Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains ix, 80 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 60-69).

Th.--Sci. biol.--Toulouse 3, 1977. N°: 764.

Made available in DSpace on 2014-06-11T19:28:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-06Bitstream added on 2014-06-13T18:58:00Z : No. of bitstreams: 1 sartori_je_me_botfca.pdf: 257358 bytes, checksum: b22cbf58843b34a23ad0f632bb89f4e0 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib. e o agente causal da antracnose do feijoeiro (Phaseolus vulgaris L.), doenca fungica de grande importancia para a cultura, pois pode causar perdas de ate 100% na producao, quando sao utilizadas cultivares suscetiveis e sementes infectadas, sob condicoes ambientais favoraveis ao desenvolvimento de epidemias. O presente trabalho objetivou avaliar a sensibilidade in vitro de 20 isolados de Colletotrichum lindemuthianum, provenientes de diferentes regioes do pais, a cinco fungicidas de diferentes principios ativos e algumas misturas (carbendazin, chlorothalonil, tiofanato metilico, chlorothalonil + tiofanato metilico, trifloxystrobin, propiconazol, trifloxystrobin + propiconazol), em cinco diferentes concentracoes (0, 1, 10, 100 e 1000 -Êg.mL-1) adicionados em meio de cultura batata-dextrose-agar (BDA). Os isolados cresceram por sete dias a 25 -C no meio de cultura BDA e apos esse periodo, discos de 0,5 cm de micelio do fungo, foram transferidos para placas de Petri com o meio BDA contendo as diferentes concentracoes de fungicidas. As placas foram incubadas por sete dias a 25 -C, avaliado o crescimento medio do diametro das colonias (em cm) e calculado os valores de porcentagem de inibicao do crescimento micelial dos isolados em relacao ao tratamento testemunha. Os resultados mostraram que para os fungicidas carbendazin e tiofanato metilico, 11 isolados fungicos foram totalmente ou parcialmente inibidos na concentracao de 1 ou 10 -Êg.mL-1. Chlorothalonil mostrou-se menos eficiente que os demais produtos pelo fato de inibir o crescimento micelial de apenas tres isolados na concentracao de 1000 -Êg.mL-1. A mistura de chlorothalonil e tiofanato metilico mostrou a inibicao total do crescimento micelial de quatro isolados a 1 -Êg.mL-1, e, a 1000 -Êg.mL-1, oito isolados mostraram-se sensiveis a mistura desses produtos... / Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib. is the causal agent of anthracnose in bean (Phaseolus vulgaris L.). This fungal disease has great importance in the crop, since it may cause yield losses of up to 100% when susceptible cultivars and infected seeds are used under environmental conditions that favor the development of epidemics. The aim of this work was to evaluate the in vitro sensitivity of 20 isolates of Colletotrichum lindemuthianum from different regions of the country, to five fungicides with different active principles and some mixtures (carbendazim, chlorothalonil, methyl thyophanate, chlorothalonil + methyl thyophanate, trifloxystrobin, propiconazole, trifloxystrobin + propiconazole), at five different concentrations (0, 1, 10, 100, and 1000 ìg.mL-1), added to potato-dextrose-agar (PDA) culture medium. The isolates were cultured for seven days at 25 °C in PDA medium, after which 0.5 cm disks of fungal mycelium were transferred to Petri dishes containing PDA medium and the various concentrations of fungicides. The Petri dishes were incubated for seven days at 25 °C. We evaluated the mean growth in diameter of the colonies (in cm) and calculated percentage values for mycelial growth inhibition of the isolates in relation to the control treatment. The results showed that 11 fungal isolates were completely or partially inhibited by the fungicides carbendazim and methyl thyophanate at concentrations of 1 or 10 ìg.mL-1. Chlorothalonil proved less effective than the other products, as it inhibited mycelial growth in only three isolates, at the concentration of 1000 ìg.mL-1. The chlorothalonil and methyl thyophanate mixture showed complete mycelial growth inhibition in four isolates at 1 ìg.mL-1, while eight isolates were sensitive to the mixture of these products at 1000 ìg.mL-1. The propiconazole and trifloxystrobin mixture was the most effective and inhibited growth... (Complete abstract click electronic access below)

Endopolygalacturonases (PGs) are the first cell wall degrading enzymes that are produced when pathogenic fungi encounter the host cell wall (Albersheim and Anderson, 1971). The role that these enzymes play in pathogenicity has been investigated for numerous pathogenic fungi. Although the results are not conclusive, there is evidence for some fungi that these enzymes are significant for their pathogenecity. Furthermore, plants contain polygalacturonase inhibiting proteins (PGIPs) in their cell walls, which are able to inhibit PGs (De Lorenzo et al, 2001; 2002). Colletotrichum SHK2148 is a pathogenic fungus causing anthracnose of lupin plants in South Africa. The identity of the fungus has been described as Colletotrichum tortuosum (Koch, 1996). However, this was based on morphological evidence only. Thus, the classification of the South African lupin- associated Colletotrichum isolates was re-assessed by comparing Colletotrichum SHK2148 on a morphological and molecular level to the recently described Colletotrichum lupinispecies (Nirenberg et al, 2002) as well as previously described Colletotrichum acutatum lupin anthracnose isolates (Talhinas et al, 2002). Based on the culture morphology, ITS and <font face=”symbol”>b</font>â-tubulin sequence data, it was concluded that Colletotrichum SHK2148 groups with C. lupini, more specifically, C. lupini var. setosum. The fungus, renamed Colletotrichum lupini SHK2148, was evaluated for its PG activity in pectin media (pH 5) over a 12 day growth period by using an agarose diffusion assay. The specific PG activity reached its highest level after three days, whereafter it decreased. Previous studies performed at the ARC, revealed that the fungus produced PG activity and this crude activity was inhibited by a PGIP produced in apple. A study was launched to isolate and characterise the gene(s) responsible for PG production. PG gene sequences from Colletotrichum gloeosporioides f.sp. malvae and Colletotrichum lindemuthianum were compared and conserved regions were identified from which primers were designed to amplify a fragment of a PG gene from C. lupini SHK2148. Inverse PCR was used to resolve the 5’ and 3’ sequences of the PG gene whereafter a complete copy of the gene was isolated from the genome of the fungus and characterised. The isolated gene was approximately 1Kb, contained a single intron of 59 bp and was very similar to the PG gene from C. gloeosporioides f.sp. malvae (cmpgII) as well as one of the PG genes (clpg2) from C. lindemuthianum. Southern blot analyses revealed that the gene was present as a single copy in the genome of the fungus. The in vitro expression of the PG gene from C. lupini SHK2148, grown in pectin media (pH 5), was investigated via northern blot analyses as well as RT-PCR, which revealed that the gene was expressed in the same time period that the highest PG activity was observed. A full cDNA copy of the PG gene was isolated using mRNA harvested from mycelia that was grown for 4 days on pectin. The cDNA copy confirmed the predicted intron position of the previously isolated genomic PG gene. Due to the unavailability of a full cDNA copy of the C. lupini SHK2148 PG gene at the time when expression studies were initiated, a complete cDNA copy was constructed by swapping an internal cDNA PG fragment with its counterpart in the complete genomic PG gene copy. The resulting cDNA PG copy was used as a template from which PG constructs were prepared for expression in Pichia pastoris. Constructs containing the PG gene with its native signal peptide, the PG gene with the β-MF signal peptide factor as well as hybrid constructs where the N terminal part of the mature PG proteins of Fusarium moniliforme and C. lupini SHK 2148 were exchanged, were transformed into P. pastoris . No PG activity was observed with an agarose diffusion assay for any of the Pichia clones. SDS-PAGE analyses were used to evaluate total protein isolations from the P. pastoris clones. The supernatant and cells of the clones were subjected to western blot analyses using antibodies directed againstAspergillus niger PG as well as F. moniliforme PG. The only positive hybridisation signal was observed between the A. niger antibody and a protein in supernatant extracts of the P. pastoris clones. However, the size of the hybridising band was very large. This could be due to glycosylation of the C. lupini SHK 2148 PG in P. pastoris, although the size increase is unusually large. The results indicated that it is unlikely that the C. lupini SHK 2148 PG was expressed in P. pastoris transformed with any of these constructs. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Plant Science / unrestricted

Anthracnose is one of the serious diseases of cowpea (Vigna unguiculata L. Walp) and common bean (Phaseolus vulgaris L.) caused by the Colletotrichum fungi. The disease is prevalent is small holder farmers’ fields due to the scarcity and high cost of the synthetic fungicides. This study was conducted with the main aim of improving food security and income of the smallholder farmers by increasing legumes, P. vulgaris and V. unguiculata thereby increasing production and improve food security and income of smallholder farmers. Investigations involved in vitro bioassaying for antifungal activities of the crude extracts on Colletotrichum lindemuthianum (Sacc. and Magn.) Bri. and Cav. and Colletotrichum dematium (Fr.) Grove var. truncata field isolates and evaluating the effect of crude plant extracts seed treatments on seed germination, emergence and control of anthracnose disease of common bean and cowpea. Furthermore, ultra-structural changes of plant extracts treated and efficacy of foliar application of extracts. The in vitro study showed that Allium sativum L., Agapanthus caulescens Spreng., Carica papaya L. and Syzygium cordatum Hochst.ex Krauss extracts have good antifungal activities against both C. lindemuthianum and C. dematium. The low concentrations (5 mg.ml-1) of Syzygium and Agapanthus water extracts and acetone extracts of Agapanthus and Carica gave a high percentage of bean seed germination, emergence, short mean emergence time (MET) and were effective in controlling the anthracnose disease. The treatment of Agapanthus (both water and acetone) extracts also increased the shoot length and dry weight of the seedlings. The Allium acetone extracts (5 mg.ml-1) was the only treatment that gave good results with respect to germination percentages, MET, shoot length, leaf area and dry mass of cowpea. Five mg.ml-1 concentrations of Syzygium and Agapanthus water extracts and acetone extracts of Agapanthus and Carica have potential as seed treatments on bean. Allium acetone extract (5 mg.ml-1) was the only potential cowpea seed treatment that could be recommended to farmers as an alternative to the synthetic fungicide. Electron microscopy revealed that principle differences were observed in the cotyledon-embryo connecting tissues of seeds treated with Agapanthus, which had few cristae in their mitochondria than the cells from other treatments. The embryonic root cells of bean seeds treated with Agapanthus had coalescing protein bodies. The embryonic root cells of cowpea and bean treated with Syzygium had fewer lipid bodies as compared to the control and the Agapanthus treated seeds. Bean plants that were foliar treated with the 15 mg.ml-1 concentrations of Allium water, Agapanthus water, Carica water, Agapanthus acetone, Carica 5 and 15 mg.ml-1 acetone, Syzygium 5 mg.ml-1 acetone extracts and the combinations (2.5 mg.ml-1 + 2.5 mg.ml-1) of Allium + Agapanthus, Allium + Carica, Agapanthus + Syzygium and Carica + Syzygium extracts registered low anthracnose (C. lindemuthianum,) disease severity and high leaf area. The cowpea plants treated with 15 mg.ml-1 water extracts of Agapanthus and the combinations of Allium + Agapanthus, Agapanthus + Carica and Agapanthus + Syzygium extracts recorded low cowpea anthracnose (C. dematium) disease severity, highest leaf area and dry mass. The study revealed that A. sativum, Agapanthus, C. papaya and S. cordatum plant extracts have antifungal activities and can be used as alternative seed treatments and foliar fungicides against the anthracnose diseases of legumes (cowpea and common bean) instead of synthetic fungicides without causing any negative effect on seed germination, emergence, ultra-structure of seeds and plant growth. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Microbiology and Plant Pathology / Unrestricted

Discula destructiva, the causal agent of dogwood anthracnose, has caused severe mortality in dogwood over the last 30 years. Although considerable research has been done with dogwood anthracnose, the infection process by D. destructiva is still obscure. A resistant cultivar of Cornus florida, ‘Appalachian Spring’, was discovered and released by the Tennessee Agricultural Experiment Station. However, the resistance mechanisms are unknown. The objectives of this research were 1) to determine the sequence of events in the infection process of D. destructiva in C. florida and 2) to determine how host resistance affects infection events of D. destructiva on flowering dogwood. At 3 days after inoculation (DAI), majority of conidia germinated and hyphae were observed on the leaf surface. Direct penetration by D. destructiva hyphae was observed without appressorium formation. At 8 DAI, hyphae were aggregated between the cuticle and epidermis and grew intracellularly in epidermal cells, palisade parachyma, and spongy mesophyll cells. At 16 DAI, chloroplasts were intact but decompartmentalized and infection sites were clearly defined. Acervuli were detected at 20 DAI and were fully developed at 24 DAI on adaxial and abaxial leaf surfaces. Sporulation (ruptured acervuli) was observed at 20 DAI. This clear understanding of the infection process can be used to look for resistance mechanisms in dogwood germplasm. A resistant line would expect to slow or inhibit one or more infection events. There was no statistical difference between the percentages of germinated conidia on susceptible and resistant cultivars of flowering dogwood one day after inoculation (DAI). However, the resistant cultivar, ‘Appalachian Spring’, significantly suppressed the growth of D. destructiva conidial germ tubes at 2 DAI, 3 DAI and 4 DAI when compared to conidial germ tubes on leaves of the susceptible cultivar ‘Cloud 9’. Observed resistance may be due to smoother wax crystals on adaxial leaf surface and significantly thicker cuticle observed on leaves of ‘Appalachian Spring’. An unknown compound, observed highly concentrated in resistant but lower in susceptible cultivars, may be important as a resistance mechanism. These strategies reduced the inoculum potential of D. destructiva and play important roles in why ‘Appalachian Spring’ is resistant to dogwood anthracnose. These results provide new ways to use conidia germination test and germ tube growth measurement for detecting resistant cultivars.

The fungus <i>Colletotrichum truncatum</i> (Schw.) Andrus and Moore causes lentil anthracnose, which is a major challenge to lentil production in Western Canada. The pathogen infects leaves and stems, resulting in defoliation, stem girdling, plant wilting, and possibly plant death. Two races, Ct0 and Ct1, have been identified in the pathogen population in Canada. However, the differences in the infection process between the two races have not been described in detail. Currently, several lentil cultivars, such as CDC Redberry, CDC Robin, CDC Rosetown, CDC Rouleau, and CDC Viceroy, have resistance against race Ct1, whereas there are no cultivars showing resistance to race Ct0. The objective of this study was to investigate differences in the infection process between race Ct0 and race Ct1 using the fully susceptible cultivar Eston and the race Ct1-resistant cultivar CDC Robin. Experiments on glass well slides showed that race Ct0 had no inherently different conidium germination rate compared to race Ct1, and that differences in conidium germination between the two races on lentil plants were the result of specific interactions between the two races and lentil resistance. Investigations of the infection process of the two races on detached and attached leaves of both lentil cultivars were conducted starting 12 h postinoculation (hpi) until 72 hpi, including conidium germination, appressorium formation, and leaf penetration. Results indicated that differences in virulence of the two races may be related to the ability of conidia to germinate and form appressoria, as well as the ability of primary infection hyphae to grow in response to cues from the lentil cultivars. Furthermore, resistance of lentil to isolates of race Ct1 appeared to involve an inhibition in and/or delay of the spread of primary infection hyphae inside the plant tissue. Results of infection studies of one isolate from each race on attached leaves did not completely agree with results of the same isolates on detached leaves. Based on this study, race Ct0 and race Ct1 do not appear to be classical physiological races, but may represent aggressive races or some intermediate forms.

The fungus <i>Colletotrichum truncatum</i> (Schw.) Andrus and Moore causes lentil anthracnose, which is a major challenge to lentil production in Western Canada. The pathogen infects leaves and stems, resulting in defoliation, stem girdling, plant wilting, and possibly plant death. Two races, Ct0 and Ct1, have been identified in the pathogen population in Canada. However, the differences in the infection process between the two races have not been described in detail. Currently, several lentil cultivars, such as CDC Redberry, CDC Robin, CDC Rosetown, CDC Rouleau, and CDC Viceroy, have resistance against race Ct1, whereas there are no cultivars showing resistance to race Ct0. The objective of this study was to investigate differences in the infection process between race Ct0 and race Ct1 using the fully susceptible cultivar Eston and the race Ct1-resistant cultivar CDC Robin. Experiments on glass well slides showed that race Ct0 had no inherently different conidium germination rate compared to race Ct1, and that differences in conidium germination between the two races on lentil plants were the result of specific interactions between the two races and lentil resistance. Investigations of the infection process of the two races on detached and attached leaves of both lentil cultivars were conducted starting 12 h postinoculation (hpi) until 72 hpi, including conidium germination, appressorium formation, and leaf penetration. Results indicated that differences in virulence of the two races may be related to the ability of conidia to germinate and form appressoria, as well as the ability of primary infection hyphae to grow in response to cues from the lentil cultivars. Furthermore, resistance of lentil to isolates of race Ct1 appeared to involve an inhibition in and/or delay of the spread of primary infection hyphae inside the plant tissue. Results of infection studies of one isolate from each race on attached leaves did not completely agree with results of the same isolates on detached leaves. Based on this study, race Ct0 and race Ct1 do not appear to be classical physiological races, but may represent aggressive races or some intermediate forms.

The objectives of studies undertaken here were to identify the species of Colletotrichum associated with coffee berry anthracnose in PNG, gain an understanding of the infection process and factors affecting it, assess the impact, if any, of anthracnose on coffee quality and identify suitable chemicals for anthracnose control. A total of 40 isolates were collected from PNG and their cultural and morphological characteristics on PDA were studied and used to identify the species. Species identification was further confirmed by molecular characterisation using RFLP and DNA sequencing of the ITS region of the rDNA. After species identification only two isolates were selected to represent C. gloeosporioides and C. acutatum for further studies. Studies on conidia germination and the effects of conidia concentration, temperature, relative humidity and pH affecting germination were done on TWA, followed by studies on the infection process on coffee berries and the influence of temperature on germination and appressoria formation in vivo. For assessment of effect of anthracnose on coffee quality, 100 samples of ripe berries were assessed for disease incidence, followed by processing of the berries to green bean and data on bean defects (black bean) together with anthracnose incidence subjected to appropriate statistical analysis. A similar procedure was followed using disease severity but the samples were from one farm only. The closing work on chemical control was done by screening 16 different fungicides for the control of C. gloeosporioides and C. acutatum. With the 40 isolates, 29 were identified as C. gloeosporioides and 11 as C. acutatum. This is the first report of C. acutatum on coffee in PNG. Identification of the species was further confirmed by RFLP groupings where C. gloeosporioides and C. acutatum were separated at 574bp and 584bp respectively and DNA sequence homology identified the PNG isolates with C. gloeosporioides and C. acutatum accessions. Optimum conditions for conidia germination in relation to spore concentration, temperature, and pH are 1 x 106 spores/ml, 21 - 29°C and pH 5 - 7 respectively for C. acutatum and for C. gloeosporioides 1 x 106 spores/ml, 25 - 31°C and pH 5 - 7 respectively. Humidity is not a limiting factor for activity of both species. Infection process for both species is similar where conidia germinate to produce the germ tube which swells at the tip to form the appressoria. The appressoria produce an infection peg which is responsible for berry cuticle penetration and cell colonisation (resulting in typical anthracnose symptom expression) and eventual sporulation. C. acutatum has not been reported elsewhere as a pathogen of coffee and this is the first report of C. acutatum causing infections on both ripe and mature green berries. Anthracnose incidence did not correlate well with coffee bean defects, but anthracnose severity v suggested that coffee quality could be affected by anthracnose. The most effective fungicide for anthracnose control is thiram alone or thiram alternating with propiconazole.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Plant Biology." Includes bibliographical references.