Genome: Zea mays mays cv. B73

Corn (Zea mays mays cv. B73).

Scientific Name
Zea mays mays cv. B73
Common Name


Maize belongs to the grass family Graminaceae that includes wheat, rice, oats, sorghum, barley and sugarcane. It is a tall, determinate annual plant producing large, narrow, opposing leaves (about a tenth as wide as they are long), borne alternately along the length of a solid stem. Unlike other grasses, which produce perfect (bisexual) flowers, maize produces male inflorescences (tassels) which crown the plant at the stem apex, and female inflorescences (ears), which are borne at the tip of condensed lateral branches protruding from leaf axils. The seed contains two sister structures, a germ from which a new plant will develop, and an endosperm which will provide nutrients for that germinating seedling until the seedling establishes sufficient leaf area to photosynthesize food material. Maize is primarily a cross-pollinating species, a feature that has contributed to its broad morphological variability and geographic adaptability. Maize varieties may range from 0.5 to 5 meters standing height at flowering, mature in 60 to 330 days from planting, produce 1 to 4 ears per plant, 10 to 1,800 kernels per ear and yield from 0.5 to 23.5 tons of grain per hectare. Kernels may be colorless (white) or yellow, red, blue or variegated with these colors in mottled or striated patterns. The crop, which is produced from 50 degrees North latitude to 40 degrees South latitude, is adapted to areas ranging from desert to high rainfall environments, and to elevations ranging from 0 to 4,000 meters above sea level.
-- Adapted from The Maize Page, Iowa State University


The McDonnell Genome Institute was chosen as the lead institution for a project, jointly sponsored by the National Science Foundation, the U.S. Department of Energy, and the U.S. Department of Agriculture, to sequence the maize genome. Other institutions that participated are Arizona Genomics Institute (AGI) Tucson, AZ, Cold Spring Harbor Laboratory (CSHL), Cold Spring Harbor, NY, and Iowa State University, Ames Iowa.

Maize is a gigantic domesticated grass (Zea mays ssp. mays) of tropical Mexican origin. The plant is used to produce grain and fodder that are the basis of a number of food, feed, pharmaceutical and industrial manufactures. Cultivation of maize and the elaboration of its food products were concomitant with the rise of pre-Colombian Mesoamerican civilizations. It is thought that maize, as we know it originated from a single domestication of another subspecies, Zea mays ssp. parviglumis. This occurred in southern Mexico about 9,000 to 10,000 years ago.

Due to its adaptability and productivity, culture of maize spread rapidly around the globe after Spaniards and other Europeans exported the plant from the Americas in the 15th and 16th centuries. Maize is currently produced in most countries of the world and is the third most planted field crop (after wheat and rice). The bulk of maize production occurs in the United States, Peoples Republic of China, and Brazil, which together account for 73% of the annual global production of 456.2 million tons. Mexico, the world's fourth largest producer of maize, currently produces approximately 14 million tons of grain annually on 6.5 million hectares (3% of world production on 5% of the world's land devoted to maize production).

Sequencing Plan

A minimal tiling path set of approximately 19,000 BAC clones was selected from the already existing maize physical map. Each BAC clone was sequenced to approximately 6-fold coverage, and “genespace” boundaries in the BAC clones will be determined. Those areas were sequence-improved and finished. Those finished and annotated sequences were submitted to GenBank and also were integrated with physical and genetic map data. Validated trace reads are available in the NCBI Trace Archive. Displays of the data are available in GBrowse. All indicated and predicted gene models will be improved, as will the overall annotation of the maize genome. Advisory Committee One Year Progress Report (2005-2006) pdf GSC/CSHL(ppt) ISU(ppt) JGI(ppt)

Updated Sequencing Plan

In order to improve the maize genome sequence we are adding additional depth to the existing capillary sequence using the Illumina 2000. We are resequencing the BACs that comprised the minimal BAC tiling path from the original B73 sequencing project by pooling the BACs in pools of 96, and generating Illumina data to greater than 150X coverage per clone. This increased depth, density of read pairs, and differential bias compared to capillary sequencing will serve as an excellent resource to further improve the maize sequence. These data, once completed, will be made available through public databases.