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The oomycete plant pathogen, Phytophthora capsici , first described by Leon H. Leonian at the New Mexico Agricultural Research Station, is distributed globally and is a critical threat to vegetable production as a cause of damping-off, foliar

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Phytophthora capsici is a soilborne Oomycete with a host range exceeding 50 plant species ( Tian and Babadoost 2004 ). This polycyclic pathogen is responsible for significant plant losses when environmental conditions are favorable ( Erwin and

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Phytophthora capsici , the causal agent of phytophthora blight, continues to threaten the livelihood of growers and the future of pepper production in the United States and globally. Growers and processors of pepper rank P. capsici as a top threat

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The oomycete Phytophthora capsici is a soilborne pathogen that causes severe and even complete yield loss in pepper worldwide ( Lamour et al., 2012 ). In Brazil, pepper root rot caused by P. capsici was observed for the first time in 1952 in São

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Fruit rot induced by Phytophthora capsici Leonian is an increasingly serious disease affecting pickling cucumber (Cucumis sativus L.) production in many parts of the United States. The absence of genetically resistant cultivars and rapid development of fungicide resistance makes it imperative to develop integrated disease management strategies. Cucumber fruit which come in direct contact with the soil-borne pathogen are usually located under the canopy where moist and warm conditions favor disease development. We sought to examine whether variations in plant architecture traits that influence canopy structure or fruit contact with the soil could make conditions less favorable for disease development. As an extreme test for whether an altered canopy could facilitate P. capsici control, we tested the effect of increased row spacing and trellis culture on disease occurrence in the pickling cucumber `Vlaspik'. Temperature under the canopy was lowest in trellis plots, intermediate in increased spacing plots, and highest in control plots. Disease occurrence in the trellis plots was significantly lower than in other treatments, indicating that preventing fruit contact with the soil reduced disease occurrence. The effect of currently available variation in plant architecture was tested using nearly-isogenic genotypes varying for indeterminate (De), determinate (de), standard leaf (LL), and little leaf (ll) traits. Plants with standard architecture had higher peak mid-day temperatures under the canopy and greater levels of P. capsici infection; however, levels of disease occurrence were high for all genotypes. Screening a collection of ≈150 diverse cucumber accessions identified to serve as a representative sample of the germplasm, revealed variation for an array of architectural traits including main stem length, internode length, leaf length and width, and number of branches; values for `Vlaspik' were in the middle of the distribution. Plant architectures that may allow for more open canopies, including reduced branching habit and compact growth, were tested for disease incidence. One of the compact lines (PI 308916), which had a tendency to hold young fruit off the ground, exhibited lower disease occurrence. The reduced disease occurrence was not due to genetic resistance, suggesting that architecture which allows less contact of fruit with the soil could be useful for P. capsici control for pickling cucumber.

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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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The pathogen Phytophthora capsici Leon. is known to be a limiting factor of chile pepper (Capsicum L.) production around the world. The genetics of the resistance is becoming better understood due to the specific nature of the host-pathogen interaction, i.e., all plant organs are subject to infection. It has been shown that phytophthora root rot resistance and phytophthora foliar blight resistance are under different genetic mechanisms. This study aimed at understanding the inheritance of resistance of phytophthora stem blight and to determine whether phytophthora stem blight was the same disease syndrome as phytophthora root rot and phytophthora foliar blight. Stem cuttings of a segregating F2 population and testcross progeny facilitated the ability to screen for two disease syndromes concurrently. When the three disease syndromes were compared separately, the F2 populations fit a 3 resistant (R): 1 susceptible (S) ratio and the testcross progenies fit a 1R:1S ratio. When comparative studies were performed (stem vs. foliar and stem vs. root), the F2 populations fit a 9R/R:3R/S:3S/R:1S/S ratio and the testcross fit a 1R/R:1R/S:1S/R:1S/S ratio. These ratios are consistent of a single gene controlling the resistance of each system. Therefore, phytophthora stem blight, root rot, and foliar blight are three separate disease syndromes.

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The inheritance of resistance to Phytophthora capsici Leonian root rot and foliar blight was compared in two different Capsicum annuum L. var. annuum pod types. The seedling was screened for phytophthora root rot, while a genetically identical stem cutting was screened for phytophthora foliar blight to determine if the same gene(s) confer resistance to both disease syndromes. The susceptible parents were `Keystone Resistant Giant #3' (`Keystone'), a bell pepper type, and `Early Jalapeño', while `Criollo de Morelos-334' was the resistant parent. Resistance was observed in both F1 populations screened for phytophthora root and foliar infection indicating dominance for resistance. Reciprocal effects were not detected. To determine if the same gene(s) conferred root rot and foliar resistance, root rot screening results were matched to the corresponding foliar blight stem cutting reaction. The segregation of resistance in the F2 generations was dependent on the susceptible parent. In the F2 generation derived from `Early Jalapeño', root rot resistance and foliar blight resistance segregated in a 9:3:3:1 (root resistant/foliar resistant: root resistant/foliar susceptible: root susceptible/foliar resistant: root susceptible/foliar susceptible) ratio. One independent, dominant gene was necessary for root rot resistance, and a different independent, dominant gene was needed for foliar blight resistance. In the F2 generation derived from `Keystone', root rot and foliar blight resistance segregated in a 7:2:2:5 (root resistant/foliar resistant: root resistant/foliar susceptible: root susceptible/foliar resistant: root susceptible/foliar susceptible) ratio. This segregation ratio is expected when one dominant gene is required for root resistance, and a different dominant gene is required for foliar resistance. In addition to these two genes, at least one dominant allele of a third gene must be present for expression of root rot and foliar blight resistance.

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Increasing disposal problems with polyethylene (PL) mulch and greater availability of compost prompted an investigation into the effects of using compost as a mulch on horizontal raised bed surfaces with living mulches (LMs) on vertical surfaces. Wood chips (WC), sewage sludge-yard trimming (SY) compost, and municipal solid waste (MW) compost were applied at 224 t·ha-1 on bed surfaces. Sod strips of `Jade' (JD) or `Floratam' (FT) St. Augustinegrass (Stenotaphrum secundatum Kuntze) or perennial peanut (Arachis glabrata Benth.) (PP) or seeds of a small, seed-propagated forage peanut (Arachis sp.) (SP) were established on the vertical sides of the raised beds before transplanting bell pepper (Capsicum annuum L.) into the beds. Phytophthora capsici reduced pepper plant stand in PL-mulched plots compared with organic mulch (OM) and LM. Despite the stand reduction, total pepper yields were highest in PL plots and, in the OM plots, decreased in the order SY > MW > WC. Early fruit yields and yield per plant were highest from plants in PL plots followed by SY. Among LMs, plants in SP plots produced highest early yields and FT produced the lowest. Plants in PL plots produced the largest fruit. When the same plots were seeded with winter (butternut) squash (Cucurbita pepo L.), plant stands were higher in MW than WC and SY. Squash yields were similar between PL and OM plots.

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(2006) concluded that plant architecture that reduces contact of fruit with the soil could be useful for control of Phytophthora capsici in cucumber ( Cucumis sativus ). If it were to be shown that proximity to the soil was detrimental to eggplant

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