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Denise V. Duclos and Thomas N. Björkman

Brassica oleracea species differ in the developmental stage of their reproductive meristems at harvest. The stage that characterizes each variety depends on its genetic makeup, environment and the interaction between them. We tested a model of arrest in B. oleracea to determine functional redundancy among the paralogous genes CAL, AP1a, AP1c, FULa, FULb, FULc, and FULd; and to resolve the immediate effect of temperature on gene expression in meristems whose developmental fate is temperature regulated. By varying temperature during reproductive development, three stages of arrest were obtained: inflorescence meristem (cauliflower), floral meristem (intermediate) and floral bud (broccoli), the latter initiated by low temperature. Gene expression was measured by quantitative real time PCR (qRT-PCR). The LFY/TFL1 ratio increased as the reproductive development advanced, mainly due to decreased TFL1 expression; influenced by a dramatic increase in AP1c toward floral bud formation. The expression patterns of the FUL paralogs indicate different roles in reproductive development. FULa was more abundant in the floral primordia, while FULb, FULc, and FULd were associated with earlier arrest at the inflorescence meristem stage. The high expression of FULc and FULd at all stages of arrest differs from their homolog in Arabidopsis. High temperature reduced AP1 and LFY expression but the meristem did not revert from reproductive to vegetative. Floral bud formation in plants recessive for AP1a and CAL reaffirm that functional redundancy among some of these genes can complement the mutations. Varying temperature alone, at a fixed developmental stage, caused little variation in the expression of genes studied, causing small significant differences in TFL1 and AP1c.

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Rachel A. Kreis, Holly W. Lange, Stephen Reiners, and Christine D. Smart

summer/autumn cauliflower ( Brassica oleracea var. botrytis L.) J. Expt. Bot. 44 1507 1514

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Lavesta C. Hand, Kayla M. Eason, Taylor M. Randell, Timothy L. Grey, John S. Richburg, Timothy W. Coolong, and A. Stanley Culpepper

Cole crop [broccoli, cabbage ( Brassica oleracea var. oleracea L.), and cauliflower ( Brassica oleracea var. botrytis L.)] and leafy green [collards and kale ( Brassica oleracea var. sabellica L.)] production in the United States

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Claude E. Thomas and E.L. Jourdain

Evaluations for resistance against race 2 of downy mildew, incited by Peronospora parasitica, were conducted on 240 U.S. Plant Introductions (PI) classified as Brassica oleracea var. botrytis (consists of both broccoli and cauliflower types). Plants were inoculated at the two-expanded leaf stage with 5.0 × 103 sporangia per ml. Inoculated plants were incubated in a dark 16C dew chamber for 24 hr and were then placed in a 22C growth chamber with a 12-hr photoperiod. On the 7th day after inoculation, plants were returned to the dew chamber for 30 hr and ratings for downy mildew reaction phenotypes were made at 9 days postinoculation on a 0-9 scale of increasing disease severity. A disease index (DI) was calculated for each entry. Based on the DI, no PI entries were highly resistant. PI entries 181860, 188562, 204765, 204768,204772,204773, 204775,204779,241612, 264656,291567,373906, and 462225 were moderately resistant. (DI of 3.1-5).

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Nathan H. Peck and George E. MacDonald

Abstract

Cauliflower (Brassica oleracea var. botrytis L. ‘Imperial 10-6’), broccoli (Brassica oleracea var. italica Plenck ‘El Centro’), and brussels sprouts (Brassica oleracea var. gemmifera Zenk. ‘Jade Cross’) were grown at 0, 84, 336, and 1344 kg of concentrated superphosphate (CSP) (0, 17.5, 70, and 280 kg P) and 0, 67, 268, and 1072 kg of potassium chloride (KC1) (0, 35, 140, 560 kg K) fertilizers per hectare, per application in a long-term plant nutrition experiment. Increasing the rate of CSP increased the concentrations of P, Ca and Mg but decreased K and Zn in leaf blades at midseason. Increasing the rate of KC1 increased the concentrations of K and Zn but decreased Ca and Mg in leaf blades. Increasing the rates of CSP and KC1 hastened maturity and increased yields of cauliflower and broccoli in harvest sequences, whereas brussels sprouts were less responsive to CSP or KC1 at one harvest. High rates of CSP without KC1 reduced the yield of cauliflower compared to the lower rates. Increasing the rate of KC1 increased the incidence of hollow stem, a quality defect, in cauliflower and broccoli. Best production of uniform maturity and yield was obtained with a combination of the CSP at 336 kg·ha−1 and KC1 at 268 to 1072 kg·ha−1 per application in a long-term rotation.

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K.T. Demchak and C.B. Smith

In a 3-year study with broccoli [Brassica oleracea var. botrytis (L.) Mill. cv. Green Comet], NP or NPK fertilizer at rates of 56N-56P-0K, 56N-56P-56K, and 56N-112P-56K (kg·ha-1) were banded in plots to which three types of lime had been applied—calcitic, calcitic with 3% Mg, or dolomitic. Fertilizer and lime controls were included. Previous liming had raised the soil pH from 5.3 to 7.2-7.4. Effects of lime on yields were greatest when no fertilizer was applied. Dolomitic lime was the most effective, increasing total yield by 49%, terminal weight by 54%, and hastening maturity. Fertilizer effects were most evident when no lime had been applied, with all fertilizer treatments increasing total yield, terminal and plant weight, and hastening maturity. Most changes occurred in the 56N-56P-OK treatment. Effects of lime when fertilizer was applied and effects of fertilizer when lime had been applied were less consistent. Lime alone, especially types containing Mg, increased leaf P, which generally followed the-same trend as total yield. Calcitic lime increased leaf Ca and dolomitic lime increased leaf Mg over other lime treatments. Calcitic lime with 3% Mg increased leaf Ca, but not leaf Mg, compared to the check. All lime treatments decreased leaf Mu, B, and Zn. Fertilizer treatments usually increased leaf N and Mn. Phosphorus uptake was increased by either lime or fertilizer application. Regression analysis strongly suggested that P was the element most responsible for yield increases.

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Jeff B. Million, James E. Barrett, Terril A. Nell, and David G. Clark

A broccoli (Brassica oleracea var. botrytis L.) seedling bioassay was used to measure paclobutrazol activity and distribution in two growing media following drench or subirrigation applications. The bioassay exhibited a saturation-type response curve for paclobutrazol concentrations up to 1000 μg·L-1 in solution and 100 μg·L-1 in the media. The concentration of paclobutrazol required to achieve one-half of the maximum observed bioassay activity was 3-fold as high in bark-based commercial potting medium as in a peat-based medium. Less than 2% of applied paclobutrazol leached out during the drench application despite the collection of up to 50 mL of leachate per 120 mL of the solution (1000 μg·L-1) that was applied per 15-cm pot. Immediately following drench application, paclobutrazol concentrations in both media were highest in the uppermost 2.5 cm and decreased downward. By 3 weeks after treatment, drench-applied paclobutrazol had moved into lower depths. Distribution of paclobutrazol was limited to the bottom 2.5 cm of media when applied as a subirrigation soak. Chemical name used: (±)-(R*,R*)-β-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

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J.B. Million, J.E. Barrett, T.A. Nell, and D.G. Clark

Three experiments were conducted to evaluate media component effects on paclobutrazol activity. In Expts. 1 and 2, a broccoli (Brassica oleracea var. botrytis L.) seedling bioassay was used to compare the activity of paclobutrazol at six concentrations (0-0.32 mg·L-1). Results from Expt. 1 indicated that an average of 4-, 5-, and 10-fold higher concentrations were required in old composted pine bark, fresh pine bark, and composted pine bark samples, respectively, to achieve the same activity observed in sphagnum peatmoss (peat) samples. Activity in coir was similar to that in peat while activity in vermiculite and perlite was greater than that in peat. Activity in a fibrous peat sample was greater than in two less-fibrous peat samples. Results from Expt. 2 indicated that paclobutrazol activity was reduced more in the fine (<2 mm) fraction of fresh and composted bark samples than in medium (2-4 mm) or coarse (>4 mm) fractions. In Expt. 3, petunia {Petunia hybrida Vilm. `Madness Red') was grown in a mixture of either 60% composted pine bark: 0% peat or 0% composted bark: 60% peat. The paclobutrazol concentration required to achieve the same size control was 14 times higher in the former mixture than in the latter. Thus, media components differ greatly in their influence on paclobutrazol activity and the bioassay procedure may serve as a useful tool for predicting media-paclobutrazol interactions. Chemical name used: (±)-(R*,R*)-β-[(4-chlorophenyl)methyl]-α-(l,l-dimethyl)-lH-l,2,4-triazole-l-ethanol (paclobutrazol).

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Rachel E. Rudolph, Carl Sams, Robert Steiner, Stephen H. Thomas, Stephanie Walker, and Mark E. Uchanski

evaluate the biofumigation performance of four Brassicas including three mustard cultivars ( Brassica juncea ‘Caliente 61’, ‘Caliente 199’, ‘Pacific Gold’) and one broccoli cultivar ( Brassica oleracea var. botrytis ‘Arcadia’) in the semiarid climate

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Denise V. Duclos and Thomas Björkman

, S. 1968 Effect of gibberellic acid and cold treatment on flower differentiation and stem elongation of cauliflower, Brassica oleracea var. botrytis Isr. J. Agr. Res. 18 133 134 Liljegren, S.J. Gustafson-Brown, C. Pinyopich, A. Ditta, G.S. Yanofsky