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- Author or Editor: L. G. Jones x
The coefficient of variation on number of replications required for significance in field trials with sweet potato (Ipomoea batatas (L.) Lam decreased in most cases as the plot length and width increased. Using 12% as an arbitrary level of acceptability for the coefficient of variation, a single-row plot 15 to 20 hills, 30.5 cm apart in length and replicated 9 to 11 times appeared to be sufficient to conduct research on the total weight of sweet potatoes. A double-row plot of the same length would require 5 to 7 replications while a triple-row plot would require 3 to 6 replications to be precise enough for research on the total weight of sweet potatoes. For satisfactory research on the total number of roots, a plot 1 row wide and 20 to 25 hills long with 5 to 9 replications appeared to be adequate. A double-row plot the same length would require 3 to 7 replications, and a triple-row plot would require 2 to 6 replications for satisfactory results.
This study was conducted as part of a stone fruit decline project to determine the effects of soil pH (3.9 to 7.0) on soil and plant nutrient imbalance and mortality of standard (Mazzard and Maheleb) and new (GI148-1 and GI148-8) rootstocks. Seedling mortality and soil Ca in all rootstocks and soil K and leaf Ca, K, Al, and Mn contents in all rootstocks but GI148-8 were higher at below optimum than at optimum soil pH. The nutrient imbalance suggests that the adaptation of these rootstocks to biotic and abiotic factors needs to be considered.
The effect of 9 potassium (KCl) treatments were compared in 1974, 1975 and 1977 on a United States Golf Association (USGA) golf green planted with ‘Tifgreen’ Bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis). The rate of applied K or number of applications had no significant influence on turfgrass quality, yield, or foliar N or P concentration. Plots receiving a single application of 0.5 kg of available K2O per 100 m2 exhibited lowest quality while those on which a total of 9.0 kg of K2O was applied in 3 applications had maximum evaluation scores. Foliar K levels were also lowest and highest in these treatments, as were the amounts of extractable K in the medium. Yearly variations in rainfall influenced turfgrass quality, yield, foliar N and K concentrations, and level of extractable K. Turf quality and foliar N levels were positively associated.
‘Centennial’ sweet potatoes (Ipomoea batatas (L.) Lam.) did not respond to increasing levels of P over an 8 year period probably due to the low soil pH and relatively high native P levels. Increasing the available soil moisture to above 25% resulted in a 3.4 MT/ha increase in yield of marketable roots over that obtained with natural rainfall but increasing the available moisture had no influence on yield. The P rate had no effect on dry matter and/or carotenoid content, firmness and splitting of processed roots. Protein content as percent of dry weight was reduced with increased P rate. Increasing the available soil moisture resulted in lower dry matter, protein, and carotenoid contents but had no influence on fiber content, firmness, or splitting.
Three sweet potato (Ipomoea batatas Lam.) cultivars that varied in vine length were compared at 5 N levels. Increasing N levels increased weight and the percentage of No. 1 grade roots of all cultivars. Vine length did not have a linear effect on yield. The long-vine ‘Centennial’ out-yielded the other cultivars, followed by the short-vine ‘L3-243’ and the intermediate-vine length ‘Goldrush’. N applications linearly increased dry matter, carotenoid (fresh and processed), protein content, and reduced fiber content of all cultivars. Cultivars varied significantly for each quality variable studied with the exception of protein content (fresh wt basis), including dry matter, carotenoids, fiber, firmness, and split roots after processing. N applications had no influence on soil P, K, Ca, Mg, or pH. Organic matter content of the soil was increased slightly by increased N applications, probably as a result of excessive vine growth, which was incorporated into the soil after harvest.
Bacteriophages specific to Xanthomonas campestris pv. pelargonii (Xcp), the causal agent of bacterial blight of geranium, Pelargonium ×hortorum L.H. Bailey, were isolated from soil and sludge samples from Florida, California, Minnesota, and Utah. Sixteen phages were evaluated for their potential to lyse 21 Xcp strains collected from around the world. The Xcp strains varied in their susceptibility to the phage isolates with 4 to 14 phages producing a lytic or highly virulent reaction. A mixture of five h-mutants was developed from phages that exhibited the broadest host-ranges and tested against the same Xcp strains. The h-mutant phage mixture lysed all 21 Xcp strains. Three experiments were designed to determine the efficacy of using a mixture of four h-mutant phages to control the spread of the bacterial blight pathogen on potted and seedling geraniums under greenhouse conditions. Plants surrounding diseased inoculated plants were treated with a phage mixture at 5 × 108 pfu/mL daily, biweekly, or triweekly, or treated with Phyton-27®, at 2.0 mL·L-1 every 10 or 14 days. In potted geraniums, daily foliar sprays of the phage mixture had reduced disease incidence and severity by 50% and 75%, respectively, relative to control plants after 6 weeks. In two plug experiments, the phage mixture applied daily also had reduced disease incidence and severity by 69% and 86%, and 85% and 92%, respectively, when compared with controls after 5 weeks. In all three experiments, disease incidence and severity were less for plants treated daily with phages than for those treated less frequently with phages or with Phyton-27®. Chemical name used: copper sulfate pentahydrate (Phyton-27®).
The phytotoxic effects on the physiology of chili (Capsicum annum L. cv. Ancho San Luis) caused by four different insecticides were evaluated. Three commercial mixes (methyl azinfos, methyl parathion CE720, and metamidophos 600 LM), and an active ingredient alone (methamidophos) were assayed; water was used as the control. The main goal was to evaluate the insecticide effects on chili using four different doses; the mean dose, recommended on the label of the product (R), a half one (1/2R), 1.5 times (1.5R) and twice the recommended dose (2R). Three frequencies of application were applied; once a week, twice a week, and once every other week, for 6 weeks from the beginning of flowering. Phytotoxicity was evaluated measuring the response of some physiological traits, Chlorophyll Fluorescence (CF), Leaf Temperature (LT), Transpiration (Tr), and Stomatal Resistance (SR). CF was measured by means of a portable chorophyll fluorscence meter; LT, Tr, and SR were measured using a LI-Cor Porometer. The doses and frequencies used are all common in commercial chili fields in Mexico. Results showed that phytotoxicity caused by insecticides can be an important damage factor to the plants, something that can cause reduction of yields. CF was shown to be the most sensitive variable to evaluate the phytotoxicity caused by insecticides. Fruit malformation was observed in all treatments. Chlorophyll content was reduced up to 25%, on average. The phosphorate insecticides affected the physiological parameters more drastically than the others. Results evidence the irreversible crop damage caused by excessive insecticide applications.
A mixture of host-range mutant (h-mutant) bacteriophages specific for tomato race 1 (T1) and race 3 (T3) of the bacterial spot pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye was evaluated for biological control of bacterial spot on `Sunbeam' tomato (Lycopersicon esculentum Mill.) transplants and field-grown plants for two seasons (Fall 1997 and Fall 1998). Foliar applications of bacteriophages were compared with similar applications of water (control) and of copper/mancozeb bactericides, the commonly used chemical control strategy for tomato seedling and field production. In 1997, the incidence of bacterial spot on greenhouse-grown seedlings was reduced from 40.5% (control) to 5.5% or 0.9% for bactericide- or bacteriophage-treated plants, respectively. In 1998, the incidence of bacterial spot was 17.4% on control plants vs. 5.5% and 2.7% for bactericide- and bacteriophage-treated plants, respectively, although these differences were not statistically significant at P ≤ 0.05. Applications of bacteriophages to field-grown tomatoes decreased disease severity as measured by the area under the disease progress curve (AUDPC) by 17.5% (1997) and 16.8% (1998) compared with untreated control plants. Preharvest plant vigor ratings, taken twice during each field season, were higher in the bacteriophage-treated plants than in either bactericide-treated plants or nontreated controls except for the early vigor rating in 1998. Use of bacteriophages increased total weight of extra-large fruit 14.9% (1997) and 24.2% (1998) relative to that of nontreated control plants, and 37.8% (1997) and 23.9% (1998) relative to that of plants treated with the chemical bactericides. Chemical names used: manganese, zinc, carboxyethylene bis dithiocarbamate (mancozeb).
Whenever supplemental irrigation was applied to sweet potatoes, root quality was reduced. Dry matter content, color of both fresh and processed sweet potatoes, firmness of the canned product, and percent protein decreased as the moisture content of the soil increased. Moisture content had little or no influence on fiber content or cortex thickness of fleshy roots.
Nitrogen levels also influenced quality factors. As N levels increased there was a reduction in flesh color and increases in protein content and firmness of the canned potatoes. Nitrogen had little effect on fiber content, dry matter content or cortex thickness.
Yearly variations occurred for dry matter content, fiber content, firmness of the canned product and flesh color.
Ten cultivars of peach (Prunus persica (L.) Batsch) were inoculated in 1967, 1968 and 1969 with the fungus Cytospora leucostoma (Pers.) Sacc. and canker development was measured each season. Seasonal differences were noted. ‘July Elberta’ was the most susceptible of the group while the rest were of intermediate susceptibility. No significant resistance to Cytospora was found.