A comparative study on Genetic Profiles and Repellent effects of murraya koenigii from four Regions in Kenya on anopheles gambiae s.s.

Abstract

Ethnobotanical analyses highlight therapeutic and chemotypic variations of geographically and ecologically diverse Murraya koenigii (Spreng) samples. However, the genetic correlation of this observation remains obscure. The present study aimed at studying the intraspecific genetic variation of Murraya koenigii and the possible effect on the bioactivity of volatiles of plant samples collected from four different geographical locations of Kenya. Genomic DNA isolated from various plant samples were screened for plastid maturase K (matK) gene polymorphisms within and among populations to estimate genetic diversity and phylogenetic relationships. Further, oils from the plant samples were tested for repellent activity against Anopheles gambiae s.s using a WHO established protocol. A total of 5 unique haplotypes that exhibited relatively moderate genetic variations were established. The overall nucleotide (π) and haplotype (Hd) diversities were estimated to be 0.04162 and 0.613, respectively. Despite relatively high non-synonymous substitutions in non-synonymous segregating sites, dN/dS ratio of 0.8924 (< 1) depicted evolutionary influences of purifying selection. Phylogenetic analysis revealed close genetic relations (less than 0.01) separate from the GenBank accession sample. There was a significant variation in mosquito repellency of oils obtained from Murraya koenigii collected from the four geographical locations. At 0.1g/ml, Malindi extract and Kibwezi extract had complete repellence at 100%, followed by Makindu extract at 97.6% and Mombasa extract at 72.7%. At 0.01g/ml, the percentage of effectiveness declined to 84.6% for Malindi extract, 97.5% for Kibwezi extract, 56.6% for Makindu extract, and 33.3% for Mombasa extract. Samples from Kibwezi maintained their effectiveness at the rest of the concentrations (45.2% at 0.001g/ml, 52.1% at 0.0001g/ml, and 35.9% at 0.00001g/ml). Malindi samples’ percentage effectiveness was 55.6% at 0.001g/ml and 25.5% at 0.0001g/ml while Mombasa samples’ percentage effectiveness was 17.1% at 0.001g/ml. Lowering concentration reduced the repellent effect of the extract in a varying manner with Mombasa extracts showing the highest reduction in repellency with reducing concentration. These findings suggest that irrespective of geographical origin, evolutionary forces of purifying selection on matK nucleotide sequence influenced the Kenyan Murraya koenigii genetic variation and bioactivity of plant volatiles.