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Oyette L. Chambliss, Arthur G. Hunter, and Richard O. Hampton

Germplasm accessions and advanced lines were evaluated for seed transmission of the seed borne viruses, cucumber mosaic (CMV), cowpea severe mosaic (CSMV), and blackeye cowpea mosaic (B1CMV). Seed samples from 822 field plots (274 out of 300 accessions in 3 replications) which had been evaluated for insect resistance in 1992 were planted in the greenhouse. Mosaic virus symptoms had been apparent throughout the 1992 field planting. Evaluation for mosaic symptoms was done at the seedling stage in the greenhouse and 89 entries exhibited seed borne virus symptoms in one or more plants. Of these, 78 were shown by ELISA (enzyme linked immunosorbant assay, direct antigen coating method) to contain at least one of the seed borne viruses for which we were evaluating.

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Janine G. Haynes, Wallace G. Pill, and Thomas A. Evans

Switchgrass (Panicum virgatum L.) is one of the perennial, native, warm-season grasses recommended as a component of wildflower meadows. Seed treatments to alleviate low seed vigor and seed dormancy of switchgrass would enhance establishment of either plug transplants or seedlings after direct sowing into the meadow. “Heavy” seeds (45.5 mg/50 seeds) of open-pollinated switchgrass stored under cool and dry conditions (average 13 °C, 30% relative humidity) for 24 months had higher germination percentage than “light” seeds (26.0 mg per 50 seeds). In factorial combination, the heavy seeds were subjected to acid scarification (8 M H2SO4 for 5 min), sodium hypochlorite treatment (5.25% NaOCl for 15 min), and moist chilling (prechilling in 0.2% KNO3, for 14 days). Acid scarification followed by NaOCl treatment additively increased germination, a response that was associated with marked corrosion of the lemma margin in the distal region of the caryopsis, as observed by scanning electron microscopy. Prechilling the seeds following acid scarification and NaOCl further increased germination. All three treatments combined (acid scarification, NaOCl, and prechilling) almost doubled the final emergence and greatly increased seedling shoot dry mass in both a warm and cool postsowing environment. However, the effectiveness of these seed treatments was lost after 32 months of dry storage.

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Dennis M. TeKrony and Dennis B. Egli

Both seed viability and vigor directly affect the performance of seeds planted to regenerate the crop. Although seed quality can influence many aspects of performance (e.g., total emergence, rate of emergence), this presentation will primarily examine the relationship of seed vigor to one aspect of performance - crop yield. Reductions in yield can be indirectly related to low seed vigor if the low vigor seed results in plant populations that are below a critical level. Thus, we investigated the direct effects of seed vigor on yield in the absence of population differences for annual crops that are harvested at three stages; during vegetative growth, early reproductive growth or at full reproductive maturity. Seed vigor affects vegetative growth and is frequently related to yield in crops that are harvested during vegetative growth or during early reproductive growth. However, there is usually no relationship between vigor and yield in crops harvested at full reproductive maturity because seed yields at full reproductive maturity are usually not closely associated with vegetative growth. The use of high vigor planting seed can be justified for all crops; however, to insure adequate plant populations over the wide range of field conditions which occur during emergence.

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J.E. Warren and M.A. Bennett

Improved germination under unfavorable soil conditions is an important safeguard against yield losses in direct-seeded crops. Osmoprimed seed has been shown to provide earlier and more uniform germination as well as improve low temperature germination. These attributes combined with the reduced rates of damping-off associated with Pseudomonas aureofaciens AB254 creates a bioosmopriming seed treatment that provides rapid germination under a wider range of soil temperatures while exhibiting the disease resistance and improved growth associated with bacterial coatings. The objective of this work is to combine biopriming and osmopriming into one procedure, thus creating an environment for adequate seed hydration and rapid multiplication of beneficial bacteria which will thoroughly colonize the seed surface. Processing tomato seeds (Lycopersicon esculentum Mill. `OH8245') were bio-osmoprimed in aerated –0.8 MPa NaNO3 at 20°C for 4 days. On the fourth day, a mixture of nutrient broth, a defoaming agent, and bacteria that have been adjusted to the same osmotic potential is added. This is done so that the removal of seeds from the tank at the end of the 7-day treatment coincides with peak populations of bacteria. Pseudomonas aureofaciens AB254 multiplies very rapidly in this environment, with colony forming units for tomato averaging 4 × 105/seed. Results will also be reported for cucumber seed (Cucumis sativus L. `Score'), which were treated using a similar procedure. Bacterial populations per seed, germination characteristics and pathogen control will be discussed.

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Daniel I. Leskovar, Daniel J. Cantliffe, and Peter J. Stoffella

`Sunny' tomato (Lycopersicon esculentum Mill.) containerized transplants were grown with the standard or conventional systems (SS) and with recently developed flotation systems (FS). Standard system and FS transplants, and direct-seeding using coated seeds were evaluated in the field for root and shoot growth and yield at Parrish, Bradenton, and Naples during fall, winter, and spring plantings. Plant growth characteristics were measured weekly before, during, and after transplanting or sowing. In the Parrish and Bradenton Fall 1987 and Bradenton Spring 1988 experiments, SS transplants had greater leaf area, root volume, shoot dry weights, and shoot: root ratios than FS transplants. During early development, the FS transplants had more lateral root growth than SS transplants, but had similar total root growth and horizontal and vertical root distribution after transplanting in the field. Transplants and direct-seeded plants allocated 72% of the total root mass in the upper 0 to 10 cm of the soil. In Fall 1987, SS transplants had between 29% and 41% more fruit yield than FS transplants at Bradenton and Parrish, respectively. In the Naples Winter 1988 and Parrish and Bradenton Fall 1989 experiments, both transplant types had similar fruit yields, but more than direct-seeded plants. Transplants grown with the flotation system are recommended for use provided that seedlings are grown and maintained with minimum hardening before establishment in the field.

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Troy A. Larsen* and Christopher S. Cramer

New Mexico onion production will begin using mechanical harvesters in the near future in order to stay competitive in today's market. Past onion breeding objectives have focused on improving onions for hand harvesting instead of mechanical harvesting. Our breeding program is starting to evaluate germplasm for bulb firmness. The objectives of this study were to evaluate hybrid lines for their bulb firmness, to compare two methods of measuring bulb firmness, and to compare bulb firmness using two different production schemes. Bulb firmness of spring-transplanted and spring-seeded intermediate-day hybrid breeding lines was measured using a digital FFF-series durometer and a subjective rating of firmness achieved by squeezing bulbs. Bulbs were rated on a scale of 1 (soft) to 9 (hard). In general, these hybrid lines produced very firm to hard onions whether the lines were transplanted or direct-seeded. Bulb firmness of these lines measured with the durometer was greater when the lines were direct-seeded (74.9) than when transplanted (73.5). Conversely, when firmness was measured with our subjective rating, transplanted onions exhibited slightly greater firmness (8.9) than direct-seeded onions (8.8). For both transplanted and direct-seeded onions, durometer readings were weakly correlated in a positive fashion with our subjective rating. In general, durometer readings gave a greater spread in firmness measurements with a range of 69.6 to 77.8 in firmness values. Subjective ratings of bulb firmness ranged from 8.5 to 9.0. Depending on the firmness of evaluated breeding lines, our subjective rating system should be adjusted to better distinguish firmness differences between bulbs.

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S.B. Sterrett, C.W. Coale Jr., and C.P. Savage Jr.

1 Assistant Professor. 2 Professor, Dept. of Agricultural Economics, Blacksburg campus. 3 Research Scientist A. Seed was kindly provided by Asgrow Seed Co., Kalamazoo, Mich., and by Peto Seed, Saticoy, Calif. The cost of publishing this

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Mary Hockenberry Meyer and Diane M. Narem

fibrous root system, medium size, and attractive, fragrant flowers. Seed or vegetative propagation and growth of prairie dropseed is slow ( Diboll, 1997 ; Fedewa and Stewart, 2011 ; Schramm, 1978 ). Germination has not been reported to be more than 53

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John T.A. Proctor, Dean Louttit, and John M. Follett

Freshly harvested, immature (green) seeds of north american ginseng (Panax quinquefolius L.) were stratified for 12 months either traditionally in buried wooden boxes outdoors, or in plastic pails in a controlled environment room [3 ± 0.2 °C (37.4 ± 0.11 °F)], 85% ± 5% relative humidity) for about 9 months followed by about 3 months at 20 ± 2 °C (69.8 ± 1.1 °F). Embryo growth in Stage II (mid-May to late August when direct seeded) was more rapid [0.016 versus 0.009 mm·d-1 (0.00062 versus 0.00035 inches/day)] under controlled-temperature conditions. Seedling emergence rate did not vary between treatments. Root dry weight (economic yield) was similar for seedling, 2, 3, and 4-year-old plants whether grown from traditionally or controlled-temperature stratified seed. Controlled-temperature stratification of north american ginseng seed is an acceptable alternative to traditional outdoor, in-ground stratification.

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Robert Wiedenfeld, Eden Hinojosa, and Robert Stubblefield

A study was conducted in subtropical south Texas in 1989 to determine the effects of planting method, polyethylene mulch, and rate of drip irrigation on cantaloupe growth, yield and quality. Irrigation at .25, .50, .75, 1.0, or 1.25 times pan evaporation had little effect on soil moisture or yield, with all water application levels keeping the soil close to field capacity. Transplanting vs. direct seeding enhanced early vine growth and caused earlier yield, although direct seeded plants later caught up and had final cumulative yields slightly higher than the transplants. Black polyethylene mulch also improved earliness and reduced the number of culls compared to bare soil, but at the lowest watering level total yields were reduced by the mulch due to deflection of the rainfall received. The combined practices of transplanting and polyethylene mulch caused approximately a 9 day earliness advantage over the treatment that was direct seeded on bare soil although final yield was unaffected. Soil salinity buildup may cause problems which would affect the position of the drip line and the frequency and amount of water applied.