Does rice fight back? total phenolics of TKMG and TN1 rice varieties as defense mechanism against rice stem borer (Scirpophaga innotata)
2018
Cacerez, J.C.A. | Abilgos-Ramos, R.G. | Dela Cruz, M.B. | Viz, J.A. | Pacada, I.G.
Phenolic compounds are secondary metabolites that play an important role in plant defense mechanism against pests and diseases. Rice stem borer (SB) is an important insect pest causing up to 30% yield loss. Thus, this study was conducted to evaluate the total phenolic content (TPC) of leaves and stems of resistant (TKM6) and susceptible (TN1) rice check varieties infested by SB. Screen house experiment was set up on PhilRice-Agusan. Samples were collected 36 days before and nine days after SB introduction. Total phenolic content (TPC) was determined using spectrophotometric method. Results showed that in comparison to the TPC values of samples before SB introduction, TPC of control and infested leaves of both check varieties decreased by 51.03% to 60.64% after SB introduction. A 12.84% and 11.07% decrease in TPC was also observed in the control stem of TKM6 and TN1, respectively. No significant change in TPC value was observed in infested TKM6 stem while a decrease of 28.04% was observed in infested TN1 stem. After SB introduction, higher TPC in the control leaves was observed in TKM6 than in TN1 while comparable TPC was observed in infested leaves of both check varieties. However, the TPC values of control and infested leaves of both TKM6 and TN1 had no significant differences. For controls stems, TN1 had higher TPC than TKM6. Higher TPC in infested stems was observed in TKM6 than in TN1. The TPC of infested TKM6 stem was 17.39% higher than the control while the TPC of infested TN1 stem was 19.09% lower than the control. The changes in TPC may demonstrate the role it plays in rice plant defense against herbivores such as SB.
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