No description available.

Growth chamber trials were performed to investigate optimal conditions for the small scale production of isolate M12-4A of Fusarium oxysporum on substrate materials that are locally available to subsistence farmers in West Africa. Field trials were conducted in Mali to evaluate the effectiveness of F. oxysporum for the control of Striga hermonthica and to determine the host range of F. oxysporum. F. oxysporum grew and colonized substrates over a range of temperatures (24, 28 and 32 C). Chopped sorghum straw pieces, straw fibres, and glumes supported abundant mycelial growth. Full colonization of the substrates was observed within 10 days. Production of infective propagules (microconidia and macroconidia) was optimum at 28 C. Optimum wetness of the substrates was obtained by soaking straw or glumes overnight. In field studies, the incorporation of 2.6 g of dried ground straw inoculum per sorghum seed pocket (120 cm$ sp2$), at a depth of 5 or 10 cm, resulted in a 60% reduction of emerged S. hermonthica 82 days after sowing. At harvest, biomass of Striga was also reduced by 70% and sorghum grain yield was almost doubled compared with the control. Sorghum, millet, maize, rice, fonio, cotton, cowpea, groundnut, okra and sorrel were immune to isolate M12-4A.

Fusarium oxysporum M12-4A fungus is being evaluated for the biocontrol of Striga hermonthica, a parasitic weed of African cereal crops. The production of M12-4A inoculum was assessed in four Malian villages using local technology and substrates. A delivery system using arabic gum to temporarily glue inoculum powder onto the crop seed was tested. In controlled conditions, coating of sorghum seeds with arabic gum and inoculum powder did not affect seed germination or inoculum viability. However, one week at 40°C significantly decreased the viability of the inoculum by 31%. Fungus growth and chlamydospore germination were also reduced by temperatures of 34 and 36°C. M12-4A was susceptible to the fungicide thiram (ED50 = 38.5mug). Field trials were conducted in Mali to evaluate the large-scale efficacy of the seed coating technology. F. oxysporum M12-4A was detected from some S. hermonthica tissue and soil samples using specific primers and Real Time PCR.

Thesis (M.Sc.). / Written for the Dept. of Plant Science. Title from title page of PDF (viewed 2008/12/10). Includes bibliographical references.

No description available.

No description available.

The following research developed an approach and methodology to simultaneously gather and integrate social and natural science farm system data of developing countries into one data base. The overall approach was based on Weber's theory of abstraction, which requires the identification of the broadest number of variables as possible. The first step to understanding the farm system was to overview a number of the key variables which represented a number of key farm components; the second step was to juxtapose and blend together the various forms of data in linear forms against a test variable of Striga infestation levels; the third step was to evaluate if the amount of knowledge gained in predicting Striga infestation levels was statistically significant by cross correlating soil nutrient levels, crop management approaches, farmers' perceptions of Striga infestation and spatial distances; the fourth step was to use parametric and non-parameterc analytical tools in conjunction with data compression to locate the best combination of parameters to better manage Striga. The final part of the process was to identify and integrate the crop, field and social data into a profile of farmer's who have the highest and lowest likelihood of being infested by Striga by using a soil nutrient concentration baseline as the indicator. The results were that natural and social science data could be successfully combined, integrated and have statistically significant cross correlations. These correlations indicate that specific spatial parameters combined with specific soil components, farmer's management and crop placement could be used as predictors of Striga infestation levels. As well the farmers' perception could be validated using natural science data.

A three-year (1991-1993) investigation was done in the field and laboratory to study the bionomics of Smicronyx guineanus Voss and Sm. umbrinus Hustache and the spatial distribution of Striga hermonthica (Del.) Benth. Studies on the life history of the weevils were undertaken. Seasonal activity and habits were established by monitoring life stages in the field. A behavioral Time Budget of Smicronyx adults was established in semi-field conditions. Dispersion patterns and the optimum sample size for Smicronyx and Striga were determined. Smicronyx adults as well as Striga plants were aggregated in the field. Smicronyx larvae were located in the upper stratum of the witchweed (93.2%) where they make galls and destroy large number of seeds. The effect of precipitation on emergence of Smicronyx adults was investigated in the insectary. The optimum rainfall required for Smicronyx adult emergence ranged from 30 to 40 mm. Good synchrony and positive association of Sm. guineanus and Sm. umbrinus with S. hermonthica were observed. There are good prospects for augmentation and/or conservation of Smicronyx populations as part of an integrated control strategy of S. hermonthica.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, June 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, June 2002. / Includes bibliographical references. Also available on the Internet.