Fungal diseases severely threaten rice productivity and food security across the Cauvery Delta. This study investigated the prevalence, morphological variation, pathogenicity, and molecular identities of three primary fungal pathogens Bipolaris oryzae, Pyricularia oryzae and Rhizoctonia solani collected across Tamil Nadu and Karaikal U.T. Field surveys revealed wide spatial variation in disease intensity, with maximum percent disease index (PDI) recorded for sheath blight (54.00% in Nannilam), blast (42.34% in Aduthurai) and brown spot (30.40% in Pattukkottai). In vitro characterisation of ten isolates per species demonstrated notable diversity in mycelial growth rates, colony pigmentation, conidial features, and sclerotial formation. Controlled greenhouse evaluations on susceptible rice cultivar BPT-5204 confirmed varying degrees of virulence among isolates, identifying Bo8 (mean PDI 28.95%), Pg7 (mean PDI 38.99%) and Rs6 (mean PDI 36.85%) as the most aggressive pathotypes for brown spot, blast, and sheath blight, respectively. PCR amplification and Sanger sequencing of the ribosomal DNA internal transcribed spacer (rDNA-ITS) region definitively confirmed species identities for the hyper-virulent isolates: B. oryzae Bo8 (558 bp; ON556554), P. oryzae Pg7 (541 bp; ON556555) and R. solani Rs6 (514 bp; ON556551). These characterised pathotypes provide critical reference strains for regional resistance breeding and targeted disease management strategies.
K. Balamurugan, K. Vigneshwaran, R. Livitha et al.· Plant cell biotechnology and...· 0 citations
Groundnut (Arachis hypogaea L.) is an important oilseed crop, but its productivity is affected by stem rot caused by Sclerotium rolfsii Sacc. Biological control using antagonistic fungi offers a potential approach for reducing dependence on chemical disease management. The present study evaluated the in vitro inhibitory activity of cell-free culture filtrates from ten native isolates of Trichoderma viride against S. rolfsii. The pathogen was isolated from infected groundnut stem tissues and identified based on colony morphology and sclerotial characteristics. T. viride isolates were obtained from rhizosphere soil samples and maintained as Tv1 to Tv10. Culture filtrates were prepared from 10-day-old potato dextrose broth cultures and incorporated into potato dextrose agar at 10%, 20%, 30% and 40% concentrations using the poisoned food technique. All isolates reduced radial mycelial growth of S. rolfsii compared with the control and inhibition generally increased with filtrate concentration. Among the isolates tested, Tv4 showed the greatest inhibitory effect, restricting pathogen growth to 27.79 mm, 19.56 mm, 12.26 mm and 0.00 mm at 10%, 20%, 30% and 40% concentrations, respectively. Complete inhibition was observed with Tv4 at a 40% concentration. Tv6, Tv7 and Tv8 also showed high inhibition at the highest concentration. These results indicate that T. viride culture filtrates can suppress S. rolfsii growth under in vitro conditions.
K. Balamurugan, K. Vigneshwaran, R. Livitha· Journal of basic and applied...· 0 citations
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