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Juan C. Díaz-Pérez, Albert C. Purvis, and J. Thad Paulk

Bolting causes significant economic losses in sweet onion (Allium cepa L.) production. Although temperature and photoperiod are considered to be the main factors that initiate bolting in onions, preliminary results suggested that low N fertilization rates increased bolting. The objective of our study was to determine the relationships of bolting, yield and bulb decay with N fertilization rates. The N fertilization rates applied ranged from the infraoptimal to the supraoptimal (from 102 to 302 kg·ha-1 N). Shoot and bulb N content increased with increasing N rates, but there were no differences in the respective shoot and bulb N contents among cultivars. Bolting incidence declined steadily with increasing N fertilization rates up to 197 kg·ha-1 N. Bolting incidence was among the highest in the cultivar Pegasus. The percent of decayed bulbs also increased at a steady rate with the rate of N applied. Total (14.7 t·ha-1) and marketable (0.8 t·ha-1) yields at the lowest N rate (102 kg·ha-1 N) were lower (P ≤ 0.01) than those at higher N rates. Rates of N ≥145 kg·ha-1 had no significant effect on either total (mean = 33.6 t·ha-1) or marketable (mean = 21.6 t·ha-1) yields. Losses in marketable yield were primarily a combination of bolting and bulb decay and were minimized at 162 kg·ha-1 N. Yield losses at low N rates were mostly due to bolting while yield losses at high N rates were mostly due to decay. Thus, excess applications of N fertilizer should be avoided since they have little effect on yields or bolting but they increase bulb decay.

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Ute Albrecht, Mireia Bordas, Beth Lamb, Bo Meyering, and Kim D. Bowman

rootstock liners from vegetative propagation have an inferior root system compared with liners derived from seed. In this study, we analyzed the root architecture and other plant traits of seven different rootstock genotypes, generated from seed, stem

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Kim D. Bowman and Ute Albrecht

regardless of whether the rootstock liner was propagated by nucellar seed, stem cuttings, or tissue culture. The increase in vegetative growth was largest when the daylength extension was provided by HPS lighting, although in most cases, LED lighting also

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William M. Randle

Field-grown `Granex 33' onions were subjected to four preplant calcium (Ca) treatments and evaluated for bulb quality and shelf-life over two seasons. Mature, cured bulbs were analyzed at harvest and after 1, 2, and 3 months of 4C storage. As preplant calcium increased, percentage of seed stems decreased, yield and soluble solids concentration increased, and then decreased, bulb firmness increased. Bulb pungency was unaffected by Ca fertility, except at the highest treatment. Percent bulb rot during storage first decreased with increasing Ca fertility, but then increased at the highest Ca treatment.

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H.M. Ariyarathne, D.P. Coyne, A.K. Vidaver, and K. Eskridge

The inheritance and heritability (H) of leaf and pods reactions and seed infection of common beans (Phaseolus vulgaris L.) to Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp) were studied in three crosses along with flower and stem color, and the association of reactions to Xcp in the plant organs. Recombinant inbred lines from the crosses `PC 50' × XAN 159, BAC 6 × HT 7719, and BelNeb 1 × A 55 were used. Quantitative inheritance patterns were observed for disease reactions in leaves, pods, and seeds. Stem and flower color were inherited qualitatively. Low to intermediate and intermediate H estimates were found for pod reactions when inoculated on the same time, allowing the infection to occur in a uniform environment. Intermediate to high H estimates were found for leaf and seed reactions to Xcp, respectively. Significant positive intermediate to moderately high correlations were found between the reactions to Xcp of the first trifoliolate with later-developed leaves and pods in all three populations. The moderately high genetic correlations between leaves and pods suggested that some common genes may control the reactions to Xcp in these plant organs. No association was detected between flower or stem color and reactions to Xcp.

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Stephanie E. Burnett, Svoboda V. Pennisi, Paul A. Thomas, and Marc W. van Iersel

Polyethylene glycol 8000 (PEG-8000) was applied to a soilless growing medium at the concentrations of 0, 15, 20, 30, 42, or 50 g·L-1 to impose controlled drought. Salvia (Salvia splendens F. Sellow. ex Roem & Shult.) seeds were planted in the growing medium to determine if controlled drought affects morphology and anatomy of salvia. Polyethylene glycol decreased emergence percentage and delayed emergence up to 5 days. Stem elongation of salvia treated with the five lowest concentrations was reduced up to 35% (21 days after seeding), and salvia were a maximum of 53% shorter and the canopy was 20% more narrow compared to nontreated seedlings 70 days after seeding. These morphological changes were attributed to PEG-8000 mediated reduction in leaf water potential (Ψw). The growing medium Ψw ranged from -0.29 to -0.85 MPa in PEG-8000 treated plants, and plant height was positively correlated with Ψw 21 days after seeding. Stem diameter of PEG-treated seedlings was reduced up to 0.4 mm mainly due to reductions in vascular cross-sectional area. Xylem cross-sectional area decreased more than stem and phloem cross-sectional area. Polyethylene glycol 8000 reduced vessel element number, but not diameter.

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Andrew Raymond Jamieson

lowbush blueberry propagated by seed, stem cuttings and micropropagation Acta Hort. 626 423 428

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Andrew Raymond Jamieson

propagated by seed, stem cuttings and micropropagation Acta Hort. 626 423 428 Johnston, S. 1935 Propagating low- and highbush blueberry plants by means of small side shoots Proc. Amer. Soc. Hort. Sci. 33 372 375

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growers with periods of 25 and ≤35 days, respectively, to consider early harvesting before the length of celery seed stems exceeded commercial standards. FLOWER COLOR PREFERENCES OF WESTERN FLOWER THRIPS (WFT) WFT is a major greenhouse insect pest that

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David C. Zlesak and Neil O. Anderson

flowers ( r = 0.26; Table 3 ). Significant differences were also found for percentage of ovules developing into viable seeds/stem between bulb lots, and initial bulb weight was a significant covariate in the ANOVA ( Table 4 ). The percentage of ovules