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) were
identified as sampling sites for banana plants to be used for endophytic fungi
isolation. Healthy appearing plants in heavily infested fields were sampled for
endophytic fungi isolation. Endophytic fungi were isolated from the plant roots,
the corm, pseudostem and the pseudostem base. A total of 2,455 Fusarium spp
isolates were isolated from the two regions. Fusarium oxysporum species was the
most prevalent endophytic fungi from banana roots and corm. They constituted
15.5% and 44.6% of all fungal isolates from Meru and Kilifi districts,
respectively. Twelve isolates belonging to F. oxysporum were selected for in
vitro bioassays against two major species of banana parasitic nematodes in the
two regions namely Pratylenchus goodeyi and Helicotylenchus multicintus. The
selected species of the endophytic fungi were cultured in Potato Dextrose Broth
(PDB) media for seven days. Fungal filtrates from the twelve isolates were
obtained after sieving and centrifuging the PDB media. One millilitre of the
filtrate was used for each treatment consisting of one hundred nematodes
suspended in 1 ml of distilled sterile water in sterile 5ml Bjorn bottles. Each
treatment was replicated three times and the experiment laid out in complete
randomised design. Mortality and paralysis were recorded after 3, 6 and 24 hours
time intervals. Corrected mortalities were calculated using Abbott’s formula. The
mortality significantly (p<0.0001) varied with the time of exposure. Culture
xiv
filtrates of F. oxysporum isolates significantly (p<0.0001) differed on their
mortality effects to the nematodes. Out of the total thirteen endophytic isolates
from Meru district, five isolates produced consistent mortalities and paralysis to
both P. goodeyi and H. multicinctus. These isolates included 5JTOC134,
5SOPB11, 4M0C321, 4SIC132 and 5MR11. Similarly five fungal isolates from
Kilifi district which demonstrated consistency in causing mortality and paralysis
were 7MIC334, 8SIC334, 11MOC143, 11SR23 and 11MOC353. The isolates
demonstrated potential biological activity against the major banana parasitic
nematodes, and can further be investigates as biological control agents against
these nematodes.
