The effects of herbicides on axenic growth of Cylindrocladium crotalariae and on the development of CBR in the greenhouse and in the field was studied. In laboratory tests, dinitramine at 1, 5, and 10 ug/ml increased axenic growth of two isolates of C. Crotalariae in herbicide-amended potato-dextrose broth (PDB). Dinoseb and dinoseb + naptalam at the same rates also increased growth, whereas alachlor, benefin, diphenamid, vernolate and 2,4-DB were found to have no consistent effect. Treatment of infested soil with dinitramine at 1, 5, 10, 50, and 100 ug/g soil had no significant effects on populations of C. crotalariae microsclerotia (ms) in a Ruston or a Woodstown loamy fine sand. Dinoseb reduced ms populations significantly (P=0.5) in Woodstown soil at 5, 10, 50, and 100 ug/g soil and in Ruston soil at rates of 50 and 100 ug/g soil. In greenhouse tests, soil treatment with dinitramine at 0.56 kg/ha but not at 0.84 kg/ha increased significantly (P=0.05) the severity of CBR in Ruston and in Woodstown soil. In Ruston soil, dinitramine increased the severity of CBR only at an inoculum density of 5 ms/g soil, but in CBR only at an inoculum density of 5 ms/g soil, but in Woodstown soil, the herbicide resulted in disease increase only at 50 ms/g soil. Additional tests showed that disease severity was increased when peanut seedlings were pretreated with dinitramine and transplanted to herbicide-free infested soil. Dinitramine treatment was postulated to alter growth and development processes in ‘Florigiant’ peanut in a way to result in increased susceptibility to CBR. Dinitramine treatment of soil did not increase disease severity in ‘NC3033’ peanut, a CBR-resistant cultivar. Dinoseb at 1.68 kg/ha increased significantly (P=0.05) the severity of CBR in Woodstown soil, but did not in Ruston soil. Higher rates of dinoseb (3.36 and 6.72 kg/ha) were found to have no effect. Field tests were conducted in microplots (77-cm diameter) to determine the effects of herbicides on CBR. The severity of pod rot caused C. crotalariae was increased significantly (P = 0.05) by pre-plant soil treatment with dinitramine at 0.56 kg/ha, but not at 0.84 kg/ha in 1979. Although not significant (P=0.05), substantial increases in root rot and top symptom severity occurred in 1979 in response to this treatment. Pre-plant soil treatments with dinoseb at 1.68, 3.36, and 6.72 kg/ha did not affect disease development in microplots in 1979. In 1980, dinitramine (0.56 kg/ha) increased the severity of both root and pod rot significantly (P=0.05) in two separate microplot tests. Dinoseb at 1.68, but not at 3.36 or 6.72 kg/ha also increased significantly the severity of CBR in these tests.. Soil assay results indicated that herbicide treatments had no consistent effect on populations of C. crotalariae ms, .Macroposthonia ornatum or Meloidogyne hapla in microplots. These results provide evidence that certain herbicides can affect the development and severity of CBR in peanut. Furthermore, the present study emphasizes that knowledge of the non-target effects of pesticides on the biosphere can be significant and must be considered in tbs development of effective disease control programs. / Ph. D.

Studies of the inheritance of morphological traits contribute to the understanding of peanut genetics. Investigations of the fertility and cytogenetics of interspecific progenies between Arachis hypogaea and wild Arachis species have provided invaluable information on the phylogenetic relationships within the genus Arachis and on the amphidiploid nature of peanut. However, the inheritance of morphological traits using interspecific progenies has not been elucidated to date. The objective of this study was to identify and to analyze genetic factors controlling growth habit, stem color, root nodulation, and leaflet size in peanut. F1 and F2 progenies were obtained from diallel crosses between A. hypogaea cvs. Argentine and T2442, and A. monticola. Fz progenies and parents were grown at the Tidewater Agricultural Experiment Station in 1985. F1 plants were grown in the greenhouse in 1986. Five, six, and seven phenotypic classes, respectively, were assigned to characterize growth habit, stem color, and leaflet size. Root nodulation was indirectly determined through leaf color. Chi-squares were computed to test homogeneity of reciprocal crosses and genetic ratios for growth habit, stem color, and root nodulation. Leaflet size distributions were analyzed graphically and independence of inheritance was tested among all traits studied. Analysis of results indicates that: 1) growth habit may be determined by four genes having two types of isoalleles, 2) the relationship between and within these four genes may be essentially additive, 3) all loci may not contribute with the same weight to growth habit phenotype, 4) purple and green pigmentations may be determined by two distinctive sets of epistatic genes, 5) the two genes responsible for green pigmentation may be duplicate, 6) more than two types of alleles may have been involved for one or more loci responsible for stem color, 7) root nodulation may be determined by three independent non-duplicate genes, 8) leaflet size may be quasi-quantitatively determined in peanut, 9) extranuclear factors may interact additively and/or epistaticly with nuclear factors determining growth habit, stem color, and leaflet size, 10) the relatively high number of segregating loci observed for all the traits studied may have resulted from the use of A. monticola as one of the parents, and 11) extranuclear factors may induce or modify relationships between traits when they interfere with nuclear genes determining these traits. / M.S.

This study indicates that peanuts can be dried continuously using supplemental heat and still retain a palatable flavor. It has brought to focus many problems heretofore recognized. / Master of Science

Higher percentages of peanuts than soybeans or cowpeas become infected when these crops are growing equal distances from a source of peanut mottle virus (PMV). The total number of aphids trapped in these crops are about equal and the reason for this differential percentage infection has not been demonstrated. Known vectors of PMV such as Aphis craccivora (Koch) and Myzus persicae (Sulzer) comprised 31% of the aphid population in peanuts compared to 14% in soybeans and 17% in cowpeas and could be responsible for the higher number of peanut infections. In addition, trapping of live aphids in peanut fields showed that viruliferoup Rhopalosiphum maidis (Fitch) were present. Laboratory studies confirmed that R. maidis could transmit PMV from peanut to peanut. This is the first report of R. maidis as a vector of PMV. Virus transmission tests using 5 aphids per peanut seedling were conducted in the greenhouse. Myzus persicae (Sulzer), Aphis craccivora (Koch), and Rhopalosiphum maidis (Fitch) were able to vector peanut mottle virus from peanut to peanut 30, 14, and 4%, respectively. In subsequent tests, where only one aphid was used per test seedling, M. persicae, A. craccivora, and R. maidis transmitted PMV at 9, 4, and 2%, respectively. The retention abilities of the three aphid species tested for PMV was low when compared to other experiments (20). Switching varieties from Florigiant to Florunner did not appear to significantly increase virus transmission rates of any of the aphid species tested in comparison to tests done with Florigiant. This is the first report of transmission testing with these three aphid species and PMV V745-473, a strain of the virus isolated from soybean in Virginia and with the Florigiant variety of peanuts. In feeding preference tests, all three aphid species tested showed a preference for settling onto a host, regardless of the host species used, to wandering at random in the feeding arena and not feeding on any host plant. A. craccivora showed the greatest propensity to wander, with only 33% of those aphids tested choosing to settle on a host. In contrast, 58% of R. maidis tested chose to settle on a host. In comparisons of feeding preferences between combinations of two host plants, M. persicae preferred chinese cabbage in 4 comparisons and soybean in 2, A. craccivora preferred both soybean and chinese cabbage in 2 comparisons each, and R. maidis preferred chinese cabbage in 4 comparisons and sorghum in 3. Chinese cabbage, soybeans, cowpeas and sorghum are preferred by these three aphid species over peanuts. Based on feeding preference it would be impossible to separate the PMV vectoring ability of these three aphid species. The three aphid species tested were able to reproduce well on the plants on which they were reared, but only A. craccivora was able to reproduce on peanuts. / M.S.

Development of early leafspot, caused by Cercospora arachidicola Hori, was monitored on' Florigiant' peanut (Arachis hypogaea L.) at two field sites in Suffolk, Virginia. In one study, plants in 27-cm-diameter plots were inoculated with 20,000 conidia and inoculation dates were replicated in five randomized complete blocks. At location one in 1985 and 1986, lesions/leaf at two weeks after inoculation correlated significantly (P ≤ 0.05) with infection indices (IND) developed by the Virginia leafs pot advisory and hours of relative humidity (RH) ≥ 95%. At location two, correlations between lesions/leaf and IND as well as hours of RH ≥ 95% were significant in 1986, but not in 1985. Certain site specific factors were believed to have altered plant susceptibility to leafspot at this site in 1985. In another study, pots with greenhouse-grown peanut were placed between unsprayed rows of field plants, heavily colonized by C. arachidicola. Plants were removed after 3, 5, and 7 days of field exposure for six consecutive weeks in 1986 and returned to the greenhouse. Lesions/leaf at two weeks after initial exposure were correlated with IND values computed by five versions of the leaf spot advisory. Significant correlations were found between lesions/leaf on plants with field exposures of 5 and 7 days and cumulative IND values and hours of RH ≥ 90% and 95%. The low incidence of lesions resulting with field exposures of only 3 days coupled with a lack of significant correlations between disease and cumulative IND values for 3 days after inoculation in both studies suggests that infection processes require several days, and that fungicides may be applied to achieve disease control during this time. / M.S.

Preventing flavor fade requires an understanding of the relationship between carbonyl amine and lipid oxidation reactions. The polyunsaturated fatty acid content of lipids in peanuts makes them more susceptible to lipid oxidation. The major by-products of the oxidation reaction are nonanal, hexanal, octanal, and decanal. These chemicals are associated with cardboardy, painty, and oxidized flavors associated with flavor fade. The carbonyl-amine reaction yields a variety of pyrazines with positive flavor attributes. Initial flavor notes were explored through sensory work, Gas Chromatography-Olfactometry, and chemical analysis. The fresh roasted volatiles produced from roasted peanuts and the aldehydes resulting from oxidation were also evaluated using GC-FID to quantify and identify the pyrazines and hexanal over a 21 day storage period. Electronic Nose was used to determine differences between storage periods. Gas chromatography-Olfactometry identified potent pyrazines contributing to fresh roasted peanutty aroma in fresh peanuts. Using GC-FID a significant decrease (p<.05) in 2-ethylpyrazine and 2,3-diethylpyrazine concentration was found over a 21-day period. No significant difference (p>0.05) was noted in the other pyrazines evaluated. A significant increase (p<0.05) was noted in the hexanal concentration over a 21-day period. The peroxide values and sensory analysis correlated directly with the GC-FID results with a significant increase (p<0.05) in peroxide value at Day 14 and Day 21, and a significant decrease (p<0.05) in fresh roasted peanuty flavor from days 0-21 and a significant increase (p<.05) in painty, cardboardy and bitter from days 7-21. The electronic nose successfully separated Day 0 and Day 21 samples from Day 7 and 14, which were also separated, but with minimal overlap. / Ph. D.

The Government of Senegal is attempting to liberalize the groundnut market. In the past, this market was highly regulated with government-set producer prices, groundnut oil processing mills owned by parastatals, and requirements that all groundnuts be sold to these quasi-governmental organizations. In recent years, these rules are being relaxed, and farmers are allowed to sell groundnuts on the open market. However, farmers continue to sell most of their groundnuts, as before, to the mills. This study attempts to shed light on the effects of this market liberalization. First, an attempt is made to provide estimates of the farmers' short-run output supply and input demand responses to price changes. A quadratic profit function model is estimated using data collected for the current study and a similar dataset collected by Akobundu [1997]. Second, a quadratic programming model is used to examine the effects of eliminating pan-territorial prices. Results indicate that the elimination of the pan-territorial price system will have an overall benefit to Senegalese society. However, as expected, groundnut producers in areas remote from the groundnut oil processing mills would face lower prices. The effects on producers and consumers in the major producing regions, however, were found to be minimal. Finally, the dissertation provides an extensive description of the economic activities of small-scale farm households in Senegal's Groundnut Basin. Differences between males and females and between household heads and other males in the household are also examined. Although females are not as involved in groundnut production, they do not seem to face discrimination in either the official or the open market. The description of the situation facing small-scale farmers provided in this dissertation is not encouraging. The quantity and timing of the rains in the Groundnut Basin add an unwelcome uncertainty to farming. Increases in population are adding pressure to the environment and are placing heavy demands on wood and grazing lands. Only eight percent of the farmers had groundnut seed multiplication ratios less than one, and sixty-seven percent had ratios less than five. The dissertation also indicates that farmers are not producing enough to feed their families. Fewer than twelve percent of the households produce a caloric surplus. Sixty percent produced less than fifty percent of their caloric needs. The study indicates that farmers are not earning enough from agricultural production to take care of normal expenses throughout the year. Thus, when combined with uncertain rains and a worsening environment, the farmers have little margin of safety. Therefore, any government policies affecting groundnut production in particular or agricultural production in general should take into account the situation already facing the farmers. / Ph. D.

Fat bloom in chocolates is the gray-white discoloration and dullness that can occur on the surface of the confectionery. Fat bloom is a common quality defect that can result from temperature fluctuations during storage. Chocolates candies with peanuts or other nut fillings are more prone to fat bloom compared to plain chocolates, due to a release of incompatible nut oils into the chocolate matrix. The overall goal of this study was to determine if differences in triacylglycerol (TAG) composition and rheological properties of high, medium, and normal oleic peanuts influence fat bloom formation. All three peanut varieties showed high concentrations of triolein. Normal oleic peanuts had a slightly higher trilinolein than high and medium oleic peanuts, which contained trilinolein in trace amounts. Peanut pastes from the three peanut varieties all had a minimum apparent yield stress, and all pastes showed varying degrees of shear thinning. The apparent yield stress of high and normal oleic pastes was higher than the apparent yield stress of medium oleic paste. The absolute value of the flow index behavior was 1 for the high oleic peanut paste, suggesting friction in the experimental apparatus, even with use of Teflon plates. The peanut chocolate candies took around 45 days for significant dulling of the chocolates with temperature cycling between 26-29 °C approximately every 26 hours. Optical microscopy scans showed differences in glossiness and surface textural attributes of the unbloomed and bloomed peanut chocolate confectionery. Consumer evaluation showed some differences in the glossiness and significant differences in surface texture of unbloomed and bloomed chocolates. A majority (62%) of the survey respondents had seen whitish discoloration in chocolates and 40% of the respondents thought this is because the chocolate had grown old. / Ph. D.

Testing several registered and experimental fungicides in the laboratory and field has resulted in the identification of two compounds possessing high levels of fungitoxicity to Sclerotinia minor, the causal agent of Sclerotinia blight of peanut. The two fungicides, ASC-66825 and RH-3486, are thought to have a different chemistry than the dicarboximide fungicides. The ED₅₀ value (dose required for 50% inhibition of mycelial growth) of ASC-66825 and RH- 3486 was 0.004 µg/ml and they were 45 times more fungitoxic to mycelial growth on glucose yeast extract agar (GYEA) than iprodione. At simulated field rates (1.12 kg/ha), none of the experimental fungicides effectively inhibited sclerotial formation in soil-plate assays, whereas all the dicarboximide fungicides (chlozolinate, iprodione and vinclozolin) significantly inhibited sclerotial formation. No cross-resistance was detected between the dicarboximide fungicides and ASC-66825 or RH-3486. During three years of field tests, RH-3486 controlled Sclerotinia blight of peanut significantly better than iprodione. The spray adjuvant, pinolene (Nu-Film-17®), significantly improved the performance of iprodione (Rovral®) over 5 years of field tests. Average yields from plots treated with iprodione and pinolene were 365 kg/ha higher and disease incidence 15% lower than plots treated with iprodione alone. Applying fungicides to experimental microplots infested with a pathogenic, dicarboximide-resistant isolate of S. minor (B-83-T2) indicated that fungicides still provided disease control in a field situation. Disease incidence was suppressed 96, 55, 62, 25 and 20% in microplots infested with isolate B-83-T2 and 97, 83, 33, 67 and 30% in plots infested with a sensitive isolate (S-2), following treatments with RH-3486, vinclozolin, iprodione, PCNB and dicloran, respectively. Sclerotia of S. minor from peanut fields treated with dicarboximides and other fungicides for leafspot control did not show field resistance to iprodione in spite of an in vitro resistance rate of 6.3% in GYEA tests containing 2 µg/ml of iprodione. Field resistance to iprodione does not seem to be a major threat to control of Sclerotinia blight of peanut with iprodione in Virginia. The use of chlorothalonil for leafspot control has been correlated with an increase in the incidence of Sclerotinia blight. Excised peanut stems obtained from plots exposed to field applications of chlorothalonil produced larger lesions after inoculation with S. minor, than stems from untreated plots. Treatment of excised stems with chlorothalonil just prior to inoculation did not enhance lesion development. However, cultures of S. minor conditioned on GYEA containing chlorothalonil at 10 µg/ml were more pathogenic on excised stems than unconditioned cultures. Chlorothalonil may increase the aggressiveness of S. minor by enhancing organic acid production without greatly inhibiting fungal growth. / Ph. D.

Sclerotinia minor Jagger myceliogenic sclerotial germination, growth, infection, and colonization of peanut (Arachis hypogaea L.) tissue was optimum at 20-25 C. Ninety-five to 100% relative humidity (RH) for more than 12 hours was necessary for germination. There was no difference in infection and colonization of main stem versus lateral branch tissue but younger plants were more susceptible than older plants. Correlation and regression analyses were conducted on data from field experiments with artificially and naturally infected plants. Important independent variables in regression models for lesion length (LL), weekly change in lesion length, or disease severity index (DSI) were: number of days with temperature ≤16.7 C (DA17), the interaction of DA17 with precipitation (DA17*P), RH, maximum temperature (TMAX), and plant height for the week prior to disease measurement, and TMAX, P, and soil moisture (SM) at 0 to 5-cm for the period two weeks prior to disease measurement. were studied in field Infection and disease development plots with modified canopy. / Ph. D.