Donor‐Plant Environment Effects on Regeneration from Barley Embryo‐Derived Callus

High levels of green plant regeneration are necessary for efficient barley (Hordeum vulgare L.) transformation. Experiments to optimize regeneration of calli derived from immature embryos have examined the effects of genotype and media components, but research on the effects of donor‐plant growth environment is lacking. Defined growth conditions in growth chambers are known to give consistent regeneration rates, but space often is limited. The objective of this project was to evaluate regeneration from barley tissue cultures of ‘Golden Promise’ and ‘Morex’ grown under greenhouse conditions, planted on four different dates, to determine optimal greenhouse planting times. Results were compared with cultures from plants grown in the growth chamber planted on the same four dates. Genotype, growth environment, and planting date had significant effects on green plant regeneration. Cultures of embryos from plants sown in the greenhouse in December resulted in significantly fewer green regenerants per plate. Regeneration was more dependent on the average solar radiation than on temperature. The best greenhouse regeneration rates for Morex were not significantly different than regeneration from growth chamber‐grown donor plants. Green plant regeneration was higher and less variable from growth chamber‐grown donor plants. Sufficient regeneration from greenhouse‐grown donor plants can be reached when natural light levels are high and temperatures are moderate.