Mississippi Sweetpotato Cultivar Evaluations for 1994, 1995, and 1996

Published by the Office of Agricultural Communications, Division of Agriculture, Forestry, and Veterinary Medicine, Mississippi State University. Edited by Keith H. Remy, Senior Publications Editor.

Sweetpotato cultivars and advanced breeding lines from several breeding programs were evaluated for yield and quality. Yield evaluations were made at the Mississippi Agricultural and Forestry Experiment Station Pontotoc Branch, Pontotoc, Mississippi. This site was selected for its close proximity to the state's principle sweetpotato growing area. Canning and baking quality evaluations for 1994, 1995 and 1996 were made at the food processing laboratory at Mississippi State University.

Procedures

Yields of sweetpotato cultivars and breeding lines were evaluated over a 3-year period, from 1994 to 1996. Inclusion of these cultivars and lines in the evaluations was determined by the national sweetpotato collaborators' group and the sweetpotato breeding program at Mississippi State University. Therefore, not all entries evaluated for yield were entered in the quality evaluations. Only the entries in the national sweetpotato collaborators' group and those breeding lines of interest to the breeding program for the current year were evaluated. All yield trials consisted of entries in a randomized complete block design with four replications.

The trials were grown, harvested, and graded in the same manner each of the 3 years. Each replication consisted of a single row plot 25 feet long. Row spacing was 40 inches and plants were spaced 12 inches apart within the row. The soil type was Faulkner silt loam and fertilizer was applied at rates recommended by the Mississippi Cooperative Extension Service according to soil test results. Irrigation was used in 1995 just before harvest to prevent injury because of dry conditions at harvest. Roots were cured at 90°F and 85% RH for 7 to 10 days after each harvest. Roots were then graded according to USDA standards for U.S. No. 1, canner, jumbo, and cull.

In 1994 the growing period was 117 days, with 'slips' transplanted to the field May 27 and roots harvested September 21. In 1995 the growing period was 92 days, with 'slips' transplanted to the field June 15 and roots harvested September 15. High early yield is a desirable trait; therefore, the 1995 crop was harvested early to evaluate entries for this trait. In 1996 the growing period was 112 days, with 'slips' transplanted to the field May 10 and roots harvested September 10.

Results

1994 Yields

The highest-yielding sweetpotatoes, L87-58, Beauregard, NC-C75, NC-C59, and NC-C58, yielded significantly more U.S. No.1 and total marketable roots than Jewel (Table 1). Yields of Regal, Centennial, L89-72, Hernandez, L89-110, Darby, W294, NC 92-08, and W285 were intermediate between the highest-yielding entries and Jewel. Centennial yielded significantly more jumbo grade roots than all but four other entries. The highest yielding white-fleshed sweetpotato was White Delight, which yielded significantly more U.S. No. 1 and total marketable roots than Nancy Hall or White Regal. Yields of Sumor and NC White were not statistically different from White Delight.

1995 Yields

U.S. No. 1 and jumbo yields were much lower in 1995 (Table 2) than either 1994 or 1996 (Tables 1 and 3) because of the early harvest at 92 days and possibly the dry conditions near harvest. NC-C59 produced the highest U.S. No. 1 yield, but its yield was not significantly different from the other high-yielding entries: NC-C58, L89-110, MS-D45, L89-72, or Jewel (Table 2). Beauregard was only significantly greater in U.S. No. 1 yield than Regal. Only NC-C59 was significantly higher than Beauregard for total marketable yield. O'Henry and NC White produced yields equal to the highest-yielding orange-fleshed entries for total marketable. O'Henry had the highest U.S. No. 1 yield of the white-fleshed entries and its yield was significantly higher than Nancy Hall or White Regal. NC White, Sumor, and White Delight were not statistically different from O'Henry.

1996 Yields

The highest-yielding sweetpotatoes, Beauregard, L89-72, L89-110, NC-C59, and NC-C58 yielded significantly more U.S. No. 1 roots than Centennial, MS-B9, 92-510, and W323 (Table 3). O'Henry was not significantly different from Nancy Hall, NC93-17, or W308 for yield of U.S. No. 1 roots. W308, a white- fleshed entry, had the highest yield of jumbo, 126 bushels per acre, which was significantly greater than 11 other entries. Beauregard also yielded the most total marketable roots, but its yield in this category was not statistically greater than NC-C59, L89-72, L89-110, NC-C58, MS-D45, or NC91-14. O'Henry was significantly greater than Nancy Hall in total marketable yield, but was not significantly different from NC93-17 or W308.

Mean yields over years (Tables 4 and 5) were provided to show the general trend in each entry's mean yield over a multi-year period. They should not be used to compare entries with each other because of a genotype by year interaction.

Canning and Baking Quality

Canning and baking quality scores are for entries in the national sweetpotato collaborators group and those breeding lines of potential interest to the breeding program in each year. No statistical analysis was performed on the canning or baking quality scores in any year due to the lack of replication. Mean quality scores are presented (Tables 8, 10, 11, 14, 16, and 17) over 2- and 3-year periods for those entries that were included in 2 or all 3 years.

Canning quality scores represent the sum of scores for color (chroma, uniformity, and attractiveness), wholeness, smoothness, firmness, moistness, lack of fiber, mouth feel, and flavor. Each category is rated on a scale of 1 to 10, with 1 being poor and 10 being excellent. The five highest scoring orange fleshed entries for total canning quality in 1994 were Regal, Centennial, NC-C75, Jewel, and L87-58 (Table 6). The entries with the lowest canning quality scores were Excel, L89-110, L89-72, W285, and W294. Most orange-fleshed entries were higher than the white-fleshed entries for total canning quality score. White delight was higher than the orange-fleshed entries Darby, W294, W285, L89-72, and L89-110. Canning quality of white- fleshed entries was highest for White Delight and lowest for Nancy Hall.

In 1995 L87-58 had the highest canning quality score of the entries evaluted, while L89-72 had the lowest score (Table 7). L89-72, NC-C75, and Jewel exhibited large changes in color quality attributes from 1994 to 1995. Jewel dropped three points in 1995 compared to 1994 in each caterogy of chroma, uniformity, and attractiveness. There were no white-fleshed entries in the 1995 canner quality evaluation.

In 1996 the entries with the highest canning scores were Jewel, Hernandez, and Beauregard (Table 8). Most orange-fleshed entries ranked higher than the white-fleshed entries for total quality score; exceptions were Centennial and W323, which were intermediate to Nancy Hall and W308.

Mean canner quality over 1994-95 ranged from a high of 82.4 for L87-58 to a low of 70.5 for L89-72 (Table 9). Mean canner quality over 1995-96 ranged from a high of 84.0 for Beauregard to a low of 75.5 for L89-110 (Table 10). Mean canner quality over the 3-year period 1994-96 ranged from 81.3 for Jewel to 74.4 for L89-110 (Table 11).

Baking quality scores represented the sum of scores for eye appeal, color (intensity, uniformity, freedom from discoloration), smoothness, moistness, lack of fiber, and flavor. Each category is rated on a scale of 1 to 10 as described above. The five highest-scoring orange-fleshed entries for total baking quality scores in 1994 were Centennial, Hernandez, Beauregard, MS-D45, and NC-C58 (Table 12). The five lowest baking quality scores were for MS-B9, W285, L89-110, MS-D22, and MS-B13. The white-fleshed entries ranked low in baking scores. White Delight ranked highest of the white-fleshed entries with a score of 58.1, while White Regal scored lowest with a score of 50.9.

The five orange-fleshed entries in 1995 with the highest total baking quality scores were NC-C59, Hernandez, L91-189, NC-C58, and L89-110 (Table 13). The five orange fleshed entries with the lowest baking quality scores were L91-150, MS-D22, NC-C75, Darby, and Jewel. The only white-fleshed entry, O'Henry, ranked twelveth overall, with a total score of 59.9.

The five orange-fleshed entries with the highest baking quality scores in 1996 were Hernandez, L89-110, MS-D45, NC91-14, and NC-C59 (Table 14). The five entries with the lowest baking quality scores were Centennial, Beauregard, W323, NC-C75, and Jewel. The white-fleshed entries again ranked low in baking quality scores. W308 ranked highest of the white-fleshed entries, with a score of 56.6, while NC93-17 scored lowest with a total score of 39.6.

Mean total baking quality scores over 1994-95 ranged from a high of 66.2 for Hernandez to a low of 56.8 for MS-D22 (Table 14). Mean baking quality for 1995-96 ranged from 70.4 for Hernandez to a low of 58.0 for Beauregard (Table 16). Mean total baking quality score for the 3-year period 1994-96 was highest for Hernandez, 68.9, and lowest for NC-C75, 60.8 (Table 17).

Summary

Over the 3-year period,1994 to 1996, Beauregard had the highest mean yield of U.S. No. 1 followed by NC-C59. Yields of U.S. No. 1 were variable from year to year, but Beauregard either produced the highest yield or was among the highest yielding entries in all years. Mean total marketable yield over the 3-year period was highest for NC-C59, followed by Beauregard.

Over the 1994-96 period, Hernandez had the highest mean baking quality score, followed by Beauregard. Quality varied from year to year, but Beauregard was among the highest each year. NC-C59 was one of the highest yielding entries over the 3-year period, and the NC-C59 baking score was only 1.5 points lower than that of Beauregard.