Antifungal efficacy of marine seaweed extracts against Alternaria sesami and Macrophomina phaseolina in sesame (Sesamum indicum L.)

In Tamil Nadu sesame is cultivated in an area of 74376 ha with average productivity of 433 kg / ha. Productivity has remained stagnant over recent decades because of its susceptibility to biotic and abiotic stresses. Root-rot and leaf spot disease of sesame caused by Macrophomina phaseolina is most serious disease-causing losses in seed yield in sesame.   Diseases caused by fungi Alternaria sesami and Macrophomina phaseolina, which cause diseases with leaf spot and root rot, respectively, usually reduce its production.The antifungal effectiveness of methanolic seaweed extracts, namely from Sargassum myricocystum, which was collected from the Gulf of Mannar in Tamil Nadu, against various infections was assessed in this study. Soxhlet extraction was used to produce the extracts, which were then examined utilizing Gas Chromatography- Mass Spectrometry (GC-MS) analysis, poisoned food techniques and field and pot experiments. The growth of A. sesami (65.33 %) and M. phaseolina (24.44 %) was strongly suppressed by S. myricocystum extract at a 3 % concentration, according to in vitro screening. GC-MS profiling revealed important antifungal substances, such as phytol and squalene. Investigations in the field revealed that treated plants had a reduced incidence of disease and a higher yield, with significant defense against Alternaria leaf spot, powdery mildew and root rot. The structural damage to fungal mycelia and the preservation of plant tissue integrity were confirmed by histopathological and Scanning Electron Microscopy (SEM) investigations. According to these results, S. myricocystum has strong antifungal and biostimulant characteristics and can be used as a sustainable bioinoculant for integrated control of diseases in sesame cultivation.