Abstract
Maize production is on risk by Gibberella ear rot (GER) caused by Fusarium graminearum. This is one of the most important ear rot diseases in temperate zones as it leads to yield losses and production of harmful mycotoxins. We investigated, for the first time, the potential use of Brazilian tropical maize to increase resistance levels to GER in temperate European flint germplasm by analyzing six interconnected biparental populations. We assessed GER symptoms in Brazil and in Europe in up to six environments (= location × year combinations) during the growing seasons of 2018 and 2019. We conducted multi-parent QTL and biparental QTL mapping, and identified four QTLs with additive gene action, each explaining 5.4 to 21.8% of the total genotypic variance for GER resistance. Among them, QTL q1 was stable across test environments, populations, and between inbred lines and testcrosses. The accuracies of genomic prediction ranged from 0.50 to 0.59 depending on the resistance donor and prediction model. Jointly, our study reveals the potential use of Brazilian resistance sources to increase GER resistance levels by genomics-assisted breeding.
Highlights
Fusarium spp. is one of the most important crop pathogens in maize (Zea mays L.) reducing yield and threatening human and animal health by mycotoxins
F. graminearum, F. verticillioides, and F. temperatum, a new species separated from F. subglutinans, are the main species causing ear rot in temperate zones (Pfordt et al 2020)
Both GER rating adjusted for FF (GER_FF) and Gibberella ear rot (GER) showed a quantitative distribution with T3 being more resistant than the adapted parental lines (Fig. 2)
Summary
Fusarium spp. is one of the most important crop pathogens in maize (Zea mays L.) reducing yield and threatening human and animal health by mycotoxins These hemibiotrophic fungi can cause diseases during all growth stages of the plant including stalk and ear rots (Munkvold et al 1997; Pfordt et al 2020). The composition of species in each environment is mainly associated with weather conditions during silking At this developmental stage, F. graminearum is favored by high precipitation and moderate temperatures whereas F. verticillioides is favored by low humidity and high temperatures (Bottalico 1998; Munkvold 2003; Pfordt et al 2020). Pigs are the main consumers of corn-cob-mix (Deutsches Maiskomitee 2020) and they are the most sensitive animals to these mycotoxins (Pierron et al 2016) For this reason, the European Union established an orientation value of maximum 0.9 mg DON kg-1 for pig feed (European Commission 2006). Little effort in breeding resistant varieties against ear rot was made in the past and nowadays most of commercial hybrids have a lower ear rot resistance than desirable (Bush et al 2004; Mesterhazy et al 2012; Zila et al 2013)
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