Hordeum jubatum L., Hordeum brachyantherum nevski, and Hordeum jubatum var. caespitosum (Scribn.) Hitchc. Plants from sites in Utah and Idaho were grown and examined in order to determine whether or not hybridization with subsequent introgression occurs among the species and if so whether there is a difference in the relative amount of gene flow between the parent species H. jubatum and H. brachyantherum in different environments. Hybridizations and morphological analyses were made using standard procedures. Biochemical analyses were made by comparing paper chromatograms of leaf extracts of plant specimens. The results indicate that in Utah populations sampled, hybridization with subsequent introgression is present. Furthermore, introgression has apparently resuted in the formation of stable introgressants in Utah. Idaho populations ampled, from a high mountain area, appeared to be stable and devoid of hybridization and introgression. Possible exlanations concerning the apparent lack of hybridization and introgression are given.

No description available.

No description available.

Schubert calculus has become an indispensable tool for enumerative geometry. It concerns the multiplication of Schubert classes in the cohomology of flag varieties, and is typically conducted using algebraic combinatorics by way of a polynomial ring presentation of the cohomology ring. The polynomials that represent the Schubert classes are called Schubert polynomials. An ongoing project in Schubert calculus has been to provide geometric foundations for the combinatorics. An example is the recovery by Knutson and Miller of the Schubert polynomials for finite flag varieties as the equivariant cohomology classes of matrix Schubert varieties. The present thesis is the start of a project to recover Schubert polynomials for the Borel-Moore homology of the (special linear) affine Grassmannian by an analogous process. This requires finitizing an affine Schubert variety to produce a matrix affine Schubert variety. This involves a choice of ``window'', so one must then identify a class representative that is independent of this choice. Examples lead us to conjecture that this representative is a k-Schur function. Concluding the discussion is a preliminary investigation into the combinatorics of Gröbner degenerations of matrix affine Schubert varieties, which should lead to a combinatorial proof of the conjecture. / Ph. D.

Finitely generated monomial algebras are studied. the bound in Bergman's description of algebras with GK-dimension 1 is improved and similar techniques are used to establish the equivalence of the periodicities of overlap graphs and Hilbert series coefficients. / Ph. D.

There is inadequate basic information available on the reproductive efficiency of peanut (Arachis hypogaea L.) cultivars and a need to determine the sources of yield improvement made in peanut over the past four decades. Therefore, a study of the reproductive efficiency (RE) of 14 virginia market-type peanut cultivars was conducted using field experiments at the Tidewater Research Center, Suffolk, Virginia, in 1983 and 1984. The 14 cultivars vary in maturity from early to late, in release dates from 1944-1981, in breeding method of development from selection within an existing cultivar to hybridization followed by selection, and in growth habit from erect to spreading. The traits studied included flower total (FT), mature pod total (MPT), seed total (ST), pod total (PDT), peg total (PGT), immature pod total (IMPDT), mature pod dry weight (MPDW), plant dry weight (PLDW), vine weight (VW) and seed weight (SW). The five methods used to measure RE were (1) MPDW/PLDW (Harvest Index), (2) MPT/FT, (3) PDT/FT, (4) PGT + PDT/FT and (5) ST/(2*FT). The results indicate that the five most recently released cultivars produced more plowers, 10% more mature pods, 9.7% more mature seeds, and 11% more plant dry weight than the nine previously released cultivars. Using Harvest Index (HI) there was a 4% increase in RE for more recent vs. older cultivars, and about an 8% higher RE for early maturing vs. later maturing cultivars. Also, there was a 3% increase in RE for erect vs. similar advantage for hybrids spreading cultivars and a vs. pure lines. A slight decrease in RE for cultivars released since 1970 vs. those released earlier was observed using Methods 2, 3, 4 and 5. In addition, there was a 4-10% advantage in RE for the two earlier maturing classes over the medium or late classes using the same methods and also a 6% increase in RE for erect vs. spreading cultivars. The growth habit of the 14 cultivars was a very important determining factor for all trait differences. HI appears to be the single best measure of RE in peanuts; however, at least one other method should also be used for obtaining the truest estimate of the RE of a cultivar. It appears that the total peanut cultivar is early maturing and erect with a high RE. This study shows that plant breeders have increased yield in peanuts by (a) increasing apparently the total number of flowers, (b) increasing the HI and (c) increasing reproductive efficiency by increasing the proportion of flowers that form mature pods. Any further increase in yield must combine these three methods of increasing yield as well as overcoming any limiting factors, such as photosynthetic capacity, in order to surpass the present yield plateau. / M.S.

Public agricultural research has been conducted in Africa for decades and has generated numerous crop technologies, while little is understood on how agricultural research affects the poor and vulnerable groups such as children, and how farmers' perceptions affect their adoption decisions. This dissertation helps fill this gap with three essays on adoption and impacts of improved maize varieties in rural Ethiopia. The first essay estimates poverty impacts. Field-level treatment effects on yield and cost changes with adoption are estimated using instrumental variable techniques, with treatment effect heterogeneity fully accounted for in marginal treatment effect estimation. A backward derivation procedure is then developed within an economic surplus framework to identify the counterfactual income distribution without improved maize varieties. Poverty impacts are estimated by exploiting the differences between the observed and counterfactual income distributions. Improved maize varieties have led to 0.8-1.3 percentage drop in poverty headcount ratio and relative reductions in poverty depth and severity. However, poor producers benefit the least from adoption due to their small land holdings. The second paper assesses the impacts on child nutrition outcomes. The conceptual linkage between maize adoption and child nutrition is first established using an agricultural household model. Instrumental variable (IV) estimation suggests the overall impacts to be positive and significant. Quantile IV regressions further reveal that such impacts are largest among the most severely malnourished. By combining a decomposition procedure with estimates from a system of equations, it is found that the increase in own-produced maize consumption is the major channel such impacts occur. The third paper explores how farmers' perceptions of crop traits affects their willingness to adopt improved maize varieties. Under a random utility framework, a mixed logit procedure is implemented to model farmer's adoption intention, where perceptions of key varietal traits are first identified, and then instrumented using a control function approach to account for potential endogeneity. Perceived yield is found to be the most important trait affecting farmers' adoption intention. Further, yield perceptions among previous adopters appear to be affected by within-village peer effects rather than the real crop performance. / Ph. D.

No description available.

No description available.

On farm variety demonstrations are conducted by the Cooperative Extension Service to demonstrate the commercial potential of new and established varieties of wheat and barley when grown under various environmental and management conditions. As part of an ongoing variety demonstration program conducted in Yuma County, Arizona for the past 20 years, this study was conducted at TLM Farms on the south Yuma Mesa on extremely coarse-textured sandy soils under sprinkler irrigation. Five hard red spring wheat, six durum and four barley varieties were evaluated under TLM Farms management using 13 ft x 275 ft randomized plots with four replications. Statistically significant yield differences were measured that suggest, when compared to previous and other studies, that variety performance on coarse textured, sprinkler-irrigated soils is different than on finer textured flood-irrigated soils.