Lactic Acid Bacteria As Biocontrol Agent Against Pathogenic Fusarium Species On Chilli Plants
Chilli plants are easily infected by Fusar-iu n species and cause enormous loss of food products as well as plants worldwide. Therefore, a suitable method is required for prevention and reduction of Fuscn-irun species affecting chilli plants. This research explored the possibility of using lactic...
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| Summary: | Chilli plants are easily infected by Fusar-iu n species and cause enormous loss of food
products as well as plants worldwide. Therefore, a suitable method is required for
prevention and reduction of Fuscn-irun species affecting chilli plants. This research
explored the possibility of using lactic acid bacteria (LAB) as bio-control against
Fusarium species on chilli plants. A total of 21 LABs were isolated from different
sources 14 from soil, 7 from fermented chilli fruits and 3 ATCC strains. Four
Fusarium species were isolated from different plants parts and identified as Fusar-icun
oxvsporum f. sp. lycopersici, F. solani, F. acwwninatunr and F. proliferation. Screening
using dual overlay assay showed that 14 from 21 LAB isolates inhibited F-us. ar-iurn
species with zone of inhibition 4.0 to 60.0 mm after 48 h incubation at 28°C. The
supernatants of Lb. acidophilus ATCC314, Lb. plantarrun ATCC8014 and three other
LAB isolates were identified as Lb. plantaruml-LAB MSS1 (isolated from soil),
Pediococcus pentosaceusl-LAB MSS5 (isolated from soil) and Lb. plantaruml-LAB
FF11 (isolated from fermented chilli fruits) using API Kit and 16rDNA genotypic
identification showed strong antifungal activity against all targeted Fusariwn species.
The supernatants of five LAB isolates showed mycelial growth inhibition against all
Fusariran species especially F. solcrni CS (isolated from chilli seeds). The antifungal
activity of the LAB supernatants was affected by enzyme treatment; the antifungal
activity was in the range of 7.44 to 86.83% depending on LAB and Fusariwn species
Pepsin reduced the antifungal activity of supernatants LAB-CFS MSS 1, IDLAB6 and
FF11 against F. oxysporwn 1. sp. lycopersici- CL. The antifungal activity was
significantly (P<0.05) reduced by pH of supernatant. Loss of antifungal activity of
LAB supernatant was observed at pH 6 to 9, reduced at pH 2 and 5, but maintained at
pH 3 and 4. Heating LAB-CFS at temperatures 80°C and 90°C for 30 min and 121 °C
for 15 ruin resulted in loss of antifungal activity in MSS5, IDLAB6 and FF11 against
F. acu, ninatum-FC, while other LAB maintained the antifungal activity (3.09 to
97.75%) after 72 h incubation at 30°C. Application of LAB-CFS to seed prior to
sowing enhanced seed germination by 97% but not for seeds infected with the fungi;
the germination rate was reduced to 50.00%. However, chilli seeds treated with
supernatant of LAB-FFI I and cells of LAB-MSSI significantly (P<0.05) increased
the germination rate to about 98% even when the seeds were sowed in soils infected
with the fungi. Significant shoot and root elongation was observed when the seeds
were treated with CFS of LAB-FF 11 before sowing with an average of 11.60±0.57 cm
after 16 day incubation in the dark. Plants treated with LAB MSS 1 (group II) showed
broadest width canopy of 80.83±10.51 cm, significantly (P<0.05) higher compared to
LAB FF1 I (group IV) and other groups. Inoculating F. solani-CS to soil resulted in
abnormal growth of chilli plants (Group VI) and plant height reached 143.67±0.41 cm
than plants treated with LAB cells and control plants. Fungi infected plants showed an
increase in dry weight of plants (77.32 g) and the water content was 77.03% which
was less than plants from others group after 65 days of transplanting. The productivity
(number of fruits/plant) was significantly (P<0.05) higher (56.33±06.11) in plants
treated with LAB FF 1I (group IV) compare to other groups. Growth of plants without
LAB or fungi was slow and productivity was 2% per plant. Plants receiving treatments
LAB MSS1 (groups II) LAB MSSI and F. solani (group III), LAB FF11 (group IV),
and LAB FF11 and F. solarri (group VI) produced chilli fruits which ripened and
turned to red within 90 d, and plant growth continued until more than 110 d. However,
plant infected with F. solani (Group VI) started to show plant death after 65 days.
Both Fusarium species and the Lb. plantarum (MSS1 and FF11) LAB were found to
be endophytic in nature. Treatment of seeds and soil with selected LAB either as cells
or supernatant resulted in rapid growth of plants in the presence of Fusarium species
Therefore, this study demonstrated that selected LAB either cells or their supernatants
could be used as bio-control against Fusarium species infecting chilli plants. Treating
the seeds or soil using LAB either cells or supernatants enhanced plant growth,
improved the productivity of chilli plants and also suppressed the growth of F. solani. |
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