Studies on Cultural, Morphological and Pathogenic Variability among the Isolates of F. verticillioides Associated with Maize Stalk Rot in Telangana State, India

Maize (Zea mays L.) is one of the important cereal crops of the world and world’s third most leading cereal crop, after wheat and rice. Maize is affected by various biotic and abiotic stresses. Among the biotic stresses, fusarium wilt of maize caused by Fusarium verticillioides is most serious disease of maize. Tweleve isolates of F. vericillioides were studied for its cultural, morphological and pathogenic variability. Microconidia were hyaline, oval to club shaped with a flattened base and measured 5.12-7.11 μm X 2.04-3.18 μm (L×W). Macroconidia were sickle shaped with 3-5 septa and measured 20.01-31.12 μm X 2.01-3.21 μm (L×W). The radial mycelial growth of test isolates ranged from 4.32 mm to 8.65 mm at 10 days after inoculationon on PDA medium. However, maximum mycelial growth was recorded by the isolate F-ISO-5 in all the three mediums and mean maximum growth of isolates were observed in CMA. The fungal colony of Fusarium isolates on PDA were initially white, floccose which turned purple to dark brown after 7 days of incubation at 28 ± 2ºC. Cultures developed pigmentation like pink, light purple, dark violet which varied with age. All the tested isolates were pathogenic on tested maize cultivar (kaveri- 50). However, the disease severity was varied among the isolates. Fusarium isolates F-ISO-7 was highly virulent which caused severe disease upon inoculation with disease score of 8.0 on 1-9 scale followed by F-ISO-1, F-ISO-3, F-ISO-4, F-ISO-5, F-ISO-6 and F-ISO-8.