Abstract
An investigation was made to develop a management strategy to control bacterial wilt of
in
eggplant, tomato and chili by using Brassica mediated biofumigation. For this, a survey was
conducted to dertermine the status of wilt incidence and severity in the major growing areas of
these three crops. The highest incidence of wilt in eggplant, tomato and chili was 70.60%
Jamalpur, 70.53% in Netrokona and 71.67% in Netrokona. The lowest wilt incidence 30, 40 and
15.47% were in Rangpur, Dinajpur and Mymensingh, respectively. The highest severity (scale of
1-5) was 5.00 in Jessore and 4.72 and 4.57 were in Kishoreganj for above crops. The lowest wilt
severity 2.65, 3.56 and 2.93 were observed in Panchagarh, Dinajpur and Mymensingh of that
crops, respectively. Pathogenic bacteria from all groups produced pink or light red color
colonies or characteristics red color colonies with whitish border on TTC medium indicated that
all isolates of R. solanacearum were virulent and confirmed by biochemical tests. Species-specific
confirmatory test of R. solanacearum was also performed by PS-1/PS-2 and Y-2 /OLI-1 primers
and all the tested isolates produced 553 bp and 288 bp fragment length. Isolates showed
positive reaction in HR test. Results of biotype and race determination showed that all the
isolates of R. solanacearum belong to race 1 and biotype 3. Dendrogram based on banding
pattern of ERIC primers showed that isolates RsT-98 and RsC-80 were high genetically
diversified and grouped into cluster 1 and cluster 2 whereas isolates RsT-19 and RsT-52 were
close to each other and placed into same sub sub group. Similarly dendrogram of REP primers
implied that isolates RsB-236 and RsB-168 were genetically diversified with the isolates of RsB222, RsT-19 and RsT-52 included in cluster 1 and cluster 2 and isolates RsB-277 and RsC-100
showed low genetic diversity and placed in same sub sub group. Likewise, dendrogram based
on BOX IR primer indicated that isolates RsB-277 was genetically diversified with the isolates of
RsB-79 and RsB-267 and placed in cluster 1 and cluster 2 while isolates RsB-168, RsC-48, RsT-78
and RsC-80 were closest to each other and placed in same group. Same aggressiveness groups
of isolates were not confined in the same cluster rather it was distributed in the clusters
randomly, indicated the genetic and geographical variation of the host. The lowest wilt
incidence was recorded from single mustard and radish biomass incorporated plots but wilt
incidence was more decreased in mustard +radish biomass added+ oxysentin drenched plots
and it was 8.33% and 4.17%, respectively. Wilt incidence decreased by 71.44%, 66.68% and
77.79% over control were in mustard and radish biomass added plots whereas wilt incidence
got more decreased in mustard +radish biomass added + oxysentin drenched plots with the
value of 86.10%, 83.32% and 88.88% in eggplant, tomato and chili respectively. Bacterial
population per gram soil was lowest in mustard biomass treated plots with 4.43x107, 11.57x107
and 5.82x107 CFU but these number were found lower in mustard + radish biomass added +
+
It
oxysentin drenched treatment with 0.94x107, 0.39x107 and 0.93x107 CFU of these crops,
respectively. Similarly bacterial population decreased over control was 86.91%, 84.79% and
77.66% in mustard biomass added plots and 76.02%, 83.32% and 56.74% was from mustard
radish biomass added + oxysentin drenched treatment in eggplant, tomato and chili.
indicated that biofumigation reduced bacterial population which leads lower wilt incidence. No
bacterial growth was observed in in vitro test after 24 and 48 hours of inoculation with
allylisothiocyanate at different concentrations. Maximum growth inhibition zone 33.33, 15.00
and 9.33 mm was observed in oxysentin, thymol and hemoxy after 96 hours, respectively. The
highest concentration of allyisothiocyanate 122.50 ng per gram soil was obtained from mustard
+ radish biomass incorporated plot through HPLC followed by 109.00 and 105.40 ng AITC per
gram soil from mustard and radish biomass incorporated plots. Highest fruit yield 62.81, 39.27
and 19.59 t/ha and 50.57, 47.92 and 15.30 t/ha were recorded from mustard biomass added and
mustard + radish biomass added + oxysentin drenched treatments in eggplant, tomato and
chili, respectively. Yield increased by 186.41%, 128.98%, 117.67% and 175.89%, 26.40% and
65.46% over control in the same treatments. BCR was also found highest in mustard biomass
added and mustard + radish biomass added + oxysentin drenched plots with the value of 8.57,
3.22, 2.23 and 6.86, 4.15, 1.73 in eggplant, tomato and chili, respectively