Plantation forests are established by planting Eucalyptus tree species to provide timber and pulp... more Plantation forests are established by planting Eucalyptus tree species to provide timber and pulp for the construction industries and to meet the energy needs in Ethiopia. Besides the extensive Eucalyptus plantations in the country, fungal pathogen-related diseases are the main challenges to successful production and management. The disease survey was conducted in the Eucalyptus growing areas of Ethiopia during 2019/2020 and 2020/2021. The objective of this research was to assess the diseases associated with Eucalyptus plant species and identify the causal fungal species. Plants of E. camaldulensis were the dominant species in the survey fields and were severely associated with stem and branch canker diseases. Diseased samples were collected and fungal species were identified as Didymellaceae according to culture morphology and affirmed by internal transcribed spacer sequence analysis. In phylogeny, isolates in the study and a reference strain formed supportive monophyletic clades with strong 90% and 95% support with Didymella coffeae-arabicae and Didymella pinodella respectively. Pathogenicity tests revealed that Didymellaceae could infect E. camaldulensis. The findings are the first reports of Eucalyptus stem canker disease caused by Didymellaceae in Ethiopia.
Ethiopian Institute of Agricultural Research East Africa Forestry Research Center Chilalo Agricul... more Ethiopian Institute of Agricultural Research East Africa Forestry Research Center Chilalo Agricultural Development Unit
Introduction: Treatment of microbial infections has become complicated due to increased resistanc... more Introduction: Treatment of microbial infections has become complicated due to increased resistance of microbes to the current drugs. The current study investigates crude extracts and seven compounds from root and stem bark of Cordia africana Lam. for antimicrobial and cytotoxic activity. Methods: Extraction was done using 50% methanol in dichloromethane, followed by chromatographic separation of compounds, whose structures were established by interpretation of spectroscopic data. The in vitro susceptibility of selected microbes to the crude extracts and pure compounds was determined. Cytotoxicity of 1, 6 and 7 was determined against the drug sensitive, CCRF-CEM and resistant CEM/ADR-5000 cells, with doxorubicin used as the standard. Results: The root bark extract of C. africana yielded six known compounds: oleanolic acid (1), 3-β-lup-20(29)en-3-ol (2) stigmast-5,22-dien-3β-ol (3), 2-(2Z)-(3-hydroxy-3,7-dimethylocta-2,6-dienyl)-1,4-benzenediol (4), 4-hydroxy-3-methoxy-benzaldehyde (5) and 7-hydroxy-4′-methoxyisoflavone (6). The stem bark extract resulted to 1 and 2 alongside, ubiquinone-8 (7) and 1-octacosanol (8). Compound 1 showed moderate activity against Enterococcus faecium (IC 50 of 14.44 µg/ mL), with vancomycin being inactive. Compounds 1, 6 and 7 showed cell viability >50% against CEM/ADR5000 and CCRF-CEM cells at 10 µM and therefore were considered inactive. Surprisingly, 1 was relatively more active compared to the standard, with cell viability of 57.93% against CEM/ ADR5000, versus 78.97% for doxorubicin. Conclusion: To the best of our knowledge, this is the first report of the eight compounds from C. africana. The cytotoxicity of 1, 6 and 7 are reported here for the first time. Traditional use of the plant extract in management of various infections may be attributed to presence of 1, which displayed moderate antimicrobial activity.
Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze reg... more Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze region and used for the production of frankincense. Frequent tapping at different rounds and at different position of the tree is made to produce frankincense. A study aiming at evaluating the health status of tapped Boswellia papyrifera was carried out on samples obtained from Metema and Humera. Galls were commonly observed on most tapped Boswellia trees and a black wood discoloration was found on the wood beneath these galls. Isolation made from the discolored part of the wood resulted in growth of fungal colonies with a white to gray fluffy aerial mycelia which later changed into blackish mycelial growth as it matures. The spore of the fungus has hyaline, ellipsoid to ovoid shaped and it has one septa. The spore has a rounded base and truncate apex. The color, the shape of the colony and the characteristics of the conidia is found to be identical with description of Lasiodiplodia theobro...
Plantations of exotic Eucalyptus make up more than 30% of Ethiopia's plantations, providing f... more Plantations of exotic Eucalyptus make up more than 30% of Ethiopia's plantations, providing fuel and construction timber to the country. Species such as E. camaldulensis, E. saligna, E. grandis, E. citriodora and E. globulus are most commonly planted. During a survey of Eucalyptus diseases in 2000 and 2001, Botryosphaeria stem canker was observed in most plantations. The disease symptoms included tip die-back, coppice failure and stem cankers characterised by kino exudation. The aim of this study was to identify the species responsible for Botryosphaeria stem canker in Ethiopia. Culture and conidial morphology, as well as DNA-based identification involving Restriction Fragment Length Polymorphisms (RFLPs) and sequencing of the Internal Transcribed Spacer regions (ITS) of the ribosomal RNA gene and the elongation factor 1-alpha (EF1-α) gene, were used to identify isolates. Pathogenicity studies were conducted in the greenhouse and under field conditions. Results showed that Botry...
30 % of Ethiopia’s plantations, providing fuel and con-struction timber to the country. Species s... more 30 % of Ethiopia’s plantations, providing fuel and con-struction timber to the country. Species such as E. camaldulensis, E. saligna, E. grandis, E. citriodora and E. globulus are most commonly planted. During a sur-vey of Eucalyptus diseases in 2000 and 2001, Botryosphaeria stem canker was observed in most plantations. The disease symptoms included tip die-back, coppice failure and stem cankers characterised by kino exudation. The aim of this study was to identify the species responsible for Botryosphaeria stem canker in Ethiopia. Culture and conidial morphology, as well as DNA-based identification involving Restriction Frag-ment Length Polymorphisms (RFLPs) and sequencing of the Internal Transcribed Spacer regions (ITS) of the ribosomal RNA gene and the elongation factor 1-alpha (EF1-α) gene, were used to identify isolates. Pathogenicity studies were conducted in the green-house and under field conditions. Results showed that Botryosphaeria parva is responsible for Botryosphaeria ...
The total area of plantation forests in Ethiopia is estimated at 972,000 ha. Species wise, eucaly... more The total area of plantation forests in Ethiopia is estimated at 972,000 ha. Species wise, eucalyptus dominates the current plantation forests, covering more than 90%. The total area of plantation forests in Amhara region is estimated at 684,000 ha, of which Industrial Plantations are 44, 600 ha and Non-industrial Small-scale Private Plantations are 639,400 ha. The application of appropriate silvicultural practice during and after planting of different plantation species is not well developed in Ethiopia. Therefore, the objective of this paper was to identify effective plantation practices in the Amhara National Regional State that can be scaled out in other similar agro ecological areas of the country. The study was conducted between September 2013 and October 2015 in ANRS in Fagta Lekoma District of Awi zone and Lay Gayent District of South Gonder Zone. Multistage sampling technique was used to select sample households. The best example of smallholder plantation practices are Acac...
During routine disease surveys of lIgEucalyptusl/Ig species in Argentina and Vietnam, symptoms of... more During routine disease surveys of lIgEucalyptusl/Ig species in Argentina and Vietnam, symptoms of a damaging stem canker disease were observed. This study identifies the causal agent of the disease as Coniothyrium zuluense . This is the first report of Coniothyrium stem canker from Argentina and Vietnam.
During the disease survey, Armillaria root rot was found to be associated with both exotic and na... more During the disease survey, Armillaria root rot was found to be associated with both exotic and native tree species. Morphological and molecular identification techniques revealed that the Armillaria sp. collected in this study is A. jitscipes. This is discussed in chapter three, where I also provide preliminary data regarding the host range and distribution of Armillaria root rot in Ethiopia. Prior to this study it was suggested that A. mellea is responsible for Armillaria root rot of 247 hard woods in Ethiopia. The current study, however, showed that at least two Armillaria spp., A. mellea and A. Jusicpes are causing Annillaria root rot in the country. Of significance is the fact that A. jilscipes was isolated from two indigenous tree species, A. abyssinica and J excelsa. Chapter four of this thesis deals with the identity of the fungus causing stem canker on Eucalyptus camaldulensis. Disease symptoms identical to those caused by Coniothyrium zuluense were commonly found on E. camaldulensis in restricted areas in Western Ethiopia. The causative agent was detennined based on DNA sequence analysis of the ITS 1, ITS 2 and 5.8S gene region and 0 tubulin genes. According to the phylogenetic tree generated for these sequence data, the Ethiopian Coniothyrium isolates seem to be closely related to C. zuluense, however, the Ethiopian isolates fonned a separate group. This may suggest that C. zuluense represents a species complex, but this needs further investigation. Coniothyrium canker is considered to be one of the most serious diseases of Eucalyptus spp. especially to the sawn timber and construction industry as it weakens and flaws the timber. It occurrence in Ethiopia is, therefore, of great importance. Disease symptoms similar to those of Botryosphaeria canker on Eucalyptus were commonly observed in all the areas where surveys were conducted. Botryosphaeria spp. are known as opportunistic stress related and endophytic pathogens on a wide range of woody plants, worldwide. In Ethiopia, symptoms similar to those associated with Botryosphaeria infection elsewhere, were found in almost all plantations surveyed. The disease was found on several Eucalyptus spp. including E. globulus, E. saligna, E. grandis and E. citriodora. Both morphological and molecular identification techniques were used to detennine the identity of the fungus and the results are presented in chapter five. It was shown that B. parva is responsible for Botryosphaeria stem canker of Eucalyptus spp. in Ethiopia and the pathogenicity of Ethiopian isolates was also tested. This pathogen can have a serious effect on Eucalyptus in Ethiopia, as growing conditions in the country are often harsh and many people rely on coppicing to reproduce their stands. All these factors are conducive to stress and thus to Botryosphaeria infection. Diplodia pinea is a fungus that commonly resides in the cones of Pinus spp. and it tends to move from these sites to infect stems, when trees are under stress. Therefore, isolations were made from Pinus patula cones to detennine whether D. pinea was present in these structures in Ethiopia. Chapter 6 of the thesis provides results of this study. It was expected that D. pinea would be the most common inhabitant of the cones. Contrary to this, a Fusicoccum sp. was found more 248 frequently than D. pinea. The results presented in this chapter show clearly that the A morphotype of D. pinea is found in cones of P. patula in Ethiopia. The Fusicoccum sp. found associated with P. patula cones is most closely related to B. parva. Results of greenhouse inoculation studies showed that both these fungi are pathogenic to Pinus tadea, with D. pinea being the more pathogenic. Serious leaf spot and shoot die-back symptoms were observed on leaves of E. globulus at several localities. The leaf blotch symptoms closely resemble those caused by Mycosphaerella spp. Even though 30 different Mycospha erella spp. are known to be associated with Eucalyptus species worldwide , the cause of Mycosphaerella leaf blotch on E. globulus in Ethiopia is not known. Morphological and DNA based comparisons were used to determine the identity of the species found in Ethiopia and the results are provided in chapter seven. I was thus able to show that three Mycosphaerella spp. namely, M marksii, M. grandis and M nubi/osa are involved in causing Mycosphaerella leaf disease of E. globulus in Ethiopia. This is the first report of these species from Ethiopia and the first report of M grandis from a country other than Australia. The results presented in the various chapters making up this thesis provide the first detailed studies on diseases of plantation trees in Ethiopia. Most tree diseases discussed in the thesis are first reports for the country. The thesis provides information on the identity of the pathogens and their significance in plantation development in Ethiopia. It also highlights the need for adequate management and silvicultural practices, as well as the need for selecting disease tolerant provenances and/or individuals. The information presented in the thesis also expands the host range and geographic distribution of all the pathogens included in the study, giving the study international significance.
Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze reg... more Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze region and used for the production of frankincense. Frequent tapping at different rounds and at different position of the tree is made to produce frankincense. A study aiming at evaluating the health status of tapped Boswellia papyrifera was carried out on samples obtained from Metema and Humera. Galls were commonly observed on most tapped Boswellia trees and a black wood discoloration was found on the wood beneath these galls. Isolation made from the discolored part of the wood resulted in growth of fungal colonies with a white to gray fluffy aerial mycelia which later changed into blackish mycelial growth as it matures. The spore of the fungus has hyaline, ellipsoid to ovoid shaped and it has one septa. The spore has a rounded base and truncate apex. The color, the shape of the colony and the characteristics of the conidia is found to be identical with description of Lasiodiplodia theobro...
A survey of diseases of exotic trees in plantations was undertaken in southern and southwestern E... more A survey of diseases of exotic trees in plantations was undertaken in southern and southwestern Ethiopia during 2000 and 2001. Our aim was to ascertain the occurrence and distribution of diseases of major plantation species and to provide a basis for further research. Root, stem and leaf samples were collected from both plantations and trees growing near farms and homesteads in and around Wondo Genet, Munessa Shashemene, Jima, Bedele, Mizan and Menagesha. Armillaria root rot was the most common disease, associated mainly with Pinus patula , but also found on Acacia abyssinica, Cordia alliodoral/ig and Cedrela odorata . Stem cankers associated with ligBotryosphaerial/ig species were common on Eucalyptus globulus, E. salignal/ig and E. citriodora . Stem canker disease associated with a ligConiothyriuml/ig species was commonly observed on E. camaldulensis . Leaf blotch associated with ligMycosphaerellal/ig species was common on E. globulusl/ig in most areas where this species is plante...
Cultivation of apple trees in the highlands of Ethiopia began in 1955. In 2014, blistering of the... more Cultivation of apple trees in the highlands of Ethiopia began in 1955. In 2014, blistering of the bark due to cankers on the main stems mostly below the grafting points, followed by dieback and eventually death of apple trees, was observed in apple orchards in the Hadiya Zone in Ethiopia. This study aimed to identify the causal agent of canker and dieback symptoms on the apple trees. Symptomatic trunks from 20 trees (ten per cultivar) were sampled. Isolations were performed from ten trunks (five per cultivar). Fungus colonies with similar cultural features were obtained from all the samples, and the morphology of a representative isolate was characterized. Phylogenetic analyses of the concatenated internal transcribed spacers 1 and 2 and 5.8S rRNA gene, large subunit and actin gene regions confirmed the identity of two isolates as Didymosphaeria rubi-ulmifolii. Pathogenicity was confirmed for one isolate by inoculations of healthy branches of ‘Anna’ and ‘Dorsett Golden’ apple trees ...
Plantation forests are established by planting Eucalyptus tree species to provide timber and pulp... more Plantation forests are established by planting Eucalyptus tree species to provide timber and pulp for the construction industries and to meet the energy needs in Ethiopia. Besides the extensive Eucalyptus plantations in the country, fungal pathogen-related diseases are the main challenges to successful production and management. The disease survey was conducted in the Eucalyptus growing areas of Ethiopia during 2019/2020 and 2020/2021. The objective of this research was to assess the diseases associated with Eucalyptus plant species and identify the causal fungal species. Plants of E. camaldulensis were the dominant species in the survey fields and were severely associated with stem and branch canker diseases. Diseased samples were collected and fungal species were identified as Didymellaceae according to culture morphology and affirmed by internal transcribed spacer sequence analysis. In phylogeny, isolates in the study and a reference strain formed supportive monophyletic clades with strong 90% and 95% support with Didymella coffeae-arabicae and Didymella pinodella respectively. Pathogenicity tests revealed that Didymellaceae could infect E. camaldulensis. The findings are the first reports of Eucalyptus stem canker disease caused by Didymellaceae in Ethiopia.
Ethiopian Institute of Agricultural Research East Africa Forestry Research Center Chilalo Agricul... more Ethiopian Institute of Agricultural Research East Africa Forestry Research Center Chilalo Agricultural Development Unit
Introduction: Treatment of microbial infections has become complicated due to increased resistanc... more Introduction: Treatment of microbial infections has become complicated due to increased resistance of microbes to the current drugs. The current study investigates crude extracts and seven compounds from root and stem bark of Cordia africana Lam. for antimicrobial and cytotoxic activity. Methods: Extraction was done using 50% methanol in dichloromethane, followed by chromatographic separation of compounds, whose structures were established by interpretation of spectroscopic data. The in vitro susceptibility of selected microbes to the crude extracts and pure compounds was determined. Cytotoxicity of 1, 6 and 7 was determined against the drug sensitive, CCRF-CEM and resistant CEM/ADR-5000 cells, with doxorubicin used as the standard. Results: The root bark extract of C. africana yielded six known compounds: oleanolic acid (1), 3-β-lup-20(29)en-3-ol (2) stigmast-5,22-dien-3β-ol (3), 2-(2Z)-(3-hydroxy-3,7-dimethylocta-2,6-dienyl)-1,4-benzenediol (4), 4-hydroxy-3-methoxy-benzaldehyde (5) and 7-hydroxy-4′-methoxyisoflavone (6). The stem bark extract resulted to 1 and 2 alongside, ubiquinone-8 (7) and 1-octacosanol (8). Compound 1 showed moderate activity against Enterococcus faecium (IC 50 of 14.44 µg/ mL), with vancomycin being inactive. Compounds 1, 6 and 7 showed cell viability >50% against CEM/ADR5000 and CCRF-CEM cells at 10 µM and therefore were considered inactive. Surprisingly, 1 was relatively more active compared to the standard, with cell viability of 57.93% against CEM/ ADR5000, versus 78.97% for doxorubicin. Conclusion: To the best of our knowledge, this is the first report of the eight compounds from C. africana. The cytotoxicity of 1, 6 and 7 are reported here for the first time. Traditional use of the plant extract in management of various infections may be attributed to presence of 1, which displayed moderate antimicrobial activity.
Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze reg... more Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze region and used for the production of frankincense. Frequent tapping at different rounds and at different position of the tree is made to produce frankincense. A study aiming at evaluating the health status of tapped Boswellia papyrifera was carried out on samples obtained from Metema and Humera. Galls were commonly observed on most tapped Boswellia trees and a black wood discoloration was found on the wood beneath these galls. Isolation made from the discolored part of the wood resulted in growth of fungal colonies with a white to gray fluffy aerial mycelia which later changed into blackish mycelial growth as it matures. The spore of the fungus has hyaline, ellipsoid to ovoid shaped and it has one septa. The spore has a rounded base and truncate apex. The color, the shape of the colony and the characteristics of the conidia is found to be identical with description of Lasiodiplodia theobro...
Plantations of exotic Eucalyptus make up more than 30% of Ethiopia's plantations, providing f... more Plantations of exotic Eucalyptus make up more than 30% of Ethiopia's plantations, providing fuel and construction timber to the country. Species such as E. camaldulensis, E. saligna, E. grandis, E. citriodora and E. globulus are most commonly planted. During a survey of Eucalyptus diseases in 2000 and 2001, Botryosphaeria stem canker was observed in most plantations. The disease symptoms included tip die-back, coppice failure and stem cankers characterised by kino exudation. The aim of this study was to identify the species responsible for Botryosphaeria stem canker in Ethiopia. Culture and conidial morphology, as well as DNA-based identification involving Restriction Fragment Length Polymorphisms (RFLPs) and sequencing of the Internal Transcribed Spacer regions (ITS) of the ribosomal RNA gene and the elongation factor 1-alpha (EF1-α) gene, were used to identify isolates. Pathogenicity studies were conducted in the greenhouse and under field conditions. Results showed that Botry...
30 % of Ethiopia’s plantations, providing fuel and con-struction timber to the country. Species s... more 30 % of Ethiopia’s plantations, providing fuel and con-struction timber to the country. Species such as E. camaldulensis, E. saligna, E. grandis, E. citriodora and E. globulus are most commonly planted. During a sur-vey of Eucalyptus diseases in 2000 and 2001, Botryosphaeria stem canker was observed in most plantations. The disease symptoms included tip die-back, coppice failure and stem cankers characterised by kino exudation. The aim of this study was to identify the species responsible for Botryosphaeria stem canker in Ethiopia. Culture and conidial morphology, as well as DNA-based identification involving Restriction Frag-ment Length Polymorphisms (RFLPs) and sequencing of the Internal Transcribed Spacer regions (ITS) of the ribosomal RNA gene and the elongation factor 1-alpha (EF1-α) gene, were used to identify isolates. Pathogenicity studies were conducted in the green-house and under field conditions. Results showed that Botryosphaeria parva is responsible for Botryosphaeria ...
The total area of plantation forests in Ethiopia is estimated at 972,000 ha. Species wise, eucaly... more The total area of plantation forests in Ethiopia is estimated at 972,000 ha. Species wise, eucalyptus dominates the current plantation forests, covering more than 90%. The total area of plantation forests in Amhara region is estimated at 684,000 ha, of which Industrial Plantations are 44, 600 ha and Non-industrial Small-scale Private Plantations are 639,400 ha. The application of appropriate silvicultural practice during and after planting of different plantation species is not well developed in Ethiopia. Therefore, the objective of this paper was to identify effective plantation practices in the Amhara National Regional State that can be scaled out in other similar agro ecological areas of the country. The study was conducted between September 2013 and October 2015 in ANRS in Fagta Lekoma District of Awi zone and Lay Gayent District of South Gonder Zone. Multistage sampling technique was used to select sample households. The best example of smallholder plantation practices are Acac...
During routine disease surveys of lIgEucalyptusl/Ig species in Argentina and Vietnam, symptoms of... more During routine disease surveys of lIgEucalyptusl/Ig species in Argentina and Vietnam, symptoms of a damaging stem canker disease were observed. This study identifies the causal agent of the disease as Coniothyrium zuluense . This is the first report of Coniothyrium stem canker from Argentina and Vietnam.
During the disease survey, Armillaria root rot was found to be associated with both exotic and na... more During the disease survey, Armillaria root rot was found to be associated with both exotic and native tree species. Morphological and molecular identification techniques revealed that the Armillaria sp. collected in this study is A. jitscipes. This is discussed in chapter three, where I also provide preliminary data regarding the host range and distribution of Armillaria root rot in Ethiopia. Prior to this study it was suggested that A. mellea is responsible for Armillaria root rot of 247 hard woods in Ethiopia. The current study, however, showed that at least two Armillaria spp., A. mellea and A. Jusicpes are causing Annillaria root rot in the country. Of significance is the fact that A. jilscipes was isolated from two indigenous tree species, A. abyssinica and J excelsa. Chapter four of this thesis deals with the identity of the fungus causing stem canker on Eucalyptus camaldulensis. Disease symptoms identical to those caused by Coniothyrium zuluense were commonly found on E. camaldulensis in restricted areas in Western Ethiopia. The causative agent was detennined based on DNA sequence analysis of the ITS 1, ITS 2 and 5.8S gene region and 0 tubulin genes. According to the phylogenetic tree generated for these sequence data, the Ethiopian Coniothyrium isolates seem to be closely related to C. zuluense, however, the Ethiopian isolates fonned a separate group. This may suggest that C. zuluense represents a species complex, but this needs further investigation. Coniothyrium canker is considered to be one of the most serious diseases of Eucalyptus spp. especially to the sawn timber and construction industry as it weakens and flaws the timber. It occurrence in Ethiopia is, therefore, of great importance. Disease symptoms similar to those of Botryosphaeria canker on Eucalyptus were commonly observed in all the areas where surveys were conducted. Botryosphaeria spp. are known as opportunistic stress related and endophytic pathogens on a wide range of woody plants, worldwide. In Ethiopia, symptoms similar to those associated with Botryosphaeria infection elsewhere, were found in almost all plantations surveyed. The disease was found on several Eucalyptus spp. including E. globulus, E. saligna, E. grandis and E. citriodora. Both morphological and molecular identification techniques were used to detennine the identity of the fungus and the results are presented in chapter five. It was shown that B. parva is responsible for Botryosphaeria stem canker of Eucalyptus spp. in Ethiopia and the pathogenicity of Ethiopian isolates was also tested. This pathogen can have a serious effect on Eucalyptus in Ethiopia, as growing conditions in the country are often harsh and many people rely on coppicing to reproduce their stands. All these factors are conducive to stress and thus to Botryosphaeria infection. Diplodia pinea is a fungus that commonly resides in the cones of Pinus spp. and it tends to move from these sites to infect stems, when trees are under stress. Therefore, isolations were made from Pinus patula cones to detennine whether D. pinea was present in these structures in Ethiopia. Chapter 6 of the thesis provides results of this study. It was expected that D. pinea would be the most common inhabitant of the cones. Contrary to this, a Fusicoccum sp. was found more 248 frequently than D. pinea. The results presented in this chapter show clearly that the A morphotype of D. pinea is found in cones of P. patula in Ethiopia. The Fusicoccum sp. found associated with P. patula cones is most closely related to B. parva. Results of greenhouse inoculation studies showed that both these fungi are pathogenic to Pinus tadea, with D. pinea being the more pathogenic. Serious leaf spot and shoot die-back symptoms were observed on leaves of E. globulus at several localities. The leaf blotch symptoms closely resemble those caused by Mycosphaerella spp. Even though 30 different Mycospha erella spp. are known to be associated with Eucalyptus species worldwide , the cause of Mycosphaerella leaf blotch on E. globulus in Ethiopia is not known. Morphological and DNA based comparisons were used to determine the identity of the species found in Ethiopia and the results are provided in chapter seven. I was thus able to show that three Mycosphaerella spp. namely, M marksii, M. grandis and M nubi/osa are involved in causing Mycosphaerella leaf disease of E. globulus in Ethiopia. This is the first report of these species from Ethiopia and the first report of M grandis from a country other than Australia. The results presented in the various chapters making up this thesis provide the first detailed studies on diseases of plantation trees in Ethiopia. Most tree diseases discussed in the thesis are first reports for the country. The thesis provides information on the identity of the pathogens and their significance in plantation development in Ethiopia. It also highlights the need for adequate management and silvicultural practices, as well as the need for selecting disease tolerant provenances and/or individuals. The information presented in the thesis also expands the host range and geographic distribution of all the pathogens included in the study, giving the study international significance.
Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze reg... more Boswell papyrifera is a tree species which is found in Amhara, Tigray, and Benshangul Gumuze region and used for the production of frankincense. Frequent tapping at different rounds and at different position of the tree is made to produce frankincense. A study aiming at evaluating the health status of tapped Boswellia papyrifera was carried out on samples obtained from Metema and Humera. Galls were commonly observed on most tapped Boswellia trees and a black wood discoloration was found on the wood beneath these galls. Isolation made from the discolored part of the wood resulted in growth of fungal colonies with a white to gray fluffy aerial mycelia which later changed into blackish mycelial growth as it matures. The spore of the fungus has hyaline, ellipsoid to ovoid shaped and it has one septa. The spore has a rounded base and truncate apex. The color, the shape of the colony and the characteristics of the conidia is found to be identical with description of Lasiodiplodia theobro...
A survey of diseases of exotic trees in plantations was undertaken in southern and southwestern E... more A survey of diseases of exotic trees in plantations was undertaken in southern and southwestern Ethiopia during 2000 and 2001. Our aim was to ascertain the occurrence and distribution of diseases of major plantation species and to provide a basis for further research. Root, stem and leaf samples were collected from both plantations and trees growing near farms and homesteads in and around Wondo Genet, Munessa Shashemene, Jima, Bedele, Mizan and Menagesha. Armillaria root rot was the most common disease, associated mainly with Pinus patula , but also found on Acacia abyssinica, Cordia alliodoral/ig and Cedrela odorata . Stem cankers associated with ligBotryosphaerial/ig species were common on Eucalyptus globulus, E. salignal/ig and E. citriodora . Stem canker disease associated with a ligConiothyriuml/ig species was commonly observed on E. camaldulensis . Leaf blotch associated with ligMycosphaerellal/ig species was common on E. globulusl/ig in most areas where this species is plante...
Cultivation of apple trees in the highlands of Ethiopia began in 1955. In 2014, blistering of the... more Cultivation of apple trees in the highlands of Ethiopia began in 1955. In 2014, blistering of the bark due to cankers on the main stems mostly below the grafting points, followed by dieback and eventually death of apple trees, was observed in apple orchards in the Hadiya Zone in Ethiopia. This study aimed to identify the causal agent of canker and dieback symptoms on the apple trees. Symptomatic trunks from 20 trees (ten per cultivar) were sampled. Isolations were performed from ten trunks (five per cultivar). Fungus colonies with similar cultural features were obtained from all the samples, and the morphology of a representative isolate was characterized. Phylogenetic analyses of the concatenated internal transcribed spacers 1 and 2 and 5.8S rRNA gene, large subunit and actin gene regions confirmed the identity of two isolates as Didymosphaeria rubi-ulmifolii. Pathogenicity was confirmed for one isolate by inoculations of healthy branches of ‘Anna’ and ‘Dorsett Golden’ apple trees ...
Uploads
Papers by Alemu gezahgne