Producing tropical teosinte seed in a temperate environment

Authors: Bernau, Vivian; North, Brady; ZIMMERMAN, DAVID - Iowa State University; Millard, Mark; Gardner, Candice

Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2020
Publication Date: 11/12/2020
Citation: Bernau, V.M., North, B.S., Zimmerman, D., Millard, M.J., Gardner, C.A. 2020. Producing tropical teosinte seed in a temperate environment [abstract]. Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting. Paper No. 127663.

Interpretive Summary: The USDA National Plant Germplasm System’s maize collection held in Ames, IA includes 439 wild accessions. Currently, only 17% (74 accessions) are available for distribution. Regenerating maize wild relatives native to Mexico and Central America in Iowa is difficult because 1) short days are necessary to induce flowering, 2) it is difficult to control the fertilization of the flowers, and 3) 100+ plants are needed to avoid reducing the natural genetic variation, preserving genetic profile. By incorporating a growth regulator into our regeneration protocol, we were able to produce plants that can be more easily moved between the field and the greenhouse. For example, in December 2019, 73,532 seeds were harvested from 134 plants of Zea luxurians (Durieu & Asch.) Bird (PI 441933 ). For this accession, 250 seeds were germinated in a growth chamber in June 2019, then transplanted to pots in the greenhouse. Following seedling establishment the pots were moved outside to grow vegetatively during the long summer days in Ames, Iowa. Bonzi, a growth regulator, was applied mid-summer to promote tillering and reduce overall plant height. As the fall frost date approached and daylength shortened, pots were moved back to the greenhouse and LED lights were set to promote flowering. After flowering was initiated, fans were used to create air movement and plants were agitated daily to facilitate pollen spread. Seed was harvested daily with a handheld vacuum. Plants were threshed by hand after they had dried to ensure all seed had been collected. Seed was cleaned using a seed blower, fractionator, and an optical sorter. With this protocol established, we are able to reliably regenerate at least one accession each year.

Technical Abstract: The USDA National Plant Germplasm System's maize collection held in Ames, IA includes 439 wild accessions from the genus Zea. Currently, only 17% (74 accessions) are available for distribution. Regenerating maize wild relatives native to Mexico and Central America in Iowa is difficult because 1) short days are necessary to induce flowering, 2) their plant physiology is not amenable to bagging inflorescences so isolation from other teosintes and cultivated maize is required during flowering, and 3) 100+ plants are needed to avoid imposing a genetic bottleneck. By incorporating a growth regulator into our regeneration protocol, we were able to produce plants that were more easily moved between the field and the greenhouse. For example, in December 2019, 73,532 seeds were harvested from 134 plants of Zea luxurians (Durieu & Asch.) Bird (PI 441933 ). For this accession, 250 seeds were germinated in a growth chamber in June 2019, then transplanted to pots in the greenhouse. Following seedling establishment the pots were moved outside to grow vegetatively during the long summer days (up to 15 hours) in Ames, Iowa. Bonzi, a growth regulator, was applied mid-summer to promote tillering and reduce overall plant height. As the fall frost date approached and daylength shortened, pots were moved back to the greenhouse and LED lights were set to promote flowering. After flowering was initiated, fans were used to create air movement and plants were agitated daily to facilitate pollen spread. Seed was harvested daily with a handheld vacuum. Plants were threshed by hand after they had dried to ensure all seed had been collected. Seed was cleaned using a seed blower, fractionator, and an optical sorter. With this protocol established, we are able to reliably regenerate at least one accession each year.