Temperate and boreal fungal floras indicate that species of the Russulaceae (the genera <i>Russula</i> and<i>Lactarius</i>) are among the dominant ectomycorrhizal fungi in forest communities. The contribution of the Russulaceae to the communities of ectomycorrhizal Basidiomycetes fruiting in red spruce and adjacent northern hardwood forests in West Virginia was evaluated and compared with other ectomycorrhizal Basidiomycetes occupying the same habitats. The Russulaceae exhibited the greatest species diversity of any family of ectomycorrhizal fungi fruiting in the stands studied (44% of the species in spruce, 39% of the species in hardwoods). Species of <i>Lactarius</i> and <i>Russula</i> were among the most productive in both forests. Species diversity, productivity, and fruiting phenology of all ectomycorrhizal Basidiomycetes were compared between red spruce and northern hardwood stands for a 3-year period. Sporocarp numbers and sporocarp frequency in 384 four m² quadrats in each forest type was used to estimate productivity. Species richness was greater in hardwoods (36 species) than in spruce (27 species). Nine species were common to both forests. Most productivity was concentrated in a few species, while most species were rare. Species-area curves were constructed for both forests. Fungal species and tree species composition in both forests were compared by principal component analysis. Fungi in spruce forests were more productive than in hardwood forests. Productivity was highly variable among the three seasons studied because of climatic variability. Sporocarp abundance and frequency were positively correlated with basal area and density of mycorrhizal trees and were negatively correlated with fern cover in hardwood forests. Fruiting seasons extended from early July to late September or early October. Numbers of species fruiting from the same four m² quadrats ranged from 0 to 7 in spruce forests and 0 to 5 in hardwood forests. Spatial patterns of sporocarps of major species were characterized by the variance-to-mean ratio, mean crowding, patchiness, and spatial autocorrelation and were found to exhibit highly aggregated, contagious patterns. Interspecific associations between pairs of major species were measured by 2 x 2 contingency tables and Cole's index of association. A taxonomie and geographic survey of <i>Russula</i> and <i>Lactarius</i> in both the quantitative study areas and in similar habitats in the Southern Appalachians was presented. / Ph. D.

Yellow poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.), families 2-8 and 540, seedlings were fumigated with 0.07 ppm ozone, 0.06 ppm sulfur dioxide 0.07 ppm ozone + 0.06 ppm sulfur dioxide, 0.06 ppm sulfur dioxide + 0.10 ppm nitrogen dioxide and 0.07 ppm ozone + 0.06 ppm sulfur dioxide + 0.10 ppm nitrogen dioxide for 35 consecutive days, 6 hr/day. Control seedlings received charcoal-filtered air. Ozone or sulfur dioxide did not significantly affect height growth or dry weight of yellow poplar seedlings. All other treatments significantly reduced height growth and dry weight after 2 weeks of fumigation. Height growth effects of loblolly pine families were not repeatable from one year to the next in replicate experiments and weekly growth trends in the two experiments were reversed. Environmental factors related to time of year were thought to be involved with this growth trend reversal. Root dry weight was found to be a more sensitive indicator of air pollution stress than either shoot dry weight, height growth or visible symptoms. Loblolly families 2-8 and 540 were not found to be differentially sensitive to pollutant treatments. Loblolly pine seedlings, nonmycorrhizal and mycorrhizal with Pisolithus tinctorius, were fumigated with 0.07 ppm ozone and 0.06 ppm sulfur dioxide singly and in combination, 6 hr/day, for 35 consecutive days. Height growth of mycorrhizal and nonmycorrhizal seedlings was not affected by fumigation. Root dry weight of nonmycorrhizal seedlings was significantly reduced by all pollutant treatments in two replicate experiments. A similar reduction in root dry weight of mycorrhizal seedlings did not occur. Shoot dry weight of nonmycorrhizal seedlings was reduced in four of six pollutant treatments, and in one of six treatments of mycorrhizal seedlings. Mycorrhizal formation was extensive regardless of treatment. Apparent photosynthesis, measured every 4 days, was variable and significant differences among treatments did not occur. Total reducing sugar concentrations of roots were an inconclusive indicator of air pollutant stress. / Ph. D.

Specific questions regarding the community structure of VAmycorrhizal fungi and the population biology of an ectomycorrhizal addressed. The Basidiomycete, distributional Suillus granulatus, were ecology of VAM fungal communities with grasses was studied across a climatic gradient in the hyper-arid central Namib dune field. VAM fungal communities were primarily structured by substrate stability and moisture availability. Five VAM species were found throughout the study area and were not host specific. Percent mycorrhizal colonization was correlated with moisture availability, whereas spore abundance was correlated with substrate stability. Moisture availability was the key factor influencing VAM fungal phenology: growth, assessed as increased colonization of roots, continued as long as moisture was available, and spore production occurred in response to declining moisture availability. While abiotic factors determine community structure of VAM fungi in the Namib dune field, preliminary studies suggest that the phytobiont mediates fungal response to these abiotic factors. Genetic analyses of S. granulatus single spore isolates using RAPD markers showed that a post-meiotic mitosis in the basidium produces heterokaryotic spores. Secondary homothallism provides an effective means for long distance dispersal, and may account for the broad geographic range of this ectomycorrhizal fungus. Secondary homothallism contributed to the failure of somatic incompatibility tests to delineate the spatial distribution of individuals in a natural population of s. granulatus. Analysis of genetic relatedness using RAPD markers demonstrated conclusively that somatically compatible individuals were not necessarily genetically identical. I concluded that RAPD marker analysis provides a more effective means for determining clonal distribution in ectomycorrhizal populations, than does somatic incompatibility testing. / Ph. D.

Bibliography: leaves 172-197.

Bibliography: leaves 146-152.

Bibliography: leaves 172-197. / xvii, 197 leaves : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002?

Thesis (Ph. D.)--Institute of Paper Chemistry, 1984. / Includes bibliographical references (p. 54-56).

Most tomato cultivars used for commercial food production are imported into South Africa. Optimal growing conditions for these specific cultivars need to be determined, as wrong cultivar choices can lead to great financial losses. Lack of information on selecting well-performing cultivars may lead to lower yield or unacceptable fruit quality. Information on the performance of tomato cultivars under South African conditions, utilizing plastic tunnels or shadenet structures under soilless cultivation is still very limited. Soilless cultivation of vegetables is becoming a preferable over in-soil cultivation due to the improved yield and quality of produce, efficient water and nutrients usage by the crop; furthermore, the grower can regulate nutrient solution, electrical conductivity and pH of the nutrient solution. To identify the optimal system for growing tomatoes hydroponically, the performance of four tomato cultivars (‘FA593’, ‘Miramar’, ‘FiveOFive’ and ‘Malory’) under different growing conditions was evaluated: directly planted in soil under 40% shadenet with drip irrigation, a closed hydroponic system under 40% shadenet, an open bag system under 40% shadenet, or an open-bag system in a temperature controlled as well as a non-temperature controlled tunnel. The study revealed that ‘Miramar’ performed better than the other cultivars in all production systems, with the exception of soil cultivation where there were no differences amongst the four cultivars. Fruit cracking was found to be directly correlated with fruit size, as the large-sized cultivars ‘Malory’ and ‘FA593’ were more susceptible than the other two cultivars. Plants grown under shadenet were prone to fruit cracking and raincheck as well as early blight. Higher yields were obtained when plants were produced in the open bag system under temperature controlled conditions and in the closed system under shadenet. Growing tomatoes in the non-temperature controlled tunnel resulted in high incidences of fruit cracking, poor yield and pre-mature fruit ripening probably due to high and fluctuating temperatures under such conditions. The average marketable yield was 88% and 59% of the total yield in the temperature controlled and non-temperature controlled tunnels, respectively. A further experiment was carried out to improve yield and quality of tunnel tomatoes using beneficial micro-organisms, i.e., arbuscular mycorrhiza fungi (AMF) at different nutrient concentrations. Tomato seedlings were treated with Mycoroot™ containing four mycorrhiza species (Glomus etunicatum, Paraglomus occultum, Glomus clarum and Glomus mossea) at transplanting and subsequently transferred to either a temperature controlled or a non-temperature controlled tunnel under the recommended (100%) or reduced (75 and 50%) nutrient concentrations. Sawdust was used as a growing medium in this experiment. Application of AMF neither enhanced plant growth, yield, nor fruit mineral nutrient concentrations; although fruit Mn and Zn concentrations in the temperature controlled tunnel increased significantly following AMF application. Plants grown in the non-temperature controlled tunnel had significantly poorer plant growth, and lower yield and lower fruit mineral concentrations, compared with fruit from plants in the temperature controlled tunnel. Tomato plants in the non-temperature controlled tunnel had higher levels of micro-elements in leaf tissue, compared with those in the temperature controlled tunnel. The highest yields were obtained from plants fertigated with 75% of the recommended nutrient concentration, as compared with the 100 and 50% nutrient concentrations. When coir was subsequently used as the growing medium, Mycoroot™ applied at seeding and transplanting did not enhance mycorrhizal colonization or fruit quality. Growing tomatoes under reduced nutrient supply reduced the total soluble solids in the juice of the fruit, but improved total and marketable yield, as well as the number of marketable fruit. This effect was more substantial in the temperature controlled than in the non-temperature controlled tunnel. Fruit firmness and leaf chlorophyll concentrations were significantly higher in plants grown in the temperature controlled tunnel. Growing tomatoes in sawdust improved the leaf Mn and Ca concentration over that of tomato plants grown in coir. Mycorrhizal colonisation did not have a beneficial effect on tomato yield and quality. The study indicated that cultivar selection was important in obtaining the highest yield and quality of tomato using the closed hydroponic system under shadenet and the open bag hydroponic system in the temperature controlled tunnel. Temperature controlled tunnels with a pad–and-fan cooling system are still an effective way of cooling the tunnel environment which resulted in high yield and high quality of tomatoes with a higher fruit mineral content than that obtained under non-temperature controlled conditions where only natural ventilation is relied on. Results also demonstrated that mycorrhizal colonization in soilless condition has limited beneficial effects in allowing for better nutrient uptake and thereby for improved yield and quality of tomatoes. Further studies, including different media, nutrient composition and concentrations, need to be carried out to investigate the possible causes of AMF failure to improve yield, despite good AMF root colonization. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Asparagus (Asparagus officinalis) is a perennial crop well suited to grow in Quebec. Despite high demand for this crop, asparagus production is declining because of asparagus root rot disease that is caused by Fusarium spp. Phosphorus is one of the most important nutrients for the production of healthy asparagus roots that may resist infection by Fusarium. The objective of this study was to determine the effects of phosphorus (P) applications on asparagus yield and soil microbial parameters. Plots receiving 0 to 200% of the P recommendation, based on the Centre de reference en agriculture et agroalimentaire du Quebec (CRAAQ) guidelines, did not differ significantly (p < 0.05) in first year yield or plant tissue concentrations. However, asparagus receiving no fertilizer had 2 to 3 times higher arbuscular mycorrhizal colonisation of roots than other treatments in May 2003. Fresh marketable yield was negatively correlated to Fusarium incidence (p = 0.0091 r = -0.51) suggesting that plants with higher yields are less susceptible to Fusarium symptoms and that producers should avoid over-harvesting low yielding plants to reduce Fusarium spread in the field. Soil microbial activity was not affected consistently by P fertilizers because of high variability in the field.

Bibliography: leaves 146-152 / 152 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, 1987