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I.L. Goldman

The effects of population density on shape and size of cylindrical red beet genotypes were evaluated in a field experiment during 1994 and 1995. Two F1 hybrids and two open-pollinated genotypes were planted in replicated trials consisting of three population densities. Yield, harvest weight, percent harvestable beets per plot, length, middle width, top width, bottom width, length × width, length to width ratio, and a shape index (SI) were measured on a sample of beet plants from each plot. The density × genotype interaction was nonsignificant for all 10 traits. Averaged over genotypes, significant differences among densities were found for harvest weight, percent harvestable beets per plot, length, middle width, and length × width. In general, greater harvest weights, a higher percentage of harvestable beets, and greater length, middle width, and length × width values were found at low density. Averaged over densities, significant differences among genotypes were measured for all 10 traits. The open-pollinated genotypes Cyndor and Cylindra exhibited lower yield, lower harvest weight, greater SI, and a higher percentage of harvestable beets than their hybrid counterparts. These data demonstrate that population density has a differential and significant effect on the shape and size of cylindrical beet genotypes.

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Arthur Villordon, Jeffrey C. Gregorie, and Don LaBonte

: Command 3ME (clomazone, 3.114 L·ha −1 ) was applied immediately after transplant and metolachlor (1.06 kg·ha −1 a.i.) was applied at 10 to 15 d after planting. Experimental treatments. To generate as much variation in storage root shape as possible, prior

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S.B. Sterrett and C.P. Savage Jr.

A procedure is described for maintaining root quality in a foundation seed program that serves a primarily processing industry. Trueness-to-cultivar root type and color is maintained through hill selections within the prefoundation seed at harvest. Internal color is examined after sprout production, but prior to planting. Each root of the prefoundation seed is lifted and cut. If any sectorial chimeras are visible or the internal color is lighter than expected for that cultivar, all sprouts from that root are discarded. Otherwise, sprouts are planted to generate prefoundation seed. Prefoundation roots not selected by hill selection are given to designated growers for production of foundation seed. Contracts with growers for foundation seed and seed distribution are the responsibility of the Virginia Crop Improvement Assn. (P.O. Box 78, Mt. Holly, VA 22524). Hill selection of `Hayman', a white-skinned, white-fleshed cultivar, over the past 20 years has essentially eliminated strings and nonenlarged roots. Improved root shape and smoothness has resulted in increased regional consumer demand for this specialty crop.

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Bassam Al-Safadi and Philipp W. Simon

Carrot tissue cultures, germinating seed, and dry seed were exposed to gamma radiation. Irradiation accelerated germination of carrot seed in the M1 generation at low doses (0.5 and 1 krad), whereas higher doses delayed germination. A high negative correlation was observed between dose and survival of plants after seed irradiation. Plant size and root weight were 20 % to 35% greater than control plants after seeds, but not tissue cultures, were exposed to low doses of gamma irradiation. Higher doses reduced M1 plant size by >50% in germinating seed and tissue culture treatments but less for the dry seed treatment. Seed production decreased while phenotypic variation of M1 plants increased with increasing gamma ray dosage. Root weight and total dissolved solids were highly variable in M2 families. Less variation was observed in total carotene content and none was seen in sugar type (reducing vs. nonreducing sugars). Induced variation in root color and root shape was also observed. Irradiation of germinating seed and tissue cultures yielded more M2 variation than irradiation of dry seed. Putative point mutations were not observed. Unirradiated carrot tissue cultures did not yield significant M2 somaclonal variation. Average root weight of M2 plants increased with increasing gamma ray dosage, especially for the dry seed treatment.

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Allan C. Thornton and Jonathan R. Schultheis

The goal of this research was to determine the effects of in-row spacing and planting time on yield and root grade of NC 98-608 over time. Two plantings were made in two grower locations (four total). An early planting was made 19 and 25 May and a late planting 19 and 24 June. NC 98-608 was evaluated at the following in-row spacings; 23, 31, 38, and 46 cm. `Beauregard' spaced at 23 cm in-row and was used as the standard comparison. Roots were harvested and graded into canner, number one, jumbo and cull grades 90, 105, and 120 days after planting for each of the planting dates and locations. Each grade was weighed. An early planting in late May resulted in roots reaching the highest percentage grade of U.S. number one roots as early as 100 days after planting, while the late planting in June resulted in roots never reaching their full number one yield potential in some cases. For an early harvest after planting (90 days after planting) the 38 cm in-row spacing produced the most marketable number one yields compared with the 23, 31, and 46 cm in-row spacings. For a later harvest time after planting (105 days or later), it appeared as though the 31 cm in-row spacing was the most economical spacing to use. Roots from the early plantings (late May) and finer textured soils appeared to have shorter roots than roots harvested from later plantings (after 15 June) or coarser textured soil. Root shape and yield was more uniform with NC 98-608 than with the Beauregard clone. With yields comparable to Beauregard, the NC 98-608 clone provides an excellent opportunity to produce a quality sweetpotato with consistent shape.

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, and Arthur Q. Villordon

resistance, superior storage root shape, and a higher dry matter content. ‘Bonita’ produces excellent numbers of uniform plants (sprouts) early in the production season. Days to harvest for ‘Bonita’, ‘Beauregard’ ( Rolston et al., 1987 ), and ‘O'Henry’ are

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Robert O.M. Mwanga, Charles Niringiye, Agnes Alajo, Benjamin Kigozi, Joweria Namukula, Isaac Mpembe, Silver Tumwegamire, Richard W. Gibson, and G. Craig Yencho

populations by participatory plant breeding (PPB) for Africa and perhaps the world ( Gibson et al., 2008 ; Mwanga et al., 2010 ). ‘NASPOT 11’ has acceptable storage root shape (long elliptic) when grown in light soils, has high dry matter (DM) (≈34%), and

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Don R. La Bonte, Christopher A. Clark, Tara P. Smith, Arthur Q. Villordon, and C. Scott Stoddard

‘Vermillion’ sweetpotato [ Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide an orange-flesh, deep-red–purple-skin cultivar with superior storage root shape, skin smoothness, disease resistance

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Don R. La Bonte, Arthur Q. Villordon, Christopher A. Clark, Paul W. Wilson, and C. Scott Stoddard

-knot nematode resistance, is desirable, and color and root shape are favorable. Initially identified and evaluated as L01-29, the cultivar is named after the Japanese word for purple (murasaki). The dark purple skin is its most distinguishing characteristic

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Claire H. Luby and Irwin L. Goldman

populations were classified as ‘Nantes’, ‘Danvers’, ‘Chantenay’, and ‘Ball’ ( Fig. 1 ) and represent those root shapes ( Simon, 2000 ). The root color populations are ‘Red’, ‘Purple’, ‘White’, and ‘Yellow’ ( Table 2 ; Fig. 2 ). Roots from a sample of plants