Plant growth promoting Bacillus species elicit defense
against Meloidogyne incognita infecting susceptible tomato in
polyhouse
Devindrappa,M1, Anju Kamra2, Dinesh
Singh3, Bharat Gawade4 and Anil
Sirohi2
Division of Crop Protection, Indian Institute of Pulse Research, IIPR,
Kanpur (UP), India
2 Division of Nematology, ICAR-Indian Agricultural Research Institute,
Pusa, New Delhi-110012, India
3. Division of Plant Pathology, ICAR-Indian Agricultural Research
Institute, Pusa, New Delhi-110012, India
4. Division of Plant Quarantine, ICAR- National Bureau of Plant Genetic
Resources, Pusa, New Delhi -110012, India
Correspondence: Anju Kamra, Division of Nematology, ICAR-Indian
Agricultural Research Institute,Pusa, New Delhi-110012, India. Email ;
anjukamra@yahoo.comABSTRACT Plant mediated induced systemic resistance against the plant-parasitic
nematode, M. incognita infecting tomato cv Pusa Ruby was
evaluated on application of four nematicidal rhizobacterial isolates
(Bacillus subtilis, B. pumilus, B. megaterium andB. cereus) as elicitors and compared with the application of a
chemical nematicide, Velum Prime. The bioefficacy trial was conducted in
pots preinoculated with the above isolates followed by M.
incognita inoculation in tomato to observe the reduction in nematode
infection at 60 days and effect on photosynthetic and transpiration
rates. The mechanism of induced resistance was assessed using qRT-PCR
for quantification of three key defense genes (PR-1b, JERF3 and CAT) at
0,2,4,8 and16 days after inoculation (DAI). The defense enzymesviz., super oxide dismutase (SOD), polyphenol oxidase(PPO),
peroxidase (PO), and phenylalanine ammonia lyase (PAL) were quantified.
Significant reduction in per cent root galling viz. 91.95 in B.
subtilis, 84.21 in B. pumilus, 83.70 in B. megateriu and
81.8 in B. cereus, was observed compared to control. The
reproduction factor was the lowest (15.83) in B. subtilis,
followed by B. pumilus (21.00), compared to 48.16 in control,
with enhanced photosynthetic and transpiration rates. The defence genes,
PR-1b, JERF3 and CAT were expressed at 2.5 to 7.5 folds in
rhizobacterial treated plants, but not in Velum Prime treatment. The
increase in enzyme levels (μmol/mg protein) for SOD was from 1.5 to
17.5, PPO from 2.1 to 7.8, PO from 1.8 to 10.2, and PAL from 1.8 to 8.7
during 0 to 16 DAI.Abbreviations:CAT,catalase; cfu/ml, colony‐forming units per millilitre; J2 second
stage juvenile, MEGA 6,Molecular Evolutionary Genetics Analysis version
6.0; NA, Nutrient agar; NCBI, National Centre for Biotechnology Centre;
PAL, Phenylalanine ammonia lyase; PGPR, Plant growth promoting
rhizobacteria; PPO, Polyphenol oxidase; PR, pathogenesis related; SOD,
superoxide dismutase
1.INTRODUCTION
The root-knot nematode, Meloidogyne incognita is a serious
constraint to crop production and causes significant damage to vegetable
crops worldwide (Gowda et al ., 2019; Perry and Moens 2013). Under
protected cultivation, losses in tomato range from 25-100 per cent
(Phani et al ., 2021,Seid et al , 2015).The nematode is an
endoparasite that feeds on the plant roots withdrawing nutrients from
the hosts, leading to weakening of entire plant and reducing
productivity. Chemical nematicides have been used for soil application;
but these are gradually being withdrawn from the global market due to
hazardous effects on human health and environment (Xiang et al .,
2018). There is a need for environment friendly and economically
feasible strategies for nematode management. The rhizobacteria suppress
the nematodes by release of toxins, antibiotics and enzymes that
interfere with the recognition patterns of nematode with its host
(Subedi et al., 2020). Several rhizobacterial species such asBacillus spp., Pseudomonas spp., Rhizobiumand,
Burkholderia, Agrobacterium radiobacter , Streptomyces spp. have
been reported to suppress M. incognita by eliciting induced
systemic resistance (Khanna et al ., 2019). The present study was
undertaken to determine the potential of four rhizobacterial isolates
(Bacillus pumilus , B. megaterium , B. subtilis andB. cereus ) which were isolated from nematode infested polyhouses
and found to be nematicidal (Devindrappa et al . 2022); in induced
systemic resistance for suppression M. incognita in tomato, by
observing upregulation in defense related genes. The validation was
conducted using qRT-PCR at 4 time intervals, after rhizobacterial
inoculations. The above parameters were also examined in plants treated
with the chemical pesticide, Velum Prime.
MATERIALS AND METHODS