Physicochemical, functional and sensory attributes of milk prepared from irradiated tiger nut (Cyperus esculentus L.)

Five tiger nut (Cyperus esculentus L.) cultivars were collected from four different regions of Ghana and irradiated. The aim of this study was to evaluate some physicochemical, functional and sensory qualities of milk produced from irradiated tiger nut samples. Analysis was carried out for pH, total solids, moisture, sugar brix and viscosity. Finally the consumer acceptability of the milk prepared from the nuts was determined by a taste panel using the parameters of colour, taste, aroma, mouth feel and overall acceptability. The sugar content varied from 6.0 ± 0.3% (Techiman) to 15.00 ± 1.00% (Asebu Ekroful) depending on the irradiation dose applied. Generally, increase in dose increased the sugar availability but decreased viscosity of the milk prepared from the nuts. The milk with the highest viscosity was from Kwahu Aduamoa and Techiman with the least viscosity from Bawjiase. Generally, no significant difference was detected by the sensory panellists with regard to mouth feel and taste among the milk samples prepared from the various tiger nut cultivars. Keywords: Tiger nut cultivar, Viscosity, Total solids, Sensory qualit

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

Crop loss, aetiology, and epidemiology of citrus black spot in Ghana

Citrus Black Spot (CBS), caused by Guignardia citricarpa, was detected for the first time in Ghana and in West Africa. The disease was first observed in the Eastern Region in 1999 with typical disease symptoms including hard spot, virulent spot and false melanose were observed on several citrus species. A survey revealed that the disease has reached epidemic levels in the citrus-producing areas of the Eastern and Ashanti regions and is spreading rapidly within these areas and to other regions of the country. Currently, CBS is the most important fruit disease of citrus in Ghana, causing about 22% crop loss. Although the disease does not cause postharvest decay and the internal quality of the fruit is not affected, significant amounts of blemished fruit are discarded at the markets. Disease incidence and severity was found to be higher on mature than on young citrus trees. Pycnidia were found on fruit with hard spot symptoms, and pycnidia and pseudothecia typical of Guignardia spp. were found on decomposing leaves. Two species, G. citricarpa and G. mangiferae, were isolated from 15% of the samples collected and identified using the Oatmeal Agar test and by PCR with species-specific DNA primers. Isolates of G. citricarpa produced CBS symptoms after 80 to 233 days on 75% of the artificially inoculated young fruit of Valencia Late sweet orange. The fungus was re-isolated from symptomatic, inoculated fruit completing Koch's postulates. Isolates of the endophyte G. mangiferae did not induce symptoms in the pathogenicity tests. In epidemiological studies, infections were detected from November to February for the minor cropping season and from May to November for the major season. Fruit of Valencia Late sweet orange were susceptible to G. citricarpa infection for up to 7 months after petal fall. Knowledge of the disease cycle in Ghana will improve methods for disease control