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.
Allan C. Thornton and Jonathan R. Schultheis
Amauri Alves Nery and Adonai Gimenez Calbo
Constant-pressure manometry, previously designed to study O2 and CO2 gas exchange in small pieces of tissue, cells, and organelles, was adapted to study bulky organs. According to this new procedure, a near-zero-volume Devaux chamber connects a manometer to the internal atmosphere volume (VG) of a plant organ covered by a layer of epoxy, submerged in unstirred water, kept at constant temperature, and kept at the same VG pressure. Equations, based on CO2 and O2 solubility at equilibrium with VG, were used to follow O2 consumption as a function of reduced internal O2 pressure over time [for organs with VG < 0.1 (v/v) and respiratory quotient (RQ) of 0.7 to 1.3] to observe the transition between aerobiosis and anaerobiosis and to measure CO2 evolution during the anaerobic phase. For those measurements, bulky-organ manometry performed consistently in tomato [VG = 6.41% (v/v)], sweetpotato [VG = 8.57% (v/v)], and potato [VG = 0.34% (v/v)]. The results indicate that constant-volume manometry is sufficiently precise to detect differences in respiratory metabolism as a function of intercellular O2 concentration in intact plant organs.
E. G. Webster, M. E. Wright, and M. E. Austin
Results of tests to evaluate periderm peeling and failure forces of container-grown roots of sweetpotato (Ipomea batatas, Lam. cv. Nemagold), conditioned to various environments, were erratic. With field-grown roots, peeling and failure forces varied with soil temperature and soil moisture and were generally highest for warm dry conditions. Temperature and moisture had approximately equal effects on periderm peeling resistance within the ranges tested. Periderm thickness decreased and peeling resistance increased as soil temperature increased, but the number of cell layers remained fairly constant.
A. Richard Bonanno, Thomas J. Monaco, and Larry K. Hammett
Seventeen herbicide treatments used in the production of sweet potato [Ipomea batatas (L.) Lam.] seed roots were evaluated for their influence on transplant production the following season. Number of transplants/root at five harvests, total transplants/root, and transplants/100 g of root were not influenced by the herbicide treatments. Weight/transplant was influenced by the herbicide treatments only at the last harvest. Total transplant weight/root and total transplant weight/100 g of root also were not influenced by the experimental treatments. No visual deleterious effects on transplant production were observed with any of the herbicide treatments.
P.P. David, A. Almazan, C.K. Bonsi, D.G. Mortley, A.A. Trotman, and G.W. Carver
Studies were conducted in a greenhouse to determine the effects of harvesting sweetpotato (Ipomea batatas L. (Lam.) cv. “TI-82-155”) shoot tips (top 10 cm) at biweekly intervals beginning 42 days after transplanting on yield of storage root and nutrient content of harvested shoot tips. Plants were grown hydroponically from vine cuttings of 15 cm length, planted in 0.15 × 0.15 × 0.12 m growth channels using a closed NFT system. Nutrient was supplied in a modified half-strength Hoagland's solution with a N:K ratio of 1:2.4. Final harvest was at 120 days when shoot biomass and yield of storage roots were measured. Biweekly topping did not affect storage root yield or shoot biomass. However, harvesting time had a significant effect on dry matter and nutrient content of shoot tips.
Dingbo Zhou and Theophanes Solomos
The mechanism of C2H4 action on plant respiration is not well understood. In the present work we treated peeled sweet potato roots (Ipomea batatas cv. MD715) with 10 ppm C2H4 in air and 3% O2 Analytical data showed a close relationship between respiration and activity of phosphofructokinase while the activity of pyrophosphate fructose-6-phosphate phosphotransferase remained constant under all experimental treatments. At the respiratory peak there was an increase in both pyruvate and fructose-2,6-diphosphate. The change in the levels of pyruvate, followed closely that of the respiration drift, while those of fructose-2,6-diphosphate did not correlated so closely. The data indicate that the stimulation of respiration by C2H4 in sweet potato roots is closely associated with an enhancement of glycolysis. The levels of ATP also increased with the rise in respiration and reflected the magnitude of the respiratory increment.
Lauren Garner, Desmond Mortley, Philip Loretan, Audrey Trotman, and Pauline David
An experiment was conducted in a greenhouse environment to determine the relationship between type of cutting and planting depth on sweetpotato [Ipomea batatas (L) Lam] storage root yield using the nutrient film technique. Vine cuttings of the cultivar 'TI-155' were planted in growth channels (122×15×15 cm) in modified half Hoagland's solution. Treatments consisted of cuttings with all leaves and shoot apex removed with two nodes inserted (2NB), cuttings with all leaves and shoot apex removed with five nodes inserted (5NB). and cuttings with four leaves and the shoot apex remaining with two nodes inserted (2NB-L). Plants were harvested 130 days after planting and yield data was taken. Plants in 2NB-L had a significantly lower percent dry matter than those of 2NB. Neither cutting type nor planting depth affected yield or yield related parameters.
A.A. Trotman, D. G. Mortley, P.P. David., and G.W. Carver
The effect of inoculation of sweetpotato (Ipomea batatas L. (Lam.)) cultivar “TI-82-155” with Azospirillum brasilense was investigated in an observational greenhouse experiment. Sweetpotato was grown in a closed hydroponic system and plant nutrients were supplied in a Modified Half-strength Hoagland's solution (N:K 1:2.4) using a nutrient film technique system (NFT). Plants were either supplied with mineral nitrogen (160 ppm) and noninoculated or were supplied mineral nitrogen (160 ppm) and inoculated. Storage root dry matter was higher under inoculation with A. brasilense. Inoculation also increased the percent total nitrogen in the shoot, leaves, and fibrous root. There was a significant difference in fresh fibrous root weight for the inoculated (262.5 g) over the noninoculated (177.1 g) treatments. Mineral nitrogen supplied in the PNS was not limiting because dry matter for plants inoculated with A. brasilense was not significantly higher than for the noninoculated control.
Walter E. Splittstoesser and Franklin W. Martin
The troptophan content was determined in 29 cultivars of tropical root and tuber crops: (Manihot esculenta Crantz, Dioscorea alata L., D. rotundata Poir., D. esculenta Burkill, D. bulbifera L., D. trifida L., Ipomea batatas L., Xanthosoma sagittifolium L. Schott, Colocasia esculenta L. Schott, Canna edulis Ker., Maranta arundinacea L., and Calathea allouia Lindl.) They contained 0.1 to 1.1 g tryptophan per 100 g protein and were below the FAO reference protein. Sufficient diversity existed between cultivars for troptophan per g of dried tissue to recommend further trials with D. alata cv. Florido, D. esculenta cv. Spindle, X. sagittifolium cv. Aguadillana and Colocasia esculenta cv. Martin. These contained 50% to 79% as much tryptophan as the FAO reference protein and have excellent cooking qualities.
Sweetpotato (Ipomea batatas L) was one crop chosen for development in Ontario in response to demand for alternative crops to tobacco and increasing demand for nontraditional vegetables. A wide range of vegetable crops can be grown in the sandy soils on the north shore of lake Erie. In 1999, there were ≈75 acres of sweetpotatoes grown in Ontario. Lack of an early cultivar to fit a short, warm season was a factor limiting production of sweetpotatoes in southern Ontario. Over an 11–growing season period, cultivars of sweetpotato from several breeding programs in the United States were evaluated for suitability to Ontario climatic conditions. Planting to harvest date season totals for heat units, precipitation, vapor pressure deficit (VPD), potential evapotranspiration, and solar radiation were calculated. Yield was regressed on these climatic variables using multiple linear regression. Of the cultivars evaluated, `Beauregard' replaced `Jewel' as the local industry standard after one season's evaluation. Of the numbered lines evaluated, NC9317 appears suitable for commercial trials. Yields varied greatly among years, and the seasonal VPD explained the largest amount of variation in year-to-year yield. Cultivars vary in their response to seasonal VPD. Yield of `Beauregard' increased with increasing seasonal VPD while NC9317 decreased. Cultivars require ability to yield in a short season and the ability to consistently produce under a range of atmospheric VPDs dictated by interannual climatic variation.