Prevalence, cultural and morphological characterization of Fusarium verticillioides associated with ear rot of maize

A roving survey was carried out in Ballari, Davanagere, Haveri, Koppal, Mandya, Mysuru, Raichur, and Shivamogga districts of Karnataka during rabi 2020-21 to determine the prevalence of ear rot of maize incited by Fusarium verticillioides. According to the survey data, Shivamogga had the highest disease incidence (36.10 %), followed by Ballari (28.34 %), while Raichur had the lowest (17.98 %). In eight maize-growing districts, the average percent incidence of Fusarium ear rot was 25.26. Twenty-four isolates of F. verticillioides were collected in different districts that varied in terms of cultural and morphological characteristics. All of the isolates had feathery mycelial growth with either a serrated or smooth edge, with colony diameters ranging from 68.33 mm to 89.33 mm and colony colors ranging from white to purple. The isolates generated septate, hyaline mycelia with verticillate branching ranging in width from 2.10 µm to 5.97 µm. Few elongated with blunt ends thin walled two to three-celled hyaline macroconidia ranging in size from 22.43 × 4.38 µm to 8.70 × 3.66 µm and plentiful single-celled oblong microconidia ranging in size from 7.78 × 2.75 µm to 4.49 × 2.30 µm formed in chains or cluster. Only Fv 9 isolate (Raichur) produced chlamydospore-like structures. The information generated during the survey will be useful in identifying endemic and risk-free areas of maize ear rot across districts. The pathogen isolates have variability concerning their cultural and morphological characters which depict the geographical distribution of the pathogen.