Since the first report of Verticillium wilt of potato in 1950, the disease has been considered to be of minor importance in South Africa. Between 1995 and 2000, however, Verticillium spp. were isolated from 146 samples of symptomatic potato plant material received from 13 of the 14 potato production areas in the country. Of 93 Verticillium isolates that were obtained, 60% were identified as V. dahliae and 8 % V. nigrescens. V. dahliae was present in nine of the regions and V. nigrescens in seven. Unidentified Verticillium species were isolated from six of the regions. Both V. dahliae and V. nigrescens were pathogenic to potato in vivo, with V. dahliae the more virulent of the two species. Ten South African potato cultivars, eight of which have recently been released, were evaluated over two seasons in a greenhouse for resistance to V. dahliae. The cultivars Aviva, BP1, Bravo, Buffelspoort, Caren, Hoevelder and Ropedi were classified as susceptible to Verticillium wilt, whereas Calibra, Dawn and Devlin were rated as very susceptible. No resistance or tolerance was evident. The efficacy of broccoli volatiles on in vitro mycelial growth of Verticillium dahliae, and the effect of incorporation of fresh and dry broccoli residues on the survival of microsclerotia of V. dahliae and infection of potato, were determined in the laboratory and greenhouse. Volatiles emanating from freshly harvested macerated broccoli leaves were inhibitory to mycelial growth of V. dahliae on medium. Fresh and dry residues incorporated into soil artificially infested with V. dahliae, significantly reduced the viability of microsclerotia of the pathogen and the rate of infection of potato plants. Dry residues were more effective than fresh residues in reducing the viability of sclerotia, but suppression of infection was independent of the state of the residues. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2005. / Microbiology and Plant Pathology / unrestricted

A linear-log model to predict yield loss due to metribuzin injury was established by Love et. al. in 1993. Two experiments were conducted in 2016 and 2017 to evaluate and improve this model for application in North Dakota (ND). Metribuzin was applied (1.12 a.i./ha) when potato plants were 20-30 cm tall at Inkster, ND. The model did not accurately predict yield loss in 2016 but performed better in 2017. Foliar injury was more correlated with yield reduction than relative plant height. Results also indicated that new models that used foliar injury at 21 days after treatment (DAT) data and at 7 DAT data, most accurately predicted total yield loss and marketable yield loss, respectively. The new model performed similar to the previous model, but unlike previous model it can predict yield loss very early in growing season (21 DAT). / USDA Specialty Block Grant Program

Potato (Solanum tuberosum L.) is the world's fourth largest food crop and large financial losses are incurred each year from wound and bruise related injuries. However, little is known about the coordinate induction of genes that may be associated with, or mark major wound-healing and periderm maturation events. Also, one of the key defense mechanisms for potato tubers is the robust barrier provided by the phellem (skin) of the native periderm. Many biological processes are involved in the formation of this stout tissue. However, little is known about induction of genes that may be associated with this process. The objectives of this research were to molecularly assess the processes of wound periderm development and maturation, and native periderm maturation in potato tubers. In this study, these processes were determined in coordination with expression profiles of selected genes. The cell cycle, cell wall protein, and pectin methyl esterase genes were determined from two diverse potato genotypes and two harvests NDTX4271-5R (ND) and Russet Burbank (RB) tubers; 2008 and 2009 harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB), and cyclin-dependent kinase regulatory subunit (StCKS1At) expression profiles were coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) expression profiles suggested involvement with closing layer formation and subsequent phellem cell layer formations. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine- and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and lastly cell wall thickening in nonmeristematic phellogen cells. StPME and StPrePME expression increased during periderm development, implicating involvement in modifications for closing layer and phellem cell formation. Collectively, these results indicate that the genes monitored were involved in and their expression profiles markedly coordinated with periderm formation and the on-set of periderm maturation; results were more influenced by harvest than genotype. Importantly, StTLRP was the only gene examined that may be involved in phellogen cell wall strengthening or thickening after cessation of cell division.

Call number: LD2668 .T4 1948 K7 / Master of Science

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Presently, the observed variation in symptoms of Potato leafroll virus (PLRV) infection in potato cultivars in South Africa cannot be reconciled with PLRV symptoms obtained 10-15 years ago, even if the different interactions between the pathogen and the cultivar are taken into account. In an effort to analyze this variation, mutations in the coat protein (CP) gene of South African isolates of PLRV were assessed. The CP gene of PLRV isolates from different areas within South Africa was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned and sequenced. Significant sequence variation in the CP gene was found within the analyzed South African isolates of PLRV. Phylogenetic analysis revealed two major clades with most South African isolates and an Australian and North American isolate grouped together and the remainder grouped with isolates from diverse countries worldwide. The deduced amino acid sequences from representatives of these two clades indicated differences in CP threedimensional structure. In an effort to produce recombinant PLRV CP for the production of antibodies specific for South African isolates of PLRV for use in enzyme-linked immunosorbent assay (ELISA), the CP gene of a South African isolate of PLRV was subcloned into a bacterial expression vector (pET14-b). Expression of full length recombinant PLRV CP was attempted in Escherichia coli strains BL21(DE3)pLysS, Rosetta-gami B(DE3)pLysS and Rosetta-2(DE3)pLysS. As this was not successful, the PLRV CP gene was subcloned in another expression vector (pGEX) for expression as an N-terminal fusion protein with glutathione-S-transferase (GST) in E. coli strains BL21(DE3)pLysS and Rosetta-2(DE3)pLysS. The recombinant GST-PLRV CP fusion protein was purified and used for antibody production in rabbits. Using western blots, the effectiveness of antibodies produced to recombinant GST-PLRV CP fusion protein was assessed for PLRV recognition. It was found that antibodies to the recombinant GST-PLRV CP fusion protein were more effective for the detection of GST than PLRV CP and that production of antibodies to the cleaved PLRV CP product would be necessary if antibodies are required for ELISA applications. / AFRIKAANSE OPSOMMING: Huidiglik kan die waargeneemde simptome van infeksie met aartappelrolbladvirus (Potato leafroll virus, PLRV) in aartappelkultivars in Suid-Afrika nie vereenselwig word met PLRV simptome wat 10-15 jaar gelede verkry was nie, selfs al word die verskillende interaksies tussen die patogeen en kultivar in ag geneem. In ‘n poging om hierdie variasie te analiseer, was mutasies in die mantelproteïen (CP) geen van Suid-Afrikaanse isolate van PLRV bepaal. Die CP geen van PLRV isolate van verskillende areas in Suid-Afrika was ge-amplifiseer met behulp van die tru transkripsie-polimerase ketting reaksie (RT-PCR), gekloneer en die nukleotiedvolgorde bepaal. Noemenswaardige nukleotied variasie is in die CP gene van die ge-analiseerde Suid-Afrikaanse isolate van PLRV gevind. Filogenetiese analises het gedui op twee hoof klades met die meeste van die Suid-Afrikaanse isolate wat saam met ‘n Australiese en Noord-Amerikaanse isolaat gegroepeer en die res wat met isolate van verskillende lande wêreldwyd gegroepeer. Die afgeleide aminosuurvolgordes van verteenwoordigers van bogenoemde twee klades het gedui op verskille in die CP driedimensionele struktuur. In ‘n poging om rekombinante PLRV CP te produseer vir die produksie van antiliggame spesifiek teen Suid-Afrikaanse isolate van PLRV om in “enzyme-linked immunosorbent assay” (ELISA) te gebruik, was die CP geen van ‘n Suid-Afrikaanse isolaat van PLRV gesubkloneer in ‘n bakteriële ekspressie vektor (pET14-b). Daar was gepoog om vollengte rekombinante PLRV CP in die Escherichia coli rasse BL21(DE3)pLysS, Rosetta-gami B(DE3)pLysS en Rosetta- 2(DE3)pLysS te produseer. Aangesien dit nie suksesvol was nie, was die PLRV CP gesubkloneer in ‘n ander ekspressie vektor (pGEX) sodat die proteïen as ‘n N-terminale fusie proteïen met “glutathione-S-transferase” (GST) in E. coli rasse BL21(DE3)pLysS en Rosetta- 2(DE3)pLysS geproduseer kon word. Die rekombinante GST-PLRV CP fusie proteïen was gesuiwer en gebruik vir antiliggaam produksie in konyne. Die effektiwiteit van die antiliggame wat teen rekombinante GST-PLRV CP fusie proteïen geproduseer was vir PLRV herkenning is deur middel van “western blots” geanaliseer. Dit was gevind dat antiliggame teen die rekombinante GST-PLRV CP fusie proteïen meer effektief was vir die herkenning van GST as PLRV CP. Gevolglik sal dit nodig wees om antiliggame teen die gesnyde PLRV CP produk te maak vir gebruik in ELISA.

Chipping varieties and model systems were used to determine the role of potato constituents on chip color. Composition was evaluated by HPLC and chip color measured using a ColorQuest colorimeter. Reducing sugar (RS) content did not completely explain color quality when present in low concentrations (<60 mg/lOOg). Levels of ascorbic acid, glutamine and a chlorogenic acid isomer, along with RS, showed high correlation with color. Sucrose was a poor estimator of chip color. Model systems used leached potato slices infiltrated with solutions containing sucrose, RS, ascorbic, chlorogenic and amino acids. Linear association of RS with L* and hue angle and quadratic relationship with chroma of chips were found. Ascorbic acid affected chroma and hue at low RS levels while chlorogenic acid was not involved in color development. Red potatoes {Solarium tuberosum and Solarium stenotomum) were evaluated as potential source of natural red colorant. Cultivars (33) were screened for anthocyanin content and qualitative composition. Monomeric anthocyanin content, determined by pH differential, ranged between 4 and 40 mg/lOOg fresh weight (fw) tuber. Varieties 5847-1 and ND04069-4 showed high anthocyanin content (>35 mg/lOOg). Anthocyanin composition was characterized by HPLC, spectral analysis and Mass Spectroscopy (MS). The major anthocyanin was pelargonidin-3-rutinoside-5-glucoside acylated with p-coumaric acid. The presence of glycoalkaloids (α-solanine and α-chaconine) was detected by MS and quantified by HPLC. Varieties NDO4069-4 and 5847-1 showed glycoalkaloid levels of 13 and 7 mg/lOOg fw, respectively. Glycoalkaloids were precipitated from pigment concentrates by alkaline treatment. The best results were obtained at pH 8.0 with 30% monomeric anthocyanin degradation and 90% glycoalkaloid precipitation. The color and pigment stability of chemically related anthocyanin extracts (red-fleshed potatoes and radishes), the effect of pigment purity, and temperature were evaluated in model juices (pH 3.5). Color (CIELch) and anthocyanin degradation was monitored for 65 wks of storage. All model juices showed color similar to FD&C Red # 40. Excellent stability was obtained with all treatments in refrigeration. Anthocyanin structure and extraction method affected pigment stability. At 25°C, higher stability was obtained on juices colored with chemically purified radish anthocyanins (22 wk half-life) and lowest with potato vegetable juice (10 wk half-life). / Graduation date: 1999

The purpose of this thesis was to compare the tensiometer and climatic methods of scheduling irrigation of potatoes under field conditions. Tensiometers were placed in a 160 acre field to maintain the crop within the optimum moisture range and schedule irrigations. An automatic solid set system was used to apply water to the potato crop. Instrumentation was used to determine daily input for the climatological method. Daily evapotranspiration (Et) was computed and Et (tensiometer) was comPared with Et (climatic). The results showed total variation of the climatic method from the tensiometer method of .62 inches or less than 5 per cent. The study indicated that the climatological method would have under irrigated the potato crop by . 62 inches during the 48 day study. Variations are also shown for each irrigation interval. Results indicated that a combination of both methods would allow the most feasible approach to scheduling irrigation of potatoes.

No description available.

This study sought to explore the relationship between spatial scale and canopy chemistry through the use of remotely sensed videography data and total nitrogen content of potato petioles. A range of broad band spectral indices were employed along with standard red and green wavelengths to define an optimum scale or range of scales in which the accuracy of predicting leaf canopy chemistry could be improved. Difficulties inherent within video imagery due to the method in which the National Television System Committee's (NTSC) analog signal is comprised were studied. Spectral quantification of the video signal was not possible within the study, instead attention centered on showing the consistent and well correlated results that could be obtained using such data. Spectroradiometer measurements were also obtained for comparison with video response. Correlation between the two sensors was low, primarily due to the nature of the respective signals. Multispectral imagery was obtained from SPOT for spatial resolution comparison. The light research aircraft employed to collect the aerial video imagery proved to be a versatile and cost effective alternative to traditional remote sensing platforms. The data produced within the study support the project objectives in defining regions of high to low prediction accuracy. A reduction in spatial scale increases the ground area represented by an individual pixel and reduces the quantity and quality of information available to the sensor. The study illustrated a possible spatial resolution breakoff point at which nitrogen content prediction accuracy is greatly diminished. / Graduation date: 1995

Thesis (Ph. D.)--University of Idaho, 2006. / Abstract. "May 2006." Includes bibliographical references (leaves 107-127). Also available online in PDF format.