M. Tech. (Biotechnology, Department of Biotechnology, Faculty of applied and computer sciences) Vaal University of Technolog / Sweetpotato (Ipomoea batatas) is an important food crop that is grown in many countries. A number of viral and fungal sweetpotato diseases have been reported worldwide. One of the major and most economic diseases of the sweetpotato is Alternaria blight which is caused by the fungal pathogen Alternaria bataticola. This disease can be managed in a short term using fungicides and cultural practices. However, a long term and inexpensive approach is through the development of resistant cultivars. A prerequisite to this approach is the knowledge of the genetic diversity of this fungal pathogen. This study assessed the genetic diversity of 25 South African isolates of A. bataticola from naturally infected leaves and stems collected from different sweetpotato growing regions in South Africa by (i) characterising the isolates based on their morphology (ii) pathogenicity tests (iii) random amplified polymorphic DNA (RAPD) (iv) variation of the ITS2 sequences and (v) prediction of the ITS2 secondary structures. The isolates revealed some variation in colony colour pigments after culturing but Koch’s postulates were confirmed by their pathogenicity tests. The analysis of RAPD and variation of the ITS2 sequences showed high levels of variation (100%) among the isolates. Dendrograms generated from these analyses had many subclusters and did not cluster the isolates according to their geographic origins. The ITS2 secondary structures were predicted and can be used to identify and distinguish the isolates. This information in addition to the genetic diversity of the A. bataticola isolates will aid plant breeders in the development of resistant sweetpotato cultivars and early management of blight disease in South Africa.

Three pages of addenda pasted inside back cover. Bibliography: leaves 166-189. Rhizoctonia solani is a complex species comprising morphologically basidiomycetous imperfect fungi. This study aimed to determine genetic diversity within R. solani AG-3 causing rhizoctonia disease of potato in South Australia. For this purpose, pectic zymogram, PCR, DNA fingerprinting and RFLP techniques were used in conjunction with traditional plant pathology procedures.

<p>Uppsatsen handlar om hur de som intervjuats ser på mat och ätande. Viktiga avsnitt är, vad som är mat och inte mat. Här tar jag bland annat upp vad som är mat enligt informanterna men också vad som inte är mat. Jag skriver om måltider och deras betydelse. Tid och tidsaspekter som rör mat avhandlas också. Kött och potatis och hur husmanskosten är normerande bearbetas i uppsatsen. Andra ämnen jag tar upp är god mat och mat som ogillas. Till sist beskriver jag det sociala runt mat och idealbilder av mat.</p> / <p>This paper is about five Swedish informants and their views on food. Important parts are what food is and what is not. The meaning of meals and their importance. Time and aspects of time surrounding food is also studied. I write about meat and potatoes and the normative values of the Swedish “husmanskost”. Other subjects are good food, disliked food, social aspects of food and ideal images of food.</p>

Population size of Clavibacter michiganensis subsp. sepedonicus in potato cv Russet Burbank and plant response as affected by drought were assessed in a greenhouse experiment. Water deficit stress and no stress treatments, and inoculum densities of 0 or 2 X 10��� cfu C. m. sepedonicus/seed piece were arranged factorially. Stem populations of C. m. sepedonicus were significantly lower in the water deficit stress treatment compared to the non-stressed treatment at every sampling date in both experiments. In seven of the eight harvests the number of C. m. sepedonicus cells/g of stem tissue for the water deficit stress treated, infected plants was a factor of 10 lower than the non-stressed treatment. Foliar symptoms of bacterial ring rot were not observed, but symptoms developed in tubers. Compared to the noninoculated control inoculum reduced aerial biomass from 12 to 21% and tuber yield from 15 to 38% in samples taken four times after the drought was terminated. Reduction of these same variables due to water deficit stress ranged from 17 to 21% and 15 to 41%, respectively, compared to the non-stressed control. Therefore, both water deficit stress and C. m. sepedonicus had similar effects on growth and tuber yield of potato. / Graduation date: 1995

Graduation date: 1994

Uppsatsen handlar om hur de som intervjuats ser på mat och ätande. Viktiga avsnitt är, vad som är mat och inte mat. Här tar jag bland annat upp vad som är mat enligt informanterna men också vad som inte är mat. Jag skriver om måltider och deras betydelse. Tid och tidsaspekter som rör mat avhandlas också. Kött och potatis och hur husmanskosten är normerande bearbetas i uppsatsen. Andra ämnen jag tar upp är god mat och mat som ogillas. Till sist beskriver jag det sociala runt mat och idealbilder av mat. / This paper is about five Swedish informants and their views on food. Important parts are what food is and what is not. The meaning of meals and their importance. Time and aspects of time surrounding food is also studied. I write about meat and potatoes and the normative values of the Swedish “husmanskost”. Other subjects are good food, disliked food, social aspects of food and ideal images of food.

Potato ground cover and spectral data were measured in the Columbia Basin during the 1990 growing season. Three spectral were correlated with ground cover; normalized difference, near infrared-red ratio, and the first derivative of the spectral curve at 750 nm. All models were statistically significant at the 99% level. Normalized was most correlated followed by the near infrared-red ratio, and the first derivative of the spectral curve at 750 nm. / Graduation date: 1992

published_or_final_version / Biological Sciences / Master / Master of Philosophy

Seed tubers conditioned to 0, 200 or 400 day-degrees above 4t were grown in land infested with Q. pallida. Plants from 400 day-degree seed emerged earlier, had larger canopies and greater dry weights early in the growing season than plants from 0 day-degree seed. However, physiological ageing reduced peak percentage ground cover and advanced crop senescence so that similar quantities of solar radiation were intercepted over the whole growth period. Overall, total and ware yields were not affected much by seed tuber physiological age. The partially resistant cultivars tested were more tolerant than the non resistant cultivars but tolerance was not usually affected by physiological age of seed tubers. The effects of nematicide treatment, initial Q. pallida population density, cultivar maturity class, cultivar resistance status and planting date on nematode multiplication, plant growth and tolerance of attack by Q. pallida are discussed. Using data from a variable temperature water bath experiment, probability and regression analysis estimated mean basal temperatures for the development of Q. pallida and Q. rostochiensis at 2.5 and S.rCi least variance analysis estimates were 3.5 and 4.rC respectively. Approximately 200 day-degrees above 3.5 and 4.rC were required from the inoculation of JJ2 of Q. pallida and G. rostochiensis to the peak numbers of JJ5 found in potato roots. From a range of chemicals tested for their ability to release antigen from Q. pallida cysts, sodium hypochlorite was found to be the most effective. Released antigen was detected using polyclonal antisera and monoclonal antibodies in an ELISA test. The potential for the development of an ELISA based diagnosis test for PCN using species-specific antibodies is discussed.

Darbo objektas – bulvės, užaugintos chemizuotame ir ekologiniame fonuose Marijampolės apskrityje, Vilkaviškio rajone, Bambinių kaime. Darbo tikslas - Palyginti bulvių veisles, išaugintas chemizuotame(tręštame mineralinėmis trašomis) ir ekologiniame (tręštame organinėmis trąšomis) fonuose derliaus dydį ir juslines savybes. Darbo metodas. Tyrimai buvo atlikti 2006 m. balandžio - rugsėjo mėnesiais. Sėkla buvo apie 20 d. padaiginta šviesioje bei šiltoje patalpoje. Fonas paruoštas lauko bandymams. Įdirbtus laukus pavasarį ekologiniame fone tręšta tik mėšlu, o chemizuotame fone patręšta specialomis subalansuotomis bulvėms skirtomis trąšomis. Stebėtas bulvių vystymasis ir augimas visą vegetaciją. Tyrimai buvo vykdomi lauko bandymų metodu..Baigus vegetacijai, bulvės buvo kasamos ir sveriamos. Nustatyta 1 bulvių kero masė g, bei suskaičiuotas gumbų skaičius vnt. Iškasta kiekvienos veislės po 10 bulvių kerų. Gumbų masė nustatyta svėrimo metodu. 2007m. vasario mėn. visoms bulvių veislėms buvo atlikta juslinė analizė. Ekologiškai ir chemizuotai augintų bulvių gumbai virti vienodomis sąlygomis: kiekviena bulvių veislė atskiruose puoduose, su lupyna, be druskos. Virimo trukmė apie 30 min. Degustacijos metodas aprobuotas ir taikomas LŽI selekcininkų, išvedant veisles. Tyrimo rezultatai parodė, kad tręšiant mineralinėmis trąšomis bulves, derlingiausia buvo ‘Vinetos‘ veislė, o tręšiant tik mėšlu bulves, derlingiausia buvo ‘Vitaros‘, Quartos‘ veislės. Geriausiu skoniu pasižymėjo... [toliau žr. visą tekstą] / The object of labour- the potatoes which has been raise up in chemistry and ecology setting in Marijampole District of Vilkaviskis in Bambinys village. The objective of labour- to compare the harvest size and quality of taste of the potatoes breeds which has been raised up in intense and chemistry setting. Method of work-the Research has been done in April-September of 2007. The seed. was germinate about 20 days at light and worm premises. The set was prepared for field experiment. In a spring the cultivate fields has been fertiled ecology set just by dung and in chemistry set just by special fertile which was balanced to potatoes. Has been observe the potatoes evolution and vegetation. The research has been done by the outdoor experiment. At the end of vegetation the potatoes been mined and weight. Was maked the weigth of one potatoes scrub (g) and counted unite of scrubs. From every breed was mined 10 unit of scrubs. The tubers weight determined by the weight method. In February of 2007 to every potatoes strains has been done savour. The tubers which has been raised up in ecology and intense setting been boiled on the same conditions: the each potatoes breed had boiled in separate pots with skin and without salt. The boil duration was about half an hour. The method of savour been created and apllyed by the LZI Selectors to do selections of breeds. The results of experiment showed that when potatoes been raised up intense the mostly harvest been ‘Vinetos’ Strain... [to full text]