Total Phenolic Content, Peroxidase and Polyphenoloxidase Activities in Ganoderma Infected Oil Palm Seedlings – Inoculated with Arbuscular Mycorrhiza Fungi (AMF)

Basal stem rot disease caused by Ganoderma boninense is the most predominant disease of oil palm plantations in Southeast Asia. Although an effective method for controlling the disease is elusive, research towards early detection and remedy for disease control measures remains crucial for plantation operation. Arbuscular mycorrhiza fungi (AMF) offers a practical alternative that should be seriously considered and implemented. This study evaluated the enzyme activities (TPC, PPO, PO activity) in oil palm seedlings inoculated with arbuscular mycorrhizal fungi (AMF) and infected with G. boninense. Artificial inoculation was conducted using oil palm germinated seeds in the nursery, and plant responses were analysed at 8, 12, 16, and 20 weeks of post-inoculation (WPI). At 20 WPI, the highest accumulation of total phenolic content (TPC) was recorded in T3 (AMF + G. boninense) with 6.09 mg/g compared to T1 (untreated), T2 (G. boninense), and T4 (AMF), which recorded TPC of 3.24 mg/g, 4.19 mg/g and 3.87 mg/g respectively with no significant difference indicating the natural presence of phenol compound in healthy tissue at concentration enough for defense, whether as free compound or in the conjugated form which released after the attack. Both T2 and T3 showed higher peroxidase (PO) levels with 122.8 unit/g tissue and 116.5 unit/g tissue compared to T1 (73.63 unit/g tissue) and T4 (80.6 unit/g tissue). The polyphenoloxidase (PPO) activity was also higher in both T2 (142.3 unit/g tissue) and T3 (111.7 unit/g tissue) compared to T1 (55.3 unit/g tissue) and T4 (36.3 unit/g tissue). Seedlings treated with AMF also showed increased plant growth compared to untreated seedlings. It was observed that T3 seedlings with AMF prophylactic treatment showed the highest chlorophyll content even with G. boninense infection.