Morpho-Molecular Insights into Fungal Etiology of Sunflower Head Rot
H. D. Chaithanya *
Department of Plant Pathology, UAS, GKVK, Bengaluru-560065, India.
B. S. Chethana *
Zonal Agricultural Research Station, AICRP on Sunflower, GKVK, Bengaluru-560065, India.
Mansi Mishra
ICAR- Division of Crop Protection, Indian Agricultural Research Institute, New Delhi-110012, India.
Vidya Mulimani
AINP on Agricultural Acarology, GKVK, Bengaluru-560065, India.
Arjuman Banu
Zonal Agricultural Research Station, AICRP on Sunflower, GKVK, Bengaluru-560065, India.
*Author to whom correspondence should be addressed.
Abstract
Background: Head rot of sunflower, caused by a complex of fungal pathogens, is an emerging constraint under warm and humid conditions in Karnataka.
Aim: The study aimed to isolate and identify the major fungi associated with head rot of sunflower through morpho-cultural and molecular characterization.
Design: Roving survey, isolation of the associated head rot fungi and proving pathogenicity. Morpho- molecular characterization of geographically diverse isolates.
Place and Methodology: A roving survey was conducted in Chamarajanagara, Chitradurga and Bengaluru districts of Karnataka. Cultural and morphological characteristics were recorded. Genomic DNA was extracted and amplified using ITS1 and ITS4 primers and the PCR products were subjected to Sanger sequencing. Multiple sequence alignment was performed using the ClustalW algorithm, and phylogenetic relationships were inferred using the neighbour-joining method.
Results: A total of nine fungal isolates were obtained from infected heads. Based on cultural and microscopic characteristics, six isolates were identified as Rhizopus spp. and three as Fusarium spp. Cultural and morphological studies revealed considerable variation among isolates in colony characteristics, growth rate and reproductive structures. Molecular identification using ITS rDNA amplification and sequencing produced amplicons of ~789 bp in Rhizopus isolates and ~600 bp in Fusarium isolates. BLAST analysis and phylogenetic reconstruction confirmed the presence of Rhizopus arrhizus, Rhizopus stolonifer, Fusarium oxysporum and Fusarium brachygibbosum. The study confirms that sunflower head rot in Karnataka is incited by multiple fungal species belonging to Rhizopus and Fusarium, highlighting the complex etiology of the disease.
Conclusion: The study confirms that sunflower head rot in Karnataka is incited by multiple fungal species belonging to Rhizopus and Fusarium, highlighting the complex etiology of the disease and emphasizing the need for integrated disease management strategies.
Keywords: Sunflower head rot, fungal pathogens, morpho-cultural characterisation, pathogenicity, Rhizopus arrhizus, Rhizopus stolonifer, Fusarium oxysporum, Fusarium brachygibbosum, ITS sequencing, phylogenetic analysis