Induction of defense responses in longkong fruit (Aglaia dookkoo Griff.) against fruit rot fungi by Metarhizium guizhouense

Abstract

The defense responses of longkong fruit were induced by an entomopathogenic fungus, Metarhizium guizhouense. The longkong fruits were dipped in a spore suspension of M. guizhouense PSUM04 at concentration of 104 spore mL−1 for 5s, then an enzyme assay, a protein assay and polyacrylamide gel electrophoresis (PAGE) were done. It was found that the longkong fruit presented small necrotic spots on their peels within 24h. β-1,3-glucanase and chitinase were detected in peel extracts at 1.33±0.09 and 0.12±0.004UmL−1, respectively. The sodium dodecyl sulphate (SDS)-PAGE showed protein bands that emerged after the fungal treatment when compared to untreated control. These proteins were a 25–27kDa group of chitinase isoforms, and β-1,3-glucanase at 43kDa. From gel diffusion method, crude extracted from the fruit peel inhibited the mycelial growth of Botrytis sp. and Fusarium sp. as 34.9±3.1 and 29.3±5.0%, respectively. Moreover, the observation from scanning electron microscope (SEM) showed abnormal shapes, twisting and cracking in both fungal mycelia and less dense mycelial growth for Fusarium sp. Thus, M. guizhouense PSUM04 was not only a bio insecticide but it was also be the biotic inducer of plant defense responses against pathogenic fungi.