Methods for maize transformation coupled with adventitious regeneration utilizing nodal section explants and mature zygotic embryos

摘要

Maize tissue may be regenerated from nodal extracts prepared from germinated mature seeds and germinated embryos grown in a medium containing plant growth regulators. Nodal section explants are secured from seedlings approximately 3-10 days old, preferably from 3-7 days old. The explants are grown on an induction medium until adventitious shoot formation is observed. The shoots are separated and elongated on an MS-based medium, and then rooted. Fast genotype-independent regeneration is obtained, in 12-14 weeks. These explants, as well as zygotic embryos, may be transformed with exogenous DNA using a biolistic approach, where DNA precipitated onto tungsten microprojectiles is accelerated at a minimum of 650 psi towards the explants at a distance of at least 7.5 cm. Improved frequency of transformation is obtained using microprojectiles which prior to DNA precipitation were frozen in glycerol, and suspending from a preparation of 2.5 M CaCl₂. The combination of transformation process and regeneration can be used, independent of genotype, to provide new commercial crop organisms.