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phytophthora root rot race-specific resistance phenotypes for P. capsici races 1, 4, 5, 6, and 12 are controlled by multiple alleles at few loci or multiple genes at different loci using a set of New Mexico recombinant inbred lines (NMRILs). This information

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Despite extensive breeding efforts, no pepper (Capsicum annuum L. var. annuum) cultivars with universal resistance to phytophthora root rot and foliar blight (Phytophthora capsici Leon) have been commercially released. A reason for this limitation may be that physiological races exist within P. capsici, the causal agent of phytophthora root rot and phytophthora foliar blight. Physiological races are classified by the pathogen's reactions to a set of cultivars (host differential). In this study, 18 varieties of peppers were inoculated with 10 isolates of P. capsici for phytophthora root rot, and four isolates of P. capsici for phytophthora foliar blight. The isolates originated from pepper plants growing in New Mexico, New Jersey, Italy, Korea, and Turkey. For phytophthora root rot, nine of the 10 isolates were identified as different physiological races. The four isolates used in the phytophthora foliar blight study were all determined to be different races. The identification of physiological races within P. capsici has significant implication in breeding for phytophthora root rot and phytophthora foliar blight resistance.

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A detached leaf screening technique was developed for studying specific interactions between pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars and isolates of the pecan scab fungus, Cladosporium caryigenum. Monoconidial isolates were obtained from leaf scab lesions on `Wichita', `Desirable', `Cape Fear', and `Elliot'. Each isolate was then inoculated onto detached leaves of each of the four cultivars and fungal growth was observed under the microscope after eight days. `Wichita', `Desirable', and `Cape Fear' isolates produced subcuticular hyphae at a much higher frequency when inoculated back onto the cultivar from which they were isolated in comparison to the other cultivars. The `Elliot' isolate was able to produce a high frequency of subcuticular hyphae when inoculated onto `Elliot' and `Cape Fear', but not when inoculated onto `Desirable' and `Wichita'. Field inoculations conducted with the `Wichita' and `Desirable' isolates validated the detached leaf protocol. The results obtained indicate that pecan scab is composed of multiple races with a high degree of specificity for host cultivars. A rapid whole-leaf staining system is presented which appears to have wide applicability to assessing fungal growth in leaves.

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Two 24-mer primers, MUSKFOM I and MUSKFOM II, were developed that amplify a 1.5-kb DNA fragment in race 1 Fusarium wilt resistant muskmelon (Cucumis melo L.), but not in race 1 susceptible germplasm tested. Three race 1 resistant cultivars and two race 1 resistant breeding lines as well as eight race 1 susceptible lines were analyzed using the two sequence-specific primers in the polymerase chain reaction. These primers should prove valuable for nondestructive determination of Fom 2 gene introgression in breeding programs.

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international collection, identified 11 unique races among them, and standardized the race nomenclature. These studies and others have uncovered genetic resistance within rose species and cultivars that is race-specific. Such race-specific resistance can only be

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study, a P. capsici race-specific resistance interaction was observed on C. annuum ( Table 2 ). Based on the total number of susceptible NMRILs, the most virulent isolate was PWB-85 from New Mexico with all of the 26 NMRILs exhibiting susceptibility

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only partial resistance, and additional QTLs are often necessary for field resistance ( Scott et al., 2001 ; Scott and Jones, 1989a ; Somodi et al., 1996 ; Wang et al., 1994 ). In addition to the use of such single, race-specific resistance genes

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-grown tomato production since the 1940s. There are three races of Fol that infect tomato, and these are distinguished based on their response to three dominant, race-specific resistance genes, each derived from wild tomato species. The I (immunity to

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physiological race identification, it is necessary that accessions used as differential hosts carry different race-specific resistance genes ( Stakman, 1919 ). Sy et al. (2008) developed a population of 76 New Mexico recombinant inbred lines (NMRILs) from

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in the southern United States so far have been classified as race 1 and can be separated into biovars 1 and 3 and sequevars 4, 5, 7, and 13 ( Ji et al., 2007 ). Ralstonia solanacearum race 3, biovar 2, sequevar 1 strains cause losses in potato and

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