Chemical control of mango anthracnose disease in Ghana

AbstractSeven different fungicides were evaluated in-vitro and in the field for their efficacy against the causal agent and incidence and severity of mango anthracnose disease in Ghana. The recommended rates of Bendazim, (Carbendazim), Funguran (Copper hydroxide), Ivory (Mancozeb), Agriette +Ivory (Fosetyl-Al +Mancozeb), Sundomil (Mancozeb+Metalaxyl), Top Cop (Copper +flowable sulphur), Mirage (Prochloraz), Bendazim+Ivory and Funguran+Ivory were mixed with potato dextrose agar (PDA) and the radial mycelial growth of the pathogen was determined on these amended media. The fungicides were applied on fruit bearing trees in a commercial farm in the Yilo Krobo District after which the disease incidence, severity and percentage of exportable fruits were determined. The results showed that the pathogen was not able to grow on PDA amended with the fungicides. In the field, Bendazim and Funguran fungicides were able to suppress the disease to a large extent resulting in the highest percentage of exportable fruits. Prochloraz solution at both ambient temperature and 53 °C were able to completely eradicate the pathogen, and prevented development of postharvest anthracnose disease symptoms.Original scientific paper. Received 30 Apr 14; revised 23 Sept 14

Pathogenicity and fungicide sensitivity of the causal agent of postharvest stem end rot disease of mango in Ghana

ABSTRACTStudies were carried out on the stem end rot disease of mango in Ghana. The incidence and severity of the disease were evaluated on mango fruits collected from major mango growing areas of Ghana. The causal agent was isolated on media and identified. The pathogenicity of the fungus and its cross-infection potential were determined on mango, avocado, papaya and banana fruits. The sensitivity of the pathogen to fungicides was determined by assessing radial mycelial growth on potato dextrose agar (PDA) amended with nine different fungicides (Bendazim, Funguran, Ivory, Topsin, Asuoku master, Kocide, Mirage, Sulphur 80 and Copper oxychloride). Stem end rot disease was prevalent in the major mango growing areas of Ghana. Two pathogens, Lasiodiplodia theobromae and Colletotrichum gloeosporioides were isolated from the disease lesions. However, only the former was able to cause stem end rot disease symptoms on the artificially inoculated fruits, confirming it as the causal agent of the disease. It was also found to be highly susceptible to Bendazim, Ivory, Topsin, Asuoku master and Mirage, whilst it was resistant to Funguran, Kocide, Sulphur 80 and Copper oxychloride.Original sciencitic paper. Received 30 Apr 15; revised 17 Oct 14

The Aetiology, Incidence and Severity of Mango Tree Decline Disease in Ghana

Mango tree decline was previously an unknown disease in Ghana. In this study, mango trees from all the major agro-ecological zones of Ghana, where mangoes are grown were surveyed for the disease incidence, severity and aetiology of a similar disease affecting the crop. Farm visits were made to some selected farms within the selected agro-ecological zones and both the local and exotic trees were inspected. The percentage of infected trees were calculated while the severity of the disease was rated on a scale of 0-5, where 0 = no symptoms and 5 = death of trees. Samples of the diseased plant parts were collected and the causal agent was isolated on media and identified. The isolated fungus was tested for its pathogenicity using mango seedlings as test crops. The disease, characterised by profuse gumming, bark cracking and die back, was found to be present in all the agro-ecological zones. The disease incidence was higher on the local variety compared to the exotic varieties. Lasiodiplodia theobromae, isolated from the diseased plant parts, was able to cause the disease on inoculated mango seedlings. The nature of the disease symptoms and its causative agent in Ghana, confirms the disease as the mango tree decline disease

Differentiation of two Botryosphaeriaceae species isolated from declining mango trees in Ghana

Lasiodiplodia theobromae is the only pathogen reported to cause mango tree decline disease in Ghana. In this study, several Botryosphaeriaceae isolates were obtained from mango tree decline disease symptoms and were identified using both phenotypic and genotypic characteristics and inoculation studies. The methods employed differentiated the isolates into two species, Lasiodiplodia theobromae and Neofussicoccum parvum. L. theobromae sporulated freely on media while N. parvum did not. Also, the species specific primer, Lt347-F/Lt347-R identified only L. theobromae while in the phylogenetic studies, L. theobromae and N. parvum clustered in different clades. L. theobromae caused dieback symptoms on inoculated mango seedlings while N. parvum did not. However, both species caused massive rot symptoms on inoculated fruits. L. theobromae was therefore confirmed as the causal agent of the tree decline disease in Ghana while N. parvum was reported for the first time as a potential pathogen of mango fruits in the country

Identification and molecular characterisation of Colletotrichum species from avocado, citrus and pawpaw in Ghana

Owing to previous identifications based solely on morphological characteristics, the identity of the causal agents of anthracnose disease of pawpaw and avocado in Ghana is in doubt. In addition, the pathogen has not been identified previously on citrus. In this study, isolates of the pathogen were obtained from anthracnose lesions on avocado and pawpaw, and atypical anthracnose lesions on citrus. The isolates were identified using PCR with speciesspecific primers, complemented by phylogenetic analysis of nucleotide sequences of the internal transcribed spacer region and partial glyceraldehyde-3-phosphate dehydrogenase gene. The pathogenicity of the isolated fungi was determined on detached matured fruits. All isolates, including those isolated from citrus, were identified as Colletotrichum gloeosporioides from the expected 480 bp PCR products amplified by PCR. The phylogenetic analysis showed that isolates from avocado and pawpaw were C. siamense, rather than C. gloeosporioides, whereas isolates from citrus were C. gloeosporioides sensu stricto. The pathogens were able to induce disease only on wounded mature fruits.Keywords: Colletotrichum gloeosporioides sensu stricto, Colletotrichum siamense, glyceraldehyde-3-phosphate dehydrogenase, internal transcribed spacer regio

Principal Component Analysis and Molecular Characterization of Reniform Nematode Populations in Alabama

U.S. cotton production is suffering from the yield loss caused by the reniform nematode (RN), Rotylenchulus reniformis. Management of this devastating pest is of utmost importance because, no upland cotton cultivar exhibits adequate resistance to RN. Nine populations of RN from distinct regions in Alabama and one population from Mississippi were studied and thirteen morphometric features were measured on 20 male and 20 female nematodes from each population. Highly correlated variables (positive) in female and male RN morphometric parameters were observed for body length (L) and distance of vulva from the lip region (V) (r = 0.7) and tail length (TL) and c′ (r = 0.8), respectively. The first and second principal components for the female and male populations showed distinct clustering into three groups. These results show pattern of sub-groups within the RN populations in Alabama. A one-way ANOVA on female and male RN populations showed significant differences (p ≤ 0.05) among the variables. Multiple sequence alignment (MSA) of 18S rRNA sequences (421) showed lengths of 653 bp. Sites within the aligned sequences were conserved (53%), parsimony-informative (17%), singletons (28%), and indels (2%), respectively. Neighbor-Joining analysis showed intra and inter-nematodal variations within the populations as clone sequences from different nematodes irrespective of the sex of nematode isolate clustered together. Morphologically, the three groups (I, II and III) could not be distinctly associated with the molecular data from the 18S rRNA sequences. The three groups may be identified as being non-geographically contiguous