Effect of Metarhizium anisopliae (MetA1) on growth enhancement and antioxidative defense mechanism against Rhizoctonia root rot in okra

Afsana Akter Mimma; Tanjina Akter; Md Ashraful Haque; Md Abdullahil Baki Bhuiyan; Md Zahid Hasan Chowdhury; Sharmin Sultana; Shah Mohammad Naimul Islam

doi:10.1016/j.heliyon.2023.e18978

Effect of Metarhizium anisopliae (MetA1) on growth enhancement and antioxidative defense mechanism against Rhizoctonia root rot in okra

Heliyon. 2023 Aug 12;9(8):e18978. doi: 10.1016/j.heliyon.2023.e18978. eCollection 2023 Aug.

Authors

Afsana Akter Mimma¹, Tanjina Akter¹, Md Ashraful Haque¹, Md Abdullahil Baki Bhuiyan², Md Zahid Hasan Chowdhury¹, Sharmin Sultana¹, Shah Mohammad Naimul Islam¹

Affiliations

¹ Institute of Biotechnology and Genetic Engineering, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh.
² Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh.

Abstract

Rhizoctonia solani is an important necrotrophic pathogenic fungus that causes okra root disease and results in severe yield reduction. Many biocontrol agents are being studied with the intent of improving plant growth and defense systems and reducing crop loss by preventing fungal infections. Recently, a member of the Hypocrealean family, Metarhizium anisopliae, has been reported for insect pathogenicity, endophytism, plant growth promotion, and antifungal potentialities. This research investigated the role of M. anisopliae (MetA1) in growth promotion and root disease suppression in okra. The antagonism against R. solani and the plant growth promotion traits of MetA1 were tested in vitro. The effects of endophytic MetA1 on promoting plant growth and disease suppression were assessed in planta. Dual culture and cell-free culture filtrate assays showed antagonistic activity against R. solani by MetA1. Some plant growth promotion traits, such as phosphate solubilization and catalase activity were also exhibited by MetA1. Seed primed with MetA1 increased the shoot, root, leaves, chlorophyll content, and biomass content compared to control okra plants. The plants challenged with R. solani showed the highest hydrogen peroxide (H₂O₂) and lipid peroxidation (MDA) contents in the leaves of okra. Whereas MetA1 applied plants showed a reduction of H₂O₂ and MDA by 5.21 and 14.96%, respectively, under pathogen-inoculated conditions by increasing antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), glutathione S-transferase (GST), and ascorbate peroxidase (APX), by 30.11, 10.19, 5.62, and 5.06%, respectively. Moreover, MetA1 increased soluble sugars, carbohydrates, proline, and secondary metabolites, viz., phenol and flavonoid contents in okra resulting in a better osmotic adjustment of diseases infecting plants. MetA1 reduced disease incidence by 58.33% at 15 DAI compared to the R. solani inoculated plant. The results revealed that MetA1 improved plant growth, elevated the plant defense system, and suppressed root diseases caused by R. solani. Thus, MetA1 was found to be an effective candidate for the biological control program.

Keywords: Antioxidant enzyme activities; Biological control; Metarhizium anisopliae; Okra; Rhizoctonia solani.