Using Portfolio Theory to Enhance Wheat Yield Stability in Low-Income Nations: An Application in the Yaqui Valley of Northwestern Mexico

This study applies portfolio theory to wheat varietal selection decisions in order to find risk-minimizing outcomes while holding historical yields constant. Potential correlation across wheat cultivar yields increases the complexity of cultivar selection decisions, with gains in one attribute (yield potential) often associated with losses in another (yield stability). Using location-specific empirical data, portfolio theory can provide producers in low-income countries a tool for developing a recommended portfolio of varieties given a desired risk-aversion level. Based on data from Mexico’s Yaqui Valley, results suggest that sowing a portfolio of wheat varieties could have lowered yield variance by 22% to 33% in Northwest Mexico.optimal variety selection, portfolio analysis, wheat, Crop Production/Industries,

The Impact of the CIMMYT Wheat Breeding Program on Wheat Yields in Mexico's Yaqui Valley, 1990-2002: Implications for the Future of Public Wheat Breeding

CIMMYT has invested a large and significant amount of public expenditures in wheat breeding research each year for several decades. Estimates of the impact of the wheat breeding program on wheat yield increases provides information to scientists, administrators, and policy makers regarding the efficacy and the rate of return to these investments, providing important information for future funding decisions. Using CIMMYT test plot data from the Yaqui Valley in Mexico from 1990-2002, regression results indicate that the release of modern CIMMYT varieties has contributed approximately 53.77 kg/ha to yield annually. The growing conditions of the experiment fields located in the Yaqui Valley approximate 40% of the developing world's wheat growing conditions. A rough estimate of the gains attributed to CIMMYT's wheat breeding program on a global scale is 304 million (2002) USD annually during the period 1990-2002. CIMMYT's total wheat breeding cost in 2002 was approximately 6 million dollars, making the benefit cost ratio approximately 50 to 1.Crop Production/Industries,

The Impact of the CIMMYT Wheat Breeding Program on Mexican Wheat Producers and Consumers: An Economic Welfare Analysis

The increase in wheat production in Mexico’s Yaqui Valley from the breeding and development of semidwarf wheat varieties released by CIMMYT is quantified for the period 1990-2002, and the costs and benefits of the wheat research program are estimated and evaluated using a two-region model of the world wheat market.Public wheat breeding, benefit/cost analysis, agricultural research, wheat varieties, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

The Impact of the Kansas Wheat Breeding Program on Wheat Yields, 1911–2006

This paper quantifies advances of the Kansas Agricultural Experiment Station (KAES) wheat breeding program for two time periods: (1) 1911 to 2006 and (2) 1977 to 2006. Using multiple regression, increases in yields of wheat varieties grown in Kansas are quantified, holding growing conditions and other improvements in productivity constant. Differences in KAES variety yields and those released by other public and private breeders are quantified. During the ‘‘new age’’ of wheat breeding (1977–2006), wheat breeding alone is found to have increased yields by 6.182 bushels per acre, or an average increase of 0.206 bushels per year.wheat yield, public wheat breeding, multiplicative heteroscedasticity, economic impact of technological change, Agribusiness, Farm Management, O13, Q16,

Enhancing Farm Profitability through Portfolio Analysis: The Case of Spatial Rice Variety Selection

This study applies portfolio theory to rice varietal selection decisions to find profit maximizing and risk minimizing outcomes. Results based on data from six counties in the Arkansas Delta for the period 1999–2006 suggest that sowing a portfolio of rice varieties could have increased profits from 3 to 26% (depending on the location) for rice producers in the Arkansas Delta. The major implication of this research is that data and statistical tools are available for rice producers to improve the choice of rice varieties to plant each year in specific locations. Specifically, there are large potential gains from combining varieties that are characterized by inverse yield responses to growing conditions such as drought, pest infestation, or the presence of a specific disease.optimal variety selection, portfolio analysis, rice, Agribusiness, Crop Production/Industries, Farm Management, Production Economics, Productivity Analysis, Risk and Uncertainty, G11, Q15, Q12,

Enhancing Farm Profitability through Portfolio Analysis: The Case of Spatial Rice Variety Selection.

The objectives of this paper is to use the large depth of existing literature on portfolio theory and apply it to rice varietal selection for 6 counties in the Arkansas Delta. Results based on 1999-2006 data suggests that combining available varieties using portfolio theory could have increased profits from 3 to 26% (dependent on location) in the Arkansas Delta. The major implication of this research is that data and statistical tools are available to improve the choice of rice varieties to plant each year in specific locations within Arkansas. Specifically, there are large potential gains from combining varieties that are characterized by inverse yield responses to growing conditions such as drought, pest infestation, or the presence of a specific disease.Rice, portfolio analysis, optimal variety selection, risk analysis., Production Economics, D81, Q16, Q12,

Altered antioxidant and trace-element status in adolescent female gymnasts

Physical activity is associated with the generation of reactive oxygen species and may lead to decreased levels of plasma antioxidants and increased oxidant stress. Some studies have reported that antioxidant supplements can reduce the consequences of oxidative stress during exercise. In this study the authors aimed to assess the chronic effects of exercise on endogenous serum antioxidant enzyme concentrations. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity were measured in adolescent girls who were either competitive gymnasts or sedentary controls. The relationship between age, body-mass index, dietary intake, trace-element status, and serum GPx and SOD was determined. The participants in the study were part of a 3-yr longitudinal investigation of exercise and peak bone-mass development in 38 competitive gymnasts and 40 healthy sedentary adolescent females 8-17 yr of age. Serum GPx and SOD were measured using colorimetric assays, and trace elements were measured using inductively coupled plasma mass spectrometry. The mean serum GPx concentrations were significantly higher in the gymnasts than in the sedentary females (157 ± 11.1 vs. 126 ± 8.8 U/ml, p < .05). In contrast, serum SOD concentrations were significantly lower in the gymnasts than in the sedentary group (7.24 ± 2.6 vs. 8.57 ± 2.3 U/ml, p < .05). Serum selenium, zinc, and copper were higher in the physically active group than in the inactive group (0.89 ± 0.03, 10.86 ± 0.39, 14.50 ± 0.50 vs. 0.81 ± 0.03, 10.32 ± 0.28, and 14.38 ± 0.42 µmol/L, respectively), although only serum selenium reached statistical significance (p < .05). The findings show that young female gymnasts have an altered antioxidant enzyme profile compared with their less physically active peer

Heterogeneous effects of warming and drought on selected wheat variety yields

Climate change is likely to significantly impact agricultural production in the Great Plains region of the Central United States. This study estimated the impact of changes in temperature and precipitation on wheat (triticum aestivum) variety yield distributions using the moment-based maximum entropy (MBME) model. This approach allows for quantification of potential weather impacts on the yield distribution, and allows these effects to vary across varieties. The unique data set matches wheat variety trial data for 1985 to 2011 with weather data from the exact trial site for 11 locations throughout Kansas. Ten widely-planted varieties with a range of biotic and abiotic characteristics were included for comparison. Weather scenarios were simulated for baseline, increased temperature (one-degree Celsius warming), decreased precipitation (tenth-percentile rainfall outcome), and a combination warming and drought scenario. Warming resulted in an 11 % yield reduction, drought a 22 % reduction, and warming and drought a cumulative 33 % reduction. These effects vary across varieties. Alternative measures of yield risk (e.g. yield variance and coefficient of variation) were also constructed under each scenario and a similar pattern of heterogeneous impacts emerges. The key findings are that (i) exposure to warming and drought lead to mean yield reductions coupled with increased yield risk for all varieties, and (ii) newer (post 2005) seed varieties have a yield advantage over older varieties, however this advantage is reduced under warming and drought conditions