Sept. and 1 Oct. 2019, which corresponded to 123 and 124 d after transplanting. Vines were detached using a walk-behind string trimmer (model ST 100; Cub Cadet, Cleveland, OH), and plastic mulch was removed by hand. Storage roots were lifted using a one
Cecilia E. McGregor and Don R. LaBonte
`White Jewel' is a yellow-and-orange fleshed spontaneous mutant of the orange-flesh sweetpotato [Ipomoea batatas (L.) Lam.] cultivar Jewel. Mutations in storage root flesh color, and other traits are common in sweetpotato. The orange flesh color of sweetpotato is due to β-carotene stored in chromoplasts of root cells. β-carotene is important because of its role in human health. In an effort to elucidate biosynthesis and storage of β-carotene in sweetpotato roots, microarray analysis was used to investigate genes differentially expressed between `White Jewel' and `Jewel' storage roots. β-carotene content calculated from a* color values of `Jewel' and `White Jewel' were 20.66 mg/100 g fresh weight (FW) and 1.68 mg/100 g FW, respectively. Isopentenyl diphosphate isomerase (IPI) was down-regulated in `White Jewel', but farnesyl-diphosphate synthase (FPPS), geranylgeranyl diphosphate synthase (GGPS), and lycopene β-cyclase (LCY-b) were not differentially expressed. Several genes associated with chloroplasts were differentially expressed, indicating probable differences in chromoplast development of `White Jewel' and `Jewel'. Sucrose Synthase was down-regulated in `White Jewel' and fructose and glucose levels in `White Jewel' were lower than in `Jewel' while sucrose levels were higher in `White Jewel'. No differences were observed between dry weight or alcohol insoluble solids of the two cultivars. This study represents the first effort to elucidate β-carotene synthesis and storage in sweetpotato through large-scale gene expression analysis.
L. K. Chua and S. J. Kays
Patterns of deposition of [14C]-photosynthate in the storage roots of Ipomoea batatas (L.) Lam. at 3 stages of development (44, 74, 105 days from planting) were distinct for each labeling period. [14C] initially accumulates in the vascular cambial region after labeling (24 hours); however, all areas of the storage root show discernable activity. Label in this region is lost with time probably through cell division with the majority of the label ending up in bundle parenchyma. Deposition of [14C]-photosynthate appears to occur for more than 24 hours reflecting either continued transport from aerial portions of the plant or redistribution within the root. Roots labeled early in their development do not have a uniform distribution of [14C] in the central stele, possibly due to later development of anomalous cambium. [14C] in the cortical region does not appear to be redistributed inward during subsequent growth of the root. [14C] deposited early in the development of the storage root was concentrated at the distal end with longitudinal bulking proceeding toward the proximal end. Invaginations along the surface of the root giving a furrowed appearance appear to be due to differential rates of activity of the vascular cambium in those regions.
Melvin R. Hall
Initiation of sweet potato [Ipomoea batatas (L.)] plant harvests from the propagating bed was later from the sparse plant producer ‘Georgia Jet’ than from the profuse plant producer ‘Georgia Red’. Also, the initiation of plant harvests from storage roots cut into longitudinal halves for inspection of internal quality before bedding was later than from whole roots. These differences were reflected in lower cumulative percentages of total plants harvested from ‘Georgia Jet’ than from ‘Georgia Red’ within 2 weeks and from longitudinal halves within 2 and 4 weeks after initiation of plant harvests. Total plant production was greater from whole than from halved ‘Georgia Jet’ roots. Total plant production was greater from halved roots immersed in Botran 75W compared to those immersed in calcium hypochlorite. Cutting and immersion treatments did not influence total plant production from ‘Georgia Red’, a profuse plant producer. ‘Georgia Jet’ roots deteriorated more than ‘Georgia Red’ in the propagating bed, and deterioration was increased by cutting and immersion in calcium hypochlorite. Presprouting did not reduce deterioration of roots in the propagating bed, but did reduce the number of days from bedding until first plant harvest. It also increased the cumulative percentage of the total plants harvested within 2 and 4 weeks after harvests were initiated and increased total number of plants produced from both small and large ‘Georgia Jet’ roots and from large ‘Georgia Red’ roots. Large roots of each cultivar produced more plants than were produced by small roots when presprouted. Large roots of ‘Georgia Jet’ also produced more plants than were produced by small roots when not presprouted, but root size did not influence total plant production from ‘Georgia Red’ roots that were not presprouted. Chemical name used: 2,6-dichloro-4-nitroaniline (Botran 75W).
Phillip A. Wadl, Livy H. Williams III, Matthew I. Horry, and Brian K. Ward
sweetpotato breeding programs. Insect-resistant (‘Ruddy’) and -susceptible (SC-1149-19) controls were also included. Vine cuttings (slips) ≈12 inches long produced annually from storage roots for all experiments were cut from plant-nursery beds no more than 3
Satoru Motoki, Tianli Tang, Takumi Taguchi, Ayaka Kato, Hiromi Ikeura, and Tomoo Maeda
components or resources of rutin ( Motoki et al., 2012a ). Unlike cladophylls, strong growth-inhibitory activity was observed in storage roots ( Motoki et al., 2006 ). Few reports are available on the active use of the cladophylls and storage roots as useful
Satoru Motoki, Takumi Taguchi, Ayaka Kato, Katsuhiro Inoue, and Eiji Nishihara
process leaves ferns from the aboveground parts and roots from the underground parts as large amounts of unusable parts, and this is an issue to be resolved. In our previous study, large amounts of rutin were noted in the cladophylls and storage roots
Ling A. Chang, Larry K. Hammett, and David M. Pharr
Flood-damage was simulated by submerging freshly harvested storage roots of 4 cultivars of sweet potato (lpomoea batatas (L.) Lam) under water for 48 hours. Root ethanol accumulation (μmoles/g fresh weight) for each cultivar was: ‘Centennial’, 38.6; ‘Jasper’, 42.9; ‘Jewel’, 48.8; and ‘Caromex’, 74.4. Storage losses due to rotting and accelerated weight loss were highest in ‘Caromex’ and second highest in ‘Jewel’. The amount of ethanol formed was not correlated with the apparent activity of either pyruvate decarboxylase or alcohol dehydrogenase. Cultivars differed upon removal from anaerobic conditions in their ability to metabolize accumulated ethanol. Cured roots of the 2 tolerant cultivars eliminated ethanol earlier than those of the 2 susceptible cultivars after anaerobic treatment. Thus, flood-damage to sweet potato storage roots may involve at least 2 factors, the rate of ethanol accumulation due to anaerobic treatment and the subsequent lag period and extent of metabolism of accumulated ethanol upon removal of anaerobic conditions.
Melvin R. Hall and Janies C. Turner
Mepiquat chloride sprays did not affect the percentage of dry weight partitioned to ‘Georgia Jet’ sweet potato [Ipomoea batatas Lam.] vines or storage roots, but with 4000 or 8000 mg liter−1 concentrations there was a tendency toward reduced vine length and reduced number of nodes. Plants grown in 2.5-liter pots were smaller than plants grown in 10-liter pots, but responded similarly to mepiquat chloride. Chemical names used: 1,1-dimethyl piperidinium chloride (mepiquat chloride).
Don R. La Bonte, David H. Picha, and Hester A. Johnson
The quantity and pattern of carbohydrate-related changes during storage root development differed among six sweetpotato cultivars [Ipomoea batatas (L.) Poir. `Beauregard', `Heart-o-Gold', `Jewel', `Rojo Blanco', `Travis', and `White Star']. Measurements were taken for individual sugars, total sugars, alcohol-insoluble solids (AIS, crude starch), and dry weight (DW) at 2-week intervals from 7 to 19 weeks after transplanting (WAT) in two separate years. Sucrose was the major sugar during all stages of development, representing at least 68% of total sugars across all cultivars and dates. Pairwise comparisons showed `Heart-o-Gold' had the highest sucrose content among the cultivars. Sucrose content increased by 56% for `Heart-o-Gold' over the 12 weeks of assay, ranking first among the cultivars at 17 and 19 WAT and possessing 27% more sucrose than the next highest ranking cultivar, `Jewel', at 19 WAT. Fructose content profiles varied among and within cultivars. `Beauregard' showed a consistent increase in fructose throughout development while `Whitestar' showed a consistent decrease. The other cultivars were inconsistent in their fructose content profiles. Glucose content profiles were similar to those for fructose changes during development. The relationship between monosaccharides was fructose = 0.7207 × glucose + 0.0241. Cultivars with the highest fructose and glucose content could be selected by breeders after 13 WAT. Early clonal selection for high sucrose and total sugars is less promising because substantive changes in clonal rank occurred for sucrose and total sugars after 15 WAT. Cultivars ranking the highest in total sugars had either more monosaccharides to compensate for a lower sucrose content or more sucrose to compensate for a lower monosaccharide content. The relationship between DW and AIS was similar (AIS = 0.00089 × DW), and DW and AIS increased with time for most cultivars. Cultivars with high DW and AIS can be selected early during storage root development.