Chemical and environmental growth regulation of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro

The need for conservation of biotic diversity is well recognized. However, improved techniques for the efficient, cost effective-preservation of plant germplasm are needed. The conservation and distribution of plant germplasm in vitro is gaining acceptance. However, increased usage is dependent upon the ability of curators to minimize culture maintenance requirements. This report examines the effect of various levels of sucrose, photoperiod, temperature, sorbitol and mannitol on minimal growth storage of Ipomoea batatas (L.) Lam. Growth was reduced 50% with a temperature reduction of from 21.1 to 15.6°C. Sucrose concentrations of 15 and 20 g l^-1 resulted in reduced plant stature with few adverse effects on plantlet viability or morphology. Reduction of photoperiod from 16 to 4 h produced smaller, slightly chlorotic, but otherwise normal plants. The addition of sorbitol or mannitol to culture media generally produced undesirable effects on gross plant morphology and loss of apical dominance. Genotype x growth retarding treatment interactions were observed for all variables examined.Abbreviations PL plant introduction - f.w. fresh weight - SE standard error     

Cryopreservation of sweet potato (Ipomoea batatas [L.] Lam.) shoot tips by vitrification

Summary Vitrification is a technically simple method for cryopreserving plant germplasm, requiring only the application of suitable cryoprotectants and rapid cooling rates. Sweetpotato (Ipomoea batatas [L.] Lam.) shoot tips obtained from in vitro plants survived liquid nitrogen (–196°C) exposure following a vitrification-inducing pretreatment. Shoot tips were treated in a stepwise manner with a vitrification solution containing 30% glycerol, 15% ethylene glycol and 15% dimethylsulfoxide in growth medium. Incubation of shoot tips for 1 to 2 h in low concentrations of the vitrification solution enhanced survival. Most surviving shoot tips developed callus, and a variable percentage subsequently formed shoots. Survival was not achieved using two-step cooling procedures. The percentage of shoot tips surviving vitrification and those subsequently forming a shoot varied widely among replications.Abbreviations BA N⁶-benzyladenine - IBA indole-3-butyric acid - EG ethylene glycol - DMSO dimethylsulfoxide - MS Murashige and Skoog (1962) minerals and vitamins - LN liquid nitrogen - PI plant introduction     

Growth and morphogenesis of immature embryos of sweet potato (Ipomoea batatas L.) in vitro

Sweet potato (Ipomoea batatas L.) embryos excised from the fertilized ovules of 6- to 12-day-old capsules were cultured on MS medium supplemented with NAA, BA, GA separately and in combinations. GA was found essential for initial morphogenesis of globular and heart stages. Seedlings were recovered from late globular stage onwards but recovery was best from advanced embryo stages. Differentiated embryos produced multiple shoots on MS medium +1M NAA÷2M BA +0.5M GA.     

Mesophyll protoplast culture of sweet potato (Ipomoea batatas L.)

Mesophyll protoplasts of sweet potato (Ipomoea batatas L.) were readilyisolated by soaking chopped leaf tissue in distilled water for 16 h prior to enzymatic digestion. Isolated mesophyll protoplasts began to divide three days after start of culture in liquid modified N₆ medium and and formed colonies after 30 days of culture. The colonies transferred to solid medium grew rapidly and differentiated into calli. Some of the calli transplanted onto regeneration medium produced roots.     

Isolation of antidiabetic components from white-skinned sweet potato (Ipomoea batatas L.)

We have already reported that white-skinned sweet potato (Ipomoea batatas L.) (WSSP) shows antidiabetic activity in streptozotocin (STZ) induced diabetic rats and genetically diabetic models (yellow KK, db/db mice and Zucker fatty rats). In this study, isolation and purification of the antidiabetic component of WSSP were attempted. Almost all antidiabetic activity was found in the cortex of WSSP. The fractionation of the antidiabetic component in the WSSP cortex was done by the following methods: dialysis of the water extract, 85% ethanol precipitation, 15% trichloroacetic acid (TCA) treatment, butyl-, phenyl-hydrophobic column chromatography, and ultrafiltration treatment. The antidiabetic component was not eliminated during dialysis and was soluble in 85% ethanol and 15% TCA, but it passed through a filter that allows the passage of substances of a molescular weight of 30,000. The uniformity of this isolated active component was analyzed using HPLC. A single peak was seen with three different columns (C8 reverse-phase column, anion exchange QA column, and gel filtration column (GFC)), indicating that the component is a uniform substance. The molecular weight of this antidiabetic component was estimated to be 22,000 by GFC analysis. This active component was presumed to be an acidic glycoprotein because it contained protein and sugar and was adsorbed onto the QA column at pH 7.0.     

Heritability of regeneration in tissue cultures of sweet potato (Ipomoea batatas L.)

Summary A population of open-pollinated progeny from 12 parents, and the 12 parents, was surveyed for in vitro growth and regeneration characteristics. Four different tissue culture procedures involving different media and the use of different explants to initiate the cultures were used. Petiole explants from young leaves were used as explants for initiation of callus cultures. These were evaluated for callus growth rate, friability, and callus color and texture, before transferring to each of three different regeneration media for evaluation of morphogenetic potential. Small shoot tips also were used to initiate callus cultures, which were evaluated for the same growth characteristics and transferred to growth-regulator free regeneration media. Regeneration occurred through root or shoot regeneration or through embryogenesis. Tissue culture treatment effects, as well as genotypic effects, were highly significant in determining: the types of callus produced, callus growth rates, color and texture on the two types of media used for the second and third subcultures. The family x treatment interaction was generally not statistically significant, affecting only callus color. Estimates of narrow sense heritability for callus growth rate in both the second and third subcultures were high enough (0.35 and 0.63, respectively) for the evaluation of parental lines for selection procedures. These characteristics were also the only early culture callus traits that were consistently correlated with later morphogenesis of the cultures. They were negatively correlated with root or shoot regeneration. The occurence of somatic embryogenesis was not correlated with early callus growth characteristics. Genetic and treatment effects were highly significant in the evaluation of morphogenetic potential, through root or shoot regeneration, or through embryogenesis. Regeneration of all types was of low frequency for all procedures, expressed in 11% of the cultures of the total population.Paper No. 9906 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7601, USA. From a thesis submitted by the senior in partial fulfillment of the requirements for the Ph.D. degree     

Isozyme modifications and plant regeneration through somatic embryogenesis in sweet potato (Ipomoea batatas (L.) Lam.)

Summary The potential of somatic embryogenesis was evaluated for 10 cultivars of sweet potato through extensive embryogenic response and isozyme analysis. Embryogenic callus was induced by incubating lateral buds on Murashige and Skoog medium containing 10 M 2,4-dichlorophenoxyacetic acid for 6–8 weeks. The frequency of embryogenic response was low, and varied with genotypes, ranging from 0 to 17%. Embryo to plantlet formation could be enhanced by the use of the combination of 2,4-dichlorophenoxyacetic acid with kinetin, both used at 0.01 M. Embryogenic callus with its potential of plantlet formation has constantly been maintained for over two years. However, after several subcultures, 0.5 to 12% of embryogenic callus reverted irreversibly into friable fast-growing non-embryogenic callus whose ability to regenerate shoots was then definitively lost. The isozymes of esterase, peroxidase, glutamate oxaloacetate transaminase and acid phosphatase investigated in this study were found appropriate to distinguish compact embryogenic from friable non-embryogenic callus in sweet potato. In fact, the callus reversion was associated with a loss of bands or a decline in isozyme activity. On the contrary, very small changes in isozyme activity or no specific changes at all were observed during the differentiation of embryogenic callus into globular embryos.Abbreviations Acp acid phosphatase - BAP 6-benzylaminopurine - cv cultivar - df degree of freedom - 2,4-D 2,4-dichlorophenoxyacetic acid - Est esterase - Got glutamate oxaloacetate transaminase - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) medium - Prx peroxidase - Tris tris(hydroxymethyl)aminomethane     

Morphohistobiochemical characteristics of embryogenic and nonembryogenic callus cultures of sweet potato (Ipomoea batatas L.)

Ipomoea batatas callus culture raised in a medium supplemented with 2,4-D (2,4-dichlorophenoxy acetic acid) alone or 2,4-D in combination with benzyl adenine, were found to be embryogenic. Supplementation of exogenous chemicals, such as 5 g/l NaCI or 0.7 g/l proline together with a mild dose of 0.2 mg/l 2,4-D, enhanced somatic embryogenesis significantly in all the genotypes tested. Morphological, growth, physiological, histological, and biochemical characteristics of the embryogenic callus were different from the nonembryogenic callus. The former was compact, slow growing, and nodular compared with the fast growing, fragile, nonembryogenic callus. The embryogenic callus tissue had more dry matter, protein and reducing sugar contents compared with the less embryogenic callus. The somatic embryogenic response remained steady in the cultures for up to 96 weeks.     

Phosphate fertiliser alters carboxylates and bacterial communities in sweet potato (Ipomoea batatas (L.) Lam.) rhizosheaths

Plant and Soil - Selenium (Se) is an essential element for mammals and its deficiency in the diet is a global problem. Plants accumulate Se and thus represent a major source of Se to consumers....     

Plant regeneration from protoplast culture of sweet potato (Ipomoea batatas Lam.)

This is the first report on successful plant regeneration from protoplasts of sweet potato. Two cultivars (Guyana and Duclos XI) of sweet potato plants propagated under in vitro conditions were used as the source of protoplasts. Green compact calli with meristematic areas were induced in the medium supplemented with 2mg1^–1 zeatin, and plant regeneration occurred when these calli were transferred onto the medium with zeatin level reduced to 0.25mg1^–1. Plant regeneration was found to be genotype-dependent, since it was only obtained for cultivar Duclos XI.Abbreviations MS Murashige and Skoog basal medium - IAA Indol-3-acetic acid - NAA naphthaleneacetic acid - 2,4-D dichlorophenoxyacetic acid - Mes 2-(N-morpholino)-ethanesulfonic acid - Cpw cell and protoplast washing solution     

Picolinic acid-induced direct somatic embryogenesis in sweet potato

Somatic embryos are being considered as an alternative material for in vitro germplasm conservation of sweet potato [(Ipomoea batatas (L.) Lam.)]. Picolinic acid was tested for somatic embryo production in sweet potato apical meristem tip cultures. Low level (0.2 mgl^-1) of picolinic acid combined with kinetin or 6-benzylamino purine (6-BAP) (1.0 and 2.0 mgl^-1) suppressed shoot growth and induced callus proliferation. Increased amount of picolinic acid (2 and 3 mgl^-1) in combination with kinetin (0.25 and 1.0 mgl^-1) induced direct somatic embryogenesis from apical meristem tips of variety Regal but not in Jewel. The primary embryos matured and germinated bipolarly yielding whole plantlets and unipolarly producing embryogenic hyperhydrated-fasciated shoots. The hyperhydrated-fasciated shoots, when cultured in picolinic and kinetin-enriched medium, produced secondary embryos. The secondary embryos also germinated bipolarly and unipolarly, resulting in subsequent cycles of embryogenesis. This recurrent embryogenesis ensures maintenance and proliferation of embryogenic tissues. Somatic embryos were also formed in mannitol-induced hyperhydrated shoots in response to picolinic acid and kinetin or 6-BAP treatment. Embryogenesis did not occur in non-hyperhydrated leaf, petiole, and internode sections.     

Cryopreservation of shoot tips from in vitro plants of sweet potato [Ipomoea batatas (L.) Lam.] by vitrification

 Routine cryopreservation of shoot tips from sweet potato [Ipomoea batatas (L.) Lam] has been hampered by their survival variability after cryogenic exposure. We examined the effects of light conditions on stock plants, sucrose preculture and cryoprotectant loading on survival after vitrification using PVS2 solution. The survival of vitrified sweet potato shoot tips cooled to approximately –208  °C was increased by preculturing with 0.3 M sucrose for 24 h at 22  °C. Survival was also enhanced by excising shoot tips immediately after the 8-h dark photoperiod. The best survival after cryogenic exposure was obtained using 2 M glycerol +0.4 M sucrose for 1 h at 22  °C followed by dehydration with PVS2 for 16 min at 22  °C. Rapid cooling was used and achieved by the immersion of foil strips into partially solidified nitrogen. Successfully vitrified and warmed shoot tips directly developed shoots on a medium containing 1 μM NAA, 0.5 μM BA and 0.1 μM kinetin with only minimum callus formation. Shoot formation occurred in all surviving shoot tips. This procedure shows promise for cryopreserving sweet potato shoot tips. Received: 2 March 1999 / Revision received: 21 September 1999 / Accepted: 29 September 1999     

Changes in caffeic acid derivatives in sweet potato (Ipomoea batatas L.) during cooking and processing

There was an obvious decrease in caffeic acid derivatives during the boiling of cube-shaped blocks of sweet potatoes. They also decreased in a mixture of freeze-dried sweet-potato powder and water maintained at room temperature. Ascorbic acid prevented the decrease, supporting the occurrence of an enzyme reaction with polyphenol oxidase (PPO). 5-O-Caffeoylquinic acid (5-CQA, "3-O-caffeoylquinic acid" as a trivial name) and 3,5-di-O-caffeoylquinic acid (3,5-CQA), major phenolic compounds of sweet potato, did not change when they were separately heated in boiling water. When the mixture of powdered sweet potato and water was heated at 100 degrees C, there was only a negligible decrease in the total amount of phenolic compounds, and portions of 5-CQA and 3,5-CQA were found to be isomerized to 3-CQA, 4-CQA, 3,4-CQA, and 4,5-CQA. The content and composition of the phenolic compounds in sweet potatoes differed between fresh and long-stored ones, as did their response to heating.     

Amylase secretion by sweet potato,Ipomoea batatas (L.) Lam., cell cultures grown on various carbon sources

Cell cultures of sweet potato grown in media containing sucrose, glucose, maltose, or starch secreted amylase into the growth medium. The growth rate of cells was not appreciably affected by the carbon source employed for growth, although cells grown on sucrose had a slightly longer lag period before exponential growth occurred. Amylase levels inside the cells were not affected by carbon source, but the amount of amylase released into the medium was drastically affected. Maltose-grown cells released the most amylase while sucrose-grown cells released the least. Cells grown in the light released about twice as much amylase as cells grown in the dark when grown on glucose, maltose, or starch.Three amylase electrophoretic forms were found in the storage root tissue from which all cultures were derived. Cells grown in culture exhibited either two or three amylase forms, depending on the carbon source. The slowest migrating root amylase was found only in cells grown on starch. The root amylase having intermediate mobility was present in all cultures, as was a form having higher mobility than the most mobile root form. The fastest migrating electrophoretic form from the root was not present in any of the cells.Paper No. 8466 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of products named, nor criticism of similar ones not mentioned.     

Assessment of sweet potato [Ipomoea batatas (L.) Lam] for bioethanol production in southern Italy

The potential of sweet potato as an alternative crop for bioethanol production has been assessed. We evaluated the amount of soluble sugars, starch and cell wall polysaccharides in tubers of three sweet potato cultivars characterized by different pulp and peel colouration: “Yellow yam” with yellow flesh and brown peel, “White yam” with white flesh and white peel and “Orange yam” with orange flesh and brown peel. The results confirm the high concentration of carbohydrates in sweet potato tubers, especially “Yellow yam”, mainly in the form of starch (67%) and soluble sugars (26%). “Yellow yam”, which is the most widespread cultivar in Salento, appeared the best choice as biomass for bioethanol production. It is characterized by high productivity (20–40 tons/ha year). Results also suggest that “Yellow yam” cultivar has great potential as a bioethanol source in southern Italy with an estimated agroindustrial production yield higher than 2032 l/ha year.     

Optimisation of somatic embryogenesis in fourteen cultivars of sweet potato [Ipomoea batatas (L.) Lam.]

Culture procedures have been developed to facilitate the induction and maintenance of somatic embryogenic tissues in 14 out of 16 tested cultivars of sweet potato [Ipomoea batatas (L.) Lam]. Both the size of the axillary bud explant and the type of auxin were found to be critical for the successful induction of somatic embryogenesis. Of the five auxins screened 2,4-dichlorophenoxyacetic acid 2,4-D and 2,4,5-trichlorophenoxyacetic acid were the most effective, with use of the latter inducing the production of embryogenic tissues in 7 cultivars which responded poorly or not at all to 2,4-D. Procedures for secondary/cyclic embryogenesis, formation of mature embryos and their conversion to plants are also described. Received: 24 September 1996 / Revision received: 16 December 1996 / Accepted 27 January 1997     

Interpretation of randomly amplified polymorphic DNA marker data for fingerprinting sweet potato (Ipomoea batatas L.) genotypes

In this paper we present a method for the generation of randomly amplified polymorphic DNA (RAPD) markers for sweet potato. These were applied to produce genetic fingerprints of six clonal cultivars and to estimate genetic distances between these cultivars. The level of polymorphism within the species was extremely high. From the 36-decamer random primers used, 170 fragments were amplified, of which 132 (77.6%) were polymorphic. Ten primers resulted in no detected amplification. Of the remaining 26 primers for which amplification was achieved, only one did not reveal polymorphism. Six primers used alone enabled the discrimination of all six genotypes. Pattern analysis, which employed both a classification and ordination method, enabled the grouping of cultivars and the identification of primers which gave greatest discrimination among the cultivars.