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., 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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detected using log and square-root transformations of severity scores. Additive effects in both families were larger than dominance effects ( Table 1 ), and in both families PR resistance from the DehyA parent decreased disease severity and was codominantly

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Phytophthora species, and more tolerant of soil salinity than J. regia ( McGranahan and Catlin, 1987 ). Despite its widespread use, the resistance of Paradox rootstock to Armillaria root disease, crown gall, and Phytophthora crown and root rot is

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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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been systematically evaluated for their response to pythium root rot, nor has the genetic basis of resistance been explored in university research ( Trejo et al., 2012 ). Complete resistance to pythium root rot is unknown in cultivated poinsettia and

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. Host plant resistance would provide an economical and environmentally friendly alternative for managing root-knot nematodes in watermelon. There are several reports describing the reactions of cultivated watermelon to root-knot nematodes. Seventy

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screening. The resistance reaction was assessed by the number of egg masses (EM) present in the root system. To do this, four 15-cm long cuttings from each genotype were transplanted into 150-cm 3 model SC-10 Super Cell Conetainers™ (Stuewe & Sons

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available that are completely resistant to phytophthora crown and root rot. A previous study of 115 diverse squash and pumpkin accessions found partial resistance present in several accessions, but no accessions with complete resistance were identified

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(CM-334) and extensive breeding efforts, no chile pepper cultivars with universal resistance to phytophthora root rot have been commercially released ( Oelke et al., 2003 ). Thus, the main objective of this study was to determine whether different

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mortality also had very few infected roots, and a low proportion of plants were girdled by root collar infection. These findings suggest that the Armillaria resistance in Myrobalan, and possibly other plums, is true resistance, rather than tolerance

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