Browse

You are looking at 61 - 70 of 27,835 items

Restricted access

Yi-Lun Liao, Wen-Shin Lin and Shu-Yun Chen

Restricted access

Te-Ming Tseng, Swati Shrestha, James D. McCurdy, Erin Wilson and Gourav Sharma

Annual bluegrass (Poa annua L.) is an annual weed that is particularly troublesome in managed turfgrass. It has been controlled conventionally with herbicides, including acetolactate synthase (ALS) inhibitors. However, resistance to ALS inhibitors has been documented throughout the southeastern United States since 2012. A rate response trial was conducted to confirm and determine the resistance level of suspected resistant P. annua biotypes from Mississippi (Reunion), followed by DNA sequencing to determine whether the mechanism of resistance is a target-site mutatio n. In addition, a fitness assay was conducted together with a susceptible biotype to determine whether resistance to ALS inhibitors is associated with decreased fitness. Reunion was at least 45 times more resistant to foramsulfuron than the standard susceptible biotype based on I50 estimates [I50 is the rate of herbicide giving a 50% response (50% visual necrosis)], requiring a predicted 331 g a.i./ha foramsulfuron for 50% control. DNA sequencing results identified a Trp574-to-Leu mutation in the ALS gene of the Reunion biotype, which has been shown by other studies to confer resistance to ALS inhibitors. Measurement of fitness parameters among the Reunion and susceptible biotypes demonstrated reduced seed yield, tillering, and flowering time in the resistant Reunion biotype, suggesting that ALS inhibitor resistance is possibly correlated to decreased fitness in P. annua. Alternative methods to control P. annua need to be considered as a result of the evolution of herbicide-resistant biotypes. An integrated management strategy to control P. annua weeds will help prevent further evolution of resistance. Because this study evaluated only the target-site mechanism of resistance, it is also necessary to determine whether the resistant biotype has reduced uptake, translocation, or enhanced metabolism as additional mechanisms of resistance. Consequently, a fitness study encompassing a more comprehensive list of plant parameters will provide conclusions of the fitness costs associated with ALS inhibitor resistance in P. annua. Chemical names: Foramsulfuron {1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)-5-formamidophenylsulfonyl] urea}.

Open access

Jeff B. Million and Thomas H. Yeager

Irrigation scheduling in container nurseries is challenging due to the wide range of plant production conditions that must be accounted for at any given time. An irrigation scheduling system should also consider weather affecting evapotranspiration to apply proper amounts of water that will ensure optimal growth with minimal runoff (container drainage). We developed an automated system that relies on routine leaching fraction (leachate/water applied) testing and real-time weather recorded on-site to make adjustments to irrigation. A web-based program (CIRRIG) manages irrigation zone inputs [weather and leaching fraction (LF) test results] and outputs irrigation run times that can be implemented automatically with programmable logic controllers. In this study conducted at a nursery in central Florida, we compared the automated technology (CIRRIG) with the nursery’s traditional irrigation practice (TIP) of manually adjusting irrigation based on substrate moisture status of core samples taken twice weekly. Compared with TIP, CIRRIG reduced water use in six of seven unreplicated trials with water savings being greater for microirrigated crops grown in large containers than for sprinkler-irrigated crops in small containers. Reduced pumping cost associated with water savings by CIRRIG was estimated to be $3250 per year, which was insignificant compared with the labor savings of $35,000 to $40,000 anticipated by the nursery using CIRRIG in lieu of TIP. At the end of the project, the necessary hardware was installed to expand CIRRIG nursery-wide and control 156 zones of irrigation.

Restricted access

Mojdeh Bahar and Robert J. Griesbach

The U.S. Department of Agriculture’s Agricultural Research Service (ARS) and universities have a long and successful history of developing enhanced germplasm and cultivars that are transferred through public release. Today, nonprotected public release may not be the most appropriate mechanism. Intellectual property (IP) protection as it pertains to the plant germplasm and cultivars is involved and complex. Unlike other scientific areas, in the United States there are three distinct mechanisms to protect plants—namely, utility patents, plant patents, and plant variety protection certificates. Each of these mechanisms offers different criteria for protection and covers different types of plants. This article is a practical tool to help research institutions and scientists decide when to consider releasing a germplasm or cultivar, which factors to consider, who should be involved, and whether IP protection is appropriate.

Open access

Scott B. Lukas, Joseph DeFrank, Orville C. Baldos and Ruijun Qin

Seed dormancy is an evolutionary adaptation for increasing seedling survival by delaying germination and is found in many families of seed plants. Although dormancy is ecologically important, it becomes problematic during agronomic production and restoration. Torrid panicgrass (Panicum torridum) is a native Hawaiian annual grass that has been identified as a re-vegetation candidate for seasonally dry areas. Torrid panicgrass seed appears to possess a nondeep to intermediate physiological dormancy. This research aimed to characterize dormancy relief parameters by 1) evaluating exogenous hormonal, reactive oxygen intermediates, and simulated combustion product treatments; and 2) determining optimized storage conditions of relative humidity (RH) and temperature over a 10-month duration. Results indicate that all exogenous chemical treatments tested were not effective at relieving the dormancy present in torrid panicgrass. Optimal storage conditions to relieve dormancy were found with seeds equilibrated to 12% RH, stored at 30 °C for a period of 8 months resulting in 55% germination. Maintenance of viability for long-term storage up to 10 months was best achieved with seeds stored at 12% RH at 10, 20, or 30 °C.

Restricted access

Ling Ma, Xingquan Rao and Xiaoyang Chen

Plans for hydroponic experiments, as well as the flooding of watersheds for ecological restoration, require abundant evaluation information regarding plant species adapted to waterlogged environments. In this study, we observed the growth rate and phenotypes of 57 plant species, including nine provenances of four species grown hydroponically. The 57 species were from 22 families and 33 genera, and their waterlogging tolerance (WT) was classified into five categories according to the results of the evaluation: excellent, good, ordinary, poor, and very poor. We found that 60% of these plant species were able to survive in hydroculture for more than 10 weeks. They showed new shoot growth and had a survival rate of more than 60%. Species with excellent or good WT developed new leaves rapidly under waterlogging stress, whereas species with ordinary or poor WT exhibited old leaves dropping from the stem soon after waterlogging stress. In addition, phenotypic divergence occurred among provenances of the same species under waterlogging stress.

Open access

Zachary N. Hoppenstedt, Jason J. Griffin, Eleni D. Pliakoni and Cary L. Rivard

Sweetpotatoes (Ipomoea batatas) are nutritious, easily stored, and well adapted to a variety of organic farming operations. This widely consumed root crop is propagated through the use of cuttings, known as slips. Slips are commercially grown primarily in the southeastern United States, and growers in the central United States still have limited access to sweetpotato planting material. Production of organic slips in high tunnels (HTs) could be a profitable enterprise for growers in the central United States given the season extension afforded by controlled-environment agriculture, which could allow growers to diversify their operations and facilitate crop rotation. In trials conducted in 2016 and 2017 at two research stations in northeast and south central Kansas, a systems comparison was used to evaluate the yield and performance of organic sweetpotato slips grown in HT as compared with the open field (OF), with four to six replications at each location. Propagation beds planted with ‘Beauregard’ seed roots in 2016 and ‘Orleans’ in 2017 were established in HT and OF under similar cultural methods and planting schedules. Slips were harvested from both treatment groups and transplanted to field plots to investigate the impact of production system on transplant establishment and storage root production. Slip yield from HT was greater than OF at both locations in 2016 (P ≤ 0.001), but this trend was inconsistent in 2017. Slips grown in HT were on average 12% less compact (slip dry weight per centimeter length) with fewer nodes than their OF counterparts in 2016. Nonetheless, mean comparisons for vine length, stem diameter, and total marketable storage root yield were not significant between HT and OF treatments (1.7 and 2.1 lb/plant, respectively). Similarly, the number of marketable storage roots for HT and OF groups was comparable (3.4 and 3.8 storage roots/plant, respectively). Although more research is needed to evaluate the feasibility of slips grown in HT and to determine recommendations for seed root planting densities, results from this study suggest that HT organic sweetpotato slip production could be a viable alternative to OF production as it relates to slip performance. According to this study, HT production could be a useful mechanism for growing sweetpotato slips, which could provide regional growers more control over planting material. Furthermore, HT slip production could promote the adoption of an underused vegetable crop that can be grown throughout many parts of the United States.

Restricted access

Brent L. Black, Tiffany Maughan, Christina Nolasco and Blake Christensen

Winter injury to raspberry floricanes commonly limits productivity in cold climates. Primocane-fruiting raspberries avoid winter injury by fruiting on first year canes, but fruit production in the high-elevation valleys of the Intermountain West is later than needed for local markets, and may be limited by early fall freezes. High tunnels were used for early spring heat to advance primocane growth and the fruiting season of two primocane-fruiting red raspberry cultivars. Tunnels were covered with plastic in March and April. Then, they were covered with shade cloth during fruit ripening. Tunnel-covered plots were compared with field plantings for primocane growth rate, fruiting season, yield, and fruit quality over two seasons. High tunnels increased cane growth rate, with the harvest season advanced by 18 to 26 days depending on season and cultivar, but they did not consistently affect the total season yield or fruit size. Low-cost two-season tunnels used in conjunction with early-season primocane-fruiting raspberries may provide a viable method for small acreage producers in harsh climates to reliably supply high-value seasonal raspberry markets.

Restricted access

Laura P. Peña-Yam, Liliana S. Muñoz-Ramírez, Susana A. Avilés-Viñas, Adriana Canto-Flick, Jacobo Pérez-Pastrana, Adolfo Guzmán-Antonio, Nancy Santana-Buzzy, Erick A. Aguilera-Cauich and Javier O. Mijangos-Cortés

The variability and genetic parameters of seven agronomic characteristics were estimated for 11 genotypes, and high values of the phenotypic coefficient of variation (PCV) of capsaicin content (CC) were obtained. Heritability (h2) was high for yield per plant (YP; 0.98) and CC (0.93). The principal components analysis (PCA) revealed that the first three components explained 94.02% of the total variation; therefore, genotypes with higher YP values and fruit weight (FW) (AKN-08, ASBC-09) were placed in quadrant I. Those with greater CC and lowest YP and FW (MBI-11, RES-05) were placed in quadrant II. The greatest fruit length (RNJ-04) was placed in quadrant III. Those with the greatest number of fruits per plant (NBA-06, RKI-01, RHC-02, RHN-03, NKA-07, and MSB-12) were placed in quadrant IV. The results showed that the genotypes studied comprise an excellent source of genetic material for Habanero pepper improvement programs.

Restricted access

Sheri Dorn, Milton G. Newberry III, Ellen M. Bauske and Svoboda V. Pennisi

Extension provides outreach to the general public and works to disseminate the latest information and research generated by land grant university (LGU) scientists. The Extension Master Gardener (EMG) volunteer program is one of the most widely recognized programs of extension, created to educate people about research-based consumer horticulture (CH) and gardening practices through a network of trained volunteers. Ideally, EMG program initiatives should address local issues and needs and align with the priorities of extension’s federal stakeholder, U.S. Department of Agriculture National Institute for Food and Agriculture (USDA NIFA). Before 2015, there were no national standards for EMG volunteer programs, and at this time, there is no official work plan or prioritization of educational programming. A quantitative national study of EMG state and local coordinators and volunteers was conducted in Fall 2016 to assess the importance of six educational-response themes (ERTs) (i.e., the strategy for EMG volunteer outreach) for program management (state and local coordinators) and program participants (EMG volunteers). The study compared theme importance between program management and participants, and, in turn, allowed a comparison with previously published historical data. Response to individual inquiry is consistently the most important ERT for EMG programs, regardless of the responder position within the program (management or volunteer). Results revealed that state and local coordinators (program management) score ERTs similarly. EMG volunteers score the importance of ERTs similarly to each other, as well, although some differences are apparent between urban, suburban, and rural programs. Although there are slight differences in the importance of response themes between program management and EMG volunteers, it appears that the EMG volunteer program has an effective organizational structure with an upper and middle management generally aligned at every level. It is plausible that the variability in importance of response themes could be attributed to nuances in local issues and needs. Historical comparison indicates that the importance of ERTs has changed over time, suggesting that themes cycle and change. Although the EMG program does not have a national plan for programming, this assessment of EMG volunteer program ERTs provides a perspective on program direction and a useful starting point for discussion. It is a timely conversation, as EMG programs are increasingly expected to be more accountable and show community impact, and these assessments serve as an important baseline for a national program poised for growth and development.