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Kevin L. Cook and Leonard M. Pike

An `intermediate leaf' hybrid pickling cucumber (TAMU 884304 X ARK H-19 `little leaf') was direct-seeded at four plant densities (94,570; 48,440; 32,290; 25,375 plants/ha) using four within-row spacings (15, 30, 45, 60cm) at two locations and two seasons. Optimum yield based on marketable fruit number, grade distribution and fruit quality occurred with 94,570 plants/ha. Optimum harvest time depended on location and season. Delayed harvest times were also evaluated. Harvests with fruit >5.1cm in diameter had severely reduced brining quality. Fruit did not enlarge or enlarged slowly to oversize. This resulted in a mixture of fruit ages within the largest marketable fruit grades. It is recommended that `little leaf' lines and their hybrids such as `intermediate leaf' be harvested when fruit 3.8 to 5.1cm in diameter appear and before oversize fruit are produced. Spacing did not significantly effect length/diameter ratio(LDR) but LDR was significantly greater for delayed harvests.

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B.K. Hamilton and L.M. Pike

A field study was conducted on TG1015Y onions (Allium cepa L.) grown in the Lower Rio Grande Valley of Texas. Treatments included two soil types (clay & loam), four harvest dates throughout the bulbing process, and two S rates [0 kg S/ha (standard) & 22.4 kg S/ha (high)]. Laboratory analysis included pyruvic acid concentration for pungency measurement, percent dry matter, and sucrose, glucose, and fructose concentrations. Harvest date influenced all variables tested. Percent dry matter generally decreased as bulbs matured (8.0 to 6.9% DM) with a slight increase at maturity (7.4% DM). Enzymatically developed pyruvic acid concentrations ranged from 3.13 to 4.03 μmole/g fresh wt. There was an upward trend of pyruvic acid over the bulbing process. Total sugars, measured by HPLC methods, tended to increase during bulb development (39.3 to 46.5 mg/g fresh wt.). However, sucrose decreased during the last two harvests causing a corresponding increase in glucose and fructose. The S treatment had no effect on any of the factors measured. The only influence by soil type was sugar concentration, with the loam field being higher in glucose.

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Carlos A. Lazcano, L.M. Pike and K.S. Yoo

A new designer carrot, `BetaSweet', with high levels of anthocyanin, betacarotene, and crispy texture was developed by the Vegetable Improvement Center at Texas A&M Univ. The new carrot contained low levels of low-volatile terpenoids, responsible for the harsh flavor in carrots and high levels of reducing sugars. Carotenoid content increased with carrot maturity and stabilize at 120 days after sowing for orange and maroon genotypes; however, the maroon genotype was 35% higher than the orange cultivar. Anthocyanin, a cancer preventive compound and not detected in ordinary orange carrots, is present in `BetaSweet' maroon carrot with 89.8 mg·100 g-1 of fresh weight. High percentage of soluble solids and succulence in the maroon cultivar seemed to contribute to the favored sweetness perception by consumers. A consumer taste panel showed a significant difference between orange and maroon genotype for sweetness, texture, and overall carrot flavor.

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S.L. Grange, D.I. Leskovar, L.M. Pike and B.G. Cobb

Poor and inconsistent germination is a problem in triploid watermelon. Nicking was shown effective in improving germination in triploid cultivars. In this experiment, we examined the effects of high and low medium moisture, and nicking on diploid and triploid seed germination. Germination for the diploid cultivar was unaffected by any treatment. At high moisture conditions, triploid seed germination was severely reduced to less than 15%, while nicking significantly improved germination up to 40%. However, this increase is still not commercially acceptable. When seed morphological components were measured for each cultivar, triploid seeds had a larger and highly variable air space as compared to the diploid seed. The data confirm that seed germination is not inhibited by the seedcoat alone, but appears to be highly sensitive to excessive water conditions.

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L.M. Pike, R.V. Maxwell, R.S. Horn, B.A. Rogers and M.E. Miller

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J. Alcala, J.F. Lopes, J.J. Giovannoni and L.M. Pike

Identification and production of onion male-sterile and maintainer lines by conventional breeding takes between 4 to 8 years, due in part to the biennial nature of onion. In addition, male sterile plants and maintainer genotypes occur at a very low frequency in onion populations (Pike, 1986). A significantly shorter and more efficient alternative involves the screening of breeding lines for cytoplasmic male sterility using PCR-based technology. Thirty short-day onion breeding lines from the Texas A&M onion program were screened for type of cytoplasm (normal or sterile). Specific amplification of a fragment of chloroplast genome was achieved using the polymerase chain reaction according to Havey (1991). Forty-eight individual onion plants were screened per line. Out of thirty lines evaluated, 13 showed 100% sterile cytoplasm, 6 showed 100% normal cytoplasm, and 11 showed both types of cytoplasm. Lines showing normal cytoplasm or both cytoplasmic types were kept and reanalyzed. Only plants presenting normal cytoplasm were grown to maturity to help in the identification of maintainer lines as part of the Texas A&M onion breeding program.

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J. Alcalá-Sáinz, K.S. Yoo, L.M. Pike and R.W. Jones Jr.

Fifteen shortday onion cultivars grown at two production locations (GB and ST) in the Lower Rio Grande Valley, Texas were evaluated for pungency levels using gas chromatography (GC) and pyruvic acid tests.

Significant differences (P=0.05) were observed between cultivars in the pyruvic acid and GC tests within each location. Pyruvic acid content ranged from 3.0 to 5.1 μmol·g-1 fresh wt. The amount of total sulfur volatiles measured by the GC method ranged from 28 × 103 to 58 × 103EU. The correlation coefficients between GC and pyruvic acid were 0.10*** and 0.18*** at the GB and ST location, respectively.

When the two locations were combined, no significant differences (P=0.05) were observed between cultivars or locations using the GC test. However, the pyruvic acid test showed significant differences between locations. This result indicated that each cultivar had a different response in pungency as influenced by production location or environment.

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Ryan L. Walker, Sunggil Kim, Javier F. Betran, Kilsun Yoo and Leonard M. Pike

Onions suffer from severe inbreeding depression, which has inhibited the development of homozygous inbred lines in breeding programs. The creation of doubled haploid (DH) lines in onion provides a unique opportunity to evaluate the utility of such lines as parents in a breeding program. For this purpose, two diallele cross experiments were conducted. The first consisted of a six-parent diallele cross using six DH lines developed at Texas A&M University. The second, a four-parent diallele cross performed with two DH lines and two inbred lines from the breeding program. Bulbs from the various crosses were evaluated for diameter, height, centers/bulb, ring thickness, number of rings/bulb, bulb weight, soluble solids content, and pungency. For some traits, general combining ability (GCA) effects explained most of the variation. However, for other traits, specific combining ability (SCA) effects predominated. For all traits, GCA and SCA were always larger than the reciprocal effects (divided into maternal and nonmaternal components). The GCA and SCA effects show an inverse correlation between the number of centers/bulb and ring thickness.

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Jeffrey T. Baker, Marvin L. Baker, D. Ron Earhart, Leonard M. Pike, Kil S. Yoo and Roger Horns

Eight individual potatoes, exhibiting a wide range of quality characteristics, were cloned at the Texas A&M Vegetable Improvement Center, College Station, Tex., in order to produce a large number of slips for field trials. Leaf photosynthetic light response for six of these clonal selections was determined during a greenhouse experiment conducted at the Texas A&M Univ. Agricultural Research and Extension Center at Overton, Tex. Photosynthesis data were fit to a rectangular hyperbola in order to estimate light saturated leaf photosynthetic rate (Amax), quantum efficiency (QE), and dark respiration rate (Rd). Significant differences (P ≥ 0.05) were detected in all three of these parameter estimates among the six clonal selections. Parameter estimates ranged from 23.4 to 28.8 μmol (CO2) m-2·s-1, 0.056 to 0.071 mol (CO2)/mol (photons), and –0.9 to –2.0 μmol (CO2) m-2·s-1 for Amax, QE, and Rd, respectively. However, these differences were not clearly related to quality characteristics determined for these clones in field trials.