2.1. Plant materials

In this study, a total of 1,143 maize accessions were collected from 20 countries (Figure ​(Figure1),1), including 11 teosinte inbred lines, 764 landraces sampled from the maize collection of the CIMMYT germplasm bank (MGB), 290 CIMMYT elite maize lines (CMLs) and 78 popcorn lines from the USDA Ames inbred collection (Romay et al., 2013). The 11 teosinte inbred lines were developed from wild teosinte materials under the Teosinte Inbred Project, 10 of which belong to subspecies parviglumis and one (ISU_TIL25) belongs to the subspecies mexicana. The teosinte information can be found in GRAMENE (http://archive.gramene.org/db/diversity/diversity_view?search_for=TIL%26object=div_passport%252Cdiv_synonym%26db_name=diversity_maize%26x=0%26y=0%26action=list). The 764 maize landraces selected originated from 20 countries representing broad adaptation and, compared with elite lines, broader genomic diversity. A panel of 290 CMLs was chosen from the complete CML set, comprising 573 lines at the time of the study. Selection of the CMLs was performed considering representation of the three major environmental adaptation groups (Lowland Tropical, Subtropical/Midaltitude and Highland Tropical subgroups), the described pedigrees (https://data.cimmyt.org/dataset.xhtml?persistentId=hdl:11529/10246) and known genomic relationships between the lines (Wu et al., 2016) in order to maximize the diversity captured by the 290 entry set. Passport information of the 764 maize landraces and the 290 CMLs can be found at http://hdl.handle.net/11529/10548183. The 78 popcorn inbred lines were obtained from the USDA‐ARS North Central Regional Plant Introduction Station (NCRPIS) in Ames, Iowa (Romay et al., 2013). Line identifiers can be found at http://hdl.handle.net/11529/10548183 and associated passport information is available from the U.S. National Plant Germplasm System at https://npgsweb.ars-grin.gov/gringlobal/search.aspx.

The geographical and adaptive distribution of the 1,143 maize collection. Lines cannot be assigned a geolocation origin so are not displayed on the map [Colour figure can be viewed at http://wileyonlinelibrary.com]

Of the 1,143 maize germplasm, 764 were open pollinated landraces and 379 were inbred lines. A summary of the descriptors for this panel of 1,143 accessions is available in Table S2. The maize materials in this study represent diverse ecological adaptation including tropical lowland, highland, subtropical/midaltitude and temperate, covering major ecotypes of maize resources developed during domestication and breeding.