Delivery Systems of Trichoderma Inoculants for the Control of Rhizoctonia Diseases in Brassica Rapa
Trichoderma spp were tested as a biocontrol agent against Rhizoctonia solani Kuhn on Brassica rapa. R. solani was isolated from infected vegetables and confirmed the pathogenic to three cultivars of Brassica causing pre-and post emergence damping-off. Confrontation assay, based on the inhibition...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2005
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| Online Access: | http://psasir.upm.edu.my/id/eprint/59/ http://psasir.upm.edu.my/id/eprint/59/1/1000548931_t_fp_2005_37.pdf |
| Summary: | Trichoderma spp were tested as a biocontrol agent against Rhizoctonia solani
Kuhn on Brassica rapa. R. solani was isolated from infected vegetables and
confirmed the pathogenic to three cultivars of Brassica causing pre-and post
emergence damping-off. Confrontation assay, based on the inhibition of mycelial
growth and colony overgrowth, showed different degrees of antagonism by
Trichoderma isolates to R. solani through competition and mycoparasitism. Two
primers (OPC-11 and OPC-15), and RAPD-PCR analysis were used to establish
the variability between the nine Trichoderma isolates. The results of which were
used to construct a Dendogram. OPC-11 generated 19 RAPD fragments
ranging from 200 bp to 3000 bp and OPC-15 generated 18 RAPD fragments
ranging from 300 bp to 4000 bp. They successfully grouped the Trichoderma
isolates into two main clusters as species aggregates viz. T. harzianum and T.
virens. The DNA polymorphism confirmed the identification based on cultural
and morphological characteristic. Two of the isolates T. harzanium (UPM40) and
T. virens (TV3) were found to establish well on and colonize the roots and
rhizospheres of B. rapa. The mixture substrate rice flour and molasses (1:4 RF:
ML w/v), incubated three days under shaked culture (100 rpm), was the best for
the inoculum production of both Trichoderma isolates. It produced the most
conidia (30 x 106 and 22.13 x 106 conidia / g dry mycelium) and mycelium (42.65
mg and 43.97 mg dry mycelium) for UPM40 and TV3, respectively, after only
three days incubation. The biomass production was highest at 30 oC incubation
temperature for both isolates. Further, desiccation for four days at this
temperature still produced good spore viability. UPM40 incorporated on oil palm
trunk and chicken dung (OPTCD) and stored at 28 oC and 20 % MC had a
significantly longer (P ≤ 0.05) shelf life than other treatments. The shelf lives of
the liquid antagonist preparations (UPM40 and TV3) on two food bases and
carriers (distilled water and ¼ strength 1:4 RF: ML medium) kept at 10 oC and
28 oC were also evaluated. UPM40 incorporated in the ¼ strength medium and
kept at 28 oC had a significantly longer shelf-life (P ≤ 0.05). The dry and liquid
formulations of UPM40 could reduce the population of viable R. solani colonies
in the infested soil. Both the applications were as effective as the fungicide
(Brassicol® 200 mg / L) in protecting the B. rapa against Rhizoctonia pre- and
post-emergence damping-off. Bio-coating the seeds of Brassica with similarly
reduced damping-off by R. solani |
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