**Mapping-by-Sequencing via MutMap Identifies a Mutation in** *ZmCLE7* **Underlying Fasciation in a Newly Developed EMS Mutant Population in an Elite Tropical Maize Inbred**

**Quan Hong Tran 1,**†**, Ngoc Hong Bui 1,**†**, Christian Kappel 2, Nga Thi Ngoc Dau 1, Loan Thi Nguyen 1, Thuy Thi Tran 1, Tran Dang Khanh 1,3, Khuat Huu Trung 1, Michael Lenhard 2 and Son Lang Vi 1,\***


Received: 14 February 2020; Accepted: 3 March 2020; Published: 6 March 2020

**Abstract:** Induced point mutations are important genetic resources for their ability to create hypoand hypermorphic alleles that are useful for understanding gene functions and breeding. However, such mutant populations have only been developed for a few temperate maize varieties, mainly B73 and W22, ye<sup>t</sup> no tropical maize inbred lines have been mutagenized and made available to the public to date. We developed a novel Ethyl Methanesulfonate (EMS) induced mutation resource in maize comprising 2050 independent M2 mutant families in the elite tropical maize inbred ML10. By phenotypic screening, we showed that this population is of comparable quality with other mutagenized populations in maize. To illustrate the usefulness of this population for gene discovery, we performed rapid mapping-by-sequencing to clone a fasciated-ear mutant and identify a causal promoter deletion in *ZmCLE7 (CLE7)*. Our mapping procedure does not require crossing to an unrelated parent, thus is suitable for mapping subtle traits and ones affected by heterosis. This first EMS population in tropical maize is expected to be very useful for the maize research community. Also, the EMS mutagenesis and rapid mapping-by-sequencing pipeline described here illustrate the power of performing forward genetics in diverse maize germplasms of choice, which can lead to novel gene discovery due to divergent genetic backgrounds.

**Keywords:** EMS; MutMap; mutagenesis; CLE7; tropical maize; fasciation; mapping
