Indication of oil palm (Elaeis guineensis Jacq.) resistance to curvularia leaf spot disease by pr-proteins producing ability

Abstract

Curvularia leaf spot disease of oil palm seedlings caused by Curvularia oryzae is an important disease and widespread in South-east Asia. In this study, the resistance of oil palm C. oryzae was indicated after treatment with 106 spores ml-1 of C. oryzae NK1. The PR-proteins (chitinase and β-1,3-glucanase) were detected within 24 hr. From the inoculated oil palm seedlings, lines 129 and 187 were indicated as susceptible and resistant lines, respectively based on activities of the pathogenesis-related (PR)-proteins. The chitinase and β-1,3-glucanase activities of line 187 were 14.03 ± 0.87 and 13.51 ± 1.04 U ml-1, while the respective activities of line 129 were much lower at 3.76 ± 0.41 and 4.31 ± 0.83 U ml-1 and not significantly different from control plant. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed accumulation of 22, 25 and 33 kDa in inoculated line 187, whereas protein bands of line 129 were not visible. The disease symptoms in the susceptible line appeared approximately on 10% of the leaf area after 72 hr of fungal inoculation while no leaf spot symptoms were visible in the resistant line. Thus, the resistance of oil palm against Curvularia leaf spot disease was successfully indicated based on PR-protein producing ability, prior to testing with inoculation.