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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

Many daphne cultivars are susceptible to fungal root pathogens and require frequent fungicide applications during production. To identify taxon differences to disease susceptibility, we evaluated 32 Daphne species and cultivars for resistance to the soil-borne pathogen, Thielaviopsis basicola (Berk. and Broome) Ferr., by both in vitro- and in vivo-based methods. Disease-free plant roots were inoculated with the pathogen through topical application of a spore suspension and observed weekly for disease development/progression. Significant variation for disease severity among the taxa evaluated was determined using a plant disease index. Plant reactions ranged from highly resistant, e.g., D. tangutica and D. retusa, to highly susceptible, e.g., D. cneorum. In addition, a high correlation was found between the in vitro and in vivo techniques for the seven selected species, indicating that they are comparable. However, the in vitro assay provided results in significantly less time than the in vivo assay.

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Margaret T. Mmbaga, Lucas M. Mackasmiel, and Frank A. Mrema

Macrophomina phaseolina is a nonspecialized soil-borne pathogen that can become a problem by causing root rot, charcoal rot, collar rot, damping-off, wilt, leaf blight, and stem blight in both agricultural and natural or landscape environments

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Nathan Shoaf, Lori Hoagland, and Daniel S. Egel

suppress development of diseases caused by several soil-borne pathogens, including Fusarium oxysporum ( Elmer and Pignatello, 2011 ; Matsubara et al., 2002 ), Rhizoctonia solani ( Jaiswal et al., 2014 ), Ralstonia solanacearum ( Nerome et al., 2005

Open access

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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M.B. Fiely and T.E. Morelock

Spinach (Spinacia oleracea L.) varies in tolerance to saturated soil conditions. Plant vigor was assessed for plants flooded in autoclaved and nonautoclaved field soil. Decline of vigor was more rapid for plants flooded in nonautoclaved field soil, indicating that flooding tolerance may be influenced by soil borne pathogens.

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M.B. Fiely and T.E. Morelock

Spinach (Spinacia oleracea L.) varies in tolerance to saturated soil conditions. Plant vigor was assessed for plants flooded in autoclaved and nonautoclaved field soil. Decline of vigor was more rapid for plants flooded in nonautoclaved field soil, indicating that flooding tolerance may be influenced by soil borne pathogens.

Open access

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

Open access

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

). Grafting is a technology that has been successfully implemented for soil-borne pathogen management; however, the effects of different rootstocks on the scion have been inconsistent across scions ( Mackey et al., 2018 ; Suchoff et al., 2019 ). The

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Hee-Ju Lee, Sang-gyu Lee, Changhoo Chun, and Jung-Myung Lee

Use of grafted seedlings is a practical method to overcome salt accumulation, deterioration of physicochemical properties of soil, and accumulation of soil-borne pathogen that farmers, as well as commercial plug seedling producers, in Korea mainly adapted. Graft-take, subsequent growth, and quality characteristics of grafted hot pepper (Capsicum annuum L.) seedlings composed of three scions and 10 rootstocks were investigated. `Manita', `Chungyang', and `Nokkwang' were cultivars of scions used—they are the major hot pepper cultivars in Korea. The ten rootstock cultivars can be categorized into three groups: cultivars specially bred for rootstocks (`Konesian Hot', `PR-380', `R-Safe', and `Tantan'); cultivars recently bred in NHRI, Korea with the potential to be rootstocks (`Wonkwang1' and `Wonkwang2'); and cultivars originally bred for fruit harvest, but used as rootstocks due to their tolerance to soil-borne pathogens (`Kataguruma', `PR-Data', `PR-Gangza', and `PR-Power'). All the plants were treated with 5 mg·L-1 diniconazole solution 2 weeks after grafting and were soaked into 1.4% salt solution for 48 hours about 5 weeks after grafting. All the grafted seedlings showed feasible growth, including normal flowering and fruit set, and any symptoms of phytophthora blight and anthracnose were not found during 17-day-long experiment. Seedlings grafted onto `Tantan' rootstock showed stronger tolerance to high salt concentration than those grafted onto other rootstocks. Use of some, such as `Wongang 1', `PR-Data' and `Kataguruma', was alleviated the salt-induced growth inhibition.