JASMONIC AND SALICYLIC ACIDS ENHANCE TOLERANCE IN OIL PALM SEEDLINGS INFECTED WITH Thielaviopsis ethacetica, CAUSING EARLY SYMPTOMS OF NECK BENDING DISEASE

Abstract

This study investigatedthe level of toleranceof oil palm seedlings toearly symptoms ofneck bending disease (caused by Thielaviopsis ethacetica) using elicitors. After a pathogenicity test, the experiment was laid out in a completely randomized experimental design consisting of  27 six-monthsold seedlings grown from Extension Work Seeds (EWS) at the Nigerian Institute for Oil Palm Research (NIFOR). The seedlings wereselected on the basis of uniformity (height, size, and leaf number)placed in treatment categories T1-T9 with triplicates: T1= Control (EWS alone), T2= EWS+ Fungus, T3= EWS + Jasmonic acid, T4= EWS + Jasmonic acid + Fungus, T5= EWS + Jasmonic acid + Fungus + N:P:K:Mg, T6= EWS + Salicylic acid, T7= EWS + Salicylic acid + Fungus, T8= EWS + Salicylic acid + Fungus + N:P:K:Mg and T9= EWS + N:P:K:Mg + Fungus.  The base of each seedling was inoculated with a mycelial  disc from a 72-hour old culture of Thielaviopsisethacetica on potato dextrose agar.After inoculation, elicitors (methyl jasmonate and salicylic acid)  and N:P:K: Mg were applied on the plants accordingly. Symptoms such as stem necrosis and frond discolouration were recorded while expression of pathogenesisgenes (EgCHI2, EgMT2, PR10, and EgEMLP) was investigated. Symptoms began tomanifest from the 5th day after inoculation while disease severity was higherin T2 seedlings. Gene expression was least in T3 (0.8035TPM)  and highest in T6 (5.4596 TPM) for shoot bases, and highest in T5 (0.68038 TPM), lowest in T4 (0.10388 TPM) for fronds, indicating  the biostimulation of defense byelicitors in the presence of T.ethacetica. Quantification of Eg CHI2 confirmed the accuracy of gene expression results.These findings indicate that jasmonic and salicylic acids may provide tolerance to oil palm seedlings infected with T. ethaceticato enable them withstand the disease.