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Abstract

Plants of sweet potato (Ipomoea batatas (L.) Lam) were exposed prior to harvest to 1 week of warm-dry, warm-flooded, cold-dry or cold-flooded soil conditions. Roots harvested from the warm-flooded soil showed more rotting during curing than roots from the other treatments, and rotting continued during storage. Roots harvested from the cold-flooded soil rotted to a lesser extent during curing but rotted rapidly during storage. Roots harvested from the cold-dry soil showed no rotting during curing; however after 52 days of storage, the number of roots with rot increased sharply. Root respiration rates from cold-flooded, cold-dry, and warm-flooded soils were not significantly different, but those rates were much higher than the rate in roots from warm-dry soil. ‘Jewel’ had a lower respiration rate than NC 317. The cold treatments stimulated sprouting of sweet potato roots during storage. ‘Caromex’ showed the highest sprouting followed by ‘Jewel’, NC 317, and ‘Centennial’.

The sweetpotato foundation seed program in Mississippi is committed to producing and supplying high-quality sweetpotato seed to the Mississippi sweetpotato industry. In 1991, a study was initiated to evaluate the effects of small heteroclinal chimeras in foundation seed roots on the root flesh quality in subsequent generations. The presence of small heteroclinal chimeras in parent seed roots did not increase the number or size of chimeras in three subsequent generations of storage roots.

Nutrient technique (NFT) and deep water culture (DWC) hydroponic systems were used to grow sweetpotao to study the effect of four nutrient solution treatments on: translocation of nutrients and plant and microbial population growth in split-root channels. 'TU-155'cuttings (15 cm) were prerooted for 30 days in sand in 4 cm CPVC pipes 46 cm in length. A modified half Hoagland (MHH) solution was supplied ad libidum. After 30 days, plants were removed and the roots of each plant were cleaned and split evenly between two channels (15 cm deep by 15 cm wide by 1.2 m long). four plants per channel. Nutrient solution treatments (replicated) were: MHH-MHH: MHH-Air, MHH-deionized water (DIW); and monovalent (Mono) - divalent (Dival) anions and cations. Solution samples were continuously collected at 7-day intervals for microbial population profiling. Plants were harvested after growing for 120 days in a greenhouse. Storage roots, when produced, were similar in nutritive components. However, no storage roots were produced in Air or Mono channels and only a few in DIW. Fresh and dry weights for storage roots and foliage were highest in MHH-MHH in both NFT and DWC in repeated experiments. Population counts indicated that nutrient solution composition influenced the size of the microbial population in NFT. Population counts were highest in Dival channels. The microbial population counts (4.20-7.49 cfu/mL) were. relatively high in both NFT and DWC systems.

Immersion of sweetpotato [Ipomoea batatas (L.)] storage roots in low concentration (5 and 50 mg·liter^-1) of gibberellic acid (GA) in solutions of benzyl adenine plus GA₄₊₇ increased early but not total plant production from bedded roots of `Georgia Jet' and `Jewel'. Immersion in 0.5 and 1 mg·liter^-1 solutions of GA₃ increased early plant production from `Georgia Jet'. Neither weight nor visual appearance of the harvested plants nor root yield from transplants were influenced by gibberellin treatments of the bedded roots.

Abstract

Recent studies showed that at harvest sweetpotato storage roots contain as much as 10 milliliters of intercellular space per 100 milliliters of root; during storage intercellular space increases to the extent that it becomes visible and is classified as pithiness or internal breakdown (1). A preliminary report shows that by accounting for the intercellular space tissue specific gravity values can be computed and correlated with drymatter content in much the same manner as for Irish potatoes (2). At harvest intercellular space for each of four varieties was relatively constant for a given variety and differed significantly among varieties (4).

Abstract

High temperature during August plantings of sweet potato [Ipomoea batatas (L.) Lam.] reduced the number of storage roots/plant, increased top weight, and gave low yield. November planting, when the temperature was relatively low, had no effect on root formation but resulted in small roots. Yields were related to the accumulated temperature of the first 60 days after planting (DAP) and the relationship was quadratic. Regression analysis revealed that the highest yield (15.3 t·ha^–1) in 1981–82 was obtained when the mean daily temperature of the first 60 DAP was 22.4°C. Analogous data for 1983–84 were 17.7 t·ha^–1 and 23.1°.

Abstract

Respiration of sweet potato roots was significantly depressed by low oxygen concentrations from 5 to 15% compared to 20% O₂, but respiration at 2.5% O₂ was high. Total sugar accumulated with low oxygen (2.5 and 5.0%) storage. Protopectin was low in roots stored at low O₂ concentrations but water soluble pectin was not significantly affected. Physical parameters Ew and δf the storage roots were high when stored at low O₂ concentrations. Ey and Ef were not significantly affected. Ew was correlated with total sugar (r = 0.79).

Abstract

The concentration and total content of P, K, Ca, Mg, N, Fe, Mn, and B in storage roots and in vines of sweet potatoes [Ipomoea batatas (L.) Lam.] was followed for a 14 week period beginning 2 months after planting. The concentration of N, P, K, Mn, and Mg in the vines and N, P, and K in the roots decreased slightly during the period. Other elements showed no definite seasonal trends. Total uptake by the vines showed little change after the second sampling period

Root growth of sweet potato [Ipomoea batatas (L) Lam.] cvs `TI-82-155', `Centennial' and `Rojo Blanco' in coarse fritted clay soil, was investigated under greenhouse conditions. The sweet potato cultivars were harvested at 41 and 82 days after planting. Dry weight of fibrous roots of all cultivars were similar at day 41. Fibrous root weight of `Rojo Blanco' increased by 5% while those of the other cultivars increased by 168%. Mean fibrous root length per centimeter depth was not significantly different among cultivars. Although fresh weight of storage roots of `Rojo Blanco' was significantly lower than those of the other cultivars, their dry weights were similar. `TI-82-155' and `Rojo Blanco' had fewer storage roots compared to the other cultivars, however, storage root length of `TI-82-155' or `Rojo Blanco' was greater than that of `Georgia Jet' or `Centennial'. Length to diameter ratio of the storage root of `Rojo Blanco' was significantly greater than that of `TI-82-155' and `Georgia Jet'.

The sweetpotato weevil is the single most critical insect pest of the sweetpotato worldwide. While male weevils can be lured to traps using a synthetic female pheromone, crop losses are not adequately reduced since damage is caused by the larvae arrising from eggs laid by female weevils in the storage roots. Identification of a female attractant could greatly enhance the control of the insect. The leaves and storage roots are known to emit volatiles that attract the female and in the following tests, we demonstrate that feeding by female weevils stimulates the synthesis of a volatile attractant which attracts additional females to the root. Undamaged, artificially damaged, and female weevil feeding damaged periderm were tested in dual-choice and no-choice olfactometers. Volatiles from feeding damaged roots were significantly more attractive than undamaged and artificially damaged roots. To test whether the volatile attractant was of weevil or root origin, volatiles were collected in MeCl2 after removal of the weevils and fractionated on a megabore DB-1 capillary column using a GC fitted with a TC detector. Fractions were collected from the exit port and their activity index (AI) determined using dual choice and no choice olfactometry. The active fraction was ascertained and active components identified via GC-MS.