Vegetable Crops Research Unit

Madison, WI, United States

Vegetable Crops Research Unit

Madison, WI, United States
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Halterman D.A.,University of Wisconsin - Madison | Halterman D.A.,Vegetable Crops Research Unit | Chen Y.,University of Wisconsin - Madison | Sopee J.,Kasetsart University | And 2 more authors.
PLoS ONE | Year: 2010

Background: The destructive plant disease potato late blight is caused by the oomycete pathogen Phytophthora infestans (Mont.) de Bary. This disease has remained particularly problematic despite intensive breeding efforts to integrate resistance into cultivated potato, largely because of the pathogen's ability to quickly evolve to overcome major resistance genes. The RB gene, identified in the wild potato species S. bulbocastanum, encodes a protein that confers broad-spectrum resistance to most P. infestans isolates through its recognition of highly conserved members of the corresponding pathogen effector family IPI-O. IpiO is a multigene family of effectors and while the majority of IPI-O proteins are recognized by RB to elicit host resistance, some variants exist that are able to elude detection (e.g. IPI-O4). Methods and Findings: In the present study, analysis of ipiO variants among 40 different P. infestans isolates collected from Guatemala, Thailand, and the United States revealed a high degree of complexity within this gene family. Isolate aggressiveness was correlated with increased ipiO diversity and especially the presence of the ipiO4 variant. Furthermore, isolates expressing IPI-O4 overcame RB-mediated resistance in transgenic potato plants even when the resistance-eliciting IPI-O1 variant was present. In support of this finding, we observed that expression of IPI-O4 via Agrobacterium blocked recognition of IPI-O1, leading to inactivation of RB-mediated programmed cell death in Nicotiana benthamiana. Conclusions: In this study we definitively demonstrate and provide the first evidence that P. infestans can defeat an R protein through inhibition of recognition of the corresponding effector protein.

Wiberley-Bradford A.E.,University of Wisconsin - Madison | Bethke P.C.,University of Wisconsin - Madison | Bethke P.C.,Vegetable Crops Research Unit
American Journal of Potato Research | Year: 2017

When stored at temperatures below 10 °C, potatoes accumulate sucrose and the reducing sugars glucose and fructose. This process, cold-induced sweetening, has been studied extensively because potatoes with elevated reducing sugar contents produce undesirable, dark-colored products and acrylamide, a suspected carcinogen, during high-temperature cooking. Potatoes in commercial storages are cooled slowly, but many research studies have used potatoes cooled rapidly. In this study, effects of cooling rate and variety on chip color, sugars, and gene expression were examined. Sucrose and reducing sugar contents were substantially lower in slowly cooled than in rapidly cooled tubers of ‘Snowden’ and “MegaChip’ for the first 11 weeks after cooling to 3 °C began. Differences in gene expression for VInv, β-amylase, SPS, AGPase and GBSS were observed between cooling treatments and varieties. Overall, the data showed that cooling rate, time in storage, and variety influenced multiple aspects of cold-induced sweetening. © 2017 The Potato Association of America

Hao L.-Y.,University of Wisconsin - Madison | Willis D.K.,University of Wisconsin - Madison | Willis D.K.,Vegetable Crops Research Unit | Andrews-Polymenis H.,Texas A&M University | And 3 more authors.
Applied and Environmental Microbiology | Year: 2012

Contaminated fresh produce has become the number one vector of nontyphoidal salmonellosis to humans. However, Salmonella enterica genes essential for the life cycle of the organism outside the mammalian host are for the most part unknown. Screening deletion mutants led to the discovery that an aroA mutant had a significant root colonization defect due to a failure to replicate. AroA is part of the chorismic acid biosynthesis pathway, a central metabolic node involved in aromatic amino acid and siderophore production. Addition of tryptophan or phenylalanine to alfalfa root exudates did not restore aroA mutant replication. However, addition of ferrous sulfate restored replication of the aroA mutant, as well as alfalfa colonization. Tryptophan and phenylalanine auxotrophs had minor plant colonization defects, suggesting that suboptimal concentrations of these amino acids in root exudates were not major limiting factors for Salmonella replication. An entB mutant defective in siderophore biosynthesis had colonization and growth defects similar to those of the aroA mutant, and the defective phenotype was complemented by the addition of ferrous sulfate. Biosynthetic genes of each Salmonella siderophore, enterobactin and salmochelin, were upregulated in alfalfa root exudates, yet only enterobactin was sufficient for plant survival and persistence. Similar results in lettuce leaves indicate that siderophore biosynthesis is a widespread or perhaps universal plant colonization fitness factor for Salmonella, unlike phytobacterial pathogens, such as Pseudomonas and Xanthomonas. © 2012, American Society for Microbiology.

Bhaskar P.B.,University of Wisconsin - Madison | Wu L.,University of Wisconsin - Madison | Wu L.,Inner Mongolia University of Technology | Busse J.S.,Vegetable Crops Research Unit | And 8 more authors.
Plant Physiology | Year: 2010

Potato (Solanum tuberosum) is the third most important food crop in the world. Potato tubers must be stored at cold temperatures to prevent sprouting, minimize disease losses, and supply consumers and the processing industry with highquality tubers throughout the year. Unfortunately, cold storage triggers an accumulation of reducing sugars in tubers. Hightemperature processing of these tubers results in dark-colored, bitter-tasting products. Such products also have elevated amounts of acrylamide, a neurotoxin and potential carcinogen. We demonstrate that silencing the potato vacuolar acid invertase gene VInv prevents reducing sugar accumulation in cold-stored tubers. Potato chips processed from VInv silencing lines showed a 15-fold acrylamide reduction and were light in color even when tubers were stored at 4°C. Comparable, low levels of VInv gene expression were observed in cold-stored tubers from wild potato germplasm stocks that are resistant to cold-induced sweetening. Thus, both processing quality and acrylamide problems in potato can be controlled effectively by suppression of the VInv gene through biotechnology or targeted breeding. © 2010 American Society of Plant Biologists.

Hogan C.S.,University of Wisconsin - Madison | Mole B.M.,University of North Carolina at Chapel Hill | Grant S.R.,University of North Carolina at Chapel Hill | Willis D.K.,University of Wisconsin - Madison | And 2 more authors.
PLoS ONE | Year: 2013

Pectobacterium species are enterobacterial plant-pathogens that cause soft rot disease in diverse plant species. Unlike hemi-biotrophic plant pathogenic bacteria, the type III secretion system (T3SS) of Pectobacterium carotovorum subsp. carotovorum (P. carotovorum) appears to secrete only one effector protein, DspE. Previously, we found that the T3SS regulator HrpL and the effector DspE are required for P. carotovorum pathogenesis on leaves. Here, we identified genes up-regulated by HrpL, visualized expression of dspE in leaves, and established that DspE causes host cell death. DspE required its full length and WxxxE-like motifs, which are characteristic of the AvrE-family effectors, for host cell death. We also examined expression in plant leaves and showed that hrpL is required for the expression of dspE and hrpN, and that the loss of a functional T3SS had unexpected effects on expression of other genes during leaf infection. These data support a model where P. carotovorum uses the T3SS early in leaf infection to initiate pathogenesis through elicitation of DspE-mediated host cell death.

Bethke P.C.,Vegetable Crops Research Unit | Bethke P.C.,University of Wisconsin - Madison | Busse J.S.,Vegetable Crops Research Unit
American Journal of Potato Research | Year: 2010

The quality of potato (Solanum tuberosum) tubers coming out of storage depends on the state of the tubers going into storage. Experiments determined the effects of vine-kill treatment and harvest date on the post-harvest physiology of potato tubers stored for up to 12 weeks. Potato cultivar Russet Burbank grown in central Wisconsin was harvested in late July when tubers were immature, in late August, and in early September after complete natural senescence of vines. Prior to the first two harvests, vines were either desiccated with diquat dibromide or were untreated. Data were collected at harvest and in storage for skin set, tuber respiration rate, and tuber sucrose, glucose, and fructose contents. Skin set at harvest was increased by use of the desiccant at the early harvest date, but not at the middle harvest date. Early harvest without vine kill resulted in elevated tuber bud-end glucose contents in storage. Early harvest with vine kill treatment resulted in increased rates of respiration in storage that persisted through December. Neither tuber sucrose nor glucose content 6 weeks after harvest was a good predictor of tuber glucose content 12 weeks after harvest. These data demonstrate that vine-kill treatment and tuber maturity at harvest have long-term effects on tuber quality. © 2010 Potato Association of America.

Duangpan S.,University of Wisconsin - Madison | Zhang W.,University of Wisconsin - Madison | Wu Y.,University of Wisconsin - Madison | Jansky S.H.,University of Wisconsin - Madison | And 2 more authors.
Plant Physiology | Year: 2013

Insertional mutagenesis using transfer DNA or transposable elements, which is an important tool in functional genomics and is well established in several crops, has not been developed in potato (Solanum tuberosum). Here, we report the application of the tobacco (Nicotiana tabacum) Tnt1 retrotransposon as an insertional mutagen in potato. The Tnt1 retrotransposon was introduced into a highly homozygous and self-compatible clone, 523-3, of the diploid wild potato species Solanum chacoense. Transposition of the Tnt1 elements introduced into 523-3 can be efficiently induced by tissue culture. Tnt1 preferentially inserted into genic regions in the potato genome and the insertions were stable during sexual reproduction, making Tnt1 an ideal mutagen in potato. Several distinct phenotypes associated with plant stature and leaf morphology were discovered in mutation screening from a total of 38 families derived from Tnt1-containing lines. We demonstrate that the insertional mutagenesis system based on Tnt1 and the 523-3 clone can be expanded to the genome-wide level to potentially tag every gene in the potato genome. © 2013 American Society of Plant Biologists. All Rights Reserved.

Vinje M.A.,University of Wisconsin - Madison | Vinje M.A.,Cereal Crops Research Unit | Willis D.K.,University of Wisconsin - Madison | Willis D.K.,Vegetable Crops Research Unit | And 3 more authors.
Planta | Year: 2011

Two barley (Hordeum vulgare L.) β-amylase genes (Bmy1 and Bmy2) were studied during the late maturation phase of grain development in four genotypes. The Bmy1 and Bmy2 DNA and amino acid sequences are extremely similar. The largest sequence differences are in the introns, seventh exon, and 3′ UTR. Accumulation of Bmy2 mRNA was examined in developing grain at 17, 19, and 21 days after anthesis (DAA). One genotype, PI 296897, had significantly higher Bmy2 RNA transcript accumulation than the other three genotypes at all developmental stages. All four genotypes had Bmy2 mRNA levels decrease from 17 to 19 DAA, and remain the same from 19 to 21 DAA. Levels of Bmy1 mRNA were twenty thousand to over one hundred thousand times more than Bmy2 mRNA levels in genotypes Legacy, Harrington, and Ashqelon at all developmental stages and PI 296897 at 19 and 21 DAA. PI 296897 had five thousand times more Bmy1 mRNA than Bmy2 mRNA at 17 DAA. However, Bmy2 protein was not found at 17 DAA in any genotype. The presence of Bmy2 was immunologically detected at 19 DAA and was present in greater amounts at 21 DAA. Also, Bmy2 protein was found to be stored in mature grain and localized in the soluble fraction. However, Bmy1 protein was far more prevalent than Bmy2 at all developmental stages in all genotypes. Thus, the vast majority of β-amylase activity in developing and mature grain can be attributed to endosperm-specific β-amylase. © 2011 Springer-Verlag (outside the USA).

del Pilar Marquez-Villavicencio M.,University of Wisconsin - Madison | Weber B.,University of Wisconsin - Madison | Witherell R.A.,University of Wisconsin - Madison | Willis D.K.,University of Wisconsin - Madison | And 2 more authors.
PLoS ONE | Year: 2011

Pectobacterium species are necrotrophic bacterial pathogens that cause soft rot diseases in potatoes and several other crops worldwide. Gene expression data identified Pectobacterium carotovorum subsp. carotovorum budB, which encodes the α-acetolactate synthase enzyme in the 2,3-butanediol pathway, as more highly expressed in potato tubers than potato stems. This pathway is of interest because volatiles produced by the 2,3-butanediol pathway have been shown to act as plant growth promoting molecules, insect attractants, and, in other bacterial species, affect virulence and fitness. Disruption of the 2,3-butanediol pathway reduced virulence of P. c. subsp. carotovorum WPP14 on potato tubers and impaired alkalinization of growth medium and potato tubers under anaerobic conditions. Alkalinization of the milieu via this pathway may aid in plant cell maceration since Pectobacterium pectate lyases are most active at alkaline pH.

Wiberley-Bradford A.E.,Vegetable Crops Research Unit | Busse J.S.,Vegetable Crops Research Unit | Jiang J.,University of Wisconsin - Madison | Bethke P.C.,University of Wisconsin - Madison
BMC Research Notes | Year: 2014

Background: Storing potato tubers at low temperatures minimizes sprouting and disease but can cause an accumulation of reducing sugars in a process called cold-induced sweetening. Tubers with increased amounts of reducing sugars produce dark-colored, bitter-tasting fried products with elevated amounts of acrylamide, a possible carcinogen. Vacuolar invertase (VInv), which converts sucrose produced by starch breakdown to glucose and fructose, is the key determinant of reducing sugar accumulation during cold-induced sweetening. In this study, wild-type tubers and tubers in which VInv expression was reduced by RNA interference were used to investigate time- and temperature-dependent changes in sugar contents, chip color, and expression of VInv and other genes involved in starch metabolism in tubers during long-term cold storage. Results: VInv activities and tuber reducing sugar contents were much lower, and tuber sucrose contents were much higher, in transgenic than in wild-type tubers stored at 3-9°C for up to eight months. Large differences in VInv mRNA accumulation were not observed at later times in storage, especially at temperatures below 9°C, so differences in invertase activity were likely established early in the storage period and maintained by stability of the invertase protein. Sugar contents, chip color, and expression of several of the studied genes, including AGPase and GBSS, were affected by storage temperature in both wild-type and transgenic tubers. Though transcript accumulation for other sugar-metabolism genes was affected by storage temperature and duration, it was essentially unaffected by invertase silencing and altered sugar contents. Differences in stem- and bud-end sugar contents in wild-type and transgenic tubers suggested different compartmentalization of sucrose at the two ends of stored tubers. Conclusions: VInv silencing significantly reduced cold-induced sweetening in stored potato tubers, likely by means of differential VInv expression early in storage. Transgenic tubers retained sensitivity to storage temperature, and accumulated greater amounts of sucrose, glucose and fructose at 3°C than at 7-9°C. At each storage temperature, suppression of VInv expression and large differences in tuber sugar contents had no effect on expression of AGPase and GBSS, genes involved in starch metabolism, suggesting that transcription of these genes is not regulated by tuber sugar content.

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