Singh et.al.

chlorotic halo on the lower leaves giving a

Pathogenicity test

typical target board appearance (Vloutoglou and

All the collected isolates of Alternaria solani were

Kalogerakis 2000. It occasionally attacks the fruit,

tested for pathogenicity on susceptible tomato

producing large sunken black spots at the stem

cultivar CO-3 by foliar spray method to assess their

end,which drop prematurely leading to a severe

virulence under greenhouse conditions. Ten days

yield loss. Constant use of chemical fungicides

old cultures of different isolates were taken and

like mancozeb and chlorothalonil have given good

ground in 50 ml of distilled water using pestle and

control of the disease but indiscriminate use of

mortar and filtered through four layers of muslin

the same have resulted in pesticide residue in the

cloth in conical flasks. Separate flasks were used

fruits and environmental hazards (López-Pérez

for individual isolates and sterile condition was

et al., 2006). Soil inhabiting microbes co-existing

maintained throughout the experiment. The culture

in the same niche as the pathogens, are potential

suspension maintained approximately at 125 cfu/

tools for controlling the pathogens (Loganathan

ml was sprayed on the leaves and stem of tomato

et al., 2014) and they possess properties of plant

plants. In control treatments the plants were sprayed

growth promotion (Lahan et al. , 2012, Ratul et al

only with distilled water. Five replications for each

2013) as well. In the present investigation, several

treatment were maintained. Inoculated plants

rhizospheric organisms have been isolated and their

were kept in manually fabricated moist polythene

efficacy against early blight pathogen was studied

chamber in a glass house for 3 days. For maintaining

both in vitro as well as in glasshouse conditions.

the humidity, a humidifier was set up in the chamber,

Trichoderma sp, Pseudomonas sp., Aspergillus sp. and

and the temperature was maintained at 30 ± 1 ° C for

Bacillus sp proved to be antagonistic to the pathogen

the development of the symptoms. Observations

Alternaria solani . Based on this performance suitable

were made at regular intervals.The pathogenicity

formulations of these microbes, both singly and in

test as above was repeated twice to confirm the

consortium, will be developed which will drastically

results. Disease intensity was recorded as per 0-5 the

reduce the chemical load of the environment and

scale (Pandey et al., 2002). where, 0 = no infection,1=

will be a safe weapon in the arsenal of farmers to

< 10%- surface area covering leaf, stem, and fruit

ward off this obnoxious pathogen in the near future.

infected by early blight, 2= 11-25%- foliage of plant

Materials and Methods

covered with a few scattered spots, 3=26-50%- many

spot coalesced on the leaves, covering surface area of

Collection, isolation and purification of A.solani

plant, 4 = 51-75% area of the plants infected, fruit also

and bio control agents

infected at apical end, defoliation and blightening

started. Sunken lesions with prominent concentric

Tomato growing areas of different agro-climatic

rings on stem, petioles, and fruit, 5= < 75% area of

zones and adjoining areas were surveyed and tomato

plant part blighted, severe lesion on stem, and fruit

plant parts showing typical symptoms of Alternaria

rotting on apical end.

blight were collected and isolated on potato dextrose

agar medium (PDA) using standard procedure

Percent disease incidence was calculated following

(Kumara 2006).

Wheeler (1969) where,

Several rhizosperic microorganisms and endophytes

PDI= (Sum of numerical rating/Number of samples

were isolated from the rhizospheric soil samples as

observed X maximum rating in scale) x 100 and

well as phylloplane of solanaceous vegetables viz .

based on the reaction

i.e., PDI value (mean of

tomato, chilli and brinjal (Vieira et al., 2004) using

five replications), the isolates can be placed into

dilution plate technique on PDA, nutrient agar (NA)

different categories (0-10%-Weakly virulent,

and selective media for Trichoderma, Pseudomonas

11-29%-Moderately virulent, 30-49%- Virulent, >

and Bacillus respectively (Elad et al. , 1981).

50%- Highly virulent).

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