Field and detached-fruit screening tests were developed for evaluating cucumber (Cucumis sativus L.) plant introduction accessions, breeding lines, and cultivars (hereafter collectively referred to as cultigens) for resistance to fruit rot caused by Rhizoctonia solani Kuhn. The factors that were examined for developing a detached-fruit test were five inoculum levels of R. solani AG-4 and two cover treatments. The major influence on disease reaction was inoculum level. The best method used 50-mm-diameter fruit placed on sterile soil inoculated with 6400 oat grains/m2 colonized with R. solani and watered initially, then misted every 3 days for 1 minute, left uncovered, and rated after 10 days for the percentage of the fruit surface covered with lesions. Field and detached-fruit tests were conducted using two different inoculum levels of R. solani (3200 and 4800 oat grains/m2). The four most resistant cultigens, based on the results of field and detached-fruit tests, were PI 163216, PI 197088, PI 357852, and PI 280096. One field and detached-fruit test pair was not significantly correlated (detached-fruit screening test one vs. field screening test one), but the other (detached-fruit test two vs. field screening test two) was correlated (r = 0.50). The detached-fruit test could be used for general classification of resistance or susceptibility. Resistant cultigens could be identified with either method, but the field test had slightly lower coefficients of variation.
Todd C. Wehner, Nischit V. Shetty, and Joseph T. Sloane
Several fungicides, including benomyl, flutolanil, iprodione, metalaxyl, and a mixture of metalaxyl and benomyl that control rhizoctonia stem rot (Rhizoctonia solani Kuhn) of poinsettia (Euphorbia pulcherriman Willd. ex Kl.) were evaluated for inhibition of poinsettia root initials and suppression of root elongation. Fungicides were applied as either foliar sprays to poinsettia cuttings in rooting cubes or as soaks of rooting cubes before sticking of cuttings. Rooting cube soaks of iprodione and benomyl and fungicide sprays of iprodione, benomyl, and chlorothalonil inhibited root initiation as measured by root counts 28 days after sticking cuttings. However, root elongation as measured by root rating was similar for all fungicides and the untreated control at 28 days. Plant height of rooted poinsettia cuttings transplanted to 400-cm3 pots was significantly less (P = 0.05) only for cuttings sprayed initially with iprodione, but not for rooting cubes soaked in iprodione 58 days after transplanting. The inhibitory effect of other fungicides on root initiation did not appear to affect plant growth once plants were transplanted. Chemical names used: methyl 1-(butyl-carbamoyl)-2-benzimidazolecarbamate (benomyl); tetrachloroisophthalonitrile (chlorothalonil); N -[3-(methylethoxy)phenyl]-2-(trifluoromethyl)benzamide (flutolanil); 3-(3,5dichlorophenyl)N -(lmethylethyl)-2,4-dioxo-l-imidazolidinecarboxamide (iprodione); N -(2,6-dimethylphyenyl)N -(methoxyacetyl) alanine methyl ester (metalaxyl).
Gladis M. Zinati
The discovery of disease suppression in certain bark composts increased the interest in using compost as growing substrate to control root rot diseases caused by Phytophthora cinnamomi. Disease suppression mechanisms include antibiosis, competition, hyperparasitism, and induced systemic resistance. Although abiotic factors may influence disease suppression, the latter is often based on microbial interactions—the two common mechanisms being general for pythium (Pythium spp.) and phytophthora root rot (Phytophthora spp.) and specific for rhizoctonia (Rhizoctonia solani). The discovery of disease suppression agents in compost led to the development of biocontrol agent-fortified compost during the last decade of the 20th century. The suggested recommendations for future research and extension outreach may include 1) development of methods to manage bacterial and viral diseases through the use of compost; 2) exploration of the potential effects of fortified compost on insect pests suppression; 3) improvement of inoculation methods of composts with biocontrol agents to produce consistent levels of disease suppression at the commercial scale; 4) development of effective fortified compost teas for suppressing foliar diseases; 5) education of compost producers on methods of production of fortified compost that suppress specific diseases; and 6) education of end-users on uses of fortified compost and its by-products.
Diane Feliciano Cayanan, Ping Zhang, Weizhong Liu, Mike Dixon, and Youbin Zheng
). Even with fungicide use, there is no completely effective treatment of Rhizoctonia solani ( Johnson and Leach, 2006 ) and Fusarium oxysporum ( Reuveni et al., 2002 ). Several disinfection techniques have been studied for their efficacy in minimize
Eric Watkins and William A. Meyer
Recently, turfgrass breeders have developed many improved turf-type tall fescue (Festuca arundinacea Schreb.) cultivars. Due to the large number of cultivars currently available to turfgrass managers and researchers, we have classified turf-type tall fescue cultivars into six groups based primarily on several morphological measurements. This type of classification is important for turfgrass breeders because many breeding decisions are made based on observations in a spaced-plant nursery. The major objective of this study was to classify tall fescue cultivars and selections based on spaced-plant measurements and to then compare those results with turf performance. A spaced-plant nursery consisting of 36 cultivars and selections was established in September 1998 at Adelphia, N.J. Plant height, panicle length, flag leaf width and length, subtending leaf width and length, and subtending internode length were measured 10 days after anthesis in 1999 and 2000. Additionally, a turf trial was established at North Brunswick, N.J., that included the same 36 cultivars and selections. The turf plots were evaluated for several traits including overall turfgrass quality, density, and susceptibility to brown patch disease. Based on principal component analysis of morphological measurements, along with turf trial data, all cultivars and selections were assigned to one of six groups: forage, early-standard, standard, early semi-dwarf, semi-dwarf, and dwarf. In turf plots, the semi-dwarf, early-semi dwarf, and dwarf groups were the top-performing types in terms of overall turfgrass quality, and the forage and early-standard cultivars had the lowest overall quality ratings. The dwarf types did not perform well under summer stress, especially in terms of brown patch disease incidence. The results of this study suggest that when developing cultivars for higher maintenance situations, turf-type tall fescue breeders should focus on the development of semi-dwarf cultivars.
Jonathan M. Bokmeyer, Stacy A. Bonos, and William A. Meyer
( Beard, 1973 ). The most devastating disease of tall fescue is brown patch caused by Rhizoctonia solani Kühn. Brown patch can reduce the overall quality and aesthetics of the turf stand ( Couch, 1985 ; Martin and Lucas, 1984 ) and reduce stand density
Ramsey Sealy, Michael R. Evans, and Craig Rothrock
formation by Rhizoctonia solani and killed the organism when hyphal discs were exposed to the oil in a petri plate assay. They concluded that the inhibition of sclerotia was in part the result of the inhibition of hyphal growth. Singh et al. (1990) found
D. Grant McCarty II, Sarah E. Eichler Inwood, Bonnie H. Ownley, Carl E. Sams, Annette L. Wszelaki, and David M. Butler
concern. Blok et al. (2000) reported that incorporated amendments (i.e., labile C source) and mulching with a polyethylene film were both necessary for mortality of Verticillium dahliae Kleb. and Rhizoctonia solani Kühn inoculum. Similarly, Goud et
Alexis K. Nagel, Guido Schnabel, Cesar Petri, and Ralph Scorza
Trichoderma viride, Rhizoctonia solani, Fusarium oxysporum, Valsa ambiens, Gibberella zeae, Ganoderma lucidum, Botrytis cinerea , and Pyricularia oryzeae ( Hu and Huang, 1994 ). Additionally, GAFP was able to provide resistance to the ascomycete fungus
Xiuling Tian and Youbin Zheng
biocontrol agents for wilt disease of kidney bean caused by Fusarium oxysporum Intl. J. Agr. Biol. 6 310 316 El-Tarabily, K.A. 2004 Suppression of Rhizoctonia solani diseases of sugar beet by antagonistic and plant growth-promoting yeasts J. Appl