DIVERSITY OF NEMATODES AND ENDOPHYTIC FUNGI ASSOCIATED WITH BANANAS CULTIVATED IN TAVETA SUB COUNTY

Abstract

Plant-Parasitic Nematodes (PPN) are small wire-like multicellular soil-inhabiting living organisms. A great proportion of these PPN are capable of causing enormous destruction to almost all cultivated crops in the tropics and subtropics. Banana PPN is root invading thus, causing destruction to primary roots in form of lesions and knots. This could hamper water flow and nutrient uptake, compromising plant stability and overall crop performance and culminating in yield losses of up to 85%. Although there exist antagonistic fungal and bacterial endophytes that could suppress the population of PPN and reduce their negative impact, the occurrence and densities of these endophytes are yet to be studied and documented. In this study, a random survey of farmers’ fields in the Taveta sub-county was carried out to evaluate the occurrence and distribution of nematodes and endophytes. Banana farms were randomly selected from the four wards Mahoo, Mboghoni, Bomeni, and Mata based on the willingness of the farmer to voluntarily participate in the research. On each farm, soil and banana roots samples were collected from three randomly selected stools where nematodes were quantified. In addition, endophytes diversity associated with these orchards were isolated and characterized with emphasis on the colony and cell morphology, and phylogenetic affiliation using partial sequences of the Internal Transcribed Spacer region (ITS) gene. The efficacy and effectiveness of biological control methods to suppress nematodes were evaluated in banana stools found to harbor nematodes above a certain threshold (index ≥ 10) using cowpeas intercrop and, application of Tithonian plant extracts and Nimbecidine® biopesticides. Cowpeas intercrop, Tithonian plant extracts and Nimbecidine were effective in suppressing the population of RKN, Helicotylenchus, Tylenchus, Pratylenchus, Aphelenchoides, Aphelenchus and Tylenchorychus while increasing the population of the free-living organisms, which further reduces the population of PPN.  Results of partial sequence analysis indicated the fungal endophyte isolates that were recovered from the samples collected from selected banana orchards to belong to the fungal domain, 90 % being affiliated to Ascomycota phylum. The key genera identified as next neighbors in BLAST comprised Penicillium, Mortierella, Aspergillus and an uncultured fungal genus with a range of identity scores of 95 – 100%.