Donor-plant environment Effects on regeneration from barley embryo-derivedcallus

High levels of green plant regeneration are necessary for efficient barley (Hordeum vulgare L,) transformation. Experiments to optimize regeneration o f calli derived from immature embryos have examined the effects of genotype and media components, but research on the effects of donor-plant growth en vironment is lacking, Defined growth conditions in growth chambers are know n to give consistent regeneration rates, but space often is limited. The ob jective of this project was to evaluate regeneration from barley tissue cul tures of 'Golden Promise' and 'Morex' grown under greenhouse conditions, pl anted on four different dates, to determine optimal greenhouse planting tim es. Results were compared with cultures from plants grown in the growth cha mber planted on the same four dates. Genotype, growth environment, and plan ting date had significant effects on green plant regeneration. Cultures of embryos, from plants sown in the greenhouse in December resulted in signifi cantly fewer green regenerants per plate. Regeneration mas more dependent o n the average solar radiation than on temperature. The best greenhouse rege neration rates for Morex were not significantly different than regeneration from growth chamber-grown donor plants, Green plant regeneration was highe r and less variable from growth chamber-grown donor plants, Sufficient rege neration from greenhouse-grown donor plants can be reached when natural lig ht levels are high and temperatures are moderate.