Padina gymnospora: A promising phyto elicitor for managing cluster bean anthracnose

Cluster bean (Cyamopsis tetragonoloba) is a vital leguminous crop cultivated worldwide, valued for its diverse values in culinary and medicinal uses. Despite the economic significance, the crop faces substantial yield losses due to anthracnose, a fungal disease in cluster bean incited by Colletotrichum lindemuthianum. This study assesses the efficacy of different seaweed extracts in suppressing fungal growth and controlling cluster bean anthracnose under in vitro conditions. Field experiment was conducted using randomised block design (RBD) in Annamalai Nagar, Cuddalore District, Tamil Nadu, involving eight treatments, including an untreated control group. Among the tested extracts, P. gymnospora (brown seaweed) exhibited the highest inhibition rates, ranging from 85.31 % to 86.54 % at 30 % concentration. Comprehensive field trials were conducted, wherein P. gymnospora was applied as foliar spray at 30 % concentration at 50, 70 and 90 days after planting. This application strategy substantially reduced anthracnose incidence by 30.16 %, 49.58 % and 64.45 % on 60th, 80th and 100th days, respectively. These findings strongly suggest that P. gymnospora is a potent bio agent that can effectively manage cluster bean anthracnose. This research investigation highlights the potential of seaweeds in enhancing crop yield and reducing the dependency on synthetic chemicals. The Gas Chromatography-Mass Spectrometry (GC-MS) results identified nine phytochemical compounds were in P. gymnospora, among which, 1,2-Benzenedicarboxylic Acid, Diethyl Ester and Naphthalene might be responsible for the suppression of the growth of C. lindemuthianum. The study also facilitates scope for the further exploitation of the seaweed based biopesticides for managing other fungal pathogens, supporting the establishment of cropping systems designed for long term resilience and sustainability.