New maize transformation method may broaden access to crop bioengineering

A collaborative team from the Boyce Thompson Institute (BTI), Iowa State University (ISU), and Corteva Agriscience has developed a more accessible method for genetically modifying maize, potentially broadening participation in crop bioengineering beyond industrial settings.

The findings, published in In Vitro Cellular & Developmental Biology—Plant, detail a transformation technique that uses the leaf whorls of young maize seedlings instead of immature embryos, a shift that reduces infrastructure requirements and accelerates the bioengineering process.

Conventional maize transformation involves extracting immature embryos from mature corn plants and introducing target genes through Agrobacterium-mediated methods. However, this procedure demands high-quality embryos, which can only be produced in controlled greenhouse conditions—resources often unavailable to academic labs. Additionally, some maize genotypes, such as the commonly used B73, are particularly difficult to transform using standard techniques.

“Few academic research groups have the infrastructure necessary for growing the high-quality maize required for transformation, so the method has largely been restricted to commercial industry,” said Dr. Joyce Van Eck, professor at BTI and co-lead author of the study.

To overcome these constraints, the research team evaluated a leaf whorl-based transformation approach originally developed by Corteva. In this method, the inner whorl of young maize seedlings—harvested approximately two weeks after germination—is used for transformation. This significantly reduces the growth period and eliminates the need for mature embryos.

The study also compared two different helper plasmids used in the transformation process: a proprietary Corteva plasmid and a publicly available alternative developed by ISU agronomy professor Dr. Kan Wang. Both plasmids were tested on two maize genotypes, including B73. The results showed that the publicly available plasmid performed comparably well, making the technique viable without reliance on proprietary tools.

According to Dr. Ritesh Kumar, a postdoctoral researcher at BTI and first author of the study, the method could facilitate functional genomics research in maize genotypes that are otherwise difficult to work with. “We are now exploring how this method will work in other maize genotypes with desirable traits, like resistance to biotic and abiotic stresses,” he said.

By reducing technical and financial barriers, the leaf whorl-based transformation technique may enable more research institutions to participate in maize bioengineering, accelerating the development of improved crop varieties in the face of climate and resource challenges.