K-State Research and Extension Staff Research and Publications

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Open Access
Transcriptome analysis in switchgrass discloses ecotype difference in photosynthetic efficiency
Serba, Desalegn D.; Uppalapati, S. R.; Krom, N.; Mukherjee, S.; Tang, Y. H.; Mysore, K. S.; Saha, M. C.; ddserba; Serba, Desalegn D.
Background: Switchgrass, a warm-season perennial grass studied as a potential dedicated biofuel feedstock, is classified into two main taxa - lowland and upland ecotypes - that differ in morphology and habitat of adaptation. But there is limited information on their inherent molecular variations. Results: Transcriptome analysis by RNA-sequencing (RNA-Seq) was conducted for lowland and upland ecotypes to document their gene expression variations. Mapping of transcriptome to the reference genome (Panicum virgatum v1. 1) revealed that the lowland and upland ecotypes differ substantially in sets of genes transcribed as well as levels of expression. Differential gene expression analysis exhibited that transcripts related to photosynthesis efficiency and development and photosystem reaction center subunits were upregulated in lowlands compared to upland genotype. On the other hand, catalase isozymes, helix-loop-helix, late embryogenesis abundant group I, photosulfokinases, and S-adenosyl methionine synthase gene transcripts were upregulated in the upland compared to the lowlands. At >= 100x coverage and >= 5% minor allele frequency, a total of 25,894 and 16,979 single nucleotide polymorphism (SNP) markers were discovered for VS16 (upland ecotype) and K5 (lowland ecotype) against the reference genome. The allele combination of the SNPs revealed that the transition mutations are more prevalent than the transversion mutations. Conclusions: The gene ontology (GO) analysis of the transcriptome indicated lowland ecotype had significantly higher representation for cellular components associated with photosynthesis machinery controlling carbon fixation. In addition, using the transcriptome data, SNP markers were detected, which were distributed throughout the genome. The differentially expressed genes and SNP markers detected in this study would be useful resources for traits mapping and gene transfer across ecotypes in switchgrass breeding for increased biomass yield for biofuel conversion.
Open Access
Genomic Tools in Pearl Millet Breeding for Drought Tolerance: Status and Prospects
Serba, Desalegn D.; Yadav, R. S.; ddserba; Serba, Desalegn
Pearl millet [Penisetum glaucum (L) R. Br.] is a hardy cereal crop grown in the arid and semiarid tropics where other cereals are likely to fail to produce economic yields due to drought and heat stresses. Adaptive evolution, a form of natural selection shaped the crop to grow and yield satisfactorily with limited moisture supply or under periodic water deficits in the soil. Drought tolerance is a complex polygenic trait that various morphological and physiological responses are controlled by 100s of genes and significantly influenced by the environment. The development of genomic tools will have enormous potential to improve the efficiency and precision of conventional breeding. The apparent independent domestication events, highly outcrossing nature and traditional cultivation in stressful environments maintained tremendous amount of polymorphism in pearl millet. This high polymorphism of the crop has been revealed by genome mapping that in turn stimulated the mapping and tagging of genomic regions controlling important traits such as drought tolerance. Mapping of a major QTL for terminal drought tolerance in independent populations envisaged the prospect for the development of molecular breeding in pearl millet. To accelerate genetic gains for drought tolerance targeted novel approaches such as establishment of marker-trait associations, genomic selection tools, genome sequence and genotyping-by-sequencing are still limited. Development and application of high throughput genomic tools need to be intensified to improve the breeding efficiency of pearl millet to minimize the impact of climate change on its production.
Open Access
Comparison of Differentially Corrected GPS Sources for Support of Site-Specific Management in Agriculture
(Kansas State University. Agricultural Experiment Station and Cooperative Extension Service. Ag. Res. Center, Hays, Kansas) Coyne, P.I.; Casey, S.J.; Milliken, G.A.
Chapter 1: Static Test. Static assessment of the relative performance of three differential correction sources for global positioning systems (GPS) available to users of precision agriculture technology in the Hays, KS area. Chapter 2: Dynamic Test. Dynamic assessment of three differential correction sources for global positioning systems (GPS) to determine suitability for precision agriculture applications in the vicinity of Hays, KS.
Open Access
2000 Report on Grains Research and Educational Programs
(Kansas State University. Agricultural Experiment Station and Cooperative Extension Service.) Kansas State University, Agricultural Experiment Station and Cooperative Extension Service.
We are pleased to provide this update on research and educational activities made possible with checkoff funds from the Kansas Corn, Grain Sorghum, Soybean, and Wheat Commissions. The Commissions provided $2,223,926 in support in fiscal year 1999 — Corn, $399,266; Grain Sorghum, $485,678; Soybean, $630,804; and Wheat, $708,178. These funds have been utilized by teams of research scientists and extension specialists to address issues that are important to our clientele. Agriculture is becoming more complex. Kansas producers depend on the Kansas Agricultural Experiment Station and Cooperative Extension Service to provide them with information that will improve their operations in order to maintain a competitive edge in an ever-changing global market. It is vital that K-State Research and Extension continues to serve Kansas producers and it is more important than ever that we supplement our limited state and federal funds with industry support. Funding from the Commodity Commissions is very much appreciated, both for the above reasons and because our association with them helps us to focus our efforts on issues important to producers. Findings reported in this publication span cropping systems, water management and quality, pest management, breeding for disease and pest resistance, genetic studies to improve quality and performance, alternative uses for end products, processing, and marketing. Because all projects have the common aim of answering real problems, Kansas producers will benefit directly. The results are already being communicated to various audiences through scientific journals, seminars, workshops, and field days, and they are being incorporated into K-State Research and Extension educational efforts.
Open Access
Effects of irrigation amount and timing on alfalfa nutritive value
Holman, Johnathon; Min, Doohong; Klocke, Norman; Kisekka, Isaya; Currie, Randall; jholman; dmin; ikisekka; rscurrie; Holman, Johnathon; Min, Doohong; Kisekka, Isaya; Currie, Randall
Most hay producers in southwest Kansas irrigate their alfalfa (Medicago sativa L.) because precipitation is insufficient for profitable rainfed production. However, water supplies in the central Great Plains are dwindling, particularly in the central and southern Ogallala Aquifer region. Irrigating many field crops in this region, including alfalfa, is therefore becoming a challenge. We determined the effects of irrigation quantity and timing on alfalfa forage nutritive value during a five-year field study of alfalfa in southwest Kansas. Nutritive value was quantified in the form of crude protein, acid detergent fiber, neutral detergent fiber, total digestible nutrients, and relative feed value. In general, applying the highest amount of irrigation (610 mm during the growing season) resulted in the lowest forage nutritive value compared to lower amounts of irrigation (0, 200, and 380 mm irrigation). Nutritive value concentrations (g kg-1) under full irrigation averaged 211 for crude protein, 316 for acid detergent fiber, and 422 for neutral detergent fiber, while concentrations (g kg-1) in rainfed production averaged 225 for crude protein, 247 for acid detergent fiber, and 370 for neutral detergent fiber. Alfalfa nutritive value was not affected whether the same amount of irrigation water was applied either before green-up and between each cutting, or before green-up and between all cuttings except between cuttings 2 and 3. However, there was a tendency for lower forage nutritive value at the fourth cutting when irrigation was withheld between cuttings 2 and 3, and that saved water was added to the amount of irrigation applied to the fourth cutting. When averaged over irrigation treatments, alfalfa nutritive value was lower from the first and second cuttings than from the third and fourth cuttings. Annual yields, averaged over years, declined from 1.53 kg m-2 with 610 mm of irrigation to 0.43 kg m-2 for rainfed production. Annual yields were the same when irrigation was distributed over the growing season or withheld between the second and third cuttings. Irrigation amounts less than full crop requirement resulted in a 13% higher dollar value product based on relative feed value, but decreasing irrigation from 610 to 380 mm reduced yield by 19%. © 2016 American Society of Agricultural and Biological Engineers.
Open Access
Emerging technologies for sustainable irrigation: Selected papers from the 2015 ASABE and IA irrigation symposium
Lamm, Freddie R.; Stone, K. C.; Dukes, M. D.; Howell, T. A., Sr.; Robbins, J. W. D., Jr.; Mecham, B. Q.; flamm
This article is an introduction to the "Emerging Technologies in Sustainable Irrigation: A Tribute to the Career of Terry Howell, Sr." Special Collection in this issue of Transactions of the ASABE and the next issue of Applied Engineering in Agriculture, consisting of 16 articles selected from 62 papers and presentations at the joint irrigation symposium of ASABE and the Irrigation Association (IA), which was held in November 2015 in Long Beach, California. The joint cooperation on irrigation symposia between ASABE and IA can be traced back to 1970, and this time period roughly coincides with the career of Dr. Howell. The cooperative symposia have offered an important venue for discussion of emerging technologies that can lead to sustainable irrigation. This most recent symposium is another point on the continuum. The articles in this Special Collection address three major topic areas: evapotranspiration measurement and determination, irrigation systems and their associated technologies, and irrigation scheduling and water management. While these 16 articles are not inclusive of all the important advances in irrigation since 1970, they illustrate that continued progress occurs by combining a recognition of the current status with the postulation of new ideas to advance our understanding of irrigation engineering and science. The global food and water challenges will require continued progress from our portion of the scientific community. This article serves to introduce and provide a brief summary of the Special Collection. © 2016 American Society of Agricultural and Biological Engineers.
Open Access
Cotton, tomato, corn, and onion production with subsurface drip irrigation: A review
Lamm, Freddie R.; flamm
The usage of subsurface drip irrigation (SDI) has increased by 89% in the U.S. during the past ten years according to USDA-NASS estimates, and over 93% of the SDI land area is located in just ten states. Combining public entity and private industry perceptions of SDI in these ten states, the major crops were tentatively identified as cotton, processing tomato, field corn, and onion. An extensive literature review of SDI usage for these four crops was performed concentrating on irrigation system comparisons, water and/or nutrient management, and SDI system design criteria. Although many crops potentially can be grown with SDI, the results presented here may be a relatively representative crosssection of the various opportunities and challenges of SDI for general crop production. © 2016 American Society of Agricultural and Biological Engineers.
Open Access
Greenhouse vegetable production: Hydroponic Systems
Marr, Charles W.
Many people think of hydroponics as growing plants in water, but hydroponic production actually is defined as growing plants without soil. This production system may use a wide variety of organic and inorganic materials. The nutrient solution, rather than the media in which the plants are growing, always supplies most of the plant nutrient requirements. This method of growing has also been referred to as nutrient-solution culture, soilless culture, water culture, gravel culture and nutriculture.
Open Access
Crop Species Diversity Changes in the United States: 1978-2012
Aguilar, Jonathan P.; Gramig, G. G.; Hendrickson, J. R.; Archer, D. W.; Forcella, F.; Liebig, M. A.; jaguilar
Anecdotal accounts regarding reduced US cropping system diversity have raised concerns about negative impacts of increasingly homogeneous cropping systems. However, formal analyses to document such changes are lacking. Using US Agriculture Census data, which are collected every five years, we quantified crop species diversity from 1978 to 2012, for the contiguous US on a county level basis. We used Shannon diversity indices expressed as effective number of crop species (ENCS) to quantify crop diversity. We then evaluated changes in county-level crop diversity both nationally and for each of the eight Farm Resource Regions developed by the National Agriculture Statistics Service. During the 34 years we considered in our analyses, both national and regional ENCS changed. Nationally, crop diversity was lower in 2012 than in 1978. However, our analyses also revealed interesting trends between and within different Resource Regions. Overall, the Heartland Resource Region had the lowest crop diversity whereas the Fruitful Rim and Northern Crescent had the highest. In contrast to the other Resource Regions, the Mississippi Portal had significantly higher crop diversity in 2012 than in 1978. Also, within regions there were differences between counties in crop diversity. Spatial autocorrelation revealed clustering of low and high ENCS and this trend became stronger over time. These results show that, nationally counties have been clustering into areas of either low diversity or high diversity. Moreover, a significant trend of more counties shifting to lower rather than to higher crop diversity was detected. The clustering and shifting demonstrates a trend toward crop diversity loss and attendant homogenization of agricultural production systems, which could have far-reaching consequences for provision of ecosystem system services associated with agricultural systems as well as food system sustainability.
Open Access
Grain sorghum response and Palmer amaranth control with postemergence application of fluthiacet-methyl
(2015-05-05) Reddy, Seshadri S.; Stahlman, Phillip W.; Geier, Patrick W.; Bean, Brent W.; Dozier, Tim; stahlman; pgeier
Palmer amaranth is a problematic weed in grain sorghum production in central United States. Due to limited herbicide options available and ever increasing herbicide-resistant weed species, there is a demand for new mode-of-action herbicides for use in grain sorghum. Fluthiacet-methyl is a relatively new active ingredient that inhibits the enzyme protoporphyrinogen oxidase in target plants. Field studies were conducted at three sites in central United States in 2010 and 2011 to evaluate crop response and Palmer amaranth control with postemergence application of fluthiacet-methyl in grain sorghum. Treatments included fluthiacet-methyl at 4.8 and 7.2 g active ingredient (a.i.) haˉ¹ alone and tank-mixed with 2,4-D amine at 260 g acid equivalent (a.e.) haˉ¹ or atrazine at 840 g a.i. haˉ¹. Carfentrazone at 8.8 g a.i. haˉ¹, atrazine at 840 g haˉ¹, and a non-treated control were also included. Fluthiacet-methyl treatments caused 9–38% crop injury at 4 ± 1 days after treatment. Tank-mixing atrazine with fluthiacet-methyl seldom affected crop injury, while mixing 2,4-D with fluthiacet-methyl often reduced crop injury. Generally, injury caused by fluthiacet-methyl alone or in combination with atrazine or 2,4-D disappeared within 3 weeks after treatment. Grain yields were reduced in one trial, when 2,4-D mixed with 4.8 or 7.2 g haˉ¹ of fluthiacet-methyl caused 18% and 13% plant lodging and 24% and 14% grain yield loss, respectively. Across site-years, fluthiacet-methyl alone at 4.8 or 7.2 g haˉ¹ provided 55–95% control of Palmer amaranth. Greater Palmer amaranth control (≥75%) with fluthiacet-methyl alone was achieved when weeds were small or density was low at the time of spraying. Tank-mixing atrazine with fluthiacet-methyl increased Palmer amaranth control and sorghum yields considerably. Tank-mixing 2,4-D with fluthiacet-methyl also increased Palmer amaranth control, but to lesser extent and less consistently than with atrazine. Results indicated that fluthiacet-methyl has potential for use in grain sorghum to combat weeds resistant to acetolactase synthase-inhibitors, triazines, and synthetic auxin herbicides. Tank-mixing atrazine or 2,4-D with fluthiacet-methyl is desirable for effective Palmer amaranth control.
Open Access
Identification of windbreaks in Kansas using object-based image analysis, GIS techniques and field survey
(2015-03-18) Ghimire, Kabita; Dulin, Mike W.; Atchison, Robert L.; Goodin, Douglas G.; Hutchinson, J. M. Shawn; atchison; dgoodin; shutch
Windbreaks are valuable resources in conserving soils and providing crop protection in Great Plains states in the US. Currently, Kansas has no up-to date inventory of windbreaks. The goal of this project was to assist foresters with future windbreak renovation planning and reporting, by outlining a series of semi-automated digital image processing methods that rapidly identify windbreak locations. There were two specific objectives of this research. First, to develop semi-automated methods to identify the location of windbreaks in Kansas, this can be applied to other regions in Kansas and the Great Plains. We used a remote sensing technique known as object-based image analysis (OBIA) to classify windbreaks visible in the color aerial imagery of National Agriculture Imagery Program. We also combined GIS techniques and field survey to complement OBIA in generating windbreak inventory. The techniques successfully located more than 4500, windbreaks covering an approximate area of 2500, hectares in 14 Kansas counties. The second purpose of this research is to determine how well the results of the automated classification schemes match with other available windbreak data and the selected sample collected in the field. The overall accuracy of OBIA method was 58.97 %. OBIA combined with ‘heads up’ digitizing and field survey method yielded better result in identifying and locating windbreaks in the studied counties with overall accuracy of 96 %.
Open Access
Dynamic factor analysis of surface water management impacts on soil and bedrock water contents in Southern Florida Lowlands
(2015-03-06) Kisekka, Isaya; Migliaccio, K. W.; Muñoz-Carpena, R.; Schaffer, B.; Li, Y. C.; ikisekka
As part of the C111 spreader canal project, structural and operational modifications involving incremental raises in canal stage are planned along one of the major canals (i.e., C111) separating Everglades National Park and agricultural production areas to the east of the park. This study used Dynamic Factor Analysis (DFA) as an alternative tool to physically based models to explore the relationship between different hydrologic variables and the effect of proposed changes in surface water management on soil and bedrock water contents in south Florida. To achieve the goal, objectives were to: (1) use DFA to identify the most important factors affecting temporal variation in soil and bedrock water contents, (2) develop a simplified DFA based regression model for predicting soil and bedrock water contents as a function of canal stage and (3) assess the effect of the proposed incremental raises in canal stage on soil and bedrock water contents. DFA revealed that 5 common trends were the minimum required to describe unexplained variation in the 11 time series studied. Introducing canal stage, water table evaporation and net recharge resulted in lower Akaike information criterion (AIC) and higher Nash-Sutcliffe (C[subscript eff]) values. Results indicated that canal stage significantly (t > 2) drives temporal variation in soil and bedrock water contents, which was represented as scaled frequency while net surface recharge was significant in 7 out of the 11 time series analyzed. The effect of water table evaporation was not significant at all sites. Results also indicated that the most important factor influencing temporal variation in soil and bedrock water contents in terms of regression coefficient magnitude was canal stage. Based on DFA results, a simple regression model was developed to predict soil and bedrock water contents at various elevations as a function of canal stage and net recharge. The performance of the simple model ranged from good (C[subscript eff] ranging from 0.56 to 0.74) to poor (C[subscript eff] ranging from 0.10 to 0.15), performance was better at sites with smaller depths to water table (< 1 m) highlighting the effect of micro-topography on soil and bedrock water content dynamics. Assessment of the effect of 6, 9 and 12 cm increases in canal stage using the simple regression model indicated that changes in temporal variation in soil and bedrock water contents were negligible (average<1.0% average change) at 500 to 2000 m from C111 (or low elevations) which may be attributed to the near saturation conditions already occurring at these sites. This study used DFA to explore the relationship between soil and bedrock water dynamics and surface water stage in shallow water table environments. This approach can be applied to any system in which detailed physical modeling would be limited by inadequate information on parameters or processes governing the physical system.
Open Access
Simulating water table response to proposed changes in surface water management in the C-111 agricultural basin of south Florida
(2015-03-06) Kisekka, Isaya; Migliaccio, K. W.; Muñoz-Carpena, R.; Schaffer, B.; Boyer, T. H.; Li, Y.; ikisekka
As part of an effort to restore the hydrology of Everglades National Park (ENP), incremental raises in canal stage are proposed along a major canal draining south Florida called C-111, which separates ENP from agricultural lands. The study purpose was to use monitoring and modeling to investigate the effect of the proposed incremental raises in canal stage on water table elevation in agricultural lands. The objectives were to: (1) develop a MODFLOW based model for simulating groundwater flow within the study area, (2) apply the developed model to determine if the proposed changes in canal stage result in significant changes in water table elevation, root zone saturation or groundwater flooding and (3) assess aquifer response to large rainfall events. Results indicate the developed model was able to reproduce measured water table elevation with an average Nash-Sutcliffe > 0.9 and Root Mean Square Error < 0.05 m. The model predicted that incremental raises in canal stage resulted in significant differences (p < 0.05) in water table elevation. Increases in canal stage of 9 and 12 cm resulted in occasional root zone saturation of low elevation sites. The model was able to mimic the rise and fall of the water table pre and post Tropical Storm Isaac of August 2012. The model also predicted that lowering canal stage at least 48 hours prior to large storm (>2 year return period storm), reduced water table intrusion into the root zone. We conclude that the impact of operational changes in canal stage management on root zone saturation and groundwater flooding depended on micro-topography within the field and depth of storm events. The findings of this study can be used in fine tuning canal stage operations to minimize root zone saturation and groundwater flooding of agricultural fields while maximizing environmental benefits through increased water flow in the natural wetland areas. This study also highlights the benefit of detailed field scale simulations.
Open Access
Modeling soil water dynamics considering measurement uncertainty
(2015-03-06) Kisekka, Isaya; Migliaccio, K. W.; Muñoz-Carpena, R.; Schaffer, B.; Khare, Y.; ikisekka
In shallow water table controlled environments, surface water management impacts groundwater table levels and soil water dynamics. The study goal was to simulate soil water dynamics in response to canal stage raises considering uncertainty in measured soil water content. WAVE (Water and Agrochemicals in the soil, crop and Vadose Environment) was applied to simulate unsaturated flow above a shallow aquifer. Global sensitivity analysis was performed to identify model input factors with greatest influence on predicted soil water content. Nash-Sutcliffe increased and Root Mean Square Error reduced when uncertainties in measured data were considered in goodness-of-fit calculations using measurement probability distributions and probable asymmetric error boundaries; implying that appropriate model performance evaluation should be done using uncertainty ranges instead of single values. Although uncertainty in the experimental measured data limited evaluation of the absolute predictions by the model, WAVE was found a useful exploratory tool for estimating temporal variation in soil water content. Visual analysis of soil water content time series under proposed changes in canal stage management indicated that sites with land surface elevation of less than 2.0 m NGVD29 were predicted to periodically experience saturated conditions in the root zone and shortening of the growing season if canal stage is raised more than 9 cm and maintained at this level. The models developed could be combined with high resolution digital elevation models in future studies to identify areas with the greatest risk of experiencing saturated root zone. The study also highlighted the need to incorporate measurement uncertainty when evaluating performance of unsaturated flow models.
Open Access
Worker injuries involving the interaction of cattle, cattle handlers, and farm structures or equipment
(2015-02-11) Fox, Shannon L.; Ricketts, Mitchell S.; Minton, J. Ernest; orcid.org/0000-0002-9150-169X; eminton; sreves
Cattle have been identified as leading sources of injuries to agricultural workers. The present study focused on worker injuries that involved the interaction of cattle, cattle handlers, and farm structures or equipment. The goal of the study was to identify opportunities for injury prevention. We examined 221 reports of injury to cattle handlers from the Consumer Product Safety Commission’s National Electronic Injury Surveillance System (NEISS). Expected interactions led to many of the cattle-handling injuries reported in the NEISS database. In almost 30% of cases, cattle pushed workers into structures such as fences, gates, posts, and walls. In another 16% to 19% of injuries, cattle struck gates and other objects, propelling them at the victims. The present research makes several important contributions to the study of cattle-handling injuries. First, the research supports an increased emphasis on the development of safer gate designs (e.g., gates that are remotely operated or that absorb energy to limit the speed at which they may be propelled by animals). Second, the research suggests a need for additional study of energy-absorbing fence and wall structures. We view these two points to be of significance because gates and associated structures (e.g., posts, fences, and walls) accounted for 45% of the injuries in the dataset, based on the associated injury narrative. Finally, the research identifies a previously unexplored source of agricultural injury data, namely the NEISS database.
Open Access
Effects of Nitrogen and Planting Seed Size on Cotton Growth, Development, and Yield
(2014-12-04) Main, Christopher L.; Barber, L. Tomas; Boman, Randall K.; Chapman, Kent; Dodds, Darrin M.; Duncan, Stewart R.; Edmisten, Keith L.; Horn, Patrick; Jones, Michael A.; Morgan, Gaylon D.; Norton, E. Randall; Osborne, Shane; Whitaker, Jared R.; Nichols, Robert L.; Bronson, Kevin F.; sduncan
A standardized experiment was conducted during 2009 and 2010 at 20 location-years across U.S. cotton (Gossypium hirsutum L.)-producing states to compare the N use requirement of contemporary cotton cultivars based on their planting seed size. Treatments consisted of three cotton varieties with planting seed of different numbers of seed per kg and N rates of 0, 45, 90, and 134 kg ha⁻¹. Soil at each trial location was sampled and tested for nitrate presence. High levels of soil nitrate (>91 N-NO₃⁻kg ha⁻¹) were found in Arizona and western Texas, and soil nitrate in the range of 45 to 73 kg N-NO₃⁻ ha⁻¹ was found at locations in the central United States. Cotton lint yield responded to applied N at 11 of 20 locations. Considering only sites that responded to applied N, highest lint yields were achieved with 112 to 224 kg ha⁻¹of applied plus pre-plant residual soil NO₃—translating to an optimal N requirement of 23 kg ha⁻¹ per 218 kg bale of lint produced. Among the varieties tested those with medium-sized seed produced higher yields in response to N than did larger and smaller seeded varieties. Varieties with larger seed had longer and stronger fibers, higher fiber length uniformity than small seeded varieties and decreased micronaire. Seed protein and oil increased and decreased slightly in response to increasing amounts of soil nitrate plus applied N, respectively.
Open Access
Kinetics of the thermal degradation of patulin in the presence of ascorbic acid
(2014-05-30) Kokkinidou, S.; LaBorde, L. F.; Floros, John D.; floros
Degradation of the mycotoxin patulin between 25 and 85 °C without and with added ascorbic acid was studied, and the effectiveness of linear and nonlinear models for predicting reaction rates was compared. In agreement with previous reports, ascorbic acid significantly increased (P ≤ 0.05) the rate of patulin degradation at all temperatures studied. The data for patulin degradation in the absence of ascorbic acid were adequately modeled using a zero-order linear kinetic model. However, the predictive abilities of zero and higher-order linear models were not adequate to describe the more complex reactions that likely occurred when ascorbic acid was added. In contrast, the nonlinearWeibull model adequately described the patulin-ascorbic acid reaction throughout the temperature range studied. Zero-order rate constants and Weibull scale values for each of the respective reactions followed the Arrhenius law. Activation energies of 58.7 ± 3.9 and 29.6 ± 1.9 kJ mol⁻¹ for the reaction without and with ascorbic acid, respectively, confirmed decreased patulin stability in the presence of ascorbic acid and suggested that the mechanisms for the 2 degradation reactions were different.
Open Access
Transcriptomics of induced defense responses to greenbug aphid feeding in near isogenic wheat lines.
(2014-05-08) Reddy, Srirama Krishna; Weng, Yiqun; Rudd, Jackie C.; Akhunova, Alina R.; Liu, Shuyu; akhunova
The greenbug aphid, Schizaphis graminum (Rondani) is an important cereal pest, periodically threatening wheat yields in the United States and around the world. The single dominant gene, Gb3-based resistance is highly durable against prevailing greenbug biotypes under field conditions; however, the molecular mechanisms of Gb3-mediated defense responses remain unknown. We used Affymetrix GeneChip Wheat Genome Arrays to investigate the transcriptomics of host defense responses upon greenbug feeding on resistant and susceptible bulks (RB and SB, respectively) derived from two near-isogenic lines. The study identified 692 differentially expressed transcripts and further functional classification recognized 122 transcripts that are putatively associated to mediate biotic stress responses. In RB, Gb3-mediated resistance resulted in activation of transmembrane receptor kinases and signaling-related transcripts involved in early signal transduction cascades. While in SB, transcripts mediating final steps in jasmonic acid biosynthesis, redox homeostasis, peroxidases, glutathione S-transferases, and notable defense-related secondary metabolites were induced. Also transcripts involved in callose and cell wall decomposition were elevated SB, plausibly to facilitate uninterrupted feeding operations. These results suggest that Gb3-mediated resistance is less vulnerable to cell wall modification and the data provides ample tools for further investigations concerning R gene based model of resistance.
Open Access
Tolerance of foxtail, proso and pearl millets to saflufenacil
(2014-04-25) Reddy, Seshadri S.; Stahlman, Phillip W.; Geier, Patrick W.; Charvat, Leo D.; Wilson, Robert G.; Moechnig, Michael J.; stahlman; pgeier
Herbicide options for weed control in millets are very limited and hence there is a need for exploring potential herbicides. Field trials were conducted at three locations in Kansas and Nebraska in 2009 to evaluate foxtail millet, proso millet, and pearl millet tolerance to saflufenacil applied preemergence (PRE) at 36, 50, and 100 g aihaˉ¹. Foxtail millet was the most sensitive of the three millets to saflufenacil. Among experimental sites, saflufenacil at 36 g haˉ¹ injured foxtail millet 59 to 99% and reduced plant stands 41 to 95%; nearly all plants died at 100 g haˉ¹. Despite early season foliar injury and up to 36% stand reduction, fodder or grain yields of proso and pearl millets were not reduced by any rate of saflufenacil compared to untreated controls. Additional trials were conductedat four locations in Kansas, Nebraska and South Dakota in 2010 and 2011 to refine saflufenacil use rate (36 and 50 g haˉ¹) and application timing [14 days early preplant (EPP); 7 days preplant (PP); and PRE] for use in proso and pearl millets. Saflufenacil applied EPP or PP, regardless of rate, caused up to 21 and 6% foliar injury and up to 21 and 9% plant stand reduction in proso and pearl millets, respectively. However, yields were not reduced by EPP or PP treatments in either milletcrop. PRE applications of saflufenacil caused the highest crop injury and stand reduction in both millets. Saflufenacil PRE at 36 g haˉ¹ caused up to 57 and 40% foliar injury and up to 42 and 24% stand reductions in proso and pearl millets, respectively; however, yields were not affected. Comparatively, saflufenacil PRE at 50 g haˉ¹ reduced yields of proso and pearl millets 36 and 52%, respectively, on sandy loam soilswith high pH (8.3) and low organic matter content (1.1%).Overall, results indicated that foxtail millet lacks tolerance to saflufenacil, but up to 50 g haˉ¹ of saflufenacil maybe safely applied as near as 7 days before planting proso or pearl millets. If situation demands, saflufenacil at 36 g haˉ¹ can also be applied PRE to either crop with risk of some crop injury.
Open Access
A simple quantitative model to predict leaf area index in sorghum
(2014-04-07) Narayanan, Sruthi; Aiken, Robert M.; Prasad, P. V. Vara; Xin, Zhanguo; Paul, George; Yu, Jianming; raiken; vara
Leaf area index (LAI) is a widely used physiological parameter to quantify the vegetative canopy structure of crops. Over the years, several models to estimate LAI have been developed with various degrees of complexity and inherent shortcomings. The LAI simulation models proposed so far for sorghum [Sorghum bicolor (L.) Moench] either lack details of the leaf area dynamics of expanding leaves or demand exhaustive measurements. The objective of this study was to develop a simple quantitative model to predict the LAI of sorghum by introducing a new method for simulation of the leaf area of expanding leaves. The proposed model relates LAI to thermal time. It calculates LAI from an algorithm considering the total number of mature leaves, the area of mature leaves, the area of expanding leaves, and plant density. The performance of the model was tested using LAI data collected using a nondestructive method under field conditions. The slope of the regression of modeled LAI on observed LAI varied for photoperiod-sensitive and -insensitive genotypes in 2010. The coefficients of determination (R²) between modeled and observed LAI were 0.96 in 2009 and 0.99 (photoperiod insensitive) and 0.95 (photoperiod sensitive) in 2010. The inclusion of expanding leaves in the model improved its accuracy. The model provides an accurate estimate of LAI at any given day of the vegetative growing season based only on thermal time and making use of default coefficients demonstrated in this research.