Thesis (Ph. D.)--West Virginia University, 1998. / Title from document title page. "December 11, 1998." Document formatted into pages; contains ix, 94 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references.

Onions are highly responsive to endomycorrhizae and improved plant growth is among the benefits associated with this symbiosis, particularly in low phosphorus soils. Although this crop is grown extensively in organic soils, few studies have been conducted on these. Onion plants (Allium cepa L. cv. Norstar) were inoculated with Glomus aggregatum Schenck & Smith, Glomus clarum Nicolson & Schenck, Glomus fasciculatum Gerdemann & Trappe, Glomus intraradix Schenck & Smith and Glomus versiforme (Karst.) Berch and grown in the field and under controlled conditions to evaluate their efficiency in newly reclaimed organic soil of low P fertility. Three species were selected to evaluate the effects of introduced endomycorrhizal fungi effects and P fertilization (equivalent to 0, 24 and 48 kg P ha$ sp{-1}$) on the growth and mineral nutrition of onion plants. / Introducing endomycorrhizal fungi in non-sterile soil did not affect the growth and mineral nutrition of onion. Crop maturity was advanced when plants were inoculated, however. Increasing levels of P fertilization did not depress root colonization and onion growth was increased significantly at the highest rate only. These results suggest that higher levels than recommended could be used in this soil. Inoculation in $ gamma$-irradiated (10 kGy, $ sp{60}$Co) soil alleviated excessive Mn absorption by onion plants. Adding P fertilizer depressed growth and root colonization when plants were inoculated with G. clarum and G. intraradix and was related to the low irradiance levels used in this study. G. versiforme appeared to be the most efficient of the introduced species.

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Thesis (MScBosb)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Experiments were conducted to investigate effects of endophyte (Acremonium coenophialum Morgan-Jones and Gams) infection of tall fescue (Festuca arundinacea Schreb.) on grazing cattle and subsequent feedlot performance, serum minerals and prolactin, intake, digestibility, bite size, and biting rate. Grazing animal performance was measured April to October, 1989 and 1990, at two locations in VA. Effects of grazing low (<5%) and high (>70%) endophyte infected tall fescue, with and without white clover (Trifolium repens L.), were studied with yearling steers. At each location, two replicates were used with a stocking rate of .3 ha/steer (116 steers/yr). At the end of grazing, all animals were finished on a high corn silage diet and slaughtered. Daily gains of steers grazing low endophyte-infected pastures were higher (P<.01) than for those grazing high endophyte-infected pastures. Cattle grazing high endophyte-infected tall fescue with clover at Glade Spring gained at the same rate as those grazing the low endophyte-infected tall fescue without clover during Summer, 1989. During 1990, cattle at Glade Spring had higher (P<.05) daily gains than did those at Blackstone. Rectal temperatures were .5 to 1 °C higher (P<.05) for steers grazing infected pastures by June of each year at both locations. Prolactin concentrations were lower (P<.01) in cattle grazing endophyte-infected fescue within 28 d of initiation of grazing at both locations. Visual evaluation indicated that steers grazing high-endophyte pastures had rough hair coats compared to those grazing low endophyte pastures (P<.01), showing evidence of tall fescue toxicosis. Serum mineral analyses indicated no consistent influence of the endophyte. During feedlot finishing, there were no detrimental effects from previously grazing endophyte-infected tall fescue on animal performance. Forage DM yield, and CP in 1990, and IVDMD in 1989 and 1990 from Glade Spring were higher (P<.05) compared to Blackstone. Forage from Blackstone was typically higher in NDF, ADF, and lignin compared to Glade Spring. Forage from Glade Spring was higher in Ca, Mg, P, and Cu, compared to Blackstone. Diet selection, digestibility, biting size, and biting rate were measured with esophageally-fistulated steers grazing low (<5%) and high (>70%) endophyte-infected tall fescue, with and without white clover. Bite size was smaller (P<.05) in July compared to May, corresponding to decreased quantity of forage available. Bite size and biting rate were not affected by endophyte infection or inclusion of clover. In vitro DM digestibility was higher (P<.05) for high endophyte-infected tall fescue in July. Animals consumed a higher percentage of clover than was available in the sward. Intake and digestibility were estimated using 48 experimental animals and four esophageally-fistulated steers. Chromic oxide sustained-release boluses and forage IVDMD were used to estimate intake. The chromic oxide boluses were determined to be reliable for predicting intake of steers during a 21 d trial involving total fecal collection. Intake was higher (P<.01) in cattle grazing low endophyte-infected tall fescue compared to animals grazing high endophyte-infected fescue. Twenty-one Angus steers (256 kg) were used to compare the effect of 0 and 40% endophyte-infected tall fescue and orchardgrass hay on DM intake, daily gain, body temperature, serum minerals, and prolactin concentrations during an 8 wk study. Quality of the diets was low, as indicated by low CP (8.1 to 10.3%), and IVDMD (41.3 to 47.1%). Daily DM intake and daily gain were higher (P<.05) for animals consuming the noninfected tall fescue compared to animals fed the other hays. Body temperature and serum prolactin were not affected by diet. These data suggest that other factors, besides endophyte infection, are important in the etiology of tall fescue toxicosis. Some of the decreased performance of steers grazing endophyte-infected tall fescue was related to lower intake. Additional research is needed to evaluate higher levels of clover to possibly ameliorate some of the problems of tall fescue toxicosis. / Ph. D.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2007. / The study was undertaken to determine the potential physiological benefits to plants provided by the double colonisation of host plant roots by endomycorrhizal (AM) and ectomycorrhizal (ECM) fungi, when growing under normal and under salt stress conditions. Plants of the Eucalyptus grandis x E. camaldulensis clone were grown in a sterile soil with 0 and 75 mM NaCl and with or without infection with the fungi Glomus etunicatum (an AM fungus) and Pisolithus tinctorius (an ECM fungus). The Eucalyptus clone formed both ECM and AM in single and double inoculation. The mycorrhizal symbiosis did not provide any nutritional benefits to the hosts. The double colonisation had no effect on plant growth under normal growth conditions while single colonisations of AM and ECM reduced growth. Double colonisation reduced host plant specific leaf mass by 12% and increased total leaf area by 43% compared with the control under these growth conditions. This colonisation also reduced photosynthesis per leaf area by 29% compared with the control. The reduced photosynthesis of the double colonisation did not result in reduced plant growth because these plants may have had a high total plant photosynthesis because of their large total leaf area. The double symbiosis however did not reduce salt stress when host plants were exposed to 75 mM NaCl, while the AM fungus increased plant dry weight by 13% compared to the control. AM and ECM colonisation in the double colonised roots under salt stress was decreased by 18 and 43% compared to that in plants under normal growth. The reduced colonisation may have reduced the fungi’s abilities to be beneficial to the host plant. The double symbiosis is recommended based on the documented positive effects of this symbiosis to plant growth and the considered possible long-term benefits to host plants growing in saline soils.