Sweetpotato is propagated vegetatively via traditional vine cutting or tissue culture using node or meristematic tissues, yet phenotypic variations among the plants are observed irrespective of the propagation method due to environmental interactions leading to mutations and/or epigenetic modifications. Methylation-mediated epigenetic modification refers to the addition of methyl groups to DNA, primarily at cytosine bases, which regulates gene expression without altering the DNA sequence. The present study focused on understanding how various propagation methods and environmental stressors (drought) affect DNA methylation patterns and epigenetic stability in commercial varieties and half-sib progenies using bisulfite sequencing. This study revealed genotype-specific DNA methylation responses to tissue culture and drought stress in sweetpotato, reflecting genotype-dependent epigenetic plasticity. Statistical analyses revealed that methylation patterns remained largely stable during tissue culture, with only minor, genotype-specific fluctuations across Meristem initiated and conventional nodal cultures. In contrast, drought stress induced unpredictable, variety-dependent methylation remodeling, reflecting active epigenetic reprogramming. Prolonged tissue culture resulted in DNA methylation enhancement, most likely due to cumulative in vitro stress; varieties maintained as greenhouse mother plants, displayed pronounced drought-induced methylation shifts. The consistent stability observed in clonal in vitro subculture supports the feasibility of long-term in vitro propagation for maintaining epigenetic stability.

Root-knot nematodes, genus Meloidogyne, are the most damaging nematodes of sweet potato, causing yield reduction and aesthetic damage of the marketable product. Several sweet potato cultivars currently grown in the Unites States have intermediate-to-high resistance to Meloidogyne incognita; however, many of these cultivars are susceptible to M. enterolobii. Therefore, the response of 69 sweet potato genotypes to M. enterolobii and M. incognita was evaluated under greenhouse conditions to identify potential sources of resistance. The cultivars 'Beauregard' and 'Jewel' were used as controls. Results showed that sweet potato genotypes were either highly resistant or highly susceptible to M. enterolobii, whereas they showed a wide-spectrum response to M. incognita, ranging from highly susceptible to highly resistant. Twenty-six genotypes were resistant to M. enterolobii and 11 genotypes were resistant to M. incognita. Combined resistance to M. enterolobii and M. incognita was observed in three sweet potato genotypes. Selected genotypes from this study will be used to incorporate the observed resistance into a commercially viable sweet potato cultivar.

Avoyelles' sweetpotato [Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide an orange-flesh, light-rose-to copper-skin cultivar with superior root shape, disease resistance to southern root-knot nematode, good storage qualities, and early harvest date.'Avoyelles' is average in production beds with proper presprouting.'Avoyelles' can be harvested 93 to 98 d after planting (DAP), which is 10 to 20 d earlier than 'Orleans' (LaBonte et al. 2012(LaBonte et al. , 2013a) ) or 'Beauregard' (Rolston et al. 1987), and has a superior US #1 grade yield (diameter, 5.1-8.9cm; length, 7.6-22.9cm).The US #1 grade yield is comparable to 'Orleans' and 'Beauregard' when harvested after 100 DAP; however, total marketable yield (US #1 grade; canner diameter, 2.5-5.1 cm; canner length, 5.1-17.8cm; jumbo is larger than US #1 in diameter or length or both, and without objectionable defects) exceeds 'Orleans' and 'Beauregard', as oversize jumbos increase in weight and number.The skin of 'Avoyelles' is mostly

Two hundred and six sweet potato genotypes descended from Fusarium wilt resistant Beauregard variety as one of the parents and those without Beauregard as a parent were inoculated with the Fusarium wilt pathogen, Fusarium oxysporum f.sp. batatas. The objectives of this study were to: (i) compare the efficiencies of different models in describing time to symptom expression and time to death among infected sweet potato genotypes and, (ii) develop predictive models. The Kaplan-Meier survival function and actuarial life tables were used for nonparametric modelling while probability plots using the Generalized gamma, Exponential, Weibull, Lognormal and Log-logistic models were used for parametric modelling. The three-parameter generalized gamma model was also used to determine the performance of the simpler nested two-parameter models. The effect of parental resistance level was significant (P = 0.05) for time to death. Genotypes with Beauregard as a parent took longer to die or show symptoms. From the nonparametric analysis, genotypes descended from Beauregard as a parent took on average 43.14 days to die compared to non-Beauregard genotypes that took 33.31 days. Mean time to symptom expression for all models ranged from 11.67 to 12.28 days. In conclusion, it is possible to model survival time using either the parametric Generalized gamma, Lognormal and Weibull models or the nonparametric model.

Sweetpotatoes are a major crop in California, ranking sixth in value among organic commodities in the state. In recent years, there has been growing consumer interest in diverse specialty varieties, particularly purple types and those associated with Asian American and Pacific Islander (AAPI) communities, some of which are currently imported into the state. In this study, we screened 45 diverse sweetpotato varieties and breeding lines under California organic conditions in a preliminary characterization of their agronomic performance. We then conducted culinary evaluations with a tasting panel of students primarily identifying as Asian/Asian American to determine the preference for each type in terms of flavor and culinary appeal. Our results indicated that major tradeoffs exist among existing germplasm, with no variety or line excelling across all agronomic and culinary traits. These results suggest that sweetpotato breeding could be an effective mechanism to combine superior agronomic traits of major commercial classes with the high culinary quality of diverse materials that are not adapted to California organic production. These results provide a strong justification for the value of sweetpotato breeding to ultimately promote a more profitable, sustainable, and just food system in the region.

‘Vermillion’ sweetpotato [Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide an orange-flesh, deep-red–purple-skin cultivar with superior storage root shape, skin smoothness, disease resistance to Fusarium wilt, and excellent storage qualities. ‘Vermillion’ is average in production beds with proper presprouting. It can be harvested up to 10 d earlier than ‘Covington’ (Yencho et al., 2008) and is similar to ‘Diane’ (Stoddard et al., 2013) in the California production region. ‘Vermillion’ and ‘Orleans’ (LaBonte et al., 2012) are similar in harvest days in the Gulf South

The response and adaption to salt remains poorly understood for beach morning glory [Ipomoea imperati (Vahl) Griseb], one of a few relatives of sweetpotato, known to thrive under salty and extreme drought conditions. In order to understand the genetic mechanisms underlying salt tolerance of a Convolvulaceae member, a genome-wide transcriptome study was carried out in beach morning glory by 454 pyrosequencing. A total of 286,584 filtered reads from both salt stressed and unstressed (control) root and shoot tissues were assembled into 95,790 unigenes with an average length of 667 base pairs (bp) and N50 of 706 bp. Putative differentially expressed genes (DEGs) were identified as transcripts overrepresented under salt stressed tissues compared to the control, and were placed into metabolic pathways. Most of these DEGs were involved in stress response, membrane transport, signal transduction, transcription activity and other cellular and molecular processes. We further analyzed the gene expression of 14 candidate genes of interest for salt tolerance through quantitative reverse transcription PCR (qRT-PCR) and confirmed their differential expression under salt stress in both beach morning glory and sweetpotato. The results comparing transcripts of I. imperati against the transcriptome of other Ipomoea species, including sweetpotato are also presented in this study. In addition, 6,233 SSR markers were identified, and an in silico analysis predicted that 434 primer pairs out of 4,897 target an identifiable homologous sequence in other Ipomoea transcriptomes, including sweetpotato. The data generated in this study will help in understanding the basics of salt tolerance of beach morning glory and the SSR resources generated will be useful for comparative genomics studies and further enhance the path to the marker-assisted breeding of sweetpotato for salt tolerance.

disease resistance, cultivar 'Bellevue' sweetpotato [Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide an orange-fleshed, copper-skinned cultivar with superior storage root shape, skin smoothness, disease resistance, and southern root-knot nematode resistance.'Bellevue' is weak in production beds, although adequate plant numbers can be achieved with proper presprouting.'Bellevue' can be harvested up to 10 days earlier than the 'Covington' (Yencho et al., 2008) in the California production region.'Bellevue' and 'Beauregard' (Rolston et al., 1987) are similar in harvest days in the Gulf South production region.The roots are elliptical and consistent in shape in varied soil types.It has a superior shape without lobing, and yields are equal and superior to 'Beauregard' for the U.S. no. 1 grade (5.1-8.9 cm diameter, 7.6-22.9cm long) in California and in the Gulf South production region.The skin of 'Bellevue' is very smooth and remarkably free of lenticels, eyes, or fine root hairs.'Bellevue' is highly resistant to southern root-knot nematode and well suited to sandy soils typical for the production area in California.Initially identified and evaluated as 'LA06-52', the cultivar is named for a thoroughfare in Atwater, CA.

cultivar, disease resistance, vegetable breeding 'Burgundy' sweetpotato [Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide an orange fleshed, red-skinned cultivar with superior storage root shape, high sucrose content, disease resistance, and southern root knot nematode resistance.'Burgundy' produces excellent numbers of uniform plants in the plant production beds.'Burgundy' can be harvested up to 10 d earlier than the Beauregard cultivar (Rolston et al., 1987) in the California production region.The two cultivars are similar in harvest days in the Gulf South production region.The roots are elliptical and consistent in shape in varied soil types.It has a superior shape and yields are similar to the red-skinned Diane cultivar for the U.S. #1 grade (5.1 to 8.9 cm diameter, 7.6 to 22.9 cm long) in California.'Diane' is the current dominant red-skinned cultivar in California, and it has a propensity to produce longer roots in the sandy soils typical for the production area; 'Burgundy' does not.Initially identified and evaluated as 'LA04-175', the cultivar is named after the deep burgundy-maroon color of its skin.

Skinning injury in sweetpotatoes ( Ipomoea batatas ) is responsible for significant postharvest loss resulting from storage diseases and weight loss. Unfortunately, there is no report on the genes involved in wound healing of sweetpotato and a better understanding will facilitate improved breeding strategies. An annealing control primer (ACP) system was used to identify genes expressed after skinning injury of sweetpotato cultivar LA 07-146 storage roots. Using 20 ACPs, 63 differentially expressed genes (DEGs) were identified. Functional annotation of the DEGs revealed that genes previously shown to respond to dehydration, those involved in wounding response, and the lignin and suberin biosynthesis pathways were induced in response to skinning. Expression analysis of 18 DEGs through quantitative reverse transcription–polymerase chain reaction (PCR) showed that DEGs involved in lignin and suberin pathways were up-regulated after 8 and 12 hours of skinning. Other genes showed up- or down-regulation in their transcript abundance depending on the time the storage root was sampled after intentional skinning. The genes up-regulated in response to skinning may be useful to identify expression markers for screening sweetpotato lines tolerant to skinning injury in breeding programs.

Bonita' sweetpotato [Ipomoea batatas (L.) Lam.] was developed by the Louisiana Agricultural Experiment Station to provide a specialty-type white-fleshed, tan-skinned cultivar similar to 'O'Henry' but with southern root-knot nematode and soil rot resistance, superior storage root shape, and a higher dry matter content.'Bonita' produces excellent numbers of uniform plants (sprouts) early in the production season.Days to harvest for 'Bonita', 'Beauregard' (Rolston et al., 1987), and 'O'Henry' are similar in the Gulf South production region; 'Bonita' in North Carolina is later by 7 days.The roots are elliptical and consistent in shape in varied soil types.Yields are equal to and mostly superior to 'O'Henry' for the U.S. #1 grade (5.1 to 8.9 cm diameter, 7.6 to 22.9 cm long) in Louisiana and other Gulf southern states.'O'Henry' is a whitefleshed, tan-skinned mutation of 'Beauregard' that was found and became commercially grown in the late 1990s.Initially identified and evaluated as L05-29, the cultivar is named after the town of Bonita, LA, located in a major sweetpotato production region.The name is also a reflection of its consistent and attractive root shape.

Adventitious roots of 'Beauregard' and 'Georgia Jet' sweetpotato were observed and anatomically characterized over a period of 60 days of storage root development. The majority of 'Beauregard' and 'Georgia Jet' adventitious roots sampled at 5 to 7 days after transplanting (DAT) possessed anatomical features (five or more protoxylem elements) associated with storage root development. The majority of 'Beauregard' (86%) and 'Georgia Jet' (89%) storage roots sampled at 60 to 65 DAT were traced directly to adventitious roots extant at 5 to 7 DAT. The two varieties, however, differed in the timing in which regular and anomalous cambia were formed. Regular vascular cambium development, i.e., initiation and completion, was observed in both varieties at 19 to 21 DAT. Formation of complete regular vascular cambium was negligible for 'Beauregard' (4%) in comparison with 'Georgia Jet' (32%) at 26 to 28 DAT. However, anomalous cambia development adjacent to xylem elements was greater in 'Beauregard' (30%) in comparison with 'Georgia Jet' (13%). Nearly 40% to 50% of samples in both varieties showed extensive lignification in the stele region. At 32 to 35 DAT, 62% to 70% of the adventitious roots for both varieties had either been initiated (developed anomalous cambium) or were lignified. The remaining adventitious roots showed intermediate stages of vascular cambium development. The adventitious root count increased up to 19 to 21 DAT and then remained constant up to 32 to 35 DAT. These accumulated results suggest that the initial stages of adventitious root development are critical in determining storage root set in sweetpotato.

Sweet potato virus disease (SPVD) is caused by dual infection of plants with Sweet Potato Feathery Mottle Virus (SPFMV) and Sweet Potato Chlorotic Stunt Virus (SPCSV). Because SPFMV and SPCSV are transmitted by aphids and whiteflies, respectively, infection in nature occurs independently rather than simultaneously. To investigate the effect of consecutive infection on symptom development and individual virus titres, plants infected with a single virus were later inoculated with the second virus. Symptoms were significantly more severe in plants infected with SPCSV followed by SPFMV compared to plants infected with SPFMV followed by SPCSV. Virus titres were not significantly different for SPCSV, but SPFMV titres, in plants infected with SPCSV followed by SPFMV, were significantly higher than all other treatments. The results indicate that the sequence of infection of sweetpotato plants with the causal agents of SPVD influence the severity of symptoms and SPFMV titres in SPVD affected plants.