Abstract
Brown rot of potato caused by Ralstonia solanacearum is an emerging threat to produce quality
potato in Bangladesh. An investigation was made to record the status of brown rot of potato and
the status of R. solanacearum in soils of different potato growing areas of Bangladesh, to assess the
genetic diversity of brown rot pathogen, R. solanacearum and to develop a management strategy to
produce quality potato.The maximum latent infection of 75% of R. solanaceaum was detected in
tuber samples collected from Thakurgaon followed by Mymensingh (55%), Rangpur and
Joypurhat (50%) while 32.5% latent infection was recorded in tubers collected from Rajshahi
followed by by Sherpur (33.67%), Cumilla and Chandpur with similar (38.33%). Virulent and
avirulent population of R. solanaceaum were recorded at (281.7x106CFU per g soil) and (445x106
CFU per g soil), respectively in rhizosphere soils collected from Thakurgaon. Significantly lower
virulent and avirulent R. solanaceaum populations were recorded at (1.9x106CFU per g soil) and
(15x106 CFU per g soil) in soils of Joypurhat and Lalmonirhat, respectively. Regression analysis
revealed a positive correlation between R. solanacearum population and percent latent infection of
potato tubers. Pathogenic bacteria from all groups produced pink or light red color colonies 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 Y-2
/OLI-1 primers and all the test isolates produced 288 bp fragment length. Results of biotype and
race determination showed that all the isolates of R. solanacearum belong to race 1 & 3 and biotype
1 & 3. Phylogenetic relationship on the basis of combined REP and ERIC-PCR analyses showed
that R. solanaceaum isolates obtained from soils and tubers collected from different potato growing
areas are distributed into 4 clusters. Cluster 1 consists of 22 isolates, cluster 2 consists of 2 isolates,
cluster 3 cluster 4 with 1 isolate each. There is no relationship between phylogenetic groups as well
as biovar and races. Considering REP, ERIC and BOX IR markers, 46% of the total isolates are
genetically identical which are belong to cluster 1 and 54% of the total isolates are genetically
different which are belong to cluster 2, 3 and 4 of these markers. Single application of mustard
based biofumigation and Bioderma were more effective than combined application of these
treatments in reducing latent infection of potato with R. solanacearum. Soil amendment made a
significant reduction in latent infection of tubers by R. solanacearum. In case of BARI Alu-13
(Granola), the maximum (94.67%) percent reduction of latently infected potato tubers with R.
solanacearum over control were obtained from mustard biofumigated plots and in case of BARI
Alu-54 (Mujika) and BARI Alu-55 (Red Fantacy), the maximum (89.77 and 81.6%) reduction of
latent infection as compared to control was observed in Bioderma applied plot considering both
year 1 and 2. The maximum (78.19, 63.44 and 72.06%) reduction of R. solanacearum population over
control was obtained from mustard biofumigated plot in case of BARI Alu-13 (Granola), BARI
Alu-54 (Mujika) and BARI Alu-55 (Red Fantacy), respectively considering both year 1 and 2. The
tubers of the two varieties carried significantly different size of population of R. solanacearum. In
case of BARI Alu-13 (Granola) and BARI Alu-55 (Red Fantacy), the maximum (32.25 and 30.18
ton/ha) yield was obtained from vermicompost amendend soil and in case of BARI Alu-54
(Mujika), the maximum (31.20 ton/ha) was observed in Bioderma applied plot considering both
year 1 and 2. The maximum BCR (1.37, 1.33 and 1.24) and (1.19, 1.18 and 1.04) were calculated
from Bioderma and mustard biofumigated applied plot in case BARI Alu-13 (Granola), BARI Alu54 (Mujika), and BARI Alu-55 (Red Fantacy), respectively. The findings of this investigation
indicate latent infection of potato tubers and R. solanacearum population varies in different regions
of Bangladesh. Latent infection of potato tubers with R. solanacearum causing brown rot of potato
can be reduced significantly through soil amendment with only mustard based biofumigation or
application of Bioderma for producing quality potato through minimizing R. solanacearum
population in soils of Bangladesh. However, further investigations are required to unravel the
complex genetic makeup of R. solanacearum and to assess the performances of mustard based
biofumigation or Bioderma either alone or in combination along with other suitable cultural,
biological and chemical control methods for producing quality potato that will completely be free
from latent infection of R. solanacearum.