Production, Utilization, Characterization and Antimicrobial Activity of Tamarind (Tamarindus Indica) Accessions from Semi-Arid Eastern Kenya

Abstract

Tamarind (Tamarindus indica L) is a fruit tree native to tropical parts of Africa and Asia. It is used as food and a source of raw material in the food industry, pharmaceuticals as well as providing ecosystem services. Despite the great value of tamarind, there is limited information related to its utilization, production, morphological diversity, genetic diversity and antimicrobial potential in Kenya. The objectives of this study were to evaluate production and utilization, morphological diversity, genetic diversity and antimicrobial activity of tamarind extracts from semi-arid Eastern Kenya. A total of 89 trees were sampled and studied. Data on production and utilization were collected through personal interviews with the farmers and the use of questionnaires and the data was analyzed using SPSS software at a significance of P<0.05. Standard descriptors for tamarind were used in morphological diversity. The data were subjected to Exlstat software for Principal Component Analysis (PCA), correlation and cluster analysis and Genstat for descriptive statistics and analysis of variance and at the significance of P<0.05. DNA was extracted using the CTAB method and amplified using ISSR markers. The molecular data were analyzed using GeneAlex and R software. Antimicrobial compounds were extracted sequentially from fruits and leaves using methanol and water. The pathogenic bacteria (Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) were cultured in nutrient agar while the pathogenic Penicillium digitatum, Colletotrichum gloeosporioides and Alternaria solani) were cultured on Potato Dextrose Agar, Malt Extract Agar and Sabouroud Glucose Agar respectively. Data on inhibition zones were collected and analyzed using SPSS and the significance of P<0.05. This study revealed that all farmers used seeds from tamarind trees as their source of planting material. Tamarind was grown for market and subsistence use, the fruit was utilized as a dessert, an ingredient in porridge and as a source of herbal medicine. The cropping system used by most farmers was intercropping with crops like cereals and legumes. Weed control and harvesting practices were carried out when necessary. Time taken for the trees to mature was approximately 5-6 years. Maturity indicators included changes in fruit color and pod brittleness. Farmers harvested less than 180kgs of tamarind fruits per tree in a season. The challenges of tamarind production included tamarind weevil infestation, harvesting from tall trees, marketing and transportation. Morphological results revealed that there were significant variations in trunk diameter at the ground, pod length, color and shape, seed shape across the counties. There were no significant differences in terminal shoot length, trunk diameter at the neck and height to the first branch, pod weight, pulp length, seed weight and the number of seeds per pod, primary and secondary branches, growth habit, seed color, roughness and brilliance, pod shape and seed shape across the counties. Quantitative PCA revealed 5 PCs. Agglomerative Hierarchical Clustering revealed 3 major clusters. Morphological variation within clusters was 66.12% and between the cluster was 33.1%. The ISSR markers revealed polymorphism of 68.7-84.7%, PIC ranges of 0.72-0.89 and genetic diversity of 0.74-0.9. Cluster analysis showed 7 distinct clusters that indicated that tamarind accessions were diverse. There were no significant differences in the inhibition zones between leaf and fruit extracts against B. subtilis. There were significant differences in the inhibition of tamarind extracts from the study regions and the extraction solvents against B. subtilis. There were significant inhibition differences in the extracts from study regions, leaf and fruit extracts and the extraction solvents against P. aeruginosa. Tamarind extracts were not effective against S. aureus, E. coli, P. digitatum, C. gloeosporioides and A. solani. Tamarind fruit and leaf extracts of accessions KB004, KB005, KB011, KB012, KB014 and KB015 had higher inhibition than ampicillin streptomycin, kanamycin and cotrimoxazole against B. subtilis and P. aeruginosa. In conclusion, tamarind was produced as an intercrop and utilized as an ingredient. The accessions showed morphological and genetic diversity and antimicrobial activity in B. subtilis and P. aeruginosa. There is a need to establish management practices in tamarind production, sensitize the public on tamarind fruit value addition. Morphological and genetic diversity data can be used in breeding for improved tamarind varieties. Antimicrobial activity information will be utilized in herbal medicine.