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J.O. Kuti, G.V. Latigo, and J.O. Bradford

Soil-borne pathogens such as Macrophomina phaseolina (the causative agent of charcoal rot) and Phymatotrichum omnivorum (the causative agent of cotton root rot) contribute to mortality of transplanted guayule (Parthenium argentatum, Gray) seedlings in southern Texas. In order to select guayule genotypes for resistance to these pathogens, it would be useful to develop reliable greenhouse inoculation procedures for screening guayule seedlings. Twelve-week-old guayule seedlings (`11591', a USDA standard breeding line) were inoculated using two inoculation methods (soil-drenching and root-dipping) in two soil media (field soil and commercial soil mix). Plants were rated for disease severity 2 to 5 months after inoculation and pathogens were re-isolated from diseased plants to establish Koch postulates. The soil drenching technique, using field soil, caused rapid development of disease symptoms that were consistent with re-isolation frequencies of pathogens from the diseased plant tissues.

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David Noshad, Andrew Riseman, and Zamir Punja

In vitro selection for improved plant resistance to toxin-producing pathogens Phytopathology. 153 52 64 Tabachnik, M. DeVay, J.E. Garber, R.H. Wakeman, R.J. 1979 Influence of soil inoculum

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Stephen B. Gaul and Michael R. Evans

Seedlings of Catharanthus roseus (L.) G. Don `Pacifica Red' were transplanted into substrates composed of either 80% sphagnum peat or coir with the remaining volume being perlite, sand, or vermiculite. The six substrates were inoculated with Pythium irregulare Buisman at 0 or 50,000 oospores per 10-cm container. The containers were irrigated daily to maintain moisture levels near container capacity. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated coir substrates. Inoculated peat substrates had an 80% infection rate and significantly reduced shoot and root fresh and dry weights as compared to uninoculated substrates. Seedlings of C. roseus were transplanted into pasteurized and unpasteurized substrates composed of 80% (v/v) coir or sphagnum peat with the remaining 20% being perlite. Substrates were inoculated with 0, 5000, or 20,000 oospores of P. irregulare per 10-cm container. No visually apparent symptoms of infection or significant differences in shoot and root fresh and dry weights were observed among the uninoculated substrates and the inoculated pasteurized coir. The inoculated pasteurized peat substrate, inoculated unpasteurized peat substrate, and the inoculated unpasteurized coir substrate grown plants had an 88% infection and a significant reduction in the shoot and root fresh and dry weights.

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Nathan Shoaf, Lori Hoagland, and Daniel S. Egel

Worldwide vegetable production valued at over $1 billion each year is threatened by phytophthora blight ( Lamour et al., 2012 ). This devastating disease is caused by P. capsici, a soil-borne oomycete pathogen that can infect a wide variety of

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Mary C. Stevens, Rui Yang, and Joshua H. Freeman

fumigant to control insect pests in stored grain ( Hooper et al., 2003 ). EDN has since been examined as a soil fumigant in the United States as well as other countries with acceptable efficacy against weed pests, plant-parasitic nematodes, and soil-borne

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Xiuling Tian and Youbin Zheng

beneficial microbes), waste DE from beer brewing, and a greenhouse nutrient solution that had been reused for more than 20 years on six water- or soil-borne plant pathogens commonly found in Ontario greenhouses. Materials and Methods Inhibition subtracts used

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Mark Hoffmann, Husein A. Ajwa, Becky B. Westerdahl, Steven T. Koike, Mike Stanghellini, Cheryl Wilen, and Steven A. Fennimore

Intensive fruit, ornamental, and vegetable production systems in the United States and elsewhere in the world rely on preplant soil fumigation to control soil-borne pathogens, pests, and weeds. These include strawberry ( Fragaria × ananassa ) and

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Brad Geary, Corey Ransom, Brad Brown, Dennis Atkinson, and Saad Hafez

alternatives to chemical fumigants in controlling soil-borne pests and minimizing hazards to nontarget organisms. Research indicates that green tissue of Brassica species can decrease the population densities of some fungal pathogens ( Mayton et al., 1996

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Andrey Vega-Alfaro, Carlos Ramírez-Vargas, Germán Chávez, Fernando Lacayo, Paul C. Bethke, and James Nienhuis

worldwide, one of the most devastating and difficult to manage plant pathogens is the soil-borne and waterborne bacterial wilt species complex. Because of the wide host range, adaptation to diverse ecological niches, and genetic diversity among strains

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Melike Cirak and James R. Myers

treatment of pc seeds increases germination and emergence to where rates are essentially equivalent to fungicide-treated white-seeded beans (Al-Jadi et al., 2016 ); therefore, soil-borne pathogens seem to be involved in this process, but what underlies