ISOLATION AND SCREENING OF ENDOPHYTIC Fusarium oxysporum FOR BIOLOGICAL CONTROL OF NEMATODES IN TISSUE CULTURE BANANAS

Abstract

Two major banana growing regions namely Meru district (Altitude: 1050 Masl,06' 34S, 037o46' 23 E) and Kilifi (17 Masl 03'4S 0" 039° 40' 0" E) district) wereidentified as sampling sites for banana plants to be used for endophytic fungiisolation. Healthy appearing plants in heavily infested fields were sampled forendophytic fungi isolation. Endophytic fungi were isolated from the plant roots,the corm, pseudostem and the pseudostem base. A total of 2,455 Fusarium sppisolates were isolated from the two regions. Fusarium oxysporum species was themost prevalent endophytic fungi from banana roots and corm. They constituted15.5% and 44.6% of all fungal isolates from Meru and Kilifi districts,respectively. Twelve isolates belonging to F. oxysporum were selected for invitro bioassays against two major species of banana parasitic nematodes in thetwo regions namely Pratylenchus goodeyi and Helicotylenchus multicintus. Theselected species of the endophytic fungi were cultured in Potato Dextrose Broth(PDB) media for seven days. Fungal filtrates from the twelve isolates wereobtained after sieving and centrifuging the PDB media. One millilitre of thefiltrate was used for each treatment consisting of one hundred nematodessuspended in 1 ml of distilled sterile water in sterile 5ml Bjorn bottles. Eachtreatment was replicated three times and the experiment laid out in completerandomised design. Mortality and paralysis were recorded after 3, 6 and 24 hourstime intervals. Corrected mortalities were calculated using Abbott’s formula. Themortality significantly (p<0.0001) varied with the time of exposure. Culturexivfiltrates of F. oxysporum isolates significantly (p<0.0001) differed on theirmortality effects to the nematodes. Out of the total thirteen endophytic isolatesfrom Meru district, five isolates produced consistent mortalities and paralysis toboth P. goodeyi and H. multicinctus. These isolates included 5JTOC134,5SOPB11, 4M0C321, 4SIC132 and 5MR11. Similarly five fungal isolates fromKilifi district which demonstrated consistency in causing mortality and paralysiswere 7MIC334, 8SIC334, 11MOC143, 11SR23 and 11MOC353. The isolatesdemonstrated potential biological activity against the major banana parasiticnematodes, and can further be investigates as biological control agents againstthese nematodes