where R1 represents the radius of the test fungus in the
direction with no bacterial colony, and R2 is the radius of
the fungal colony in the direction of the bacterial colony.
The antagonism due to volatile compounds was evaluated
by preparing a bacterial lawn on nutrient agar plates. After
incubation for 24 h, the lid was replaced by a plate
containing an agar block of the test fungus grown on potato
carrot agar (PCA). The two plates were sealed together
with parafilm. Control sets were prepared in similar
manner, without bacteria in the bottom plate. Such sealed
sets of petri dishes were incubated at 28 C. The PGI was
calculated using the formula: