Plant Growth-Promoting Potential of Endophytic Fungi (PGPEF) isolated from Avicennia marina in enhancing growth parameters of chili plants

Abstract

Endophytic fungi are known to produce a wide range of bioactive secondary metabolites, including phytohormones that promote plant growth through various mechanisms. This study aimed to identify and characterize Plant Growth-Promoting Endophytic Fungi (PGPEF) associated with Avicennia marina and to evaluate their potential as bio inoculants for enhancing seed germination and growth performance of chili plants under greenhouse conditions. Putative fungal endophytes were isolated from tissues of A. marina collected from the Batticaloa Lagoon, Sri Lanka, and assessed for their production of plant growth-promoting hormones, namely indole-3-acetic acid (IAA) and gibberellic acid (GA). Based on its phytohormone production levels, a promising isolate, AVEN 01 (identified as Fusarium sulawesiense through ITS sequencing), was selected for cross-inoculation into chili (Capsicum annuum) plants under controlled pot-scale conditions to evaluate its effects on plant growth parameters. Chili seeds were surface sterilized, treated with a systemic fungicide for four hours, and then primed in a fungal mycelial suspension of F. sulawesiense for 12 hours before sowing. Seedlings were transplanted into sterile pots containing sterile potting mixture (T1), pots containing sterile potting mix inoculated with F. sulawesiense (T2). T1, T2 and control (T3 - seeds treated with systemic fungicide and sown in sterile potting mix), were maintained under greenhouse conditions (30 °C, 70% relative humidity, 8:16 hours light/dark photoperiod). Treatments were arranged in a completely randomized design with eight replicates. One-way ANOVA revealed that T2 showed significant results (p<0.05) in germination and plant growth parameters. By 12 weeks (during harvesting), T2 exhibited the highest values for plant height (42.25 ± 1.81 cm), leaf number (116.5 ± 5.55), chlorophyll content (55.19 ± 3.82 SPAD units), stem diameter (2.20 ± 0.10 mm), number of flowers (25.87 ± 1.88), number of pods (20.75 ± 2.25), and pod length (5.75 ± 0.13 cm). T2 showed around 1.5 times higher values on its parameters when comparing control and other treatments. These findings highlight the potential of F. sulawesiense as an effective PGPEF for enhancing chili growth under controlled conditions.