Genome-wide association study leads to novel genetic insights into resistance to Aspergillus flavus in maize kernels

Guomin Han,Fangzhi Xiang,Cuiping Li,Ronghao Cai,Fang Tao,Xuewen Wang,Yang Zhao,Qianqian Zhao,Beijiu Cheng

doi:10.1186/s12870-020-02404-5

Guomin Han, Fangzhi Xiang + Show 7 more

Open Access

https://doi.org/10.1186/s12870-020-02404-5

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Abstract

BackgroundFungus infection in staple grains affects the food storage and threatens food security. The Aspergillus flavus is known to infect multiple grains and produce mycotoxin Aflatoxin B1, which is mutagenic, teratogenic and causes immunosuppression in animals. However, the molecular mechanism of maize resistance to A. flavus is largely unknown.ResultsHere we used corn kernels to investigate resistance genes to A. flavus using genome-wide association study (GWAS) of 313 inbred lines. We characterized the resistance levels of kernels after inoculating with A. flavus. The GWAS with 558,529 SNPs identified four associated loci involving 29 candidate genes that were linked to seed development, resistance or infection, and involved in signal pathways, seed development, germination, dormancy, epigenetic modification, and antimicrobial activity. In addition, a few candidate genes were also associated with several G-protein signaling and phytohormones that might involve in synergistic work conferring different resistance during seed development. Expression of 16 genes out of 29 during kernel development was also associated with resistance levels.ConclusionsWe characterized the resistance levels of 313 maize kernels after inoculating with A. flavus, and found four associated loci and 16 candidate maize genes. The expressed 16 genes involved in kernel structure and kernel composition most likely contribute to mature maize kernels’ resistance to A. flavus, and in particular, in the development of pericarp. The linked candidate genes could be experimentally transformed to validate and manipulate fungal resistance. Thus this result adds value to maize kernels in breeding programs.

Highlights

Fungus infection in staple grains affects the food storage and threatens food security
Corn and other grains are susceptible to A. flavus infection at pre- and post-harvest, leading to accumulation of toxic aflatoxin B1 which is very stable and difficult to remove during processing [2]
Less Aflatoxin B1 was produced in the kernels of resistant inbred lines than that of susceptible lines (Fig. S1)

Summary

Introduction

Fungus infection in staple grains affects the food storage and threatens food security. The Aspergillus flavus is known to infect multiple grains and produce mycotoxin Aflatoxin B1, which is mutagenic, teratogenic and causes immunosuppression in animals. Known as maize (Zea mays L.), is one of the most important cereal crops, grown throughout the world for both feed stock and food. Food security has been frequently threatened by toxic contamination produced by fungal infection [1]. Fungal species in Aspergillus genus, e.g., soil borne A. flavus, are known to produce aflatoxins, a carcinogenic mycotoxin affecting human and animals [1]. Corn and other grains are susceptible to A. flavus infection at pre- and post-harvest, leading to accumulation of toxic aflatoxin B1 which is very stable and difficult to remove during processing [2]. It is well known that some corn accessions, e.g., the Tuxpan in Mexico, possess

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