Molecular and Morphological Diversity of Arbuscular Mycorrhizal Fungi Associated with Carissa edulis along the Lake Victoria Basin of Kenya

Abstract

Carissa edulis is a tropical plant of Apocynaceae family that is commonly used for herbal medicine purposes. In Kenya, a study by Kenya Medical Research Institute (KEMRI) showed that an aqueous total extract preparation from the roots of C. edulis has remarkable anti-herpes simplex virus activity. Due to the medicinal value of the species, it is overexploited and its natural range is threatened and requires conservation interventions. Studies have shown that the species has beneficial relationships with Arbuscular mycorrhizal fungi (AMF) which acts as a biofertilizer, and can enhance restoration of its population. However, no study has been under taken to document the diversity of these fungal species within this pant species. This study aimed to determine molecular and morphological diversity of AMF in the roots of C. edulis within Lake Victoria region of Kenya. A cross sectional, laboratory based prospective study was carried out from the roots of C. edulis collected from 6 sites within the Lake Victoria region of Kenya. Replicate root samples were collected from each site. AMF was assessed by morphological characterization of the spores and sequencing of small sub unit rDNA. Four genera were identified morphologically which included Glomus, Acaulospora, Scutellospora and Gigaspora. Molecular analysis of 18S rDNA from the roots of C. edulis using nested PCR yielded the expected results of 1100 bp using NS1 and NS4 primer pairs and 800 bp by AML1 and AML2 primer pairs. RFLP results revealed band pattern of different sizes against 100 molecular marker implying molecular diversity of AMF. After sequencing and phylogenetic analysis using Mortierella zychae as an outlier, four genera were revealed but were not consistent with those of morphological analysis. These included Glomus, Acaulospora, uncultured Glomeromycotina and uncultured Rhyzophagus. In both the analyses Glomus and Acaulospora were identified of which Glomus was the most predominant genera. In all the six sampling sites there were good numbers of spores; 59% mean AMF spore count in the soil and 55.42% root AMF spore infection, confirming the association between C. edulis and AMF. Based on the findings of this study, further research should be done to identify more AMF genera that sporulate with C. edulis for potential application in its restoration. Besides, studies should be done to compare between SSU rDNA gene and internal transcribed spacer regions (ITS) genes would yield better result in molecular characterization of AMF.