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The objective of this study was to identify a sweetpotato canopy type ideally suited to suppress weed growth. With this knowledge, breeders could select sweetpotatoes that require less weed control. Diverse canopy types, ranging from upright, short-internode bunch types to long-internode trailing types, were compared in a split-plot design (hand-weeded and weed treatments). We also included lines with deeply lobed leaves (palmate) and more entire-leaf types. Our results show no significant differences between lines for total ground surface area covered after 6 weeks of growth, no differences in weed dry weight at harvest and few differences in canopy dry weight at harvest. Total ground surface area covered correlated positively with total yield, and weed dry weight correlated negatively to total yield. We were unable to identify individual lines that yield better when pressured with weeds compared to the hand-weeded control, but we were able to identify lines that yield poorly when pressured with weeds compared to the hand-weeded control. These results demonstrate the difficulty in categorically identifying a superior canopy.
A user-friendly, menu driven, database program was developed to facilitate storage, retrieval, and manipulation of data associated with a sweetpotato breeding program. The database is written in FoxBASE+ for IBM and compatible personal computers. The database consists of a variety of test options with statistical capabilities for analysis of raw test data for commonly evaluated factors used to screen sweetpotato selections. The database also contains options which permit the user to query the stored data. An important feature is the summarization of test data for individual selections based on all the tests it has been entered into. Overall means, SDs and comparisons with user specified checks are listed in a printout for each factor along with morphological descriptors, parentage, and a note section. The database also assists the user in field research through recording of plot plans, data collection forms and related data query options.
Iron and zinc are micronutrients essential to the human diet but are in deficient supply to many in the tropics. Fortifying the micronutrient content of staple crops like sweetpotato [Ipomoea batatas (L.) Lam.] would go far in alleviating this intractable problem. This article presents estimates of broad-sense heritability for iron and zinc content in sweetpotato roots using a technique based on full-sibling families. Among individual genotypes, iron and zinc concentration varied by a fourfold and sixfold difference, respectively, whereas dry matter concentration showed a threefold variation. Family mean estimates varied significantly for the three traits. High broad-sense heritability for iron (H = 0.74), zinc (H = 0.82), and dry matter concentration (H = 0.93) were obtained among full-sibling families. These results suggest that traditional breeding strategies like mass selection could improve the micronutritional value of sweetpotato and that true sweetpotato seed, which has no international phytosanitary restrictions on transfer, can be used to quickly estimate heritability.
The influence of a black polyethylene tunnel cover (BTC) was evaluated for its effect on quantity and quality of sweetpotato [Ipomoea batatas (L.) Lam.] transplants in plant beds in Louisiana and North Carolina. Use of BTC increased production of `Beauregard' transplants from 63% to 553% in comparison with the bare ground control. `Jewel' was less responsive; BTC treatments increased transplant production by at least 48% in Louisiana over the bare ground control, but no increase was observed in North Carolina. Individual transplant weight was at least 34% less in BTC treatments than in the control. The first harvest of cuttings in BTC beds was at least 14 days prior to that in control beds. Transplant quality was assessed as yield of storage roots in repeated trials that extended throughout the normal growing season. Yield of storage roots was not affected by BTC in early season plantings, but was frequently lower for BTC treatment transplants in middle and late season plantings. We therefore do not recommend this method as a means of increasing sweetpotato plant production from bedded roots.
The yield of three generations of virus-tested plants of `Beauregard' sweetpotato (Ipomoea batatas) was assessed in Louisiana over a 4-year period in 15 yield trials. Treatments included virus-infected foundation `Beauregard', virus-tested `Beauregard' mericlone, B-63 [generation 1 (G-1)], and three generations of B-63 (G-2, G-3 and G-4). Generations refer to the number of continuous years virus-tested plants are grown in the field. Use of G-2 virus-tested `Beauregard' transplants increased yields of U.S. no. 1 grade roots by 16% in comparison with virus-infected, foundation `Beauregard'. Total marketable yield was also higher (11%) using B-63 G-2 transplants in comparison to virus-infected, foundation `Beauregard'. Use of B-63 (G-1), G-3 and G-4 generation transplants did not increase yields in any grade in comparison to virus-infected, foundation `Beauregard' by planting plots amidst virus-infested sweetpotato fields. Generation one B-63 transplants were greenhouse grown and often appeared less robust after planting. Yet we were unable to show significant yield differences between greenhouse derived B-63 (G-1) and field-grown B-63 (G-1) in separate tests; other factors may be involved.