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  • Author or Editor: Daniel Leskovar x
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Broccoli, cabbage, and cauliflower were grown in the greenhouse on fallowed soil (FS) or on soil previously cropped with broccoli CBS) for three years. Fertilization levels (kg/ha) were none, 67N-22P, and 135N-44P. Inhibition of root and shoot growth components, and leaf color was evaluated at 30, 44, 58, and 72 days after seeding. Shoot and root growth of cauliflower, grown on BS, progressively declined over time, while that of broccoli and cabbage either increased or remained unaffected. Application of fertilizer (67N-22P) improved the shoot growth of cabbage but did not alleviate the symptoms associated with allelopathy, i.e., stunted growth, leaf chlorosis, reduced leaf area, observed in cauliflower. Whole plant extract of broccoli decreased percent germination of cauliflower, and reduced the speed of germination of all three test crops in the order of cauliflower>broccoli>cabbage.

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The Habanero pepper, a distinct cultigen of Capsicum chinense, has become increasingly popular in American markets due to its unique flavor and aroma. It is extremely pungent compared to other commonly cultivated hot peppers. This attribute restricts its culinary uses. The objective of the Habanero pepper improvement project was to breed for important flavor compounds in the absence of genes involved in capsaicin synthesis. Intensive selection in large breeding populations was carried out to identify individual plants producing fruit with good aroma and flavor and low capsaicin concentrations. An initial cross was made between a non-pungent selection of C. chinense out of PI 543188 and a highly pungent, typical Habanero pepper from Yucatan. A series of sib-selections following a single backcross of a non-pungent F2 individual to the Habanero line were carried out in field and greenhouse plantings at Weslaco. Six subsequent generations of inbreeding resulted in a highly uniform, novel variety-TAM Mild Habanero (TMH). The fruit of TMH is very similar in size and shape to the recurrent parent. Color is yellow-orange as opposed to the deep orange of the Yucatan Habanero (YH), but aroma and flavor are extremely similar. In contrast, total capsaicin concentration of TMH fruit at Weslaco averaged 154 μg·g-1, compared to 12,704 μg·g-1 for the YH. Field trials conducted in south Texas showed that TMH consistently matured about 10 days earlier, had significantly higher levels of beta-carotene (7.6 μg·g-1 compared to <0.5 μg·g-1 in YH) and out-yielded YH by 25%. These traits make TMH an ideal cultivar for Fall production in south Texas.

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Poor seedling emergence and stunted growth were observed in cauliflower (Brassica oleracea L., Botrytis group) and cabbage (Brassica oleracea L., Capitata group) crops when planted after three consecutive monocrops of broccoli (Brassica oleracea L., Italica group). This study was conducted to assess seed, seedling, and plant growth responses of broccoli, cabbage, and cauliflower to broccoli residue (leaves, stem + roots, and whole plant) extracts, broccoli residue incorporation, or soil previously cropped to broccoli. Osmotic potential, electrical conductivity, and pH of extracts were measured, rate (T50) and total germination were determined. Filter-sterilized leaf extract delayed T50(7.5 d) and reduced total germination (22%) of cauliflower compared to broccoli or cabbage. Similarly, plant height, shoot dry weight, and leaf area of cauliflower were significantly reduced when grown on broccoli soil in the greenhouse. Cabbage and cauliflower had low total marketable yields with more culled heads when grown in the field previously cropped to broccoli. Therefore, a potential growth inhibition of cabbage and cauliflower exists when following a continous cropping of broccoli.

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This experiment was conducted to determine the effects of deficit irrigation and growing season on fruit quality, carotenoid content and yield of red-, orange-, and yellow-fleshed diploid and triploid watermelon. Irrigation rates were 1.0 evapotranspiration (ET) and 0.5 ET. Diploid cultivars were Summer Flavor 710 (red), Tendersweet (orange), and Summer Gold (yellow). Triploid cultivars were Summer Sweet 5244 (red), Sunshine (orange), and Amarillo (yellow). Four-week old containerized transplants were planted in the field at TAES-Uvalde on 27 Mar. and 21 May 2003. Deficit irrigation imposed after plants were fully established reduced the individual fruit weight and size in the early planting. Soluble solids content (SSC) and firmness was not affected by irrigation rate in both plantings. SSC varied across cultivars and increased with maturity, particularly for the triploid cultivar Amarillo. In general, triploids were firmer than diploid cultivars. Total carotenoid content was not affected by irrigation during early planting. Diploid and triploid red-fleshed watermelon cultivars had significantly higher carotenoid content than orange- and yellow-fleshed cultivars. The major carotenoid was lycopene (more than 65%), followed by prolycopene (20%) and B-carotene (7%).

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Polyethylene mulch is widely used for vegetable production in the United States as a tool to conserve water, control weeds, and produce earlier and cleaner products (i.e., less attached soil). However, the increasing labor costs for mulch removal and disposal after harvest and soil environmental pollution are major concerns. The objective of this study was to assess fruit yield and quality, mulch deterioration, soil microbial activity, and nutrient changes in ‘Stargazer’ watermelon (Citrullus lanatus) grown with degradable plastic mulch. The deterioration rates of degradable mulch were 7%, 37%, 57%, and 92% after 120, 210, 300, and 365 days, respectively, of placing the mulch in the field. However, the extra difference in using degradable mulch was calculated as $58.6/acre (polyethylene $600.9/acre vs. degradable $659.5/acre), including all costs associated with laying and disposing. One year after placing mulch in the field, the nitrate content and total and active fungi numerically increased (P = 0.08) in soils with the degradable mulch compared with polyethylene mulch. However, there were no statistical differences in soil phosphorus, potassium, organic carbon, and total and active bacteria. Extra-large fruit size yield (category >24.0 lb) from the polyethylene mulch treatment was higher than that from degradable mulch, whereas the 18.0- to 24.0-lb category was lower than that with degradable mulch. However, total yield and total soluble solids from both mulches were statistically similar. Considering the complete deterioration (less waste), mulch removal cost (not required), microbial associations (higher fungi abundance and activity), and similar yield and fruit quality of degradable mulch compared with polyethylene, the implementation of degradable mulches in commercial watermelon field practices is promising.

Open Access

Onions (Allium cepa L.) are easily outcompeted by weeds because of slow germination and relative growth rates. Therefore, high percentage of seed germination and root vigor are important traits to improve field performance. The effects of exogenous plant growth regulators (PGRs), 2-chloroethylphosphonic acid (ethephon, Eth), indole-3-acetic acid (IAA), trans-zeatin (tZ), and 1-aminocyclopropane-1-carboxylic acid (ACC) were evaluated on the germination and root growth of ‘Don Victor’ (yellow) and ‘Lambada’ (red) onion seedlings. Seeds were soaked for 10 hours in hormonal solutions and water (hydro-priming). Seed germination improved with Eth (30 and 100 μm), Eth (100 μm) + IAA (10 μm), and IAA (3 μm) treatments. Root surface area (RSA) increased in response to Eth at 30 and 100 μm, Eth + IAA, and 3 μm IAA. Root length (RL) and root diameter (RD) were enhanced by 1 μm tZ and 100 μm ACC. Eth reduced RL and RD, whereas IAA showed no effects. A subsequent experiment evaluated synergistic effects of different PGRs. Treatment of seeds with ACC (250 μm) + tZ (0.5 μm) and ACC (250 μm) + tZ (0.5 μm) + Eth (20 μm) enhanced RL and RD. RSA was unaffected by ACC + tZ + Eth. The results suggest that exogenous PGRs could be useful to enhance germination, RL, and RSA of onion seedlings.

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In the United States, most short-day onions are direct seeded. With this method, plant stands can be reduced because of extreme temperatures, weed pressure, and soil-borne diseases. Containerized transplants offer an alternative method of stand establishment with less seedling losses while producing uniform bulb sizes and high marketable yield. However, the use of transplants is not a widespread commercial practice because of the high cost of production. This study aims to select the best transplant strategies to improve onion crop performance in semiarid regions of southwest Texas or similar environments. Three sequential transplanting dates of early, mid, and late season (14 Nov., 8 Dec., and 9 Jan.) and two seedling densities of one seed per cell (T1) and three seeds per cell (T3) were evaluated on growth, yield, bulb quality, and phytonutrient content of three onion cultivars, two yellow (‘Caramelo’ and ‘Don Victor’), and one red (‘Lambada’). During early development, late-transplanted onions had an increase in plant height and greater leaf elongation rate than early and midtransplanted onions, whereas early plantings required more days to reach maturity than mid and late plantings. Overall, early and midtransplanting dates resulted in higher yields than late plantings. Although increasing seedling density (T3 vs. T1) did not significantly reduce marketable yield in early plantings, T1 produced a higher number of jumbo and colossal bulb sizes than T3. Onion quality was mostly affected by cultivar and not by transplant strategies. The technique of establishing onions from transplants grown from one plant per cell (T1) or multiple plants (T3) from early November to early December provides a practical and economical alternative to achieve earlier crops, while reducing the length of the production season, as planting date is delayed.

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Spinach (Spinacia oleracea L.) seed germination can be inhibited by high temperatures. An understanding of thermoinhibition in spinach is critical in predicting germination and emergence events. The purpose of this study was 3-fold: 1) to determine seed germination percentage and rate of spinach genotypes—`Cascade', `ACX 5044', `Fall Green', and `ARK 88-354'—exposed to constant and alternating temperatures; 2) to determine the nature and extent of inhibition imposed by the pericarp; and 3) to investigate leachate and oligosaccharide involvement in thermoinhibition. Germination inhibition began at >20 °C constant temperature and was totally suppressed at 35 °C. Alternating temperatures at 30/15 °C (12-hour day/12-hour night) resulted in greater germination than a constant 30 °C. The genotype sensitivity to supraoptimal temperatures was in the order of `ARK 88-354' ≤ `Fall Green' < `ACX 5044' < `Cascade', but the highly thermoinhibited `Cascade' seeds retained the ability to germinate when shifted to lower incubation temperatures. The pericarp inhibited germination, since seeds deprived of the pericarp had ≈90% germination at 30 °C. `ACX 5044' and `Cascade' had higher ABA content in the pericarp than `ARK 88-354' and `Fall Green'. Before imbibition at 30 °C, raffinose levels in each genotype were in the order of `ARK 88-354' > `Fall Green' > `Cascade'. After 48 hours of imbibition, sucrose and glucose levels were highest and raffinose levels were lowest in `ARK 88-354' and `Fall Green' seeds, while `Cascade' seeds remained less active metabolically. These data suggest that the pericarp apparently acts as a physical barrier as well as a source of inhibitors during thermoinhibition.

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The objective of this work was to determine the effect of within-row plant spacing and mulching on growth, quality, and yield of an experimental semi-savoy spinach (Spinacea oleracea L.) genotype `Ark-310' to produce a high quality fresh market product. Within-row spacings were 15 and 25 cm, and mulching treatments were bare-soil and black polyethylene mulch. Plants were destructively sampled weekly (1995-96) or bi-weekly (1997-98) for leaf area (LA), leaf number, leaf dry weight (LDW) and root dry weight (RDW) measurements. Plants grown on plastic mulch at 25-cm spacing had greater LA, LDW, and RDW than when grown at 15-cm spacing on mulch or bare-soil. Leaf number and specific leaf area (LA/LDW) were less affected by either spacing or mulching. The amount of soil on harvested leaves was lower on plants grown on plastic mulch in both years. In one year, total yields (MT/ha-1) were 42% higher at 15-cm than at 25-cm plant spacing, while mulch increased yields by 20%, independently of plant spacing. These effects were not evident in the year with higher rainfall (1997-98).

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