AUTHOR=Wang Guiying , Zhao Yanming , Mao Wenbo , Ma Xiaojie , Su Chengfu 

TITLE=QTL Analysis and Fine Mapping of a Major QTL Conferring Kernel Size in Maize (Zea mays)

JOURNAL=Frontiers in Genetics

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2020.603920

DOI=10.3389/fgene.2020.603920

ISSN=1664-8021

ABSTRACT=<p>Kernel size is an important agronomic trait for grain yield in maize. The purpose of this study is to map QTLs and predict candidate genes for kernel size in maize. A total of 199 F<sub>2</sub> and its F<sub>2</sub><sub>:</sub><sub>3</sub> lines from the cross between SG5/SG7 were developed. A composite interval mapping (CIM) method was used to detect QTLs in three environments of F<sub>2</sub> and F<sub>2</sub><sub>:</sub><sub>3</sub> populations. The result showed that a total of 10 QTLs for kernel size were detected, among which were five QTLs for kernel length (KL) and five QTLs for kernel width (KW). Two stable QTLs, <italic>qKW-1</italic>, and <italic>qKL-2</italic>, were mapped in all three environments. Three QTLs, <italic>qKL-1, qKW-1</italic>, and <italic>qKW-2</italic>, were overlapped with the QTLs identified from previous studies. In order to validate and fine map <italic>qKL-2</italic>, near-isogenic lines (NILs) were developed by continuous backcrossing between SG5 as the donor parent and SG7 as the recurrent parent. Marker-assisted selection was conducted from BC<sub>2</sub>F<sub>1</sub> generation with molecular markers near <italic>qKL-2</italic>. A secondary linkage map with six markers around the <italic>qKL-2</italic> region was developed and used for fine mapping of <italic>qKL-2.</italic> Finally, <italic>qKL-2</italic> was confirmed in a 1.95 Mb physical interval with selected overlapping recombinant chromosomes on maize chromosome 9 by blasting with the Zea_Mays_B73 v4 genome. Transcriptome analysis showed that a total of 11 out of 40 protein-coding genes differently expressed between the two parents were detected in the identified <italic>qKL-2</italic> interval. GRMZM2G006080 encoding a receptor-like protein kinase FERONIA, was predicted as a candidate gene to control kernel size. The work will not only help to understand the genetic mechanisms of kernel size of maize but also lay a foundation for further fine mapping and even cloning of the promising loci.</p>