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- Author or Editor: Christopher S. Cramer x
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The relationships between fruit yield and yield components in several cucumber (Cucumis sativus L.) populations were investigated as well as how those relationships changed with selection for improved fruit yield. In addition, the correlations between fruit yield and yield components were partitioned into partial regression coefficients (path coefficients and indirect effects). Eight genetically distinct pickling and slicing cucumber populations, differing in fruit yield and quality, were previously subjected to modified half-sib family recurrent selection. Eight families from three selection cycles (early, intermediate, late) of each population were evaluated for yield components and fruit number per plant in four replications in each of two testing methods, seasons, and years. Since no statistical test for comparing the magnitudes of two correlations was available, a correlation (r) of 0.7 to 1.0 or –0.7 to –1.0 (r 2 ≥ 0.49) was considered strong, while a correlation of –0.69 to 0.69 was considered weak. The number of branches per plant had a direct positive effect on, and was correlated (r = 0.7) with the number of total fruit per plant over all populations, cycles, seasons, years, plant densities, and replications. The number of nodes per branch, the percentage of pistillate nodes, and the percentage of fruit set were less correlated (r < |0.7|) with total fruit number per plant (fruit yield) than the number of branches per plant. Weak correlations between yield components and fruit yield often resulted from weak correlations among yield components. The correlations among fruit number traits were generally strong and positive (r ≥ 0.7). Recurrent selection for improved fruit number per plant maintained weak path coefficients and correlations between yield components and total fruit number per plant. Selection also maintained weak correlations among yield components. However, the correlations and path coefficients of branch number per plant on the total fruit number became more positive (r = 0.67, 0.75, and 0.82 for early, intermediate, and late cycles, respectively) with selection. Future breeding should focus on selecting for the number of branches per plant to improve total fruit number per plant.
Currently, both hybrid and inbred pickling cucumber cultivars are being grown commercially in the United States. Heterosis for yield in pickling cucumber has been previously reported. However, heterosis has not been repeatable in other studies. The objective of this study was to determine the existence of heterosis and inbreeding depression for yield in pickling cucumber. Six pickling cucumber inbreds (`Addis', `Clinton', M 12, M 20, `Tiny Dill', `Wisconsin SMR 18') were hybridized to form four F1 hybrid families (`Addis × M 20, `Addis' × `Wis. SMR 18', `Clinton' × M 12, M 20 × `Tiny Dill'). Within each family, F2, BC1A and BC1B generations were also formed. Thirty plants of each generation within each family were grown in 3.1-m plots for four replications in the spring and summer seasons of 1996 at the Horticultural Crops Research Station in Clinton, N.C. Data were collected at once-over harvest for total, marketable, and early yield in terms of number (1000 fruit/ha) and weight (Mg/ha). In addition to yield, a fruit shape rating was collected for each plot. High parent heterosis for yield (total and marketable fruit weight) was only observed for `Addis' × `SMR 18' grown in the summer season. The three other families did not exhibit heterosis for total, marketable, and early yield. Heterosis for shape rating was not observed for any family. `Addis' × `Wis. SMR 18' also exhibited inbreeding depression for total fruit weight, marketable fruit weight, early fruit number, and early fruit weight during the spring season and for marketable fruit number and marketable fruit weight during the summer season.
Onions grown in New Mexico are currently harvested manually at 80% tops down (TD). Mechanical harvesting is a matter of urgency for growers in order to remain competitive and to reduce their cost and time. The objective of this study was to find the effect of different harvest stages on bulb quality. Twelve different onion cultivars were sown in Feb. 2004 in Las Cruces, N.M. The experiment was laid out in split-plot design with four harvest treatments based on physiological maturity—20% TD, 80% TD, 1 week after 80% TD, and 2 weeks after 80% TD as whole plots, with cultivars as sub-plots. After curing, data on harvest date, bulb diameter, height, firmness, number of growing points, average center diameter, fleshy scale number, and scale thickness were collected. Maximum number of scales was observed when bulbs were harvested 2 weeks after 80% TD, while average scale thickness was greatest when bulbs were harvested 1 week after 80% TD. Significant treatment by cultivar interaction was observed for bulb firmness. Cultivars Cimarron, Sierra Blanca and NMSU 04-52-2 produced firmer bulbs in all treatments, while NuMex Casper, NuMex Jose Fernandez and NuMex Centric produced firmer bulbs than others, only at 20% TD. Maximum bulb firmness was observed in NMSU 04-28 and NMSU 03-52-1 than others, when harvested 1 or 2 weeks after 80% TD. Overall, bulbs harvested 1 to 2 weeks after 80% TD exhibited firmer bulbs with more scales and greater scale thickness.
Onions grown in New Mexico currently are hand-harvested. In order to remain competitive and to lower production costs, growers will need to harvest onions mechanically. The current recommendation for harvest time is when 80% of onion tops have fallen. The objective of this study was to measure several bulb quality traits when bulbs were harvested at four different stages. Twelve short- and intermediate-day onion cultivars of different maturities were sown during Sept. 2004 in Las Cruces, N.M. Bulbs were harvested at four stages of physiological maturity: 20% tops down (TD), 80% TD, 1 week after 80% TD, and 2 weeks after 80% TD. After curing, data on harvest date, bulb diameter, height, firmness, number of growing points, average center diameter, fleshy scale number, and thickness were collected. For most traits, no differences existed among the different treatments. For the earliest-maturing cultivars, the maximum bulb firmness and number of scales were observed when bulbs were harvested 2 weeks after 80% TD. For later-maturing cultivars, the maximum number of scales was observed 1 week after 80% TD, while the maximum bulb firmness was observed at 2 weeks after 80% TD. For latest-maturing cultivars, bulbs harvested at 1 week after 80% TD were firmer than bulbs harvested at other times. For later-maturing cultivars, average scale thickness was greatest when bulbs were harvested 2 weeks after 80% TD. From this work, a delayed harvest of 1 to 2 weeks after 80% TD resulted in firmer bulbs with more scales.
Numerous short-day onion accessions maintained at the Plant Genetic Resources Unit (PGRU) of Geneva, N.Y., were in danger of being lost from the U.S. germplasm collection due to sub-standard viability and low seed supply of those accessions. Seed regeneration of short-day onions at Geneva, N.Y., has been difficult because of improper daylengths and environmental conditions. A project was initiated in Sept. 2001 between PGRU and the onion breeding program at New Mexico State University to regenerate 75 accessions that were in the most danger of being lost from the collection. Even though germination rates were low for most accessions, plants were recovered from 72 accessions. Two accessions did not produce bulbs as it was likely they were long-day accessions. Of the remaining accessions, two accessions produced bulbs but did not produce seed. Several accessions bolted during bulb production and plants were covered with crossing cages, crosses were made, and seed was collected. Seed of 54 accessions were sent to PGRU to be incorporated back into the collection and to become available for distribution. Seventeen accessions produced less than 35 g of seed and were retained in order to produce additional seed in a second regeneration step. Some of the short-day accessions that have become available include `Amarela Globular Rio Grande', `Babosa', `Baia Performe Sintese No. 22', `Beth Alpha', `Burgundy', `California Early Red', `Dehydrator No. 5', `Early Crystal', `Eclipse L303', `Imperial 48', `New Mexico Yellow Grano', `Pusa Red', `Red Bermuda', `Red Creole', `Red Grano', `Red Patna', and `Rio Grande'.
Disinfected midrib sections of Mussaenda `Queen Sirikit' ≈3 to 4 mm in size were cultured on a basal medium of Murashige and Skoog salts and vitamins, 87.7 mm sucrose, and 5 g Sigma agar/liter supplemented with several concentrations of indole-3-acetic acid (IAA) (0, 5.0, 10.0, 20.0 μm) and 6-benzylaminopurine (BAP) (0, 0.5, 1.0, 2.5, 5.0, 10.0, 25.0, 50.0 μm). Cultures were subculture onto the same treatment after 5 weeks and observed weekly for 15 weeks for the presence of somatic embryos. As somatic embryos were produced, they were subculture onto basal medium supplemented with 0.5, 1.0, 2.5, or 25.0 μm BAP. Callus was first observed at 2 weeks in cultures grown on basal medium supplemented with 5.0–20.0 μm IAA and 0–50.0 μm BAP. Somatic embryos were observed at 8 weeks on basal medium supplemented with 5.0–10.0 μm IAA and 2.5–5.0 μm BAP. Callus cultured on 0–10 μm IAA and 5.0–10.0 μm BAP produced the greatest number of somatic embryos by 15 weeks. Somatic embryos subculture to basal medium supplemented with 25.0 μm BAP proliferated shoots, while eliminating BAP from the medium resulted in root and callus production. Shoots and entire plants were removed from in vitro conditions and successful] y acclimated to greenhouse conditions. Somatic embryo-derived plants flowered sporadically 25 to 35 weeks after removal from in vitro conditions. Variations in sepal number and leaf number per node were observed at 1% to 5%.
Mussaenda, a tropical ornamental shrub developed in the Philippines is being examined as a potential greenhouse potted crop in the United States. Showy sepals of white, picotee, pink or red and fragrant, yellow flowers make Mussaenda an attractive patted plans however, the profuse upright growth habit of some Mussaenda cultivars is undesirable for pot plant culture. With this in mind experiments were conducted to determine the effects of three growth regulators at two concentrations each, as well as the application method and the number of applications on Mussaenda plant height.
Three growth regulators, daminozide (B-Nine), ancymidol (A-Rest), and paclobutrazol (Bonzi) were applied at two commercially recommended rates and two application methods (spray or drench). The treatment were daminozide at 2500 ppm and 5000 ppm (spray), ancymidol at 33 and 66 ppm (spray) and at 0.25 and 0.50 mg/pot (drench), and paclobutrazol at 25 and 50 ppm (spray) and at 0.125 and 0.25 mg/pot (drench). In subsequent experiments, the same growth regulators were applied with an increase in concentration and either two or three applications. The treatments were daminozide at 5000 ppm (spray), ancymidol at 66 and 132 ppm (spray) and at 0.50 and 1.0 mg/pot (drench), and paclobutrazol at 50 and 100 ppm (spray) and at 0.25 and 0.50 mg/pot (drench).
The most attractive potted plants were produced with two applications of daminozide at 5000 ppm or two applications of ancymidol at 0.5 mg/pot (drench). Higher concentrations or additional applications excessively reduced plant height. Three spray applications of 132 ppm ancymidol also produced an attractive potted plant. Paclobutrazol sprays or drenches at any concentration or application number were ineffective for reducing Mussaenda `Queen Sirikit' plant height.