Agronomy and Crop Sciences Commons^™

Gata-Family Transcription Factors In Magnaporthe Oryzae, Cristian F. Quispe

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The filamentous fungus, Magnaporthe oryzae, responsible for blast rice disease, destroys around 10-30% of the rice crop annually. Infection begins when the specialized infection structure, the appressorium, generates enormous internal turgor pressure through the accumulation of glycerol. This turgor acts on a penetration peg emerging at the base of the cell, causing it to breach the leaf surface allowing its infection.

The enzyme trehalose-6- phosphate synthase (Tps1) is a central regulator of the transition from appressorium development to infectious hyphal growth. In the first chapter we show that initiation of rice blast disease requires a regulatory mechanism involving an …

Transpiration-Use Efficiency Coefficient Of Seven Weed Species As Affected By Fraction Of Transpirable Soil Water And Growth Stage, Venkatarao Mannam

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Transpiration-use efficiency coefficient (Kc) describes the amount of biomass produced per unit transpiration at a given vapor pressure deficit. A series of greenhouse experiments were conducted to determine the K_c values of seven weed species and to measure how K_c values were affected by fraction of transpirable soil water (FTSW) level and plant growth stage. Experiments were conducted using a factorial design with 4 levels of water stress (0.3, 0.4, 0.7, and 1.0 FTSW) and two harvest times (first bloom and seed maturity). After plants attained a predetermined size, each plant was sealed at the base using a …

Herbicide-Resistant Risk Assessment: Response Of Common Nebraska Weeds To Dicamba Dose, Roberto J. Crespo

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Dicamba-resistant soybeans are being developed to provide an additional herbicide mechanism of action that can be used in soybean, and to provide a tool to help manage or mitigate the evolution of other herbicide-resistant weed populations. The objectives of this thesis were to assess the risk of common Nebraska weeds developing resistance to dicamba, quantify baseline dose-response to dicamba of high-risk weed species, and survey the variability in dicamba dose-response among populations of those species. Twenty-five weed scientists were asked to estimate the risk likelihood of ten weed species evolving resistance to dicamba following the commercialization of dicamba-resistant soybean. Palmer …

Biology, Systematics, Phylogenetic Analysis And Dna Character-Based Species Diagnosis Of The False Root-Knot Nematode Nacobbus Aberrans (Thorne, 1935) Thorne & Allen 1944 (Nemata:Pratylenchidae), Angel Ramirez-Suarez

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The False Root-Knot nematode Nacobbus aberrans is a plant parasitic nematode that causes yield losses in several crops and plant protection agencies have established regulations to prevent infestations from spreading to new agricultural areas. The taxonomic status of the nematode has been the subject of controversy due to wide degree of variation exhibited by the species. This variability has led to the suggestion that N. aberrans is actually a species complex rather than a single species. In order to test this hypothesis, we compared twelve N. aberrans populations, which include isolates from western Nebraska, two distinct regions of Mexico and …

Twin-Row Production And Optimal Plant Population For Modern Maize Hybrids, Mitchell J. Novacek

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Maize (Zea mays L.) is widely grown for food, feed, and fuel, and optimal yield will be required to meet increasing demand due to world population growth and increased biofuel usage. This requires matching of the best maize hybrids with optimal plant population and spacing. Modern maize hybrids have increased “crowding stress” tolerance, and Bt (Bacillus thuringiensis) hybrids now resist European corn borer and corn rootworm which has created interest in altering row configuration and increasing plant population.

Three Bt hybrids were evaluated from 2009 to 2010 near Mead, NE at target populations from 69136 to 106173 …