Evaluation of suitable antagonists in the management of early blight of tomato cultivar CO-3

In vitro screening of rhizospheric microorganisms

(ALT-4), having concentration of approximately 125

and endophytes against Alternaria solani

cfu/ml was sprayed over the plants PDI was assessed

The rhizospheric microorganisms and endophytes

15, 30 and 45 days after, treatment following Wheeler

isolatedfromtherhizosphericregionandphylloplane

(1969) and percent disease control was calculated

respectively of infected plants were used against

using the following the formula of Kishore et al.,

highly virulent isolate of A. solani selected through

(2005)

pathogenicity test. Fourteen days old A. solani

C-T/C × 100, where C = disease developed in control,

isolate as well as the rhizospheric microorganisms

and T = disease developed in treatment

and endophytes were considered for dual culture

study following Sumana et al., (2012). Inoculation

Result and Discussion

was done by placing a disc of 5mm each of both, at

the two opposite extremes on Petri plates (90 mm.)

Collection, isolation and purification of pathogen

and a Petriplate comprising only of the pathogen

and bio control agents

( A. solani ) was also maintained as a control. The

Fourteen isolates of A.solani were collected from

plates were incubated at 28ºC±2ºc for six days. Three

different parts of India, isolated and purified and

replications for each treatment were maintained.

designated as ALT1, ALT2, ALT3, ALT4, ALT5,

Percent inhibition of mycelial growth for Alternaria

ALT6, ALT7, ALT8, ALT9, ALT10, ALT11, ALT12,

(figures in parenthesis in Table 2 indicates percent

ALT13, and ALT 14. Among the several rhizospheric

control) isolate against each antagonist as compared

microorganisms and endophytes collected, thirty

to pathogen control was calculated followingVincent

nine were isolated from the rhizosphere and

(1947).

phyllosphere of solanaceous crops. Out of these,

I=C-T/Cx100

28 were fungi and 11 were bacteria. Morphological

identification of these microbes revealed that 18

Where, I= Per cent inhibition of the mycelial growth,

were Trichoderma species (T1,T2,T3,T4,T5,T6,T7,

C= mycelial growth in control, T= mycelial growth in

T8,T9,T10,T11,T12,T13,T14,T15,T16,T17,T18),

10

treatment.

were Aspergillus species (F1, F2, F3, F4, F5, F6, F7, F8,

F9, F10), 6 were Pseudomonas species, (PS1, PS2, PS3,

Greenhouse evaluation of efficient antagonists

PS4, PS5, PS6), and 5 were Bacillus species (BAS1,

against A. solani

BAS2, BAS3, BAS4 and BAS5).

Based on in

vitro

screening of rhizospheric

microorganisms and endophytes against Alternaria

Pathogenicity test

solani, six (T-2, T-8, T-17, F-4, Ps-4 and BAS-

On the basis of pathogenicity test and degree of

2) efficient antagonists were evaluated for their

virulence of isolates were assessed and it was

efficacy as biocontrol against Alternaria blight under

observed that, out of 14 isolates of Alternaria solani ,

greenhouse conditions. Susceptible tomato variety

6 isolates (ALT-2, ALT-4, ALT-7, ALT-8, ALT-12 and

CO-3 (obtained from the Seed Production Unit,

ALT-14) were found highly virulent, 7 isolates (ALT-

Crop Improvement Division, IIVR, Varanasi) was

1, ALT-3, ALT-5, ALT-6, ALT-10, ALT-11 and ALT-

transplanted in pots containing sterilized soil and

13) were found to be virulent and 1 isolate (ALT-9)

sand mixture. Five replications for each treatment

was moderately virulent (Tab 1). Among the highly

were maintained. Culture suspension of the selected

virulent isolates, ALT4 had the maximum PDI;

antagonists was sprayed over the plants, each having

hence, it was used in further experiments, viz. in vitro

a concentration of 125 cfu/ml. After 72 hours culture

screening and green house experiments.

suspension of highly virulent isolate of A. solani

129