A Global Screening Assay to Select for Maize Phenotypes with a High Tolerance or Resistance to Fusarium verticillioides (Sacc.) Nirenberg Rots

Abstract

Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes rots in maize around the world and produces mycotoxins that contaminate grains, making this species a significant health concern for both animals and humans. One of the best approaches to address rots is to identify highly tolerant or resistant genotypes that can be used for genetic improvement. The aim of the study was to evaluate dose-response assays to tolerance or resistance for Fv rots throughout the maize life cycle. These tests assessed the effects of Fv during post-germination development and the seedling (V2) stage by seed infection, the plantlet (V4) stage by substrate infection, and in the reproductive phase in maize stalks (R2 stage) and ears (R6 stage) by R1 stage inoculation. In all assays, the doses were effective at distinguishing contrasting phenotypes. Severity, root fresh weight, and aerial length were the most informative parameters at the V2 and V4 stages. Evaluation of the stalk necrosis area between and within the internodes of susceptible genotypes revealed significant differences among doses, and a positive correlation between necrosis and conidia concentration was observed in internodes. Injecting eight million conidia in the ear was sufficient for selecting different phenotypes. A total of 85% of the genotypes conserved their same capacity to respond to Fv infection throughout the maize life cycle, so that screening at the early vegetative stage (e.g., V2) could be useful for distinguishing contrasting phenotypes in the reproductive stage. Implementing these screening assays in a maize breeding program could be valuable for classifying the degrees of resilience of maize germplasms to Fv rots. This global screening has the potential to be employed to select against other Fusarium species.

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

“…There are claims that Fusarium spp. inoculums enhance root growth without compromising germination (Roman et al, 2020), but we noticed a reduction in root growth using the paper towel approach. There are reports of a constant decline in maize root length following Fusarium spp.…”

Cell wall-related genes and lignin accumulation contribute to the root resistance in different maize (Zea mays L.) genotypes to Fusarium verticillioides (Sacc.) Nirenberg infection

“…Fv secretes mycotoxins that cause neural tube defects, cancer, craniofacial anomalies, and other birth defects in humans and animals ( Marasas et al., 2004 ; Riley et al., 2006 ; Riley et al., 2015 ). One strategy to bring down this pathogen and its harmful effects from the food chain is to develop maize hybrids that are resistant to Fv rots ( Roman et al., 2020 ); studies of contrasting phenotypes in maize could also help to understand plant mechanisms used for defense or resistance against the Fusarium infection process.…”

“…Previously described protocols were used for seedling preparation ( Warham et al., 1996 ; Román, 2017 ; Roman et al., 2020 ). Briefly, the seeds were superficially disinfected by sonication (2.8 L Ultrasonic Bath, Fisher Scientific) in sterile distilled water with Tween 20 (five drops of Tween 20/100 ml of distilled water) for 5 min.…”

“…Recently, Wang et al (2022) analyzed the fungal pathogenic response to maize-susceptible B73 and reported the importance of diterpenoids, phenylpropanoid, and lignin (cell wall) pathways during disease resistance in ear rot. Specifically, Fv can cause rot throughout the life cycle of maize, from seed to post-germination to the reproductive stage, in ears and kernel tissue (Wu et al, 2011;Roman et al, 2020). In the case of root rot, Fv colonizes the roots via injuries or wounds generated by the emergence of lateral roots or root growth (Wu et al, 2011).…”

A review on mechanisms and prospects of endophytic bacteria in biocontrol of plant pathogenic fungi and their plant growth-promoting activities

“…In maize cultivation, fungi are considered critical pathogens, with Fusarium spp. being causal agents for infecting roots, stalks, ears, and kernels [ 7 ]. In addition to yield loss, Fusarium can reduce grain quality by releasing fumonisin or deoxynivalenol [ 8 , 9 ].…”