Morphological characterization, pathogenicity screening, and molecular identification of Fusarium spp. isolates causing post flowering stalk rot in maize

Authors: HARISH, J - Central Agricultural University; JAMBHULKAR, PRASHANT - Central Agricultural University; BAJPAI, RUCHIRA - Central Agricultural University; MEENAKSHI, ARYA - Central Agricultural University; BABELE, PIYOOSH - Central Agricultural University; CHATURVEDI, SUNIL - Central Agricultural University; KUMAR, ANIL - Central Agricultural University; Lakshman, Dilip

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2023
Publication Date: 3/31/2023
Citation: Harish, J., Jambhulkar, P., Bajpai, R., Meenakshi, A., Babele, P., Chaturvedi, S., Kumar, A., Lakshman, D.K. 2023. Morphological characterization, pathogenicity screening, and molecular identification of Fusarium spp. isolates causing post flowering stalk rot in maize. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2023.1121781.
DOI: https://doi.org/10.3389/fmicb.2023.1121781

Interpretive Summary: The stalk rot of maize caused by multiple Fusarium species poses significant obstacles to maize cultivation worldwide. Due to the significant diversity of pathogenic Fusarium species in different agroecological zones of India, traditional control efforts against Fusarium stalk rot become challenging and sometimes unsuccessful. Therefore, cultivating resistant cultivars remains the most sustainable alternative to stalk rot disease management. Seventy-one isolates were collected from 40 sites in five agroclimatic zones of India to assess the morphological diversity of Fusarium spp. associated with maize stalk rot disease in the field. Based on morphological traits, Fusarium isolates were divided into 11 clusters, and using morphological traits the Fusarium species were identified as F. oxysporum, F. verticillioides, F. acutatum, F. andiyazi, Gibberella fujikuroi var. moniliformis, and F. nygamai. Furthermore, the pathogenicity of the isolates was tested on maize, both in vitro and in two cropping seasons, and the five most virulent isolates were identified for future screening of maize inbred lines for disease resistance. The inferences made from those experiments will be highly useful for better management of the stalk rot of maize in India and neighboring countries. The information gathered will also be helpful to plant pathologists, mycologists extension workers, and farmers.

Technical Abstract: Post Flowering Stalk Rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of taxonomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India in order to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into 9 clusters. In-vitro, Kharif, and Rabi seasons were utilized to investigate the pathogenicity of Fusarium spp.-causing PFSR. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vitro situations and high disease severity in field experiments. Based on the examination of pathogenicity in in-vitro, Kharif, and Rabi field trials and molecular identification, the ten most virulent isolates, were F. acutatum (FUR11), F. verticillioides (Davanagere), Gibberella fujikuroi var. moniliformis (F59), F. acutatum (F10), F. verticillioides (Raichur), F. verticillioides (F21), F. andiyazi strain (F18), F. verticillioides (F13), F. verticillioides (FUR15), and F. verticillioides (FUG9). The distribution of virulent isolates was specific to geographical locations with a hot, humid climate. Morphological characterization, molecular identification, and information on the geographical distribution of virulent Fusarium isolates will be helpful for the efficient management of PFSR, including screening for resistance in maize-inbred lines.