EFFICACY OF PHYTOCHEMICALS FROM FOUR SPECIES OF ALOE IN THE CONTROL OF SOME PLANT PATHOGENS

Abstract

Aloe plants, like other lilies are rich in phytochemicals which are known to have pronounced biological and physiological consequences for microbes. This study is aimed at determining the phytochemical constituents and the antimicrobial properties of the leaf and root extracts of four species of aloe on some pathogens of agricultural importance in order to determine the appropriate parental genotypes for breeding of new variety of aloe with more potent phytoconstituents. The four species of aloe used are Aloe keayi, Aloe macrocarpa var. major, Aloe schwenfurthii and Aloe vera. Their antibacterial properties were investigated using Bacillus cereus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa Pseudomonas syringae pv phaseolicola, Xanthomonas axonopodis pv. manihotis, Xanthomonas axonopodis pv. vignicola, Staphylococcus aureus while Sclerotium rolfsii, Trichoderma rubrum, Colletotrichum lindemuthiamum were used to investigate their fungicidal properties. Proximate analysis reveals that all the four aloe species under investigation are rich in nutrients but A. schwenfurthii can be stored for a longer period because it contains low amount of water. Phytochemical screening shows that the leaf and the root extracts of the four aloe species contain alkaloids, tanins, saponins, terpenoids, flavonoids, cardiac glycosides, phytates and oxalates. However, steroids are present only in the root and leaf of Aloe macrocarpa var. major and Aloe schwenfurthii. Though the study establishes that the four aloe species contain biorationals with antibacterial and antifungicidal properties, the phytochemicals are highly concentrated only in the root and leaf of A. marcrocarpa var. major and the root of A. schwenfurthii var. major. This presents A. macrocarpa var. major and A. schwenfurthii as the most suitable parental genotypes for the breeding of an aloe with more potent biocides.