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J. C. Bouwkamp and R. N. McArdle

Abstract

Selection of seedlings for early development of storage roots, either directly or indirectly using cold temperature (7°-10°C), increased the proportion of high-yielding genotypes in subsequent populations. Although both techniques described are somewhat inefficient, retaining some low- and high-yielding genotypes, they may be useful in selection at the seedling stage, permitting the breeder to evaluate a larger number of seedlings.

Open access

M. C. Acock and J. O. Garner Jr.

Abstract

A high fertilizer rate reduced the number but not the weight, of storage roots of sweet potatoes [Ipomoea batatas (L.) Lam.] grown in greenhouse pots. Increased water availability had little effect on the small, bush type ‘Vardanian’ but enhanced growth and yield of the large, prostrate type L I-207. Differences between conditions of this experiment and field conditions are discussed.

Open access

Franklin W. Martin

Abstract

Callousing and rooting occur rapidly when young but nearly full-sized leaves of sweet potato [Ipomoea batatas (L.) Lam.] are planted in sterile sand, covered with a transparent chamber, and partially shaded. Rooted leaves show unusual growth phenomena including leaf enlargement, petiole swelling, and storage roots which may sprout and generate normal plants.

Free access

Yan Wang and Stanley J. Kays

The sweetpotato weevil (SPW) [Cylas formicarius elegantulus (Summers) (Coleoptera: Curculionidae)] is the single most devastating pest of the sweetpotato [Ipomoea batatas (L.) Lam.] worldwide. Attempts to develop host-plant resistance have been only moderately successful due in part to deficiencies in parent and progeny selection methods. Host-plant phytochemicals play critical roles in insect behavior, modulating a cross-section of key behavioral decisions. Thus, identification of the phytochemicals the female weevil uses in decision making could greatly facilitate development of host-plant resistance. The volatile chemistry of the sweetpotato was studied in relation to the host-finding behavior of the female weevil. Critical biologically active volatiles were determined via isolation (Tenax trapping), fractionation (gas chromatography-thermal conductivity detector), identification (gas chromatography and gas chromatography-mass spectroscopy), and bioassay (olfactometry). Differences in volatile chemistry among sweetpotato clones that may relate to differences in resistance or susceptibility to the female SPW were assessed. Volatile extracts from storage roots (site of oviposition) and aerial plant parts were attractive to female SPW, the former being substantially greater. In total, 33 compounds were identified from storage roots and aerial plant parts, including 23 terpenes. Three oxygenated monoterpenes (nerol, Z-citral, and methyl geranate), found in storage roots but not aerial plant parts, were identified as attractants. The sesquiterpene volatile fraction was repellent to female SPW with α-gurjunene, α-humulene, and ylangene active in the concentration range emanating from storage roots. The aerial plant parts emanated a higher composite concentration of sesquiterpenes than storage roots. Differences in the relative attraction among four sweetpotato cultivars to female SPW was inversely correlated with the composite concentration of headspace sesquiterpenes. Selection of clones with decreased volatile attractants and/or increased deterrents using an analytical means of quantification may significantly facilitate developing resistance to the SPW.

Open access

Ajmer S. Bhagsari and Silas A. Harmon

Abstract

Field experiments were conducted during 1979 and 1980 growing seasons with sweet potato [Ipomoea batatas (L.) Lam.] genotypes at different stages of growth to determine leaf net photosynthetic rates (Pn) and photosynthate partitioning patterns. Net photosynthesis was measured in an open system with an infrared analyzer on the youngest and the fully expanded leaves still attached to the plant. Photosynthesis rates differed significantly in both years. Photosynthesis varied from 19.1 to 32.4 mg CO2dm−2hr−1 in 1979 and from 25.8 to 36.9 mg CO2dm−1hr−1 in 1980. A new selection, 75-96-1, averaged highest both years. Percentages of photosynthate partitioning to storage roots also differed significantly. About 45 days after planting, ‘Centennial’ and ‘Georgia Jet’ diverted the highest percentage, about 28%, of the total dry matter to the storage roots. But ‘Georgia Red’ diverted the highest percentages of photosynthate (51.0 and 56.4) to the storage roots 75 and 90 days after planting, respectively. Photosynthate partitioning to storage roots ranged from 11.2 to 56.4%, 90 days after planting. Final root yield correlated significantly (r = 0.69 to 0.87) with photosynthate partitioning at all stages of growth. During 1980, Pn and total dry matter yield also were significantly correlated. Harvest index was significantly correlated (r = 0.89) with final storage root yield. But Pn did not significantly correlate with either storage root yield or photosynthate partitioned to roots. Stomatal density was 2 to 3 times more on the abaxial than the adaxial surface of the leaves. Percentages of neither leaf nitrogen nor chlorophyll content of leaves differed significantly. High-yielding genotypes generally initiated storage root formation earlier and also partitioned more photosynthate to storage roots than low-yielding genotypes.

Free access

Ki-Cheol Son, Ray F. Severson, Richard F. Arrendale, and Stanley J. Kays

Methodology was developed for the extraction of surface components of sweetpotato [Ipomoea batatas (L.) Lam.] storage roots. Surface components of storage roots were quantitatively extracted with methylene chloride using 8-minute ultrasonication. After removal of the solvent, the extract was treated with 3 Tri Sil-Z:1 trimethylsilylimidazol (v/v) to convert components with hydroxyl moieties to silyl ethers and then separated on a SE-54 fused silica capillary column. Distinctly different gas chromatography profiles were found between lines displaying moderate levels of resistance (`Resisto', `Regal', `Jewel') to the sweetpotato weevil [Cylas formicarius elgantulus (summers)] and weevil-susceptible lines (`Centennial', SC 1149-19, W-115), indicating a possible role of surface components in insect response. Chromatographic fractionation techniques were developed for separation of major components or groups of components. The results will allow subsequent bioassaying for the presence of an ovipositional stimulant(s) and other weevil behavior-modulating compounds and their chemical characterization.

Free access

Lewis W. Jett and T.P. Talbot

`Beauregard' and `Darby' sweetpotato cultivars were developed and released by the Louisiana Agricultural Experiment Station in 1987 and 1994, respectively. In total acreage, `Beauregard' is the dominant cultivar of sweetpotato grown in Louisiana and the remaining United States. However, very little is known about the growth characteristics of these two cultivars. Therefore, the objectives of this research were to examine storage root and shoot growth. Uniform transplants of both cultivars were transplanted in mid-July 1995 at the LSU Sweet Potato Research Station and sequentially harvested biweekly. Optimum leaf area of both cultivars was attained ≈60 days after transplanting. `Beauregard' had less leaf area than `Darby' at each stage of development, but partitioned more assimilates to the storage roots. At harvest, the harvest index of `Beauregard' was ≈75% compared with 50% for `Darby'. `Beauregard' had a significantly greater total yield of storage roots than `Darby'.

Free access

Arambage Abesinghe and James O. Garner

Storage roots of `Beauregard' and `Centennial' were used to identify varietal differences in fatty acid composition in plasmalemma lipids during storage conditions. Total plasmalemma fatty acid composition of glycolipids and phospholipids in storage roots of `Beauregard' and `Centennial' did not differ. The fatty acid composition of MGDG and DGDG in storage root plasmalemma was >50% unsaturated fatty acids in `Beauregard'. The high percentage of 18:2 (65.44%) fatty acid compared to `Centennial' (19.70%) and 79.35% total unsaturated fatty acid content in MGDG may contribute to low temperature tolerance in `Beauregard'. The higher percentages of 16:1 and 22:1 fatty acids in `Centennial' compared to `Beauregard' contributed to MGDG fatty acid unsaturation. However, these fatty acids have not been related to chilling tolerance.

Open access

D. R. Shelton and M. L. Lacy

Abstract

Harvesting a young planting of asparagus (Asparagus officinalis L.) for 4 or 6 weeks the second year after transplanting 1-year-old crowns, followed by harvesting for 8 or 10 weeks the third year, reduced yields significantly the fourth year. Carbohydrate levels in asparagus storage roots decreased during harvest and continued to decrease after harvest during fern production. Carbohydrate levels increased in storage roots after stalks had matured, and were restored to preharvest levels by mid- to late summer. All treatments possessed comparable levels of storage carbohydrates by the end of the season. Asparagus storage carbohydrates were identified as fructose-oligosaccharides, which varied considerably in size, mobility, and percent fructose and glucose. The largest oligosaccharides were composed of ∼ 90% fructose, ∼ 10% glucose; molecular weights did not exceed 4,000.

Free access

Peter B. Ojong, Victor Njiti, Zibao Guo, Ming Gao, Samuel Besong, and Sandra L. Barnes

The objective of this study was to characterize and quantify five commonly occurring flavonoids (quercetin, luteolin, apigenin, myricetin, and kaempferol) in storage roots and leaves of 10 sweetpotato [Ipomoea batatas L. (Lam.)] accessions: SC1149, ‘Excel’, ‘Vardaman’, ‘Hernandez’, ‘Picadito’, ‘Porto Rico’, ‘GA90-16’, PI531116, NC98-608 (Covington), and ‘Beauregard’ (B94-14-G2). The flavonoids were present in varying amounts (quercetin comprised greater than 79% and 55% of the mean flavonoid content in sweetpotato leaf and root samples, respectively) and were found to be more concentrated in the leaves (0.65% to 2.76% dry weight) than in the storage roots (0.27% to 1.69% dry weight). The results indicate significant variability in flavonoid content among different sweetpotato accessions, suggesting that there is the potential for genetic manipulation of sweetpotato to influence flavonoid content and profile through traditional breeding or biotechnological approaches.