Differences in Ear Rot Resistance and Fusarium verticillioides-Produced Fumonisin Contamination Between Polish Currently and Historically Used Maize Inbred Lines.

Elżbieta Czembor,Agnieszka Waśkiewicz,Jerzy H Czembor,Łukasz Stȩpień,Marta Puchta,Urszula Piechota

doi:10.3389/fmicb.2019.00449

Abstract

Poland is the fifth largest European country, in terms of maize production. Ear rots caused by Fusarium spp. are significant diseases affecting yield and causing grain mycotoxin contamination. Inbred lines, which are commonly used in Polish breeding programs, belong, mostly, to two distinct genetic categories: flint and dent. However, historically used lines belonging to the heterotic Lancaster, IDT and SSS groups were also present in previous Polish breeding programs. In the current study, 98 inbred lines were evaluated across a 2-year-long experiment, after inoculation with F. verticillioides and under natural infection conditions. Lancaster, IDT, SSS and SSS/IDT groups were characterized as the most susceptible ones and flint as the more resistant. Based on the results obtained, the moderately resistant and most susceptible genotypes were defined to determine the content of fumonisins (FBs) in kernel and cob fractions using the HPLC method. Fumonisin's content was higher in the grain samples collected from inoculated plants than in cobs. The association of visible Fusarium symptoms with fumonisin concentration in grain samples was significant. Conversely, the cobs contained more FB1 under natural infection, which may be related to a pathogen's type of growth, infection time or presence of competitive species. Using ddRADseq genome sampling method it was possible to distinguish a basal relationship between moderately resistant and susceptible genotypes. Genetic distance between maize genotypes was high. Moderately resistant inbreed lines, which belong to IDT and IDT/SSS belong to one haplotype. Genotypes which belong to the flint, dent or Lancaster group, and were characterized as moderately resistant were classified separately as the same susceptible one. This research has demonstrated that currently grown Polish inbred lines, as well the ones used in the past are a valid source of resistance to Fusarium ear rot. A strong association was observed between visible Fusarium symptoms with fumonisin concentration in grain samples, suggesting that selection in maize for reduced visible molds should reduce the risk of mycotoxin contamination. NGS techniques provide new tools for overcoming the long selection process and increase the breeding efficiency.

Highlights

Maize has become one of the most important crops for food and feed production worldwide–both as silage and crop residue
In summary the objectives of this study were: (i) to evaluate the variation of Fusarium ear rots (FER) resistance and mycotoxin contamination caused by F. verticilliides among a broad base of early, midearly and late groups of maize elite inbred lines belonging to currently used flint and dent groups as well as historical heterotic groups such as Lancaster, IDT, Stiff Stalk Synthetic (SSS), and (ii) to estimate the level of genetic diversity among and within these groups using next-generation sequencing (NGS) technology
The effects of maize heterotic groups and inbred lines on disease severity differed between years

Summary

Introduction

Maize has become one of the most important crops for food and feed production worldwide–both as silage and crop residue. It is used industrially for starch and oil extraction. Maize grain is mostly contaminated with fumonisins produced by F. verticillioides and F. proliferatum, and/or by deoxynivalenol and other trichothecenes along with zearalenone produced by F. graminearum, which affect the health of human and animals (Desjardins and Plattner, 2000; Logrieco et al, 2002; Bennett and Klich, 2003; Munkvold, 2003b; Oldenburg and Ellner, 2005; Voss et al, 2006; Dorn et al, 2009; Czembor et al, 2014, 2015; Gallo et al, 2015; Stoycho, 2015; Miedaner et al, 2017). Fusarium verticillioides can cause disease, at all developmental stages of the plant, in some cases without displaying any symptoms and, fumonisins are present in symptomless infected kernels (Desjardins and Plattner, 2000; Desjardins et al, 2002; Miedaner et al, 2010)

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