Molecular Basis of Resistance to Fusarium Ear Rot in Maize

Abstract

The impact of climate change has been identified as an emerging issue for food security and safety, and the increased incidence of mycotoxin contamination in maize over the last two decades is considered a potential emerging hazard. Disease control by chemical and agronomic approaches is often ineffective and increases the cost of production; for this reason the exploitation of genetic resistance is the most sustainable method for reducing contamination. The review focuses on the significant advances that have been made in the development of transcriptomic, genetic and genomic information for maize, Fusarium verticillioides molds, and their interactions, over recent years. Findings from transcriptomic studies have been used to outline a specific model for the intracellular signaling cascade occurring in maize cells against F. verticillioides infection. Several recognition receptors, such as receptor-like kinases and R genes, are involved in pathogen perception, and trigger down-stream signaling networks mediated by mitogen-associated protein kinases. These signals could be orchestrated primarily by hormones, including salicylic acid, auxin, abscisic acid, ethylene, and jasmonic acid, in association with calcium signaling, targeting multiple transcription factors that in turn promote the down-stream activation of defensive response genes, such as those related to detoxification processes, phenylpropanoid, and oxylipin metabolic pathways. At the genetic and genomic levels, several quantitative trait loci (QTL) and single-nucleotide polymorphism markers for resistance to Fusarium ear rot deriving from QTL mapping and genome-wide association studies are described, indicating the complexity of this polygenic trait. All these findings will contribute to identifying candidate genes for resistance and to applying genomic technologies for selecting resistant maize genotypes and speeding up a strategy of breeding to contrast disease, through plants resistant to mycotoxin-producing pathogens.

Analysis of Fusarium ear rot and fumonisin contamination in testcrosses of a maize biparental population

“…The genetic factors affecting the FER tolerance found in our study can be used as valuable guidelines in breeding programs targeting improved hybrid FER tolerance since they were mapped in a densely genotyped maize population, and studies of genetic factors affecting FER are rare in densely mapped populations (Lanubile et al 2017). The experimental design used in the current study did not include artificial inoculation, which may have been the reason for the low or no genetic correlations between DI and fumonisin contamination, although moderate to strong phenotypic correlations indicate that lowering the DI should consequently result in lower FUMc.…”

“…As agronomic control methods of fumonisin contamination often fail, and there is a considerable genetic variability for FER resistance in maize germplasm (Santiago et al 2013, Schwantes et al 2018, genetic improvement might be the optimal strategy in future maize breeding for tolerable fumonisin contamination in food and feed (Maschietto et al 2017). To date, many QTL studies were conducted in populations with low-density genetic maps, and QTL studies in densely mapped populations are rare (Lanubile et al 2017). The relative efficiency of selection for FER resistance is greater in testcrosses than in inbred lines, and due to mainly additive gene action, the general combining ability of the inbreds is more important than the specific combining ability (Löffel et al 2011, Hung andHolland 2012).…”

A Genome-Wide Association Study To Understand the Effect of Fusarium verticillioides Infection on Seedlings of a Maize Diversity Panel

“…The cultivation of resistant germplasm is an efficient way to reduce yield loss and mycotoxin contamination, however, no maize genotypes immune to Fusarium infection have been identified and many commercial hybrids have less resistance than desired (Lanubile et al 2010;Zila et al 2013). Resistance to F. verticillioides in maize, which was mainly focused on Fusarium ear rot (FER), has been studied in different surveys based on artificial inoculation in field (Drepper and Renfro 1990;Reid and Zhu 2005;Reid et al, 2009;Lanubile et al 2011Lanubile et al , 2017Zila et al 2013;Maschietto et al 2017), greenhouse (Danielsen et al 1998;Lanubile et al 2013Lanubile et al , 2014aMaschietto et al 2016) and laboratory trials (Ju et al 2017;Atabaki et al 2018).…”

In Vitro Fumonisin Biosynthesis and Genetic Structure of Fusarium verticillioides Strains from Five Mediterranean Countries

“…Fumonisins occur worldwide in maize, including Mediterranean [4,8,24,25] farming areas, where this is one of the most widely cultivated crops [26,27]. Fumonisin accumulation in maize grains can occur in the field, following preharvest infections, and possibly continue during grain storage [28].Contaminations strongly impair maize grain quality because of the negative impact on animal and human health [29]. Fumonisin mycotoxins can be divided into four main groups, with the most abundant fumonisins found in nature included in the B group: fumonisin B 1 (FB 1 ), fumonisin B 2 (FB 2 ) and fumonisin B 3 (FB 3 ).…”

“…Fumonisins occur worldwide in maize, including Mediterranean [4,8,24,25] farming areas, where this is one of the most widely cultivated crops [26,27]. Fumonisin accumulation in maize grains can occur in the field, following preharvest infections, and possibly continue during grain storage [28].…”