Abstract:
The low country live wood termite, Glyptotermes dilatatus is an economically important
insect pest of low grown tea. The termite colony initiated by a pair of alates in rotted tea
stumps move to the heartwood by making feeding galleries. They disperse wood rot fungi
while feeding on heart wood of tea bush. The damage symptoms vary with the type of
cultivar. Objective of the present study is to study the chemical constituents in susceptible
and resistant cultivars.
Extracts of the debarked healthy stems of tea cultivars, TRI 2023 & TRI 4042 (susceptible)
and TRI 2027 & TRI 4049 (resistant) were evaluated for the antifeedant and antifungal
activities against G. dilatatus and Fusarium sp. which is common in the termite body, termite
galleries and rotted tea stems using no choice feeding bioassay and antifungal assay
respectively. Extract of TRI 2027 obtained using CHCl3 showed a higher antifeedant activity
(P<0.05, LSD) against G. dilatatus than that of TRI 2023, TRI 4042 or TRI 4049. The
highest antifungal activity was observed in the extracts of both resistant cultivars (TRI 2027,
TRI 4049) than that of susceptible cultivars (P<0.05, Tukeys mean separation test).
Fractionation of stem extract of TRI 2027 indicated that caffeine is one of the major bioactive
compounds that showing antifeedant and antifungal activities. Antifeedant and antifungal
activities were detected at 160 mg/ mL and 0.8 mg/ mL concentrations respectively. Mean
caffeine contents of heartwood of resistant and susceptible cultivars were quantified using
colorimetric method. Results revealed that the caffeine content of resistant cultivars TRI
2027 and TRI 4049 (0.52±0.26, 0.34± 0.07 mg/g) were greater ( t=3.28,df= 14, P=0.0055)
than that of the susceptible cultivars, TRI 2023 and TRI 4042 (0.21±0.08, 0.22±0.01 mg/g)
resulting a strong positive correlation between caffeine content and antifeedant and antifungal
activities of the extracts of heartwood of tea cultivars. Hence caffeine is proven to be
potential biochemical parameter to evaluate resistance of tea cultivars against G. dilatatus and
Fusarium sp.
