Search Results

You are looking at 51 - 60 of 79 items for

  • Author or Editor: Daniel Leskovar x
Clear All Modify Search

The aim of this study was to determine whether aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, would affect earliness, increase yield, and improve overall at harvest and postharvest quality of melon (Cucumis melo L. group Cantalupensis, `Sol Real'). Field experiments were conducted during two seasons with AVG (124 g·ha–1 a.i.) applied as spray or soil injected into the root zone with a single or double application between 7 d and 21 d before harvest. The AVG soil injection method increased earliness compared with AVG spray in one season. Total marketable yield increased with AVG injection but not with the AVG spray method compared with the control. Regardless of method of application, AVG did not affect fruit firmness, rind thickness, netting, or soluble solids content when measured at harvest. However, AVG spray decreased fruit size and seed cavity in one season. Similarly, AVG spray did not affect fruit quality after storage, whereas AVG soil injection increased fruit firmness. Overall, melon yield and fruit quality responses to preharvest AVG applications were superior for the soil injection than the spray method.

Free access

Introduction of artichokes in the Wintergarden of Texas, an area with mild winters and hot summers, depends on the development of strategies that will overcome limiting climatic conditions for bolting, earliness, and length of harvest. Cultivars with different bolting requirements were evaluated at two planting times and irrigation rates. The cultivars Emerald, Experimental Red, Imperial Star, Green Globe, and Purple Romagnia were transplanted in the field on 27 Sept. and 3 Dec. 2004, and evaluated at 100% and 75% crop evapotranspiration rates (ETc) at Uvalde, Texas (29°1' N; 99°5' W). Harvests started on 24 Mar. and 21 Apr. 2005 for the first and second planting dates, respectively. Yield increased more than 3-fold for the first compared to the second planting date. Irrigation rates did not affect yield, water use efficiency, or head quality. The cultivars Emerald, Imperial Star, and Experimental Red were earlier than Green Globe and Purple Romagnia. The highest yield was measured for cv. Imperial Star, while the largest head weight was for cv. Green Globe. Total fibers, crude protein, and phenolic compounds concentration depended on cultivar, whereas the total sugar concentrations in the edible part of the head were similar among cultivars. Head weight, percentage of heart, and crude protein concentration decreased, whereas total fiber content increased as the harvesting season progressed. Integrating environmental and cultivar strategies aimed at earliness, large head size, and enhanced level of health-promoting compounds, will contribute to the potential production of globe artichokes in the region.

Free access

Globe artichoke is a native crop of the Mediterranean region with about 80% worldwide production. It is estimated that about 3,000 ha are grown in the U.S., mostly in California. Artichoke crop can be grown as a perennial, by vegetative cuttings, or as annual by seeds. Crop production can be limited by freezing winter temperatures leading to irreversible plant damage or by high summer temperatures causing poor head quality. Successful artichokes production, particularly in areas with constraining climatic conditions, requires proper selection of cultivars and planting dates. Cultivars with low vernalization requirements are more prone to a short growing season. The application of GA3 to overcome the lack of low temperatures and fulfill the vernalization requirements of early cultivars is well known. The goal of this multi-year project is to select production strategies contributing to earliness, extension of harvesting period, and improved yield and head quality under a variety of environmental conditions in Croatia and Texas. Selecting cultivars with different maturity groups and planting dates enabled harvesting period from autumn to late spring depending on locations. When GA3 was applied (12.5 to 125 ppm) on a naturally vernalized crop from autumn planting, early yield was substantially increased without affecting earliness. Conversely, application of GA3 (30 or 45 ppm) on nonvernalized plants established during late spring or summer was necessary for fall harvest in the Croatian locations. Head quality evaluated as head weight and size, or crude protein and total fiber concentration, progressively decreased during late spring harvest in Texas. Shifting the harvesting period towards early spring may be essential for improving head quality and for increasing the market share. To achieve adequate yields, longer harvesting period, and superior head quality, it is necessary to develop and adjust cultural practices for the specific growing area.

Free access

Fruit color and carotenoid composition are important traits in watermelon. Watermelon fruit color inheritance has revealed that several genes are involved in color determination. Carotenoids are known to have various functions in plants and animals, such as providing antioxidant activity and other health benefits for humans, and UV protection and pigmentation for plants. Differential gene activity in the carotenoid biosynthetic pathway may result in different color determination of mature fruit. Eight genes encoding enzymes involved in the pathway were isolated and their structures were characterized. While obtaining full-length cDNA of these enzymes, two single-nucleotide polymorphisms were detected in a coding region of lycopene β-cyclase (LCYB). These SNP markers showed cosegregation with red and canary yellow fruit color based on the genotyping of two segregating populations. This will lead to development of a codominant molecular marker for the selection of LCYB allele, which may allow breeders to distinguish between red and canary yellow watermelon fruit colors at the seedling stage.

Free access

Agricultural communities in the semiarid regions of the world are constantly being affected by water scarcity, increased regulations restricting water use, strong competition for irrigation water with the urban sector, and severe drought periods. Conversely, the consumer demand for high-quality and nutritious foods is increasing rapidly. A 2-year field study evaluated growth, yield, and bulb quality in response to precision planting density and deficit irrigation of onion (Allium cepa L.) in southwest Texas. Seeds of short-day sweet onion cv. Texas Grano 1015Y were planted in the field on 11 Nov. 2007 and 30 Oct. 2008 at two planting densities (PDs), 397,000 (standard) and 484,000 (high) seeds/ha. Three irrigation rates using growth stage-specific crop coefficients and subsurface drip were imposed after plants were fully established, 100%, 75%, and 50% crop evapotranspiration rates (ETc). Total rainfall plus irrigation received for each irrigation rate were 594, 501, and 413 mm in 2008 and 662, 574, and 486 mm in 2009. In both seasons, there were consistent trends in growth, yield, and quality parameters. Leaf fresh weight was unaffected by PD but was reduced by deficit irrigation at 50% ETc. Although increasing planting density reduced the average bulb size by 12%, it increased the number of marketable bulbs by 21% to 33% and marketable yield by 7% to 14%. In contrast, deficit irrigation showed a trend to reduce both the number of bulbs and bulb size with yield reductions of 8% to 13% at 75% ETc and 19% to 27% at 50% ETc. Neither planting density nor deficit irrigation rate had a significant effect on soluble solids content, pungency, or quercetin contents. These results suggest that growers of short-day onions in semiarid regions could adjust PDs to target high-value bulb sizes. Implementing water-conserving practices (deficit irrigation at 75% ETc rate) would result in a decrease of high-value bulb grades and modest losses in yield but not flavor or nutritional components.

Free access

Hot and humid conditions create challenges for tomato production under a controlled environment. Low tomato productivity is related to the lack of stress tolerance of existing cultivars and their ability to maximize fruit set and yield. The aim of this study was to evaluate the effectiveness of three management strategies, cultivar selection, grafting, and plant density, for the growth and production efficiency of organically grown hydroponic tomatoes under adverse environmental conditions in Qatar. The experiment used a split-split plot design with ‘Velocity F1’ and ‘Sigma F1’ as the main plot treatments and a factorial arrangement of grafting combinations and planting densities (3.5 and 5.5 plants/m2) as subplots. Tomato cultivar Velocity F1 grafted on Maxifort F1 resulted in greater vegetative growth and improved phenological attributes than nongrafted Velocity F1. Grafted ‘Velocity F1’ plants grown at 3.5 plants/m2 had an increase in leaf photosynthetic rates (18%), less transpiration loss (16%), and less electrolyte leakage (15%) while maintaining stomatal conductance and intercellular CO2 concentrations. At 9 weeks after transplanting, canopy growth was higher (24%) and flowering occurred earlier (3 days) with grafted ‘Velocity F1’ transplants than with nongrafted transplants. Higher fruit sets (20%), pollen viability (22%), and fewer flower drops (17%) were also observed for grafted ‘Velocity F1’ transplants than for nongrafted transplants. Marketable fruit yields were higher (26%) with grafted ‘Velocity F1’ grown at 3.5 plants/m2 than with nongrafted ‘Velocity F1’. Both grafted ‘Velocity F1’ and ‘Sigma F1’ fruits retained acceptable fruit color (L*, a*, b*, C*, °h), firmness, °Brix, titratable acidity, weight, and prolonged shelf life by 4 additional days than nongrafted ones. We conclude that grafted tomato ‘Velocity F1’ grown at a plant density of 3.5 plants/m2 was the best management strategy for enhancing seedlings quality, plant growth, and postharvest quality and alleviating abiotic stresses under this protected environment and hydroponic system.

Open Access

At the Vegetable and Fruit Improvement Center, plant breeding has produced pepper lines with enhanced beneficial phytochemical levels. TAM `Dulcito' is a new jalapeño cultivar with no detectable levels of capsaicin, but increased levels of lutein. In greenhouse cultivation, it contained 122 ppm of this important human health-related compound, which aids in prevention of macular degeneration. This is a significant improvement over popular cultivars, such as `Grande', which contained 25 ppm or less. In addition to improved lutein levels, `Dulcito' also possesses resistance to three important potyviruses: TEV, PepMoV, and PVY. In field trials at Weslaco, Texas, `Dulcito' outyielded both TAM `Mild Jalapeño 2', and `Mitla'. This new cultivar produces a concentrated set of large, thick-fleshed fruit with few cuticular cracks. Because of its lack of pungency, it should be useful for the processing industry. TAM `Tropic Bell' is a medium-sized, blocky bell with enhanced levels of both ascorbic acid and lutein compared to other cultivars. Grown under greenhouse conditions, it contained 100 ppm lutein compared to 6 ppm in `Jupiter'. It also contained 660 ppm ascorbic acid at the green stage, compared to less than 100 ppm for three commercial bell cultivars tested. `Tropic Bell' produced yields equal to both `Valiant' and `Summer Sweet' commercial hybrids at Weslaco. Fruit of `Tropic Bell' were slightly smaller than the hybrid cultivars. TAM `Tropic Bell' possesses resistance to the same three potyviruses as `Dulcito' and demonstrated excellent tolerance to Phytophthora capsici in a controlled inoculation. These two new cultivars will be useful for production in locations with high potyvirus pressure or as specialty market items for health-conscious consumers.

Free access

Weighing lysimeters are used to measure crop water use during the growing season. By relating the water use of a specific crop to a well-watered reference crop such as grass, crop coefficients (KC) can be developed to assist in predicting crop needs using meteorological data available from weather stations. This research was conducted to determine growth stage-specific KC and crop water use for onions (Allium cepa L.) and spinach (Spinacia oleracea L.) grown under south Texas conditions. Seven lysimeters, consisting of undisturbed 1.5 × 2.0 × 2.2-m deep soil monoliths, comprise the Texas AgriLife Research–Uvalde lysimeter facility. Six lysimeters, weighing ≈14 Mg, have been placed each in the middle of a 1-ha field beneath a linear low-energy precision application irrigation system. A seventh lysimeter was established to measure reference grass reference evapotranspiration. Daily water use for onion and spinach was measured at 5-min intervals. Crop water requirements, KC determination, and comparison with existing Food and Agricultural Organization (FAO) KC values were determined over a 2-year period for each crop. The KC values determined over the growing seasons varied from 0.2 to 1.3 for onion and 0.2 to 1.5 for spinach with some of the values in agreement with those from FAO. It is assumed that the application of growth stage-specific KC will assist in irrigation management and provide precise water applications for a region of interest.

Free access