The effect of fibrous root infection by S. ipomoea on disease on storage roots and production of marketable yield in the susceptible sweetpotato cultivar `Jewel' was evaluated in field experiments in 3 years. Drip irrigation (main plots) reduced disease on fibrous roots in plots not treated with sulfur or fumigated, but did not significantly increase yields in any year. Sulfur (subplots) reduced the severity of the disease on fibrous roots in nonfumigated plots in 2 years, but reduced yields by 21-33% in 2 of 3 years. Fumigation of soil with Telone C-17 (sub-subplots) reduced the percentage of diseased storage roots produced per plot from 71%, 8%, and 22% in nonfumigated plots to 52%, 3% and 6% in fumigated plots in 1988, 1989 and 1990, respectively and reduced the severity of disease on fibrous roots in all years. Only fumigation increased the yield of marketable storage roots by 68% and 19% in two of three years. The severity of disease on fibrous roots was positively correlated with the percentage of diseased storage roots produced per plot (r = 0.84) and the number of diseased storage roots produced per plant (r = 0.64), and was negatively correlated with the number of storage roots produced per plant (r = -0.66). Yield of marketable storage roots was negatively correlated with both the severity of disease on fibrous roots (r = -0.77) and the percentage of diseased storage roots produced per plot (r = -0.73). These data demonstrate the importance of fibrous root disease in this pathosystem. Management strategies that reduce disease on fibrous roots may ultimately lead to increased yield of storage roots.
Jean B. Ristaino and Charles Averre
Arthur Villordon, Don LaBonte, and Julio Solis
roots, and storage roots during the initial storage root bulking stage as determined using destructive sampling and scanner-based minirhizotron system in sweetpotatoes grown in Chase, LA. z Minirhizotron-based measurement of adventitious root development
Darbie M. Granberry, R. A. Conover, and Booker T. Whatley
Seedlings of sweet potato [Ipomoea batatas (L.)], which failed to form storage roots, produced good yields of sweet potato roots of acceptable size and grade when propagated asexually by vine cuttings.
D. R. Tompkins and R. D. Horton
In field plantings, root pieces of ‘Centennial’, ‘Julian’, and ‘Jewel’ sweet potato (Ipomoea batatas L.) treated with (2-chloroethyl)phosphonic acid (ethephon) sprouted earlier than controls. Ethephon treatments increased the number of sprouts on ‘Centennial’ root pieces. In some tests, ethephon treated root pieces had increased yields of storage roots. Gibberellic acid (GA) increased the number of sprouts per root piece but did not influence the percentage of sprouted root pieces. GA promoted the growth of enlarged root pieces with few storage roots.
David Graper and Will Healy
Non flowering Alstroemeria `Regina' plants were divided into aerial components: stems and apical and basal leaves or underground components: rhizome, storage roots, stele and fibrous roots. Samples were collected from distal and proximal ends of the rhizome to allow comparisons between structures of different ages. Ethanol soluble sugars were extracted and measured using HPLC. Starch was degraded to glucose using amyloglucosidase and measured.
There were no age differences in the starch, total soluble sugar (TSUGAR) or total soluble carbohydrates (TCHO) in the rhizome or aerial portions of the plant. There was a preferential partitioning of starch, sucrose, TSUGAR and TCHO to underground plant parts. The storage roots were the primary sink for the stored carbohydrates. Stems contained large concentration of glucose while fructose was found in storage roots and old stems. Sucrose was found primarily in old steles and storage roots. Starch was partitioned almost exclusively into the storage roots with no difference due to age of the storage root. Up to 42% of the TCHO in the old storage roots was composed of a carbohydrate which co-chromatogramed with melezitose using HPLC.
S.M.A. Crossman, M.C. Palada, and J.A. Kowalski
A study was conducted to evaluate the effect of irrigation on yield and sweetpotato weevil (SPW) infestation of sweetpotato storage roots. Sweetpotato was grown in plots under controlled soil moisture regimes. The treatments were rainfed (no applied irrigation) and irrigation applied to maintain soil moisture levels at 20, 40, and 60 kPa, based on tensiometer readings. The 40- and 60-kPa treatments produced the highest yield of root biomass. Irrigation applied at 40 kPa produced significantly more medium-sized storage roots (8.1 t·ha–1) than the rain-fed treatment, which produced 4.4 t·ha–1. All of the irrigation treatments produced significantly more marketable storage roots with a lower mean damage index (MDI) than the rain-fed treatment. There was an inverse relationship between MDI and soil moisture levels among the irrigation treatments. A significantly higher percentage of storage roots (51.5%) from the 20-kPa treatment were rated in the Damage Index (DI)-1 (uninfested roots) category than from the rain-fed treatment (27.7%). Additionally, the percentage (29.4%) of storage roots from the rain-fed treatment rated in the DI-6 (most severe) category was significantly higher than the applied irrigation treatments, with 13.9%, 13.9%, and 6.0% respectively, for the 60-, 40-, and 20-kPa treatments. Irrigation therefore has potential to increase sweetpotato yields while reducing SPW infestation levels.
Sharon R. Funderburk and Wanda W. Collins
Crimson clover Trifolium incarnatum L.) was used as a N source for sweet potato [Ipomoea batatas (L.) Lam.]. Treatments were designed to compare estimated N delivery by clover incorporation amounts of N delivered by inorganic fertilizer. Plants were sampled every 14 days and sectioned into four parts: shoots, stem tips, fibrous and storage roots. Dry matter content was significantly influenced by time. Total plant dry matter was lowest in the highest inorganic N treatment. Nitrogen concentration (DWB) decreased over time and was highest in the highest inorganic N treatment. Similar vine weights were noted in N and clover treatments while number of storage roots per plant was unaffected by treatment as was weight per storage root, which increased linearly over time. No significant difference existed between the high and low N application treatment or late clover incorporation treatment in any grade of storage roots except culls, which were 90% lower in clover treatments than in N fertilizer treatments.
R. C. Sloan Jr., P. G. Thompson, W. B. Burdine Jr., J. L. Main, and P. D. Gerard
`Beauregard' storage roots which were discarded from the Mississippi sweetpotato foundation seed program because of the presence of flesh mutations were bedded in Spring 1991. After the plants were pulled from the roots, the roots were further examined, and the flesh mutations were characterized by size and frequency. The progency from the original roots were examined for flesh mutations for three generations in 1991, 1992, and 1993. The degree of mutation in the original root did not influence the degree of mutation in succeeding generations of storage roots. In 1992 and 1993, the degree of mutation in the third and fourth generation roots did not differ from that of storage roots grown from plants from the foundation seed plant beds.
Melvin R. Hall
Poor cosmetic appearance of fresh-market sweet potatoes [Ipomoea batatas (L.) Lam.] associated with harvesting injuries has led to the abandonment of mechanical sweet potato harvesters in some areas. There has been increased concern that damage associated with mechanical harvesting could be magnified during storage in cultivars such as ‘Georgia Jet’ (1), which are not suited for long-term storage even when properly cured. An additional concern is that mechanical harvesting may reduce the propagation potential of the bedded storage roots. This note describes the influence of dropping and washing on abrasion, cracking, percent weight loss during storage, and formation of sprouts on storage roots of ‘Georgia Jet’ sweet potato.
M. C. Acock and J. O. Garner Jr.
Differences in storage root initiation among sweet potato (Ipomoea batatas Lam.) plants of the same cultivar were generated by treating them with different amounts of a slow-release fertilizer (19N-3P-10K). Activity of cell-wall-bound invertase (cwb invertase) was monitored during storage root initiation to determine whether differences in its activity could be associated with differences in storage root formation. Cwb invertase activity was increased in roots of plants receiving the lower amount of fertilizer and producing the greater number of storage roots. NAA enhanced cwb invertase activity in excised storage roots.