Molecular Characterization and Morphological Variation of Various Fusarium spp. Associated with Post Flowering Stalk Rot of Maize in India

Abstract

Maize (Zea mays L.) is the vital cereal crop around the world and is the third wide grown cereal crop in India for food grain purposes. Field surveys were conducted from 2019–2020 recorded stalk rot incidence ranged from 23–50% in several maize growing districts of Southern Rajasthan, India. On the basis of primary symptoms, typical symptoms were observed after flowering season and it starts with the drying of the lower leaves and premature wilting, internal decay and discoloration of stalk tissue, lower internodes turned into grey-green color and stalks are hollow and weak leading to the lodging of the plant and directly reducing maize yield. We identified associated pathogens with post flowering stalk rot disease severity and incidence and Fusarium considered as major threat in all the maize growing regions. Consequently, in this research, identification was confirmed as “Fusarium spp”. by morphological and molecular sequence analysis. “Fusarium” species associated with stalk rot incidence were isolated on PDA. No. of 12 fungal isolates were isolated from Post Flowering Stalk Rot complex from different localities. All Isolates were identified as Fusarium, based on colony character, conidial and morphological characters. However, identification of 10 primarily selected isolates of Fusarium was confirmed by molecular characterization. Based on morphological characteristics, 10 isolates were classified as F. verticillioides (5 isolates) and 2 isolates as Fusarium proliferatum, 1 isolate of Fusarium luffae, 1 isolate of Fusarium pallidoroseum and 1 isolate of Fusarium oxysporum. Colony diameter of isolates ranged between 65.80 to 90 mm. All the ten isolates of Fusarium spp. showed notable variations in conidial morphology. Molecular variability of the ten isolates was carried out by choosing 10 RAPD markers of Operon series. Ten primers produced scorable bands with high percentage of the polymorphism (91.1%). Similarity coefficient among all these isolates of Fusarium spp. based on amplifying DNA using RAPD primers was estimated using Jaccard coefficient of similarity and thus similarity matrix was generated (62.5–85.4%). Dendrogram was constructed based on molecular data generated by 10 RAPD primers using NTSYS Pc (numerical taxonomic and multivariate analysis system) version 2.02.e UPGMA clusters analysis grouped Fusarium spp. isolates into two clusters with 0.32% similarity coefficient.