| dc.description.abstract | Bacillus spp. were isolated from the surface of healthy bean roots. Greenhouse experiments
were conducted to determine the effect of Bacillus spp. on root-knot nematodes and plant
growth.Bean plants were treated with Bacillus isolates and nematodes and data on galling,
egg mass and biomas were recorded. The isolates tested had varying (P=0.05) effects, with
the majority of them reducing galling in beans. Out of 250 isolates evaluated, 93% reduced
galling when compared to the control (water) with 12% of them being were more effective
than carbofuran. Twenty percent of the isolates were found to promote plant growth. A
laboratory experiment was conducted to assess the effect of culture filtrates Bacillus spp on
mobility of second-stage Meloidogyne juveniles. Culture filtrates of the twenty Bacillus
isolates tested immobilized more than 80% of the juveniles treated.
Twenty Bacillus isolates were selected due to their high activity against root-knot nematodes.
The isolates were tested under sterile and non-sterile soil conditions. Galling and egg mass
indices were lower in sterile soil than in non-sterile soil conditions. Fewer juveniles were
recovered from sterile soil than in non-sterile soil.
The effect of selected Bacillus isolates on nodulation in beans was determined using
nitrogen-free sterile sand in the greenhouse. Nodulation was variably (P=0.05) affected by
treatment of bean plants with Bacillus spp. Four out of 20 selected isolates promoted
nodulation, eleven isolates had no effect while six isolates suppressed nodulation. Growth
promotion was confirmed in 17 out of the 20 Bacillus isolates selected from the preliminary
trial. A greenhouse test to assess the effect of combining Bacillus and Rhizobium spp. on
root-knot nematode showed varied reactions. Galling index was relatively lower in plant
treated with some Bacillus and the rhizobia inoculants. The lowest galling was recorded in
XIV
plant treated with Bacillus isolate K194 with a mixture of Rhizobium leguminosarum biovar
phaseoli and R. tropici.
Selected carriers (ondiri peat, filter mud, cow manure, charcoal dust, and compost) and
adhesives (methyl cellulose, sugar and gum arabic) were evaluated on their ability to support
high Bacillus populations during their application in nematode control. Charcoal dust as a
carrier mixed with Bacillus isolates was the most effective in nematode control, while cow
manure was the least effective. Application of Bacillus isolates using carriers resulted
significant (P=O.05) increased shoot and root weight as compared with the controls. Galling
index was low in plants treated with Bacillus isolates using gum arabic and sugar as
adhesives.
The potential Bacillus spp. as biocontrol agents of root-knot nematode, Meloidogyne spp. and
its ability to promote plant growth was demonstrated under greenhouse conditions. These
results show that Bacillus spp. can be incorporated in nematode management package.
Application of Bacillus spp. in root-knot nematode management would therefore have an
added advantage of enhancing nitrogen supply. Further work to determine the effect of these
isolates under field condition should be carried out. | en |
