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.
M. Courtney, M. Mcharo, D. La Bonte and W. Gruneberg
James M. Dangler
Transparent polyethylene is used to enhance sweetpotato [Ipomoea batatas (L.) Lam.] transplant production in hotbeds and unheated field beds. Black plastic is used also in unheated field beds. The use of these bed covers, however, frequently results in transplant damage due to overheating. Despite the positive results obtained by using rowcovers in sweetpotato transplant production, recommendations for their use are not included in extension publications. Successful adoption of rowcovers by sweetpotato transplant producers in Alabama is illustrated.
Christopher A. Clark, Washington L. da Silva, Ramón A. Arancibia, Jeff L. Main, Jonathan R. Schultheis, Zvezdana Pesic van-Esbroeck, Chen Jiang and Joy Smith
Two distinct syndromes have emerged in some production areas that have caused losses of sweetpotato (Ipomoea batatas) storage roots during postharvest storage: a complex of fungal rots (end rots) progressing from either end of storage roots and a necrotic reaction (internal necrosis) progressing internally from the proximal end of storage roots. This study was conducted in multiple environments to evaluate whether the use of preharvest ethephon application and storage with or without curing after harvest could be used to screen sweetpotato breeding lines for susceptibility/resistance to these two disorders. Treating vines with ethephon 2 weeks before harvest and placing harvested roots directly into storage at 60 °F without curing resulted in the greatest incidence of end rots in each state and there were significant differences in incidence among the sweetpotato genotypes evaluated. However, when ethephon was not used and roots were cured immediately after harvest, the incidence of end rots was low in all the genotypes evaluated except for one breeding line. Incidence and severity of internal necrosis were greatest when ethephon was applied preharvest and roots were cured immediately after harvest, but two cultivars, Hatteras and Covington, had significantly more internal necrosis than all others.
Jim C. Cervantes-Flores, G. Craig Yencho, Kenneth V. Pecota, Bryon Sosinski and Robert O.M. Mwanga
Resistance to root-knot nematodes [Meloidogyne incognita (Kofoid & White) Chitwood] in sweetpotato [Ipomoea batatas (L.) Lam.] was studied in a mapping population consisting of 240 progeny derived from a cross between ‘Beauregard’, the predominant cultivar in the United States, and ‘Tanzania’, an African landrace. Quantitative trait loci (QTL) analyses to locate markers associated with resistance to root-knot nematodes (RKN) were performed using genetic maps based on parental segregation in ‘Beauregard’ and ‘Tanzania’ consisting of 726 and 947 single-dose amplified fragment length polymorphism (AFLP) markers, respectively. RKN resistance in the progeny was highly skewed with most of the progeny exhibiting medium to high levels of resistance. Single-point analysis of variance and interval mapping revealed seven consistently significant QTL in ‘Tanzania’ and two significant QTL in ‘Beauregard’. In ‘Tanzania’, three QTL were associated with reduction in resistance as measured by the number of RKN egg masses and explained ≈20% of the variation. Another four QTL had positive effects on resistance and explained ≈21% of the variation. Other minor QTL explained ≈2% or less of the variation but were not always consistent across geographical locations. In ‘Beauregard’, two QTL had positive effects on RKN resistance and explained ≈6% of the observed variation. Based on molecular and phenotypic data, RKN resistance in sweetpotato is hypothesized to be conferred by several genes, but at least nine AFLP markers (seven from ‘Tanzania’ and two from ‘Beauregard’) are associated with genomic regions that have the biggest effect in the number of egg masses of RKN produced in the root system.
Ramón A. Arancibia, Jeffrey L. Main and Christopher A. Clark
Tip rot, or restricted end rot, is a new sweetpotato (Ipomoea batatas) disease/disorder in Mississippi with unknown etiology. Since pathogen isolations have been inconsistent, a relationship of this disorder with stress is proposed. This disease/disorder is manifested as a restricted lesion at or close to the proximal end of the storage root and appears after 2 to 4 weeks in storage. In many cases, the lesion necrosis expands internally. On-farm and research station studies with preharvest foliar applications of ethephon were conducted in Mississippi to determine the potential association of tip rot with ethephon-induced stress. In addition, the effects of ethephon rate and interval between application and harvest on tip rot were investigated. After 1 to 2 months in storage, tip rot incidence was observed mostly in storage roots from ethephon-treated plants. The increase in tip rot incidence was well correlated with ethephon rate. These results suggest that preharvest applications of ethephon trigger a response that results in the tip rot disorder.
Elisa Mihovilovich, Humberto A. Mendoza and Luis F. Salazar
Combining ability for resistance to Sweetpotato Feathery Mottle Virus (SPFMV) was evaluated in seven sweetpotato [Ipomoea batatas (L.) Lam] clones. A diallel mating design was used, which resulted in 16 full-sib families. Families were evaluated for SPFMV resistance under greenhouse conditions in a randomized complete-block design. Resistance was tested by grafting Ipomoea nil `Scarlet O' Hara' infected with the russet crack strain of SPFMV (RC-SPFMV) onto individual plants of the families being evaluated. Symptomless plants were further indexed by cleft grafting virus-free Ipomoea setosa Ker plants onto the tested plants. Those plants in which the virus was not recovered by this test were considered resistant. Analysis of variance for SPFMV resistance revealed significant general combining abilities (GCA). Two clones, DLP-886 and TN90.300, exhibited significant positive GCA for SPFMV resistance. No significant specific combining abilities (SCA) were detected among the crosses. Breeding for resistance to SPFMV should focus on careful selection of resistant parents. In addition, results suggest that additive gene action is important in resistance to SPFMV.
Arthur Q. Villordon, Don R. La Bonte, Nurit Firon, Yanir Kfir, Etan Pressman and Amnon Schwartz
of adventitious roots in sweetpotato ( Ipomoea batatas ) Aust. J. Bot. 52 551 558 Carroll, H. Villordon, A. Clark, C. LaBonte, D. Hoy, M. 2004 Studies on Beauregard sweetpotato clones naturally infected with viruses Intl. J. Pest Manage. 50 101 106
Ramón A. Arancibia, Cody D. Smith, Don R. LaBonte, Jeffrey L. Main, Tara P. Smith and Arthur Q. Villordon
Consumption of sweetpotato (Ipomoea batatas) has increased in the past decade in part because of its nutritional and health attributes, and because of the availability and convenience of processed products. The sweetpotato processing industry is expanding and supplying more sweetpotato products than ever before. Unlike the medium-sized roots (U.S. no.1) preferred for fresh market, large (jumbo) roots is accepted and in certain cases desired by the processing industry, and overall yield is preferred over strict sizing requirements and aesthetic appeal. Therefore, this study investigated the yield increase and grade proportions in response to plant spacing and extension of the growing period to improve profitability of the production system. Experiments with ‘Beauregard’ and ‘Evangeline’ sweetpotato were conducted in Mississippi and Louisiana during 2010 and 2011. Treatments consisted of a combination of early and late planting date and delay in harvest, in-row plant spacing, and row width. Yield increase was inconsistent with delaying harvest and appears to depend on environmental conditions at harvest late in the season. Marketable yield was consistently greater in early plantings than late plantings. Yield of U.S. no.1 grade was unaffected by delaying harvest regardless of planting date. Delaying harvest in early plantings contributed to increase jumbo-sized roots and marketable yield. The economic assessment of delaying harvest in early plantings indicated a gain in net benefit either when hand harvested for fresh market or field run bulk harvested for processing. Row width and in-row plant spacing had only a marginal effect on yield of canner grade (small-sized roots). The economic assessment of changing plant density indicated no gain in net benefit, which indicates that choice of plant density can depend on other factors.
Robert O.M. Mwanga, Benson Odongo, Charles Niringiye, Agnes Alajo, Benjamin Kigozi, Rose Makumbi, Esther Lugwana, Joweria Namukula, Isaac Mpembe, Regina Kapinga, Berga Lemaga, James Nsumba, Silver Tumwegamire and Craig G. Yencho
Five sweetpotato [ Ipomoea batatas L. (Lam.)] cultivars named NASPOT 7 (Namulonge Sweetpotato 7), NASPOT 8, NASPOT 9 O (Namulonge Sweetpotato 9 orange-fleshed), NASPOT 10 O, and Dimbuka-Bukulula were approved for release by the Ugandan Plant
Desmond G. Mortley, Stephanie Burrell, Conrad K. Bonsi, Walter A. Hill and Carlton E. Morris
Sweetpotato [ Ipomoea batatas (L.) Lam] is a herbaceous, perennial plant that is grown mainly for its edible storage roots, although the leaves and tips are consumed as a green vegetable ( Villareal, 1982 ; Woolfe, 1992 ). The storage roots are