Broccoli Seedlings Research Articles

Effect of Wirestem Severity on Survival and Head Production of Transplanted Broccoli and Cabbage.

Field experiments were conducted with transplants of Brassica oleracea with known severity levels of wirestem caused by Rhizoctonia solani anastomosis group 4. Seedlings of broccoli and cabbage were grown in steamed soil infested with R. solani at 5 to 25 sclerotia/kg. Two weeks after inoculation, plants were separated into five severity classes based on wirestem symptoms, then transplanted into fumigated field plots in the spring and fall of 1995. The percentage of plants with and without aboveground symptoms was assessed at 14 and 42 days after transplanting. Marketable-sized heads were harvested eight times. In both seasons, percentages of symptomless plants, surviving (symptomless plus symptomatic) plants, and plants producing a marketable-sized head decreased as wirestem severity increased. Only 33 and 29% of cabbage transplants with >75% of the stem circumference girdled survived and produced a marketable head, respectively, compared with 95 and 83% of healthy transplants, respectively. For broccoli, only 15% of transplants with girdled stems survived and produced heads in spring but, in the fall, 74 and 72% of transplants with girdled stems survived and produced heads, respectively. Percentage of plants producing a marketable-sized head was highly correlated (P = 0.0001) with percentage of symptomless plants at 14 days after transplanting and percentage of surviving plants at 42 days after transplanting.

Responses of Broccoli Seedlings to Light Quality during Low-temperature Storage in Vitro: I. Morphology and Survival

Broccoli (Brassica oleracea L. Botrytis group `Green Duke') seeds were cultured in vitro photoautotrophically (without sugar in the medium) or photomixotrophically (with sugar in the medium) for 3 weeks at 23 °C and 150 μmol·m-2·s-1 photosynthetic photon flux (PPF). Vessels were then stored at 5 °C under 1.6, 4.1, or 8.6 μmol·m-2·s-1 of white (400-800 nm), red (600-700 nm), or blue (400-500 nm) light. Concentrations of CO2 inside the vessels were monitored until equilibrium was reached. Light compensation point was reached at 3.5 μmol·m-2·s-1 for photoautotrophic seedlings and at 6.5 μmol·m-2·s-1 for photomixotrophic seedlings. Therefore, in the long-term storage experiment, seedlings were stored for 4, 8, or 12 weeks at 5 °C in darkness or under 5 μmol·m-2·s-1 (average light compensation point) of white, red, or blue light. Illumination during storage was necessary to maintain dry mass, leaf area, and regrowth potentials of in vitro seedlings. All seedlings stored in darkness were of poor quality and died when transferred to the greenhouse. Red light during storage increased seedling dry mass and chlorophyll content and improved overall appearance, whereas blue light decreased chlorophyll content and increased stem elongation. The addition of 2% sucrose to media increased dry mass and leaf area and maintained overall seedling quality during illuminated storage. However, plantlets stored for more than 4 weeks did not survive poststorage greenhouse conditions, regardless of light treatment.

Responses of Broccoli Seedlings to Light Quality during Low-temperature Storage in Vitro: II. Sugar Content and Photosynthetic Efficiency

Broccoli (Brassica oleracea L. Botrytis group `Green Duke') seeds were cultured photoautotrophically (without sugar) or photomixotrophically (with sugar) in vitro for 3 weeks at 23 °C and150 μmol·m-2·s-1 photosynthetic photon flux (PPF). In vitro seedlings were stored for 0, 4, 8, or 12 weeks at 5 °C in darkness or under 5 μmol·m-2·s-1 of white (400–800 nm), blue (400–500 nm), or red (600–700 nm) light. Photosynthetic ability and soluble sugar contents were determined after removal from storage. Photomixotrophic seedlings contained approximately five times more soluble sugars than did photoautotrophic seedlings. Dark storage reduced soluble sugars in both photoautotrophic and photomixotrophic plants, but photosynthetic ability was maintained for up to 8 weeks in the latter whereas it decreased in the former. Illumination in storage increased leaf soluble sgars in both photoautotrophic and photomixotrophic seedlings. Soluble sugars in stems decreased during storage regardless of illumination, but remained higher in illuminated seedlings. Red light was more effective in increasing or maintaining leaf and stem soluble sugars than was white or blue light. Regardless of media composition or illumination, storage for more tan 8 weeks resulted in dramatic losses in quality and recovery, as well as photosynthetic ability. Seedlings stored for 12 weeks comletely lost their photosynthetic ability regardless of media composition or illumination. The results suggest that carbohydrate, supplied in the media or through illumination, is essential for maintenance of photosynthetic ability during low-temperature storage for up to 4 or 8 weeks.

Biosynthesis of sulfur volatile compounds in broccoli seedlings stored under anaerobic conditions

Abstract Sterile broccoli seedlings were used to investigate the effects of anaerobic atmosphere on biosynthesis and emission of sulfur volatile compounds which are responsible for off-odors in controlled and modified atmosphere stored broccoli. The identification of methanethiol, dimethyl sulfide, dimethyl disulfide and hydrogen sulfide in the head space of anaerobically stored broccoli seedlings confirmed that undesirable odors in broccoli are of plant origin. Evidence in support of the enzymatic origin of these volatiles was also obtained by using aminooxyacetic acid which is a potential inhibitor of pyridoxal phosphate-dependent enzymes; the production of sulfur volatiles was delayed and reduced by more than 95%. However, an anaerobic atmosphere had no inducible effect on the activities of cystine lyase, S-alkylcysteine lyase and cysteine desulfhydrases. These pyridoxal phosphate-dependent enzymes are thought to be involved in the production of volatile sulfur compounds by catalyzing the respective breakdown of cystine, cysteine and S-methyl- l -cysteine. The results suggest that these enzymes are not limiting factors in the production of sulfur volatiles in broccoli. However, the analysis of the contents of free sulfur amino acids and their derivatives showed an important increase in potential substrates for the synthesis of volatile sulfur compounds such as cysteine, methionine and S-methylcysteine as a result of anaerobic treatment. This increase usually preceeded or corresponded with the increased emission of sulfur volatiles. Results obtained by monitoring individual free amino acid content variation as a function of storage time, under anaerobic conditions, suggested enhanced conversions among sulfur amino acids. Other sources of sulfur amino acids, such as protein degradation and de novo synthesis, might explain the increase in these amino acids under anaerobiosis.

Differential Tolerance of Broccoli (Brassica oleracea) Cultivars to Preemergence Application of Oxyfluorfen

The tolerance of 10 broccoli cultivars to preemergence (PRE) applications of oxyfluorfen was evaluated in greenhouse and field experiments. Differences in tolerance among cultivars were expressed as differences in seedling injury ratings and growth and stand reduction. The cultivars ‘Pinnacle’ and ‘Mercedes’ were most tolerant, ‘Embassy’ and ‘Early Dawn’ were least tolerant, and other cultivars were intermediate in tolerance. Broccoli seedling weights and stand counts averaged across 10 cultivars and oxyfluorfen application rates of 0.125, 0.25, and 0.5 kg/ha were 70 and 81% of control, respectively, for the two fall-planted experiments and 39 and 50% of control, respectively, for the spring-planted experiment. Differences in tolerance among cultivars were less distinct in the cooler spring than in the warmer fall season. Oxyfluorfen application that caused stand and early growth reduction did not always affect broccoli head weight or quality or delay harvest.

Studies on the Allelopathic Effect of Corn Spurry (Spergula arvensis L.) on Cole Crops and English Pea

These studies were initiated to investigate severe growth inhibition observed when some vegetable crops were infested with corn spurry (Spergula arvensis L.). Interference by a natural population of the weed reduced the shoot weights of English pea (Pisum sativum L.) and collard (Brassica oleracea L.) by 93% and 72%, respectively. In a greenhouse experiment where light competition by corn spurry was prevented, broccoli (Brassica oleracea L.) shoot weights were reduced by corn spurry, but pea weights were not different from the controls. Homogenized corn spurry shoot tissue incorporated into a greenhouse potting medium inhibited the growth of both species, and a concentration effect was observed. Sequential hexane, dichloromethane, methanol, and 50% aqueous methanol extracts of corn spurry root and shoot tissue were tested for inhibitory activity using millet seed germination and broccoli seedling growth bioassays. Dichloromethane, methanol, and aqueous methanol shoot extracts were inhibitory to broccoli; whereas all shoot extracts inhibited millet germination. Shoot extracts were more inhibitory than root extracts. Further fractionation of the inhibitors using a combination of reversed-phase sephadex LH-20 and silicic acid column chromatographic procedures showed that a major portion of the millet germination inhibition was due to sucrose esters (SE). Preliminary characterization of the esters showed that there were four different SE groups. The major groups contained either octanoic or dodecanoic acid along with butanoic and petanoic acids. All groups inhibited seed germination at concentrations as low as 20 ppm. This is the first report of the SE class of defense chemicals in plant species outside of the solanaceae family.

Influence of Several Container Media Components on Paclobutrazol Efficacy

A broccoli seedling bioassay was used to compare the activity of paclobutrazol applied at six concentrations to 20 media component samples mixed 1:1 (v:v) with vermiculite. Results indicated that 4-, 5-, and 10-fold higher media paclobutrazol 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. Paclobutrazol bioassay activity in coir was similar to the activity observed in peat, while activity in vermiculite and perlite was greater than in peat. In a second trial, 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 a third trial, petunias grown in a 60% composted pine bark:0% peat mix required a »14-times higher drench paclobutrazol concentration to achieve the same size control as petunia grown in a 0% composted bark:60% peat mix. It was concluded that media components differed greatly in their influence on paclobutrazol activity and that the bioassay procedure might serve as a useful tool for predicting media–paclobutrazol interactions.

Effects of Anaerobic Atmosphere on the Metabolism of Sulfur Volatile Compounds Produced by Broccoli

Objectionable off-odors are produced by broccoli (Brassica oleracea, L.) when it is held under anaerobic conditions. These off-odors were attributed to sulfur volatile compounds mainly methanethiol (MT) and hydrogen sulfide. The present study was undertaken to investigate the effects of anaerobic conditions on the metabolism and emission of sulfur volatiles by broccoli. Inhibition assays using aminooxyacetic acid (AOA)—a potential inhibitor of pyridoxal-phosphate-dependent enzymes-confirmed the enzymatic origin of these volatiles. However, anaerobic atmosphere had no inducible effect on the enzymes cystine lyase, cysteine desulfhydrases and S-alkylcysteine lyase. These pyridoxal-phosphate-dependent enzymes thought to catalyze the respective degradation of cystine, cysteine and S-methyl-L-cysteine to sulfur volatiles showed no significant activity increase. Storage of sterile broccoli seedlings under anaerobic atmosphere resulted in an important increase of the content of sulfur amino acids that corresponded to an increased emission of sulfur volatiles. Cysteine and methionine content increased particularly at 24 hours and decreased later. Whereas, S-methyl-L-cysteine content increase was more obvious after 48 hours. The results suggest a possible involvement of the pathways for synthesis and breakdown of sulfur amino acids via methionine.

Distribution of Paclobutrazol in Media Following Drench Applications

Drench applications of paclobutrazol (PBZ) are becoming increasingly popular as a means for controlling height in potted plants, and research is being conducted to quantify the distribution of PBZ following applications. In one trial, 120 ml of 0 or 1 mg 1-1 PBZ were applied to 15-cm pots filled with either Vergro Klay Mix (no bark) or Metro Mix 500 (bark). A bioassay using broccoli (Brassica oleracea L. Italica) seedlings was used to quantify PBZ in leachates and media following treatment drenches. Leachate PBZ concentrations were lower for Vergro than for Metro Mix 500; however, leachates for both media were <0.1 mg·liter–1. Concentrations of PBZ in media decreased with depth and were four to 10 times higher in the uppermost 2.5 cm than in lower horizons. For the uppermost 2.5 cm of media, higher PBZ concentrations were recovered in Metro Mix 500 than in Vergro. A follow-up study will compare surface vs. subsurface application methods on the movement of PBZ into pots.

Contrasting effects of sewage sludge and commercial fertilizer on egg to adult development of two herbivorous insect species

Municipal sewage sludge containing heavy metals had a toxic effect on the development of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), one of two herbivorous insects commonly found in an Ohio old-field which had been subjected to long-term sewage sludge application. Soils were removed in 1992 from an old-field following 11 years of heavy nutrient enrichment (1978 to 1988) with applications of either sewage sludge (Milorganite(®)) containing heavy metal contaminants or urea-phosphate fertilizer. Egg to adult development rate and survival of the blackfaced leafhopper, Graminella nigrifrons (Homoptera: Cicadellidae), and the cabbage looper was determined on maize (leafhopper) and broccoli (looper) seedlings grown in soils from sludge-treated, fertilizer-treated, or untreated control plots of the old-field. Fertilizer and sludgetreated soils had higher levels of N. P and organic matter, and a lower pH than the untreated control soils, while sludge-treated soils contained significantly higher concentrations of Cd, Cu, Pb, and Zn. Maize appeared to be unaffected by the three soil treatments, and survival and rate of egg to adult development of the leafhopper was not affected. Broccoli seedlings grown in both the high nutrient fertilizer and sludge soils were greener and larger than broccoli grown in control soils. However, the cabbage looper had significant larval and pupal mortality (25 to 40%) and prolonged egg to adult development on sludge-grown broccoli compared to control and fertilizer treatments. As assimilation into the food chain of heavy metals and other organic pollutants, such as PCBs, is in part a function of the interaction of soil chemistry and type of plant, the application of municipal sludges to old-fields needs to be carefully monitored, as contaminants may have significant developmental and behavioural effects on some secondary links in the old-field food chain.

Preservation of Conidia of Broccoli Downy Mildew Fungus with Cryogenic Protectants by Freezing at -80.DEG.C..

Conidia of the downy mildew fungus (Peronospora parasitica) which is an obligate parasite were well preserved by freezing at -80°C using suitable cryogenic protectants. The germination rate of the conidia which were suspended in distilled water and frozen at -20°C or -80°C was very low compared with the untreated control. However, the germination rates of the conidia suspended in 5% dimethyl sulfoxide (DMSO) and 5% skim milk were 74.8% and 32.8% of the control, respectively, even after freezing at -20°C. On the other hand, in the preparations directly frozen at -80°C, the germination rate of the conidia decreased markedly in comparison with that after freezing at -20°C. Nevertheless, in the preparations of conidia frozen by the two-step freezing method at -20°C for 24hr followed by -80°C for 24hr, the germination rate remained the same as that in the preparations frozen only at -20°C. During the storage at -20°C, the conidia suspended in 5% DMSO+5% skim milk lost their germination ability after one month. The conidia suspensions which were supplemented with 10% DMSO+5% skim milk or 10% DMSO+10% skim milk and frozen by the two-step method at -20°C and at -80°C, showed a higher germination rate at least up to a period of 12 months. Moreover, these preparations exhibited a high pathogenicity to the broccoli seedlings. Based on these results, it was suggested that the conidia of the broccoli downy mildew fungus treated with protective substances such as 10% DMSO+5% skim milk or 10% DMSO+10% skim milk which were pre-frozen at -20°C for 24hr followed by -80°C could be well preserved for a long period of time.

The polyglutamate nature of plant folates

Folylpolyglutamates were extracted from a variety of higher plant tissues and cleaved to p-aminobenzoyl polyglutamates by acid-base and ZN-HCl treatments. After purification as azo dyes and reconversion to p-aminobenzoylpolyglutamates these derivatives were separated according to their glutamyl chain lengths by HPLC on Partisil SAX. Polyglutamate concentrations were calculated by reference to standard calibration curves. Tomato leaf extracts contained relatively high folate contents (7.55 nmol/g fr. wt) and these were mainly hexa- (23%) and heptaglutamates (30%). Carrot root extracts had low folate contents (0.22 nmol/g fr. wt) with diglutamates accounting for 69% of the folate recovered after chromatography. Carboxypeptidase treatments of broccoli floret extracts indicated that the folylpolyglutamates principally contained γ-glutamyl linkages. [ 3H]Glutamate and [ 14C] p-aminobenzoate were incorporated into the polyglutamates of broccoli seedlings but equilibrium of the label with the endogenous pools was not attained after a 48 hr pulse feeding. Difrerential, oxidative cleavage of broccoli leaf folates into three polyglutamate pools showed that the formyl- and methylfolates were mainly (80%) diglutamyl derivatives. The methylene and unsubstituted folates of this tissue were principally (78%) hexaglutamates.

MINIMUM TILLAGE AND NITROGEN INTERACTIONS IN PRODUCTION OF FALL BROCCOLI

Raised beds approximately 20 cm tall by 76 cm wide were formed on 1.8 m centers in the spring of 1988 and 1989. Beds were either left bare or seeded with rye (Secale cereale) or hairy vetch (Vicia villosa) at 84 or 45 kg ha-1 respectively. All plots were sprayed with glyphosate in August of each year. In 1988, a 30 cm strip was tilled in the center of each bed. In 1989, there was no tillage or mowing.The design was a randomized complete block with four levels of nitrogen (45, 90, 134, and 179 kg ha-1) at each soil cover. Broccoli seedlings were transplanted in double rows on 30 cm spacings into the plots each year in late August.Height of the raised beds was maintained with both rye and vetch. Broccoli yields were highest in the bare soil treatments In 1988, the lowest yield was with vetch, and in 1989 the lowest yield was with rye. There was a positive linear yield response to nitrogen. The number of heads harvested did not differ significantly between soil covers

Control of Insect Pests on Fall Broccoli, 1989

Abstract ‘Packman’ broccoli seedlings were transplanted into a Lily sandy loam soil at the Plateau Experiment Station, Crossville on 29 Aug. Ten treatments were replicated 4 times and arranged in a randomized complete block design. Plots were 3 rows × 15 ft spaced 36 inches between rows and 14 plants/row. Blocks were separated by 5 ft alleys. Insecticide treatments were applied on 29 Aug and 12 Sep using 2.5 gal compressed CO2 hand sprayers at 30 gal/acre and 40 psi. Flea beetle (FB) and cabbage looper (CL) counts were based on number of insects/14 plants. Yield was measured from the center row of each plot (equal plant population) on 24 Oct. Plots treated with Javelin and Dipel were sprayed only with Sevin SOS (1.5 lb (AI)/acre) for flea beetle control on 28 Aug.

Chinese Broccoli Insect Control, 1989

Abstract Chinese broccoli seedlings were transplanted to one-row plots located at Fayetteville, AR, on 10 Aug. Plots were separated by 6 ft bare ground and each plot held 12 plants at 2-ft intervals. Experimental design was a randomized complete block (4 treatments × 4 replications). Sprays were applied 1, 15 and 22 Sep with a hand held CO2 sprayer equipped with one Spraying Systems TX6 nozzle and calibrated to deliver 12.8 gpa. ICW and CL were counted on each plant on 5, 18, and 25 Sep. Plants were rated for foliar damage 20 Sep and 6 Oct.

Control of Insect Pests on Fall Broccoli, 1987

Abstract Seven insecticides were evaluated at the Plateau Experiment Station, Crossville. ‘Packman’ broccoli seedlings were transplanted into a Lily sandy loam field on 14 Aug. Plots were 3 rows × 15 ft replicated 4 times in a randomized complete block design. Blocks were separated by 5-ft alleys and row spacing was 36 inches with 15 plants/row. Insecticide treatments were applied on 26 Aug, 9 Sep, and 8 Oct using 2.5-gal compressed C02 hand sprayers at 30 gal/acre and 40 psi. Flea beetle, aphid, and cabbage looper counts were based on number of insects/15 plants. Yield was measured from the center row of each plot (equal plant population) on 3 Nov. Plots treated with both rates of San 415 were also sprayed with Sevin 80S (1.5 lb [AI]/acre) for flea beetle control on 9 Sep.

Studies on subirrigating culture by capillary movement from water-storage pipes

Each of four types of“pipe-beds”was established in the open air (Fig. 1, Table 1). After preliminary tests on various structures of beds and fertilizer concentrations, this experiment was made on the effects of structures of beds on the growth of broccoli. Broccoli seedlings were raised in a “ditch-ded”. It was also devised to make water rise by capillarity. Seeds were sown on August 4, 1967. Four seedlings were planted in each bed on August 26. Water was poured into the water-storage pipe continually to fill the capacity of 8 liters as the water level lowered to leave around 2 liters. Liquid fertilizer (20 cc of 10-5-8) was supplied into the pipe once every week.The results are shown in Table 2 and Fig. 2. It is censidered that the C-type bed is satisfactory for most crops. For root crops the soil underneath the medium should be cultivated.The studies are on the exploratory stage. Further studies should be made on the spacing of water-conducting pipes, the depth of plastic mulch placed in the central half of the bed, proper ingredients and amounts of fertilizer, and other things.When these problems are solved, the method of water and fertilizer application is not only effective and efficient for plant growth and for saving labor but also not too expensive for construction and also durable.

DEVELOPMENTAL STUDIES WITH BRASSICA SEEDLINGS

DEVELOPMENTAL STUDIES WITH BRASSICA SEEDLINGS