Phenotypic Plasticity and the Invasiveness of Three _Taraxacum_ Species

*Background/Question/Methods* 
Many factors have been found to be associated with the success of invasive species. Phenotypic plasticity, the ability of a plant genotype to respond to different environmental conditions by producing different phenotypes, is thought to play an important role plant invasions. In three major experiments, I tested the hypothesis that the invasive _Taraxacum officinale_ (common dandelion) and its non-invasive congener _T. laevigatum_ will exhibit different phenotypic plasticity in germination, growth, and reproduction. I also proposed that their responses to various environments could be used to assess the invasive behavior of a potential crop species: _T. kok-saghyz_.

*Results/Conclusions* 
The results revealed complicated responses of the three species in various environments. The invasive _T. officinale_ showed higher germination in high alternating temperature, and accumulated more biomass than the non-invasive _T. laevigatum_ in favorable greenhouse conditions. Surprisingly, _T. laevigatum_ germinated better than _T. officinale_ in other stressful environments (dark, low water potential, long aging period), and also exhibited higher fecundity in favorable greenhouse conditions. In field experiments, however, the performance of _T. officinale_ was overwhelmingly better than _T. laevigatum_, which suffered very high mortality and failed to survive for more than two growing seasons. These results suggest that _T. officinale_ might benefit from its ability to grow, reproduce, and survive in various environments, while _T. laevigatum_ relies on seed reproduction to maintain its population. With the exception of germination, the responses of _T. kok-saghyz_ were more like _T. officinale_ than _T. laevigatum_, which suggested that this species has some potential to behave as a weed

Improving Food Security in East Africa Through the East African Vegetable Crop Integrated Rest Management (IPM) Innovation Lab (EAVCIPLM-IL)

IMPACT. 1: The EAVCIPM-IL will build the capacity of local host country institutions and communities to implement IPM research and technology transfer programs using participatory agricultural research practices and on-farm research. -- 2. The EAVCIPM-IL will develop and disseminate improved IPM technologies to local farmers that reduce crop losses due to pests, reduce pesticide use, and enhance agricultural productivity and farmer income. -- 3. The EAVCIPM-IL will develop policy recommendations that will enhance the capacity of host country institutions to develop and implement effective IPM research and locally-adapted, gender-appropriate, IPM technology transfer programs.OSU PARTNERS: College of Food, Agricultural, and Environmental Sciences: Office of International Programs in Agriculture; Department of Horticulture and Crop Science; Department of Plant Pathology; Department of Entomology; School of Environment and Natural Resources; Ohio State ExtensionCOMMUNITY PARTNERS: United States: Primary: U.S. Agency for International Development (USAID); Virginia Tech University; University of California, Davis; Secondary: Sustainable Intensification Innovation Lab at Kansas State University; International Primary: Sokoine University of Agriculture - Tanzania; University of Hawassa – Ethiopia; Kenya Agricultural and Livestock Research Organization (KALRO) – Kenya; Mikocheni Agriculture Research Institute – Tanzania; International Institute for Tropical Agriculture (IITA) – Tanzania; Secondary: Real IPM Company –Kenya; Seeds of Expertise for the Vegetable Sector of Africa (SEVIA) - TanzaniaPRIMARY CONTACT: John Cardina ([email protected]); Mark Erbaugh ([email protected])The Ohio State-led East African Vegetable Crop IPM Innovation Lab aims to develop, implement, and scale-up IPM technologies for selected vegetable crops in Feed the Future (FtF) priority areas in Tanzania, Ethiopia and Kenya. The overall goal of this USAID-funded project is to build the capacity of host country institutions to implement effective IPM research and locally-adapted, gender-appropriate technology transfer programs that increase environmental benefits, farm productivity, and incomes, and inform national and regional policy

Seed Burial Physical Environment Explains Departures from Regional Hydrothermal Model of Giant Ragweed (Ambrosia trifida) Seedling Emergence in U.S. Midwest

Robust predictions of weed seedling emergence from the soil seedbank are needed to aid weed management. A common seed accession (Illinois) of giant ragweed was buried in replicate experimental gardens over 18 site years in Illinois, Michigan, Kansas, Nebraska, Ohio, and South Dakota to examine the importance of site and climate variability by year on seedling emergence. In a nonlinear mixed-effects modeling approach, we used a flexible sigmoidal function (Weibull) to model giant ragweed cumulative seedling emergence in relation to hydrothermal time accumulated in each site-year. An iterative search method across a range of base temperature (Tb ) and base and ceiling soil matric potentials (ψb and ψc) for accumulation of hydrothermal time identified optima (Tb = 4.4 C, ψ b = −2,500 kPa, ψ c = 0 kPa) that resulted in a parsimonious regional model. Deviations between the fits for individual site-years and the fixed effects regional model were characterized by a negative relationship between random effects for the shape parameter lrc (natural log of the rate constant, indicating the speed at which emergence progressed) and thermal time (base 10 C) during the seed burial period October through March (r = −0.51, P = 0.03). One possible implication of this result is that cold winter temperatures are required to break dormancy in giant ragweed seeds. By taking advantage of advances in statistical computing approaches, development of robust regional models now is possible for explaining arable weed seedling emergence progress across wide regions

Chloroplast genome resources and molecular markers differentiate rubber dandelion species from weedy relatives

Rubisco large subunit genes (rbcL) from the Asteraceae. (DOCX 29 kb

Implications of Climate Change for Agricultural Pest Management

Termination ReportThe University Archives has determined that this item is of continuing value to OSU's history.The thermal requirements of crops and insect pests differ significantly; their differential thermal requirements will govern how climate change impacts pest management needs and practices. To investigate the impact of climate change on pest management and the implications for farming communities, we have connected EPIC, a field-scale crop management model, with a temperature-driven model of insect population development (GILSM). EPIC was used to model the corn and soybean rotation common in the Midwest, and GILSM was programmed to model the growth of nine insect pests of corn and/or soybeans. Output from the model system was input to a geographic information system covering the eight-state corn-belt (Indiana, Illinois, Iowa, Kansas, Kentucky, Missouri, Nebraska and Ohio). The models were driven using GFDL-CM2 climate scenario data developed for the period 1901-2100 as part of NOA and IPCC investigations of global climate change. Over the past 100 years, crop productivity has increased several fold as a result of improved cultivation methods, fertilizers and pesticides, and plant breeding. In order to remove the confounding of changes in technology and possible climate change over the past century and unknown changes to come in the next century, a standard crop production protocol was used from 1901-2100. Using the crop production practices used most commonly in 2000 (the midpoint of the period), EPIC/GILSM was run for four 50 year periods (1901-1950, 1951-2000, 2001-2050 and 2051-2100) and the changes in crop yield and insect abundance were examined between periods. Nine insect pests found throughout the region were modeled to examine the range of likely responses of insect pests to climate change and the possible change in crop protection needs over the next 100 years. As expected, the model predicted little or no change between the first and second periods. For most species, change was maximum in the third period and less during the fourth period. In every case the isoclines for pest population density and crop productivity moved northwards, but at different rates, resulting in the isoclines for crop damage increasing as they moved northward. In two cases the pest abundance declined locally even as productivity increased, resulting in a net increase in productivity. No allowance was made for changes in agronomic practices or improvements in breeding pest resistance, both of which have helped to improve productivity over the past century.SEEDS-The OARDC Research Enhancement Competitive Grants Program: Interdisciplinary Team Research Competitio

Weed Seedbanks of the U.S. Corn Belt: Magnitude, Variation, Emergence, and Application

Seedbanks and seedling emergence of annual weeds were examined in arable fields at eight locations in the Corn Belt. Seed densities were estimated by direct seed extraction from each of several soil cores in each sampled plot. Average total seedbank densities ranged from 600 to 162 000 viable seed m⁻² among locations. Coefficients of variation (CV) typically exceeded 50%. CV for seed densities of individual species usually exceeded 100%, indicating strongly aggregated distributions. CV were lower for species with dense seed populations than those with sparse seed populations. Variance of total seedbank densities was unstable when \u3c 10 cores were examined per plot, but stabilized at all locations when ≥ 15 cores were analyzed, despite a 12-fold difference in plot size and 270-fold difference in seed density among locations. Percentage viable seed that emerged as seedlings in field plots ranged from \u3c 1% for yellow rocket to 30% for giant foxtail. Redroot pigweed and common lambsquarters were the most frequently encountered species. Emergence percentages of these species were related inversely to rainfall or air temperatures in April or May, presumably because anoxia and/or high temperatures induced secondary dormancy in nondormant seed. From 50 to 90% of total seed in the seedbank were dead. This information can be employed by bioeconomic weed management models, which currently use coarse estimates of emergence percentages to customize recommendations for weed control

Local Conditions, Not Regional Gradients, Drive Demographic Variation of Giant Ragweed (Ambrosia trifida) and Common Sunflower (Helianthus annuus) Across Northern U.S. Maize Belt

Knowledge of environmental factors influencing demography of weed species will improve understanding of current and future weed invasions. The objective of this study was to quantify regional-scale variation in vital rates of giant ragweed and common sunflower. To accomplish this objective, a common field experiment was conducted across seven sites between 2006 and 2008 throughout the north central U.S. maize belt. Demographic parameters of both weed species were measured in intra- and interspecific competitive environments, and environmental data were collected within site-years. Site was the strongest predictor of belowground vital rates (summer and winter seed survival and seedling recruitment), indicating sensitivity to local abiotic conditions. However, biotic factors influenced aboveground vital rates (seedling survival and fecundity). Partial least squares regression (PLSR) indicated that demography of both species was most strongly influenced by thermal time and precipitation. The first PLSR components, both characterized by thermal time, explained 63.2% and 77.0% of variation in the demography of giant ragweed and common sunflower, respectively; the second PLSR components, both characterized by precipitation, explained 18.3% and 8.5% of variation, respectively. The influence of temperature and precipitation is important in understanding the population dynamics and potential distribution of these species in response to climate change

Weed Seed Bank Emergence across the Corn Belt

Field experiments, conducted from 1991 to 1994, generated information on weed seedbank emergence for 22 site-years from Ohio to Colorado and Minnesota to Missouri. Early spring seedbank densities were estimated through direct extraction of viable seeds from soil cores. Emerged seedlings were recorded periodically, as were daily values for air and soil temperature, and precipitation. Percentages of weed seedbanks that emerged as seedlings were calculated from seedbank and seedling data for each species, and relationships between seedbank emergence and microclimatic variables were sought. Fifteen species were found in 3 or more site-years. Average emergence percentages (and coefficients of variation) of these species were as follows: giant foxtail, 31.2 (84%); velvetleaf, 28.2 (66); kochia, 25.7 (79); Pennsylvania smartweed, 25.1 (65); common purslane, 15.4 (135); common ragweed, 15.0 (110); green foxtail, 8.5 (72); wild proso millet, 6.6 (104); hairy nightshade, 5.2 (62); common sunflower, 5.0 (26); yellow foxtail, 3.4 (67); pigweed species, 3.3 (103); common lambsquarters, 2.7 (111); wild buckwheat, 2.5 (63), and prostrate knotweed, 0.6 (79). Variation among site-years, for some species, could be attributed to microclimate variables thought to induce secondary dormancy in spring. For example, total seasonal emergence percentage of giant foxtail was related positively to the 1st date at which average daily soil temperature at 5 to 10 cm soil depth reached 16 C. Thus, if soil warmed before mid April, secondary dormancy was induced and few seedlings emerged, whereas many seedlings emerged if soil remained cool until June