerant rootstocks to control Phytophthora root rot (PRR) of avocado has long been proposed as the ultimate method for managing the disease ( Zentmyer, 1957 , 1963 ) and research on developing PRR

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John R. Yeo, Jerry E. Weiland, Dan M. Sullivan, and David R. Bryla

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

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Chrislyn Ann Particka and James F. Hancock

Black root rot (BRR) is a widespread disease of strawberry that causes the death of feeder roots and the degradation of structural roots resulting in an overall decrease in productivity ( Maas, 1998 ). By the 1950s, BRR had been reported in many

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S.L. Krebs

Root rot caused by the soil-borne pathogen Phytophthora cinnamomi is one of the deadliest and most costly diseases in rhododendron culture. Unfortunately, the majority of cultivars appear to be susceptible to this fungus. Host resistance does occur, but it represents a tolerance of rather than immunity from the disease. A breeding program has been initiated to develop a broader array of root rot resistant cultivars and to determine the genetic basis for resistance. Greenhouse inoculations and screenings of 48 contemporary cultivars yielded seven clones with moderate to high levels of resistance to P. cinnamomi. Protocols for evaluation at the seedling stage were developed in order to screen large breeding populations of about 200 seedlings per cross. Root rot tolerance appears to have low-moderate heritability in these rhododendron populations. Groups of progeny with one resistant parent had a slower mortality rate and higher survivorship (avg. 10%) after 2 months of disease pressure than crosses in which both parents were susceptible (0 survivorship). A recurrent selection strategy is planned to increase the frequency of alleles for resistance in breeding populations of rhododendrons.

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Emma C. Lookabaugh, Brian Whipker, and Barbara B. Shew

Pythium root rot is one of the most common diseases of commercially grown poinsettia and P. aphanidermatum is the predominant species causing pythium root rot in North Carolina ( Lookabaugh et al., 2015 ). Under favorable environmental conditions

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Wendy K. Hoashi-Erhardt, Patrick P. Moore, Gwenyth E. Windom, and Peter R. Bristow

Root rot caused by the persistent soilborne oomycete Phytophthora fragariae var. rubi is a serious disease of red raspberry in the Pacific Northwest and worldwide. It can decrease the vigor and yield of raspberry plantings and require

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Rachel P. Naegele and Mary K. Hausbeck

., 2012b ; Parada-Rojas and Quesada-Ocampo, 2019 ). Host resistance to diverse isolates of P. capsici is an important management tactic and a focus for pepper ( Capsicum annuum ) breeding programs globally. In pepper, the pathogen can cause root rot

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Sangho Jeon, Charles S. Krasnow, Gemini D. Bhalsod, Blair R. Harlan, Mary K. Hausbeck, Steven I. Safferman, and Wei Zhang

, 2013 ; Stanghellini et al., 1996a , 1996b ). Pythium root rot causes plant stunting, wilt, and death and can also reduce horticultural quality of infected crops ( Tompkins and Middleton, 1950 ). The pathogen can become established in a greenhouse

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Kyle E. LaPlant, Gregory Vogel, Ella Reeves, Christine D. Smart, and Michael Mazourek

are cultivated for food as immature fruit (summer squash) and mature fruit (winter squash and processing pumpkins), and they are also grown for fall decorations, such as jack-o’-lanterns and gourds ( Paris, 2016 ). Phytophthora crown and root rot