Browsing by Author "Honger, J.O."
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Item Aetiology and Importance of Foliage Diseases Affecting Citrus in the Nursery at the Agricultural Research Station (A.R.S.). Kade.(University of Ghana, 2004-06) Honger, J.O.; Oduro,K.A; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Crop ScienceA research work was carried out at the Agricultural Research Station to determine the disease status of the seedlings and budlings in the nursery. Field surveys were carried out on three separate occasions between October and December 2003 during the dry season and repeated in March to May 2004 in the rainy season. Four diseases were detected. These were citrus scab, citrus canker, greasy spot-like disease and brown leaf spot of rough lemon. The causal agent for brown leaf spot was confirmed to be Altemaria citri, and that for citrus canker was confirmed to be Xanthomonas campestris pv. citri, a bacterium that has not been previously reported in Ghana. Pathogens for scab and greasy spot-like disease could not be isolated and identified. Brown leaf spot and scab were found to be restricted to rough lemon, which is used as rootstock in the nursery and therefore could not be transferred to the field. Comparatively, citrus canker and greasy spot -like disease were found to have a wide host range and have infected the following citrus varieties in the nursery: late Valencia (sweet orange), waiters (grapefruit) Cleopatra mandarin, satsuma mandarin and ponkan (mandarins), king disemis and ortanique (hybrids); and the rough lemon. The two diseases have a potential of being transferred to the field as they infect the scion as well. Both the incidence and severity of the diseases in all the species and varieties of the citrus studied were higher in the rainy season than in the dry season. The use of blunt syringe in inoculation studies of the-canker disease gives quick results as compared to the spraying method. Studies on the effect of the diseases on yield, to complete their importance were not feasible within the period of the study.Item Characterisation of the Causal Agent of Mango Anthracnose Disease in Ghana(University of Ghana, 2014-05) Honger, J.O.; Offei, S.K.; Oduro, K.A.; Odamtten, G.T.This research work was carried out to update information on the nature, the identity of the causal agent and the importance of mango anthracnose disease in Ghana. It was also to determine the effect of the disease on the juice quality of fruits and come up with appropriate control measures in the country. A field survey was carried out in 12 administrative districts of Ghana in 2010 and 2011 to assess the disease incidence and severity. The effect of the disease on yield/fruit quality was assessed in a commercial farm by determining the percentage of fruits that dropped or could not be marketed due to the disease. The pathogen causing the disease was isolated from the diseased lesions and characterised using cultural, morphological, biochemical and molecular approaches. The total soluble solids and acidity content of infected fruits were measured as means of determining the effect of the disease on juice quality of the fruits. The susceptibility of the different strains of the pathogen to fungicides available in Ghana was assessed using PDA amended with the fungicides after which efficacy of fungicides was evaluated in the field. The results show that two different symptoms, a sunken dark lesion and cracked skins were observable in Ghana. The disease was not found in the field in 5 out of the 12 districts surveyed and the incidence ranged from 0% in the Hohoe, Berekum, Kintampo, Savelungu/Nanton and Tolon/Kumbungu districts to 100% in the Kwaebibrem and Kumasi metro districts in both the 2010 and 2011 major mango growing seasons. The severity index of the disease on a scale of 0-5 ranged from 0 to 3.8 in 2010 and 0 to 3.7 in 2011. The disease was found to cause shriveling of fruit panicles and blemishes on skin of fruits resulting in yield loss of 4.5% in the major season and 29.9% in the minor season in a mango orchard in the Yilo Krobo district. Colletotrichum gloeosporioides sensu lato was confirmed as the causal agent of the disease. From a total of 45 isolates, 16 (35%) were identified as Colletotricum asianum while 29 (65%) were identified as Colletotrichum species. Artificial inoculations confirmed the pathogenicity of isolates of the pathogen on mango and induced similar disease level on Haden, Irwin, Julie, Keitt, Kent, Palmer and Tommy Atkins cultivars of mango. Cross-infection studies showed 32 (32%) of the isolates were the mango bio-type of the pathogen while 68 (68%) were very virulent on all the three types of fruit and were isolates that may have cross-infected mango in the field. Analysis of the secondary metabolites of the two types of strains of the pathogen indicated they may be producing the same kind of toxin. Analysis of the total soluble solid and titratable acidity content of the fruit showed that the disease does not significantly affect the juice quality of mango fruits (p>0.05). The pathogen was found to be highly susceptible to 8 different fungicides available on the Ghanaian market. The fungicides were able to reduce the incidence and severity of the disease significantly (p<0.05) in the field eve. At the postharvest phase dipping of fruits in prochloraz solution both at ambient temperature and at 53oC were found to eradicate pathogen on harvested fruits even if the fruits did not receive any preharvest treatment on the field. To minimize cost, the prochloraz dip at ambient temperature is recommended for postharvest control of the disease.Item Identification and species status of the mango biotype of Colletotrichum gloeosporioides in Ghana( European Journal of Plant Pathology, 2014-11) Honger, J.O.; Offei, S.K.; Oduro, K.A.; Odamtten, G.T.Research work was carried out to identify and ascertain the species status of the mango biotype of Colletotrichum gloeosporioides infecting mangoes in Ghana. Forty five isolates of Colletotrichum species were collected from 12 districts in Ghana while five each were obtained from mango fruits from Florida, Mexico and Puerto Rico. The entire internal transcribed spacer region, partial beta-tubulin gene and partial glyceraldehyde-3-phosphate dehydrogenase gene of isolates were sequenced and used in phylogenetic studies. The results of the sequence analysis of the first ribosomal transcribed spacer (ITS 1) region showed that 35 % of the isolates from Ghana and all the five isolates from Mexico were the mango biotype of C. gloeosporioides, while the others were not. Phylogenetic studies showed that the mango biotype of the pathogen was Colletotrichum asianum but not C. gloeosporioides as previously thought. However, the other isolates that were not the mango biotype were identified as Colletotrichum siamense and Colletotrichum species which had probably cross-infected mango from other fruit crops in the field.Item Importance, etiology and management of the tear stain disease symptoms of mango fruits in Ghana(Springer, 2022) Honger, J.O.; Narh, S.; Lambon, J.B.The tear stain symptom refers to slightly raised blisters which reduce the aesthetic value of mango fruits in Ghana. The dis ease incidence, severity and percentage of exportable mango fruits on infected mango trees were determined in the coastal savannah zone of Ghana in 2019. Samples of disease fruits were collected and the causative agent isolated and identified using phenotypic and genotypic characteristics. Selected copper based fungicides, namely, Cuprous oxide (750 g/kg), Copper oxychloride (500 g/kg) and Mancozeb (800 g/kg) either solely or in combination with Acibenzolar-S-methyl were applied in the field to determine their effect on the disease incidence and severity and on the percentage of exportable fruits. The disease incidence ranged from 9.4% to 11.0% in the major season and 37.3% to 45.0% in the minor season. Severity ranged from 0.08 to 0.1 in the major season and 1.4 to 2.1 in the minor season. The fungus isolated showed the characteristic short conical spores with rounded edges, an indication that it was C. gloeosporioides. The combination of gene sequences of the ITS region and the partial actin gene identified the fungus as C. siamense. All fungicides evaluated were able to reduce the disease incidence and severity on treated trees and resulted in a higher percentage of exportable fruits compared to non treatment control trees.Item Molecular characterization, pathogenicity and copper sensitivity of Xanthomonas citri pv mangiferaeindicae, the causal agent of mango bacterial black spot disease in Ghana(Taylor & Francis Group, 2021) Honger, J.O.; Osabutey, S.; Nyaku, S.T.; Lambon, J.B.Recent outbreak of the mango bacterial black spot disease has resulted in massive damages to the Ghanaian mango industry. Research was carried out to confirm the etiology of the disease. Diseased mango fruits and leaves were collected from Greater Accra (Asutuare and Dodowa), Eastern (Akuse, Somanya) and Volta (Juapong) regions, and the sus pected causal bacterium was isolated. The pathogen was identified as Xanthomonas citri pv mangiferaeindicae based on cultural and morphological characteristics and sequence analysis of the cpn60 gene. The pathogenicity of the bacterial pathogen on mango and cashew was determined and its sensitivity to some selected copper based fungicides available in Ghana was evaluated by the agar diffusion bio-assay. All strains of the pathogen were able to cause disease symptoms on artificially inoculated mango and cashew leaves. The pathogen was highly sensitive to Copper oxychloride, Copper hydroxide and Coprous oxide at very low concentrations.