Four F2:4 populations of peanut (Arachis hypogaea L.) resulting from the complex cross Tamrun 96 X Tx901639-3 X Sun Oleic 95R were grown in three disease nurseries over a 2 year period. Three separate selection techniques were applied to determine which technique would provide the most effective method for selecting a multiple disease resistant, runner-type peanut. Technique I involved selection at a tomato spotted wilt virus nursery during the first cycle of selection and transferring the selections to a Sclerotinia minor (Jagger) nursery for a second cycle of selection in year two. Technique II was the reciprocal of Technique I. Technique III involved selection of the populations at a multiple disease nursery for two consecutive years. Selections were based on disease ratings, growth habits, pod and seed characteristics, and oleic/linoleic acid ratios. Disease ratings were scored as percentage infection on a scale of 0 (0% plot infected) to 10 (100% plot infected). Disease severity was also rated on a scale of 1 (symptoms noted, but no yield effects) to 10 (plant death, no yield). There were two final selections for each population using each selection technique that were yield tested over a 2 year period to determine which technique was superior. The yield tests were conducted using completely randomized block design at all three disease nurseries with an additional disease-free site included. Data for disease ratings, yield, grade, and value per hectare were combined within locations across years. All three selection techniques provided lines with more disease resistance than the parents; however, there was no difference detected between the effectiveness of the three techniques in terms of disease resistance, yield, grade, or value per hectare.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Agronomy and Farming Systems, 2000. / Bibliography: leaves 189-202.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references.

The first chapter gives an overall introduction to Arachis hypogaea L., the crop that was studied in this thesis. The literature reviewed touched on various aspects of the crop in general such as the importance of peanut as a crop, its botanical description, origin and distribution world-wide. Different marker studies done on A. hypogaea L. and their extents have also been reviewed. The chapter also looked at the oryzacystatin-1 (OC-1) gene as a possible candidate gene for peanut improvement in South Africa (Chapter I). Agronomic data was collected in an attempt to observe and evaluate variability amongst the 18 commercially cultivated peanut lines from South Africa. The growth habits, growth seasons, testa colours, total oil percentages and oleic and linoleic acid ratios were the agronomic characters used to study variation (Chapter II). One South African commercially cultivated peanut line, JL 24, was transformed with the oryzacystatin-1 (OC-1) gene, which was isolated from rice. Three to four week old plantlets were vacuum infiltrated with Agrobacterium during the transformation process and various methods were used to analyze the putative transformants (Chapter III). Two types of DNA markers along with phynotypic data were used to examine polymorphism among 18 South African peanut lines and a transformed line. The amplified fragment length polymorphisms (AFLPs) and simple sequences repeats (SSRs) were the two DNA markers used in this study to determine the level of variation amongst these lines (Chapter IV). / Dissertation (MSc (Genetics))--University of Pretoria, 2008. / Genetics / unrestricted

Soybean (Glycine max L. Merr.) is one of the most important crops of the world. Among the various viruses infecting soybean, peanut mottle virus is most commonly found on soybeans in areas where they are grown in close proximity to peanuts. This research was conducted with the primary objective of identifying new genes for resistance to peanut mottle virus. To assign a gene symbol to the resistance gene in cultivar CNS, it was crossed with 'Peking'. Both the F2 and F2:3 lines segregated in a ratio which is expected when one dominant and one recessive gene at two different loci are segregating. Previous studies indicate the presence of one dominant gene in CNS and one recessive gene in Peking for resistance against PMV. This clearly suggests that Peking and CNS possess different resistance genes, which are non-allelic to each other. Now that, all the allelism tests are complete, the resistance gene in CNS can be assigned a gene symbol of Rpv3. PI 486355, a resistant line, was crossed with susceptible cultivars Lee 68 and Essex to study the mode of inheritance of resistance. This PI was found to possess two independent dominant genes for resistance to peanut mottle virus. It was also crossed with 'York' and CNS which are known to have resistance genes at the Rpv1 and Rpv3 loci, respectively. Data from inoculations of F2 and F2:3 progenies indicated that one gene was allelic to Rpv1 and the other is at a locus different from both Rpv1 and Rpv3. PI 398593 was crossed with Lee 68, York, Peking and CNS for studying the nature of resistance genes present in it. No certain conclusions can be drawn regarding the nature of the resistance gene(s) at this stage because of inconsistent behavior of the PI itself. The F2 data of the crosses of PI 398593 with Lee 68, York and CNS supported a recessive nature of the resistance gene present in the PI. F2 plants of the cross PI 398593 x Peking segregated but, not in the expected ratio. F2:3 data of only one cross (PI 398593 x York) supported the recessive nature of the PI resistance gene whereas the other two crosses (PI 398593 x CNS and PI 398593 x Peking) did not support these findings. From the data available it appears that the resistance is at least partially influenced by the environment. The mode of inheritance of resistance in PI 96983, 'Kwanggyo', 'Toano', 'Jizuka', 'Raiden' and 'Suweon 97' was studied by crossing these cultivars with PMV susceptible cultivars and inoculating the F2 populations of these crosses. In all these cultivars resistance is governed by a single dominant gene. PI 96983, Toano, Jizuka and Suweon 97 were also crossed with York to determine the allelic relationships. Resistance genes in all these cultivars were found to be allelic to Rpv1. Since each of the cultivars also has a single dominant gene at the same locus for resistance to soybean mosaic virus, it is possible that resistance to both viruses is controlled by the same gene. / Master of Science

This study was conducted to measure the intake; nutritive value and digestibility of peanut hay (Arachis hypogaea L.). Fourteen Holstein heifers (BW= 408 plus/minus 32 kg; Age = 15.4 months plus/minus 0.5) were randomly allocated to two diets: peanut hay (PH) and corn silage (CS) adlibtum for 26 days. The PH consisted of 66:34 forage: concentrate (F:C) and CS diet contained 57:43 F:C ratio. Peanut hay at 91.8% DM contained 8% CP, 64% NDF, 51.9% ADF and 8 % ash. DMI and CP was not different across the treatment diets (P>0.05). NDF and ADF intake was different between the diets with PH being greater (P<0.01). Feed Efficiency using the feed to gain ratio was different across the diets (P<0.0001). Dry matter digestibility was 75.37% for CS diet and 68.53% for PH diet. Peanut hay basal diets formulated to contain low F:C ratio can increase growth in dairy heifers.

An algorithm was developed for assessing disease risk and improving fungicide timing for control of Sclerotinia blight of peanut, caused by Sclerotinia minor. A 5-day index (FDI) of disease risk was calculated daily by multiplying indices of moisture, soil temperature, vine growth and canopy density and summing the values for the previous 5 days. Spray thresholds of FDI 16, 24, 32, 40, 48 were compared to a 60, 90, 120 DAP (days after planting) schedule and the standard demand program. Field trials in 1994 indicated that fluazinam (0.58 kg a.i./ha) applied at an FDI of 32 performed similarly to the demand program and was more efficient than the DAP schedule. However, the original FDI 32 algorithm triggered sprays 13 days subsequent to disease onset in 1995, indicating the need for improved vine growth and temperature parameters as well as DAP-dependent FDI thresholds. Results from 1996 and 1997 demonstrated that algorithms with new vine growth and temperature parameters coupled with DAP-dependent thresholds performed as well or better than the original FDI 32 algorithm, demand program, or DAP schedule. Protection intervals of 7 and 14 days improved the performance of iprodione (1.12 kg a.i./ha) while fluazinam provided protection for up to 21 days when applied according to the original FDI 32 algorithm. Planting date was evaluated for its effect on disease and fungicide use patterns. Late planting (20-28 May) delayed disease onset and reduced early season disease incidence three of the four years tested. When averaged across planting dates, the original FDI 32 algorithm performed as well or better than the demand program in 1994 and 1995, as did algorithms utilizing new vine growth and temperature parameters with DAP-dependent thresholds in 1996 and 1997. Chemicals for altering plant architecture were compared to defoliation by corn earworm and leaf spot for suppression of Sclerotinia blight. Chlorimuron (8.8 g a.i./ha) and withholding fungicide for leaf spot control demonstrated the most significant disease suppression and yield improvement. Results show the importance of fungicide timing and plant growth and canopy architecture modification for control of Sclerotinia blight of peanut. / Ph. D.

Including peanut (Arachis hypogaea L.) in crop rotations is common for eastern Virginia and the Carolinas, as it thrives in the long growing season and sandy soils. Boron (B) is widely deficient, and is more prone to leeching in sandy soils. Applied B has difficulty reaching growing points as B has reduced phloem mobility in peanuts. Current B fertilization recommendations are based on only three studies from the early 70s. Many changes have been made in cultivar breeding since then. This research examines if recommended B application rates and times are still necessary for optimal yield, plant health and seed quality for current cultivars. Two experiments in seven fields compared four total amounts of B applied (0, 0.3, 0.6, and 1.1 kg ha-1), and application time (planting; beginning peg, R2; full seed, R6; planting and R2; planting and R6), and runner and Virginia market types, newer and obsolete cultivars, with or without B fertilization. Leaf B was elevated only directly after fertilization (p=0.004, p<0.001), and in relation to total B applied (p<0.001), but seed B content was unaffected. Yield was not impacted by B rate or application time. Yield was higher (p=0.012) for newer cultivars when B fertilized, but no different than obsolete cultivars with B. Seed from obsolete cultivars had higher (p=0.010) B, no difference between market types or B fertilization. Germination of all seed was 97%. Based on this research, it is not necessary to apply B for optimal yield, plant health and seed quality for current cultivars. / Master of Science in Life Sciences

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