Abstract
BackgroundFusarium verticillioides is a common maize pathogen causing ear rot (FER) and contamination of the grains with the fumonisin B1 (FB1) mycotoxin. Resistance to FER and FB1 contamination are quantitative traits, affected by environmental conditions, and completely resistant maize genotypes to the pathogen are so far unknown. In order to uncover genomic regions associated to reduced FER and FB1 contamination and identify molecular markers for assisted selection, an F2:3 population of 188 progenies was developed crossing CO441 (resistant) and CO354 (susceptible) genotypes. FER severity and FB1 contamination content were evaluated over 2 years and sowing dates (early and late) in ears artificially inoculated with F. verticillioides by the use of either side-needle or toothpick inoculation techniques.ResultsWeather conditions significantly changed in the two phenotyping seasons and FER and FB1 content distribution significantly differed in the F3 progenies according to the year and the sowing time. Significant positive correlations (P < 0.01) were detected between FER and FB1 contamination, ranging from 0.72 to 0.81. A low positive correlation was determined between FB1 contamination and silking time (DTS). A genetic map was generated for the cross, based on 41 microsatellite markers and 342 single nucleotide polymorphisms (SNPs) derived from Genotyping-by-Sequencing (GBS). QTL analyses revealed 15 QTLs for FER, 17 QTLs for FB1 contamination and nine QTLs for DTS. Eight QTLs located on linkage group (LG) 1, 2, 3, 6, 7 and 9 were in common between FER and FB1, making possible the selection of genotypes with both low disease severity and low fumonisin contamination. Moreover, five QTLs on LGs 1, 2, 4, 5 and 9 located close to previously reported QTLs for resistance to other mycotoxigenic fungi. Finally, 24 candidate genes for resistance to F. verticillioides are proposed combining previous transcriptomic data with QTL mapping.ConclusionsThis study identified a set of QTLs and candidate genes that could accelerate breeding for resistance of maize lines showing reduced disease severity and low mycotoxin contamination determined by F. verticillioides.
Highlights
Fusarium verticillioides is a common maize pathogen causing ear rot (FER) and contamination of the grains with the fumonisin B1 (FB1) mycotoxin
The aim of this work was the mapping of Quantitative Trait Locus (QTL) and identification of candidate genes for Fusarium ear rot (FER) resistance and reduced FB1 contamination in a F2:3 progeny, derived from the cross between a resistant (CO441) and a susceptible (CO354) commercial maize line previously used for molecular characterization of response to Fusarium [31,32,33,34,35]
The LOD value thresholds obtained by permutation test varied from 3.9 to 4.3 for all considered traits, but we considered as “stable” QTLs with LOD values close to the threshold, if mapping to the same position of another QTL determined in another year/sowing time/ inoculation technique, or for another trait
Summary
Fusarium verticillioides is a common maize pathogen causing ear rot (FER) and contamination of the grains with the fumonisin B1 (FB1) mycotoxin. Fusarium ear rot (FER) is a common disease of maize (Zea mays L.), which reduces grain yield and quality worldwide. The fungus Fusarium verticillioides (Sacc.) Nirenberg is the primary causal agent of FER, in Southern Europe [1, 2] and in the United States [3]. This pathogen is the major producer in the grains of fumonisin mycotoxins, including fumonisin B1 (FB1). In a 3-years study (2009–2011), fumonisin contamination was detected in 90% of Southern European corn samples, with an average level of 2,200 ppb and a maximum level greater than 11,000 ppb [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
