Exploration of natural products from botanicals and fungal root endophytes for the management of cowpea mosaic virus
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Date
2017
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Department of Plant Pathology, College of Agriculture, Vellayani
Abstract
The present study entitled “Exploration of natural products from botanicals and fungal root endophytes for the
management of Cowpea mosaic virus” was carried out at Department of Plant Pathology, College of Agriculture, Vellayani
during 2014-2016, with the objective to develop serological and molecular tools for the early detection of Cowpea mosaic
virus; and its management using natural products from botanicals and fungal root endophytes.
Cowpea mosaic virus was maintained in local lesion host Chenopodium amaranticolor and cowpea (Vigna
unguiculata var. sesquipedalis (L.) Verdcourt) variety Sharika by mechanical inoculation. On the newly emerged trifoliate
leaves of cowpea, typical symptoms like mosaic and vein banding followed by leaf distortion were expressed seven days
after inoculation (DAI). In C. amaranticolor, symptoms were expressed five DAI and on the inoculated leaves, localized
yellow chlorotic lesions were observed. Fungal root endophytes Piriformospora indica and Fusarium pallidoroseum were
maintained by continuous subculturing in Potato dextrose agar medium. The P. indica produced nine centimetre radial
growth on nine DAI whereas F. pallidoroseum produced nine centimetre radial growth on five DAI in petri dishes.
Serological studies carried out using Direct antigen coating – Enzyme linked immunosorbent assay (DAC-ELISA)
and Dot immunobinding assay (DIBA) and molecular detection viz., Reverse transcription-polymerase chain reaction (RT-
PCR), identified the mosaic causing virus in cowpea as Blackeye cowpea mosaic virus (BlCMV).
Botanicals for the management of BlCMV were first screened on C. amaranticolor to find out their efficiency.
Among the seven botanicals, Phyllanthus niruri recorded more than 80 per cent inhibition of local lesions in C.
amaranticolor even at one per cent concentration. Highest inhibition (94.84 per cent) was observed for pre inoculation
application of P. niruri at five per cent concentration.
Standardization of co-cultivation method for the fungal root endophytes with C. amaranticolor and cowpea were
conducted in jam bottles but no colonization of any fungal endophytes were observed in both C. amaranticolor and
cowpea. Colonization studies in vermiculite-perlite (3:1) medium at the rate of 1% (w/v) conducted in protrays showed no
colonization during the co-cultivation studies of F. pallidoroseum with both cowpea and C. amaranticolor. In case of P.
indica, no colonization was observed for C. amaranticolor whereas 40.70 per cent root colonization was recorded in
cowpea.
In a study conducted to determine the effect of age of seedlings on colonization pattern observed using compound
microscope, the highest efficiency (42.30 per cent) was recorded for five day old seedlings at twenty days after
co-cultivation. Root biomass, number of secondary roots, tertiary roots, number of leaves and leaf area also showed high
values for five day old seedlings at twenty days after co-cultivation whereas shoot biomass and root hairs per unit area
showed highest values for seven day old seedlings at twenty days after
co-cultivation.
The best antiviral principle (AVP) and fungal endophyte viz., Phyllanthus niruri and Piriformospora indica
respectively were evaluated in cowpea against BlCMV. Vulnerability of cowpea plants to BlCMV was found to reduce
with P. niruri and P. indica treatments compared to that of control plants.
The biochemical analysis to study the mechanisms involved revealed that cowpea plants pre inoculated with P.
niruri was found to be superior followed by pre inoculation treatment with P. indica except for total sugar where maximum
values for healthy was followed by pre inoculation treatment with P. niruri. Many defense and pathogenesis related (PR)
proteins were induced in response to various treatments. The induction of novel proteins were more in cowpea leaves
which were treated with P. niruri and P. indica than in control plants.
Thus it is proved by serological and molecular detection methods that the virus causing mosaic disease in cowpea is
BlCMV. For the management of this virus pre inoculation treatment of P. niruri (extract of one gram sample in 100 ml
water) and pre inoculation treatment of P. indica (one gram mycelia in 100 ml vermiculite-perlite media) has been proved
to be effective. It can be further validated under field condition.
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