Search Results

You are looking at 61 - 70 of 79 items for

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

Successful field establishment of vegetable transplants often depends on the ability of young seedlings to tolerate various biotic and abiotic stresses after transplanting. Treatments that limit transpirational water loss could improve plant survival and stand establishment. In this study we evaluated growth and physiological responses of pepper (Capsicum annuum L.) seedlings to foliar application of chemical plant regulators [abscisic acid (ABA) and aminoethoxyvinylglycine (AVG)] or physical film-forming barriers [AntiStress (AS), Transfilm (TF), and Vapor Gard (VG)] during transient 4-day water deficit cycles. During two 4-day water deficit cycles, stomatal conductance (g s) and net CO2 assimilation rate (ACO2) were unaffected by the application of physical materials, but differed for ABA and AVG. Compared with untreated control plants, ABA reduced g s (47% to 69%) and ACO2 (37% to 57%) by the end of the second water deficit cycle, whereas AVG increased gs (27% to 60%) during the first desiccation cycle. Leaf (ψlf) and stem (ψst) xylem water potential of plants treated with film-forming materials generally decreased at the same rate as those of untreated plants, whereas application of AVG caused earlier and more pronounced decline of ψlf. Application of ABA enabled the maintenance of ψlf and ψst during two desiccation cycles, and thus prevented an increase of electrolyte leakage and leaf abscission. Growth rates of all plant components were reduced after ABA applications. However, allometric relationships showed similar patterns of dry matter allocation in leaves and shoots among ABA, TF, VG, and untreated control plants. Application of AS reduced allocation of dry matter to leaves, whereas AVG enhanced it at the expense of roots. These data indicate that water deficit tolerance of pepper seedlings only occurred with foliar application of ABA. This effect was associated with improved plant water relations, increased cell membrane stability, reduced leaf abscission, and a transient reduction in plant growth rates.

Free access

Chile peppers are economically important crops in southern regions of the United States. Limited information is available on irrigation management with low-quality water or on salt-affected soils. The objective of this study was to determine the relative salt tolerance of 20 genotypes of chile peppers. In Expt. 1, seeds of selected pepper types (Anaheim, Ancho, Cayenne, Paprika, Jalapeño, Habanero, and Serrano) were germinated in potting mix and seedlings were grown in 2.6-L pots. Six weeks after sowing, salinity treatments were initiated by irrigating plants with nutrient solutions of different electrical conductivities (ECs): 1.4 (control), 3.0, or 6.0 dS·m−1. After 1 month of initiating treatments, shoots were harvested and dry weights were determined. All plants survived and no visual salt injury was observed regardless of pepper variety and treatment. There were no statistical differences between control and saline solution treatments in final height and shoot dry weight of Habanero 1, ‘Early Jalapeño’, ‘AZ-20’, ‘NuMex Joe E. Parker’, and ‘NuMex Sandia’. In Expt. 2, seeds of 20 genotypes were directly sown in 2.6-L containers filled with loamy sand. Saline water irrigation was initiated 37 days after sowing by irrigating plants either with saline (nutrient solution based, similar to Expt. 1) or nutrient solution (control). More than half the genotypes did not have 100% survival in the salinity treatment. Ancho 1, Ancho 2, Cayenne 1, ‘Early Jalapeño’, and ‘AZ-20’ had 100% survival regardless of salinity treatment. No plants of ‘TAM Mild Habanero’ survived when irrigated with saline water and less than half of the plants survived in the control. The relative tolerance of chile genotypes to salinity varied with substrate in some genotypes. From the combined results of the two experiments, the 20 pepper genotypes were ranked for salt tolerance based on seedling survival, visual quality, and growth. ‘Early Jalapeño’ and ‘AZ-20’ were relatively tolerant to salinity among the 20 genotypes, whereas ‘TAM Mild Habanero’ and ‘Ben Villalon’ were sensitive. Ancho 1, Ancho 2, Cayenne 1, and Cayenne 2 also had relatively high tolerance based on survival and visual quality, although shoot growth was reduced significantly.

Free access

Globe artichoke [Cynara cardunculus L. var. scolymus (L.) Fiori] has been recently introduced as a specialty crop in southwest Texas. Marketable yield, yield components, quality, and phenolic compounds of artichoke heads were investigated in response to three irrigation [50%, 75%, and 100% crop evapotranspiration (ETc)] regimes and four nitrogen (0 to 10, 60, 120, and 180 kg·ha−1) rates under subsurface drip irrigation. Field experiments were conducted over three seasons (2005–2006, 2006–2007, and 2007–2008) at Uvalde, TX. Irrigation was more effective than nitrogen (N) rates to optimize crop yield and head quality. Marketable yields significantly increased at 100% ETc compared with 75% and 50% ETc, whereas a 20% to 35% yield reduction occurred at 50% ETc across seasons. This yield reduction was associated with a decrease in both number of marketable heads and head weight and with reductions in plant physiological responses as measured in the last season. The lack of yield responses to N rates was in part the result of high pre-plant soil NO3-N and NH4-N levels. Total phenolics and chlorogenic acid of artichoke heads increased as the harvesting season progressed and were highest at 50% ETc during mid- and late harvests in one season. Based on these results, we estimate that under these environmental conditions, ≈700 mm (for a bare soil system) of water inputs and 120 kg·ha−1 or less of N (rate depending on soil available N) appear sufficient to obtain high marketable yields, superior size, and nutritional head quality of artichokes.

Free access

Identifying tomato genotypes that can thrive and produce abundantly under arid climatic conditions and addressing the growing food demand caused by population growth are pressing concerns for food security. This research aimed to assess the growth, physiological, phenological, fruit yield, and postharvest quality of tomato genotypes cultivated in an organic hydroponic system in Qatar, where abiotic stress conditions prevail. Ten different tomato genotypes were carefully evaluated, and comprehensive data regarding their growth and development were collected and analyzed. The performance of these tomato genotypes across all traits related to yield and quality showed significant variations. Notably, the ‘Velocity’ and ‘Sigma’ genotypes consistently exhibited robust vegetative growth and improved phenological characteristics compared with the other tomato cultivars. Specifically, ‘Velocity’ and ‘Sigma’ displayed increased leaf assimilation rates (35% and 32%), stomatal conductance (14% and 11%), and reduced transpiration loss (50% and 44%) compared with ‘SV4129TH’. These genotypes also showed lower electrolyte leakage (32% and 28%) and maintained higher intercellular CO2 concentrations. Furthermore, ‘Velocity’ exhibited an accelerated flowering pattern, with the first flowering occurring 4 days sooner and 50% flowering occurring 5 days sooner than that of ‘SV4129TH’. ‘Velocity’ also demonstrated superior fruit set (14%), pollen viability (24%), and fewer incidences of flower drops (36%) compared with ‘SV4129TH’. Notably, ‘Velocity’ outperformed ‘SV4129TH’ in terms of marketable fruit yields, with a 32% higher yield. In addition to its impressive yield, ‘Velocity’ exhibited superior postharvest quality, including firmness, Brix level, acidity, and color. Therefore, overall, ‘Velocity’ and ‘Sigma’ emerged as promising genotypes with strong abiotic stress tolerance capabilities. The correlation analysis of these traits provided valuable insights into the selection and breeding of genotypes that can withstand abiotic stress conditions, laying the foundation for effective comparisons and selections of genotypes suitable for organic hydroponic cultivation in stressful environments.

Open Access

Restrictions on pumping water from underground aquifers are limiting vegetable production in Southwest Texas. To determine yield, quality, and water use efficiency (WUE) of muskmelon (Cucumis melo L. group Cantalupensis, `Caravelle'), six irrigation systems with varying input levels and their interactions with stand establishment (containerized transplants vs. direct seeding) were examined. Irrigation systems were: 1) pre-irrigated followed by dryland conditions; 2) furrow/no mulch; 3) furrow/mulch (40-μm-thick black polyethylene); 4) surface drip (0 cm depth)/mulch; 5) subsurface drip (10-cm depth)/mulch; and 6) subsurface drip (30-cm depth)/mulch. Field experiments were conducted on a silty clay loam soil during four seasons (1995-98). In 1995, marketable fruit yields were greater for subsurface drip systems at 30-cm depth than for furrow systems, with or without plastic mulch. Transplants grown with surface drip irrigation produced 75% greater yield in the 9-count fruit class size during early harvest than did those grown with subsurface drip (10- or 30-cm depth), but total yield was unaffected by drip tape depth placement. In 1996, the driest season of these studies, direct-seeded plants had higher total yields than did transplants; yield was greatest for direct-seeded plants on subsurface drip placed at 10- or 30-cm soil depth, and for transplants on subsurface drip at 10-cm depth. Soluble solids content was minimally affected by irrigation method, but was higher in fruit from transplants than in those from direct-seeded plants in 3 years. Across all seasons, the average water applied for drip systems was 53% lower than that for conventional furrow systems, and WUE was 2.3-fold as great.

Free access

Regulations restricting water use, competition for water with large urban sector, coupled with extreme high temperatures have placed a large strain on farming areas in south Texas. In addition, consumer demand for healthy vegetables has increased. The objective of this work was to determine yield and fruit quality to deficit irrigation rates and irrigation systems on poblano pepper cv. Tiburon. In 2002, an experiment was conducted at the TAES-Uvalde with a Center pivot using three irrigation rates, 100%, 80%, and 60% evapotranspiration rates (ETc). Transplants were established on beds 1.0 m apart with plants within rows 45 cm apart. In 2003, we compared production efficiency of four irrigation systems in a urban-rural environment near San Antonio. Beds were 0.9 m (single-row) or 1.8 m (double-row) between centers. Irrigation systems were: 1) furrow irrigation with one line/single beds, 2) subsurface drip (SDI)-no mulch, with one line/single bed, 3) SDI-no mulch, with two lines/double bed, and 4) SDI-white mulch with two lines/double bed. In 2002, summer ratooning of the spring-planted crop under deficit irrigation (<100% ETc) allowed a fall crop with a 2.0 fold yield increase, larger fruit size (greater than 10 cm length) and significantly lower defects caused by sunburn or blossom end rot compared to summer production. In 2003, SDI-white mulch had a 2.4-fold yield increase and 760 mm water savings compared to furrow. Fruit vitamin C content was not affected by irrigation, however, mature red fruits had a 3.6 fold increase compared to mature green fruits. Combining deficit irrigation with ratooning we were able to produce marketable poblano fruits. Additional water savings and increased yield were demonstrated by SDI technology.

Free access

Gene identification and characterization can be utilized for the identification of respective functions and their relationship to flesh color inheritance. Phytoene synthase (PSY), which converts two molecules of GGPP into phytoene, is the first committed step of the pathway. Previous phylogenetic analysis of PSY has indicated that PSY duplication is common in Poaceae, but rare in dicots. Degenerate PCR and RACE were used for PSY cloning. Three members of PSY gene family (PSY-A, PSY-B and PSY-C) were identified. PSY-A shared higher identity with PSY-C than PSY-B. PSYC shared 96% identity with melon PSY. PSY-C also showed a high homology with tomato PSY1, even higher than PSY-A and PSY-B. It showed a similar gene expression pattern, so we propose that PSY-C is a homologue to PSY1. RT-PCR analysis indicated that PSY-B has a different transcriptional behavior from PSY-A, similar to tomato PSY2. Therefore, PSY genes appear to be under different regulatory mechanisms. Deduced protein sequence of PSY1 or PSY2 between species has higher homology than between PSY1 and PSY2 within species. Phylogenetic analysis indicated that watermelon PSY gene family is very distantly related. Watermelon and carrot PSY gene families did not appear to cluster as closely as in Poaceae or tomato. This indicates that watermelon and carrot PSY genes are not conserved as much as PSY in tomato or Poaceae. There was no particular pattern in phylogenetic relationship of dicots. Poaceae PSY genes showed a clustering into a PSY1 group and PSY2 group. PSY duplication in watermelon provides additional evidence that PSY duplication may be a common phenomenon in dicots. They are likely to be duplicated evolutionarily a long time ago, possibly even prior to the evolution of monocot and dicot divergence.

Free access

Improving irrigation water management for crop production is becoming increasingly important in South Texas as the water supplies shrink and competition with urban centers in the region grows. Crop simulators and crop evapotranspiration (ET) are appealing methods for estimating crop water use and irrigation requirements because of the low investment in time and dollars required by on-site (in-field) measurement of soil and/or crop water status. We compared the effectiveness of the Crop.m.an/EPIC crop simulator and Crop-ET approaches estimating the crop water use for irrigation scheduling of spinach. In-ground weighing lysimeters were used to measure real-time spinach water use during the growing season. We related the water use of the spinach crop to a well-watered reference grass crop to determine crop coefficients (Kc) to assist in predicting accurate crop needs using available meteorological data. In addition, we ran several simulations of CropMan to evaluate the best management for growing spinach under limited water availability. Results show the possibility of saving about 61 to 74 million m3 of water per year in the 36,500 ha of irrigated farms of the Edwards aquifer region if proper irrigation management techniques are implemented in conjunction with the newly developed decision support systems. We discuss the implications of the use of these technologies for improving the effectiveness of irrigation and for reducing irrigation water requirements in South Texas.

Free access

Cowpea [Vigna unguiculata (L.) Walp.] planters can produce variable within-row seed spacing. We determined whether precision planting of cowpea would produce a yield advantage over more random planting at the same rate. Studies were conducted from May 1992 to Feb. 1993 at three locations: Uvalde, Texas; Bixby, Okla.; and Fort Pierce, Fla. Seeds of the indeterminate, small-vine cowpea cultivars Mississippi Silver and Pinkeye Purplehull BVR were hand-planted at 42 per 3.15 m of row. Seeds within rows were either spaced uniformly at 7.5 cm [control, with sd = 0] or in one of two random sequences (sd = 4.8). At harvest, in Oklahoma and Florida, mean within-row spacings were similar, but sd values of random-sequence plots remained greater than those of control plots. Control plots averaged four more plants at harvest than random-sequence plots in Texas. However, seed yield (seed dry weight per hectare) and harvest index were unaffected by uniformity of within-row spacing at all three locations. Thus, precision seeding of indeterminate, small-vine cowpea cultivars seems unlikely to produce a yield advantage over more random planting at the same rate.

Free access

The effect of zero, one, and two fruits per vine on plant growth and reaction to Monosporascus root rot/vine decline were investigated. In the first study, four cultivars with differing levels of tolerance were evaluated (`Primo', `Deltex', `Caravelle', `Magnum 45'). Vine decline ratings were taken weekly during the harvest period for 4 weeks. Treatments with no fruit showed delayed and less-severe vine decline symptoms. Temperature also effected vine decline symptom expression. In a Fall test, with lower temperatures during fruit maturity, symptoms were delayed in all treatments and often absent in treatments with no fruit load. Vine decline symptom expression is greatly effected by physiological (fruit load) and temperature stress. A subsequent study was conducted to more precisely quantify the effect of various fruit loads on shoot/root partitioning and vine decline symptoms. In addition to growth parameters root disease ratings were taken. `Caravelle', the most-susceptible genotype, was grown under differing fruit loads as mentioned above in Weslaco and Uvalde, Texas. As fruit load increased, root size decreased. Increased vine decline symptoms were observed under higher fruit loads. The implications on germplasm screening and breeding for resistance will be discussed.

Free access