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Stacie Grange, Daniel I. Leskovar, Leonard M. Pike, and B. Gregory Cobb

Triploid or seedless watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] cultivars often have erratic germination and low seedling vigor. The morphology of the seedcoat on two triploid cultivars—Tri X 313 and Tri X Sunrise—was examined by scanning electron microscopy (SEM) to identify structural differences compared to diploid seeds. Triploid seeds incubated with oxygen-enhanced treatments that included nicking, 1% hydrogen peroxide (H2O2), and 40% oxygen were investigated at low and high medium moisture levels. Triploid seed has a thicker seedcoat with a dense endotesta layer and a larger and highly variable air space surrounding the embryonic axis as compared with diploid seed. All cultivars rapidly imbibed water (≈50% of the original weight) during the first hour of imbibition, with a faster increase for triploids than for diploids. High moisture affected germination to a lesser extent in diploid than triploid seeds. Triploid germination under low medium moisture ranged from 96% to 76%, but was severely reduced to <27% under high medium moisture. Triploid seed germination was significantly improved at high moisture by H2O2 and by 40% oxygen. Triploid watermelon seed is very sensitive to submerged conditions, possibly due to a combination of physiological and morphological defects. The rapid imbibition and excess water collected in the seedcoat and air space surrounding the embryo, could reduce oxygen diffusion and impair metabolic pathways leading to normal germination and seedling development.

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Juan Pablo Arce-Ochoa, Frank Dainello, Leonard M. Pike, and David Drews

`Pavo', a commercially grown, virus-susceptible squash (Cucurbita pepo L.) hybrid, and two experimental virus-resistant transgenic squash hybrids, XPH-1719 and XPH-1739, were tested for field performance. The two transgenic squash hybrids possess the desired fruit and plant characteristics of their parental line, `Pavo', plus resistance to zucchini yellow mosaic virus and watermelon mosaic virus 2 (XPH-1719), and resistance to zucchini yellow mosaic virus, watermelon mosaic virus 2, and cucumber mosaic virus (XPH-1739). Percent emergence and days to flowering were similar among the three hybrids. XPH-1719 and XPH-1739 were equally effective in producing a high percentage of quality marketable fruit and yields with 90% and 13,800 kg·ha–1 and 87% and 16,500 kg·ha–1, respectively. XPH-1719 and XPH-1739 demonstrated their outstanding virus resistance over `Pavo' by producing only 3% and 14% symptomatic plants, respectively, compared to 53% for `Pavo'. They also produced the lowest percentage of infected fruit, 0% and 7%, respectively, with `Pavo' at 26%.

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Carlos A. Lazcano, Frank J. Dainello, Leonard M. Pike, Marvin E. Miller, Lynn Brandenberger, and Larry R. Baker

Baby-style carrot Daucus carota Mill. cv. Caropak was studied under four population densities, three different numbers of lines per bed, and harvested under three root size harvest parameters in the Rio Grande Valley of Texas. Four phases in the baby-style carrot process were evaluated. Length of the roots at harvest and projected values for total waste and marketable yield were estimated. Length was affected by root size at harvest, the most desirable root length occurred when harvested at 25%-35% roots diameter >2 cm. The longer roots (16.55 cm) were in the treatments with 6 seed lines per bed and 197 plants/m2. Population density affected the fresh and cut weight in the baby-style carrots process with the highest weight at 321 plants/m2. Percent of cut waste was the same at the three-root size at harvest with 21.65% of crowns and tips cut. The percent of graded waste was lowest when harvested at the biggest root size, 14.23% and four seed lines per bed produced the highest waste with 18.14. Seed lines per bed affected the quality of the roots in the graded step. Based on a 40% peeling waste projection the lowest total waste was estimated at 59.69% and the highest projected marketable yield of 19.4 t/ha of final product when roots were harvested using the 25%-35% root diameter parameter. Root size at harvest is the main factor affecting projected marketable yield of baby-style carrots in South Texas.

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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.

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Carlos A. Lazcano, Frank J. Dainello, Leonard M. Pike, Marvin E. Miller, Lynn Brandenberger, and Larry R. Baker

Carrot (Daucus carota Mill. cv. Caropak) was studied under four population densities, and three numbers of seed lines per bed, and was harvested under three root size harvest parameters. Four phases (cutting, grading, peeling, and marketable yield) in the cut-and-peel baby carrot process were evaluated. Root length was most desirable when plots were harvested when 25% to 35% of the roots measured >2 cm in diameter. Roots were longest (14.7 cm) in the treatments containing six seed lines per bed. The harvest criteria of 25% to 35% root diameter >2 cm also produced the highest fresh mass (48.1 t·ha-1), and the highest cut and graded mass (37.7 and 32.3 t·ha-1, respectively). A population density of 321 plants/m2 produced the highest fresh and cut mass. Percent cut waste (21.6% crowns and tips) was not affected by root size at harvest, but percent graded waste was lowest (14.2%) when plants were harvested at the greatest root size. Four seed lines per bed produced the highest graded (18.4%), and total waste (61.2%), but not cut waste. The lowest total waste, estimated at 59.7% and the highest projected marketable yield (19.4 t·ha-1) occurred when roots were harvested using the 25% to 35% root diameter >2-cm parameter. Total waste and marketable yield were obtained using a fixed waste value of 40% in the peeling phase (peeling, polishing, and grading before packing). This percentage could vary depending on the equipment specifications and quality control of a given processing facility. Root size at harvest proved to be the main factor affecting projected marketable yield of cut-and-peel baby carrots at the population densities used in this study.

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Carlos A. Lazcano, Frank J. Dainello, Leonard M. Pike, Marvin E. Miller, Lynn Brandenberger, and Larry R. Baker

Carrot (Daucus carota Mill. cv. Caropak) was studied under four population densities, and three numbers of seed lines per bed, and was harvested under three root size harvest parameters. Four phases (cutting, grading, peeling, and marketable yield) in the cut-and-peel baby carrot process were evaluated. Root length was most desirable when plots were harvested when 25% to 35% of the roots measured > 2 cm in diameter. Roots were longest (14.7 cm) in the treatments containing six seed lines per bed. The harvest criteria of 25% to 35% root diameter >2 cm also produced the highest fresh mass (48.1 t·ha-1), and the highest cut and graded mass (37.7 and 32.3 t·ha-1, respectively). A population density of 321 plants/m2 produced the highest fresh and cut mass. Percent cut waste (21.6% crowns and tips) was not affected by root size at harvest, but percent graded waste was lowest (14.2%) when plants were harvested at the greatest root size. Four seed lines per bed produced the highest graded (18.4%), and total waste (61.2%), but not cut waste. The lowest total waste, estimated at 59.7% and the highest projeced marketable yield (19.4 t·ha-1) occurred when roots were harvested using the 25% to 35% root diameter >2-cm parameter. Total waste and marketable yield were obtained using a fixed waste value of 40% in the peeling phase (peeling, polishing, and grading before packing). This percentage could vary depending on the equipment specifications and quality control of a given processing facility. Root size at harvest proved to be the main factor affecting projected marketable yield of cut-and-peel baby carrots at the population densities used in this study.