Seed production systems for daikon or Chinese winter radish (Raphanus sativus L., Longipinnatus Group) were investigated in the Winter Garden of southwest Texas in 1992 and 1993. Planting dates ranged from October through March. Bed configurations (number of rows × bed spacings) were 2 × 0.96 m, 2 × 1.93 m, 3 × 1.93 m, and 4 × 1.93 m. Within-row spacings were 5, 10, and 15 cm. Crops were grown using minimum fungicide and insecticide amounts, while no attempt was made to control weeds chemically. Seed was harvested between May and June. Seed yields (kg·ha–1) increased for planting dates of October to November. Lower seed yields from the January or later plantings appear to be related to increased disease and insect pressures. Total and medium class size (≥3 and ≤4 mm in diameter) seed yields were highest at 40 rows × 1.93 m bed spacings and 10 cm within-row plant spacings. Germination and percent coatless seeds were unaffected by bed configuration and within-row plant spacings. The closest within-row spacings (5 cm) increased the risk of plant lodging and delayed plant maturity.
Daniel I. Leskovar and A. Kipp Boales
Claudia Cunha, Muhammet Tonguç and Phillip D. Griffiths
Chloroplast DNA (cpDNA) was used to identify polymorphisms between crucifer species using the polymerase chain reaction-random fragment-length polymorphism (PCR-RFLP) technique. Ten primer pairs based on cpDNA gene sequences were used to amplify cpDNA fragments in Brassica oleracea L., B. rapa L., B. nigra (L.) Koch, B. napus L., B. carinata Braun, B. juncea (L.) Czern, and Raphanus sativus L. accessions. Amplified DNA sequences were then digested using 11 restriction enzymes to identify polymorphisms between the 7 species. Of the 110 combinations, 38 generated polymorphisms that discriminated one or more of the species. Genotyping of these polymorphisms in 10 accessions of each of the diploid species (B. oleracea, B. nigra, B. rapa and R. sativus) did not reveal segregating polymorphisms among accessions within species, indicating that they can be used to help determine species identity. Ten accessions of each of the amphidiploids B. napus, B. carinata and B. juncea were genotyped to infer their maternal ancestry. The diploid source of cpDNA in B. carinata was B. nigra in all accessions tested and B. rapa for nine of ten B. juncea accessions tested. Two B. napus accessions amplified polymorphisms shared with B. rapa, and eight accessions produced unique polymorphisms from neither B. rapa, B. oleracea or B. nigra. The polymorphisms identified in this study can be used to help confirm identity of the diploid crucifer species for taxonomic and conservation studies.
Jeffrey Richards, Sharon Edney, Neil Yorio, Gary Stutte, Matthew Sisko and Raymond Wheeler
Environmental factors such as light intensity (PPF) and/or air temperature may be limiting engineering constraints in near or long-term space missions. This will potentially affect NASA's ability to provide either dietary augmentation to the crew or maintain a large-scale bioregenerative life support system. Crops being considered by NASA to provide supplemental food for crew consumption during such missions consist primarily of minimally processed “salad” species. Lettuce (Lactuca sativa L. cv. Flandria), radish (Raphanus sativus L. cv. Cherry Bomb II), and green onion (Allium fistulosum L. cv. Kinka) are being evaluated under a range of PPF and temperature environments likely to be encountered in space systems. Plants were grown for 35 days under cool-white fluorescent (CWF) lamps with light intensities of 8.6, 17.2, or 26 μmol·m-2·d-1, at air temperatures of 25 and 28 °C, and 50% relative humidity, and 1200 μmol·mol-1 CO2. Regardless of temperature, all three species showed an increase in edible mass with increasing light levels. When grown at 28 °C, edible mass of radish was significantly reduced at all lighting intensities compared to 25 °C, indicating a lower optimal temperature for radish. Understanding the interactions of these environmental factors on crop performance is a critical element to defining future missions that incorporate plant-based life support technologies.
Sharon Edney, Jeffrey Richards, Matthew Sisko, Neil Yorio, Gary Stutte and Raymond Wheeler
Development of a crop production system that can be used on the International Space Station, long duration transit missions, and a lunar/Mars habitat, is a part of NASA's Advanced Life Support (ALS) research efforts. Selected crops require the capability to be grown under environmental conditions that might be encountered in the open cabin of a space vehicle. It is also likely that the crops will be grown in a mixed-cropping system to increase the production efficiency and variety for the crew's dietary supplementation. Three candidate ALS salad crops, radish (Raphanus sativus L. cv. Cherry Bomb II), lettuce (Lactuca sativa L. cv. Flandria) and bunching onion (Allium fistulosum L. cv. Kinka) were grown hydroponically as either monoculture (control) or mixed-crop within a walk-in growth chamber with baseline environments maintained at 50% relative humidity, 300 μmol·m-2·s-1 PPF and a 16-hour light/8-hour dark photoperiod under cool-white fluorescent lamps. Environmental treatments in separate tests were performed with either 400, 1200, or 4000 μmol·mol-1 CO2 combined with temperature treatments of 25 °C or 28 °C. Weekly time-course harvests were taken over 28 days of growth. Results showed that none of the species experienced negative effects when grown together under mixed-crop conditions compared to monoculture growth conditions.
J.O Becker and U.K. Schuch
A rapid screening system was developed to identify plant-beneficial rhizobacteria useful in protecting nursery seedlings against damping-off caused by Rhizoctonia solani. Ornamental and agricultural crops were planted into 100 soil samples that were collected from various fields throughout California. More than 7000 bacterial strains from the rhizosphere of these crops were isolated and tested in vitro for antibiosis against R. solani AG4. In a second tier, 600 active strains were tested in planting trays seeded with radish (Raphanus sativus `Cherry Belle'). Each planting cell filled with commercial potting mix contained millet-grown R. solani inoculum in the center and eight radish seeds at the periphery. Bacteria were cultured for 24 hr at 25°C in 10% tryptic soy broth and were applied as a drench at 1 × 107 cfu/cc to each cell. Trays were incubated in a growth chamber at 21°C and a 10-hr photoperiod. Post-emergence damping-off occurred within 8 to 9 days after planting, and no further losses were observed after 14 days. Approximately 0.5% of the original 7000 bacterial strains tested reduced damping-off significantly. Fifteen bacterial strains controlled Rhizoctonia damping-off by 30% to 60% compared to the non-treated control.
Sachiko Matsubara and Hegazi H. Hegazi
Callus initiation and growth and plantlet regeneration were studied using eight cultivars of Raphanus sativus L., including six Japanese radishes, one Chinese and one small `Comet' radish. The basal medium was composed of Murashige and Skoog inorganic salts, 2.0 mg myo-inositol/liter, 0.5 mg each of nicotinic acid and pyridoxine·HCl/liter, and 0.1 mg thiamine·HCl/liter, 30 g sucrose and 2 g Gelrite/liter. High callus yields were obtained on basal medium containing (mg·liter-1) 0.1 2,4-D and 1.0 BA for two Japanese radishes and 0.1 NAA and 1.0 kinetin for `Comet' radish. Shoots were regenerated from callus by subculturing on basal medium containing 0.1 or 1.0 mg BA/liter and then transferring to basal medium. Rooting occurred on basal medium. Although callus was obtained in all eight cultivars, shoots and plantlets were regenerated only from `Moriguchi', `Nerima Shirinaga', and `Comet'. Chemical names used: 2-(l-naphthyl) acetic acid (NAA); N-(phenylmethyl)-lH-purine-6-amine (BA); 2,4-dichlorophenoxy acetic acid (2,4-D); 6-(furfurylamino)purine (kinetin).
Neil C. Yorio, Gregory D. Goins, Hollie R. Kagie, Raymond M. Wheeler and John C. Sager
Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 μmol·m-2·s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.
I.J. Warrington and R.A. Norton
Plants of chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura], radish (Raphanus sativus L.), corn (Zea mays L.), and cucumber (Cucumis sativus L.) were grown under 8-, 12-, 18- or 24-hour daylengths and at three photosynthetic photon fluxes (PPF) within each daylength to evaluate growth and development responses to daily quantum integral (PPF × duration). For the same daily quantum integral, dry matter accumulation and leaf area development were less under 24-hour than under 18-hour daylengths with chrysanthemum and radish. With corn and cucumber, these values were similar under 12-, 18-, and 24-hour daylengths. In all of the species, leaf area and dry matter development were lowest under the 8-hour daylength. Continuous (24-hour) daylength produced some growth abnormalities in radish and chrysanthemum. Specific leaf weight in all species and flower node count in cucumber were linearly related to daily quantum integral up to the highest values examined (73.5 mol·day-1·m-2). All species showed expected photoperiod responses with respect to flowering, but the rate of floral development and number of flower buds formed were highest under the highest PPF (and highest daily quantum integral) treatments. The results indicate that field phenotypes can be obtained in controlled environment (CE) conditions, providing the field daylength and daily quantum integral conditions are reproduced.
Vegetable growers in the northeastern United States who want to use cover crops are limited by the relatively short growing season and by a lack of cover crop species options. Seven cover crops that winter-kill under NE US conditions were evaluated in on-farm trials for their suitability for following early harvested vegetables. Plots of oilseed radish (Raphanus sativus), white senf mustard (Brassica hirta), phacelia (Phacelia tanacetifolia), oats (Avena sativa), and a bare control were planted on 25 Aug. and 8 Sept. 1993, following a lettuce crop. In the early planting, oilseed radish, white senf mustard, and phacelia produced more than 3000 kg·ha–1 dry matter in 11 weeks, while oats produced just more than 2000 kg·ha–1. A smaller proportion of the accumulated biomass from these cover crops remained on the surface in the spring compared to oats. In the first planting, 80–107 kg·ha–1 N were accumulated in the above-ground biomass of the cover crops. On 3 and 16 Sept. 1994, plots of oilseed radish, white senf mustard, oats, yellow mustard (Brassica hirta), forage kale (Brassica oleracea), forage turnip (Brassica rapa), canola (Brassica napus cv. Sparta), and a bare control were established following potatoes. All cover crops except kale produced more than 3800 kg·ha–1 dry matter by late November in the early planting.
Kevin Charles*, Mathieu Ngouajio and Darryl Warncke
Cover crops are commonly used to improve soil fertility and enhance crop performance. Field experiments were conducted to determine the effects of different cover crops and fertilizer rates on celery growth and development. The experiment was a two-way factorial with a split plot arrangement. The main plot factor was cover crop and included cereal rye (Secale cereale), hairy vetch (Vicia villosa), oilseed radish [Raphanus sativus (L.) var. oleiferus Metzg (Stokes)], and no cover crop. The sub-plot factor was fertilizer rate with three levels: full (160, 80, 400), half (80, 40, 200), and low (80, 0, 0) kg/ha of N, P2 O5, K2 O, respectively. The cover crops were grown during Fall 2002 and incorporated prior to celery transplanting in May 2003. During celery growing season, stalk length, above and below ground biomass were assessed at 23, 43, 64, and 84 days after planting (DAP). The biomass produced by oilseed radish (719 g/m2) exceeded that of cereal rye (284 g/m2) and hairy vetch (181 g/m2). At 23 and 43 DAP, celery fresh root (4.8 and 11.4 g/root) and shoot (6.1 and 53.6 g/shoot) biomass of oilseed radish exceeded the values of all other cover crops. At 84 DAP however, celery shoot fresh weight was similar in all cover crop treatments. Celery plants were tallest in the cereal oilseed radish and rye treatments early in the season; however final plant height at harvest was not affected by type of cover crop. The amount of fertilizer applied had a significant effect on celery growth starting at 64 DAP and continued until harvest. These results suggest that the large biomass produced by oilseed radish played an important role in early season celery growth.