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Subject: search.filters.subject.Grapes -- Diseases and pests

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    Glycerol production by four common grape moulds, Aspergillus, Botrytis, Penicillium and Rhizopus : a thesis presented in fulfilment of the requirements for Master of Science in Microbiology at Massey University
    (Massey University, 1989) Ravji, Rajesh Govind
    The production of glycerol by the grape moulds Aspergillus niger, Penicillium italicum, Rhizopus nigricans and Botrytis cinerea growing in juice from Chasselas and Black Hamburg grapes was examined. Juice from both free-run and homogenized whole grapes was filter sterilized and inoculated with single pure cultures of the moulds above. The four juice types were incubated at 25° C for 26 to 29 days. The inoculated juices were incubated in different air relations and during the 26 to 29 day incubation period, samples were taken periodically for the analysis of glycerol, glucose and fructose by HPLC. After 26 to 29 days, the moulds were harvested by filtration so that dry mycelial weights could be obtained. Large differences in glycerol production were noted among the grape moulds. Under similar conditions of cultivation in Chasselas juice, R. nigricans and B. cinerea produced significantly more glycerol than A. niger and P. italicum. The levels of glycerol never exceeded 0.5g/100mL, whereas all cultures of B. nigricans and li. cinerea exceeded this level after 15 to 18 days of incubation. In Black Hamburg juice glycerol was not detected in cultures of A. niger and P. italicum. The levels of glycerol produced by all the four moulds were lower in Black Hamburg than in Chasselas juice. Overall more sugar was utilized in Black Hamburg juice than in Chasselas juice under similar conditions. B. cinerea utilized the most total sugar in Chasselas juice than all the other moulds, while R- nigricans utilized the most total sugar in Black Hamburg juice than all the other moulds. In Chasselas juice B. cinerea and R- nigricans displayed a preference for glucose over fructose, while in Black Hamburg juice no preference was evident. The pattern of sugar utilization over the incubation period between Chasselas and Black Hamburg juice was markedly different. In Chasselas juice under most cultivation conditions the four moulds utilized glucose and fructose throughout the incubation period, while in Black Hamburg juice there was rapid utilization during the first three days followed by a reduced rate of sugar utilization in the latter stages of incubation. The four moulds differed in their production of mycelial dry weight. These differences were most marked in Chasselas juice where ­B. cinerea, depending on air relations, produced five to seven times more mycelial dry weight than R. nigricans and more than twice the mycelial dry weight produced by A. niger and P. italicum. In Black Hamburg juice B. cinerea produced two to three times more mycelial mass than the other three moulds. At present in the Californian wine industry an HPLC method is currently under investigation, where the level of glycerol in the grape juice is used as an indicator of fungal rot of the grapes. This study has demonstrated that certain grape moulds do not produce the same amount of glycerol and that the level of glycerol is not related to the mycelial growth. Thus this investigation has established that glycerol may not be used as a suitable indicator of fungal rot.
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    A taxonomic study of Cercospora vitis (Lév.) Sacc., the causal organism of a leaf spot disease on grapes : a thesis ... for the degree of Masterate of Agricultural Science
    (Massey University, 1970) Harvey, Ian C.
    A leaf spot disease of grapes caused by a dematiaceous fungus is described for the first time in New Zealand. Literature on the taxonomy of the causal organism is reviewed and reveals a pleurality of binomials that have been applied to the fungus. The main features in contention are the correct basionym, symptomatology, conidium shape and degree of conidiophore compactness. These were studied in relation to the taxonomy of the causal organism and from results obtained it was finally placed in the genus Cercospora, where the binomial becomes C. vitis; the legitimate specific epithet for the fungus. Cultural studies of the pathogen provided further supporting evidence for placement in the genus Cercospora. An apparatus for photomicrographically recording conidium ontogeny and spore germination patterns of filimentous fungi is described. Classification schemes of the Fungi Imperfecti are reviewed and all were found to have certain shortcomings with respect to the classification of the causal organism. A proposed alternative scheme is outlined. The disease does not become manifest until late in the growing season and hyphal swellings in the stomata (stomatopodia) are found to constitute the form in which the pathogen persists during a latent infection period. A disease cycle is synthesised from results of glasshouse infection experiments, field observations, and reports from the literature,
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    The development of diagnostic tools for the grapevine pathogen Eutypa lata : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Genetics at Massey University
    (Massey University, 2001) Jones, Paula Elizabeth
    Eutypa lata is the causal agent of Eutypa dieback on grapevines. The fungus invades the vine and grows there unnoticed, possibly for several years, causing discolouration and deformation of the vine shoots and leaves. Most berries fail to establish on these shoots and the fungus eventually kills the vine. The damaging effects of this fungus have had a notable financial impact on the grape and wine industry world wide and E. lata is at present the primary constraint on vineyard longevity in many places including California and Australia. Little is known about the occurrence and distribution of Eutypa dieback within New Zealand. This is due mainly to difficulties associated with identification of the disease in grapevines. To develop a molecular probe for the identification of E. lata from grapevine wood the Polymerase Chain Reaction (PCR) amplified the Internal Transcribed Spacers (ITS1 and ITS2) and the intervening 5.8S gene of ribosomal DNA (rDNA) from representative isolates. The sequences of the E. lata ITS regions were used to design two pairs of primers, each of which was subsequently shown to be specific for the amplification of predicted-size fragments from genomic DNA of E. lata. The primer pairs were further tested using template DNA extracted from healthy grapevines and from other fungi commonly isolated from dieback diseased grapevines but no PCR amplification was observed. Simple DNA extraction protocols, leading to the rapid release of DNA, were tested to enable identification of E. lata from pure culture and grapevine wood; however, a suitable DNA extraction method from these materials was not found. Currently the only known source of inoculum is ascospores, which are released from perithecia during and immediately after rainfall. However, few perithecia have been found in New Zealand vineyards. This has prompted the study of the mating habits of E. lata. As the sexual stage of E. lata cannot be obtained in culture at present, the analysis of its mating system must be performed in natural populations. Molecular characterisation of the mating type at the outset of a mating project allows significant savings in time and effort as it drastically reduces the number of crosses that must be set up. So far, cloning of mating type (MAT) genes from fungi has been hampered by low conservation among them. Most ascomycete fungi have one mating type gene with two alternative forms or idiomorphs (MAT1-1 and MAT1-2). One of the pair of MAT genes. MAT1-2, encodes a protein with a conserved DNA binding motif called the high mobility group (HMG) box. There is sufficient sequence conservation at the borders of the HMG box to allow PCR amplification. New Zealand isolates of E. lata, including sixteen single ascospore isolates from one perithecium, were tested for the presence of a MAT1-2 idiomorph using this PCR based approach. Five different sets of primers were used which were designed to anneal at different target sites with different specificities. PCR products of the expected size were obtained and sequenced, but despite exhaustive attempts to optimise PCR specificity, none of these had convincing homology to fungal mating type genes. Progress on the basic aspects of the genetics of E. lata will continue to be hampered until the organism is induced to complete its life cycle in culture. Molecular studies into the mating type genes which regulate sexual compatibility and sexual reproduction in the fungus should lead to a deeper understanding of the life-cycle of E. lata and the critical influence of sex on population genetics. In addition, it will provide a scientific basis for a management program urgently needed to minimise the impact of this disease.