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- Author or Editor: M. Riley x
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Two studies were performed to evaluate techniques for screening verticillium wilt of Capsicum annuum L. The first study tested inoculation methods. The original method involved mixing the inoculum with planting medium in a cement mixer for 1 h. Seeds then were planted in the infested medium. In the new technique, inoculum is poured directly into the row, and seeds are placed directly on top of the inoculum. Inoculum levels of 2000 and 1000 mcrosclerotia/g of soil were tested in the new “in-row” method. The disease severity of the “in-row” plants was significantly less than the plants inoculated by the original method. A significant difference remained between resistant and susceptible lines. There was no difference between inoculum levels. The second study compared three commercial planting media to the standard soil used in previous screenings. Disease severity did not differ among media, and all media showed significant differences between resistant and susceptible C. annuum lines.
Three commercial planting media (Sunshine Mix#1, Sunshine Mix#5, and Metro Mix 360) were compared with the standard soil mixture prepared at New Mexico State Univ. for their effectiveness in differentiating Verticillium wilt—resistant and susceptible accessions of chile (Capsicum annuum L.) Each medium was infested with Verticillium dahliae Kleb. microsclerotia and planted with the resistant and susceptible accessions. When susceptible populations exhibited severe symptoms, individual plants were rated for disease severity (1 = no symptoms to 9 = death). Mean disease severities of populations differed among planting media, and, regardless of medium, resistant and susceptible populations were readily differentiated. Mean disease severities of plants grown in Sunshine Mix #1 and Sunshine Mix #5 differed from those grown in the standard University soil mix, but all media provided reliable screening tests. Mean disease severities of plants grown in Metro Mix 360 were most similar to those of plants grown in the University mix. Furthermore, greater differentiation was apparent between resistant and susceptible accessions in Metro Mix 360 than in accessions grown in the University medium.
Container nurseries broadcast apply granular formulations of herbicides over-the-top of container crops and then apply irrigation. Depending upon spacing and plant architecture, up to 80% of the applied herbicide may land on the surfaces surrounding containers where it is then available to move offsite in irrigation runoff water. This study measured the amounts of isoxaben and trifluralin (from Snapshot 2.5TG) lost from a container nursery site during an irrigation event and monitored the dissipation of each in containment pond water. A 1.22 hectare container nursery production area was treated with Snapshot TG at 112 kg product/hectare and 1.27 cm irrigation was applied. Water samples were collected from the runoff water before it entered into the collection pond at the following time intervals: 0.25, 0.5, 1.5, 2.5, and 3.5 hours after runoff began. Water samples were also collected in the containment pond before treatment, after treatment, and then 1-3, 5, 7, 14, 29, and 60 days after treatment. Nearly 17% of the applied isoxaben was lost in the runoff water immediately following application. Isoxaben concentrations in the containment pond water decreased from a high of approximately 30 ppb immediately following the first runoff event to below lppb 60 days after application. No trifluralin was detected in the runoff or catch pond water.
Four sweetpotato breeding lines were tested for their sodium tolerance in sand culture. All plants were grown in the greenhouse in sterilized sand and watered daily with a modified half-Hoagland solution (N: K-1:2:4). Four sodium levels (0, 35, 70, and 105 ppm) were applied to the breeding lines in a split-plot design with four replications. Soil leachate was collected every 2 days and was measured for P, Na concentration, and electrical conductivity. Plants were grown for 60 days. Preliminary results from analysis of soil leachate showed an increase in EC as sodium concentration increased 5 days after treatments were initiated. Potassium and Na concentration varied with each breeding line tested. Storage root fresh and dry weight were significantly affected by Na levels (i.e., lines tested were tolerant ≤70 ppm Na).
The purpose of this review is to promote a discussion about the potential implications of herb production in controlled environments, focusing on our recent works conducted with feverfew. Research suggests that the content of secondary metabolites in medicinal plants fluctuates with changing environmental conditions. Our studies with feverfew (Tanacetum parthenium [L.] Schultz-Bip., Asteraceae) lend support to this hypothesis. Feverfew plants exposed to different water and light conditions immediately before harvest exhibited changes in content of some secondary metabolites. The highest yield of parthenolide (PRT) was in plants that received reduced-water regimes. Phenolics concentration however, was higher in plants receiving daily watering. Light immediately before harvest enhanced accumulation of PRT, but reduced the phenolic content. Notably, PRT decreased at night whereas total phenolics decreased during the photoperiod and increased at night. PRT also increased with increased plant spacing. UV light supplementation increased PRT only in plants that had undergone water stress, whereas phenolics increased when UV was applied to continuosly watered plants. Clearly, production of medicinal plants under greenhouse conditions is a promising method for controlling levels of phytochemicals through manipulation of light and water as discussed here, and possibly other environmental factors such as temperature and daylength. However, better understanding of how the environment alter secondary metabolite levels is needed as it was revealed that manipulating the environment to favor increased accumulation of one group of phytochemicals could result in a decline of other key metabolites.
Abstract
‘Beauregard’ sweet potato [Ipomoea batatas [L.] Lam.] was developed by the Louisiana Agricultural Experiment Station to combine resistance to diseases and insects of local importance with good horticultural and culinary characteristics. This cultivar, first designated L82-508, is named after Louisiana's renowned civil engineer and “Napo-lean in Grey,” Gen. P.G.T. Beauregard.