Somatic embryo (embryoid) formation from immature-embryo-derived calli was quantified in replicated experiments involving 10 Triticum aestivum L. genotypes. Several published media formulations, which had previously been optimized for wheat tissue culture, were tested for each genotype. Embryos from each plant were randomly assigned to each medium. Percentage precocious germination of immature embryos and mean percentage scutellar callus per explant were recorded. Embryoids per callus were determined by microscopic examination at 28 and 56 days. There were highly significant differences among genotypes, media, and individual plants from which explants were taken. A medium based on double the Murashige and Skoog (MS) inorganic salt concentration was significantly better than other media. Inclusion of all MS vitamins appeared essential for optimal response. Two genotypes were tested in a second experiment where both 3,6-dichloro-o-anisic acid (9.05 pM) and 6-furfurylaminopurine (0.46#M) were substituted for 2,4-dichlorophenoxyacetic acid (4.52 #M) in either double or normal MS medium. This substitution significantly increased embryoid formation at 28 days. Additions of either 6-furfurylaminopurine or coconut water increased precocious germination of both embryo explants and embryoids.

Nine experiments were conducted to determine effects of various culture medium addenda on inducation of embryogenic calli from immature embryos of a responsive Triticum aestivum L. genotype (PCYT 10). Effects were quantified by counting somatic embryos (embryoids) per callus. Optimal auxin concentrations to induce and maintain somatic embryogenesis were 3.62 #M 2,4-dichlorophenoxyacetic acid (2,4-D) or 9.05/~M 3,6-dichloroo-anisic acid (dicamba). In general, dicamba permitted formation of significantly more embryoids than 2,4-D. Kinetin (6-furfurylaminopurine) at 2.56#M or 4.65 #M significantly increased percentage scutellar callus when added to 2,4-D or dicamba-containing medium, respectively. Kinetin at 4.65 #M significantly increased the numbers of embryoids formed when added to medium containing either synthetic auxin. Significantly fewer embryoids formed when cultures were incubated under diffuse light (16-h photoperiod). Casein hydrolysate (200mgl -l) or L-arginine (0.23 mM) had no effect on numbers of embryoids formed, whereas L-tryptophan (0.20mM) enhanced such formation with 2,4-D and decreased such formation with dicamba. Two additional experiments generally demonstrated that response to auxin source in the genotypes ND 7532, PCYT 20, Yaqui 50, and Oasis was similar to that in PCYT 10. The higher molar concentration of dicamba required to induce embryogenic callus coupled with more evident embryoid precocious germination and a more rapid rate of tissue necrosis upon extended incubation without subculture suggests that dicamba is metabolized more rapidly than 2,4-D in T. aestivum callus cultures.

Nine experiments were conducted to determine effects of various culture medium addenda on induction of embryogenic calli from immature embryos of a responsive Triticum aestivum L. genotype (PCYT 10). Effects were quantified by counting somatic embryos (embryoids) per callus. Optimal auxin concentrations to induce and maintain somatic embryogenesis were 3.62 #M 2,4-dichlorophenoxyacetic acid (2,4-D) or 9.05/aM 3,6-dichloro-oanisic acid (dicamba). In general, dicamba permitted formation of significantly more embryoids than 2,4-D. Kinetin (6-furfurylaminopurine) at 2.56 #M or 4.65 #M significantly increased percentage scutellar callus when added to 2,4-D or dicamba-containing medium, respectively. Kinetin at 4.65/aM significantly increased the numbers of embryoids formed when added to medium containing either synthetic auxin. Significantly fewer embryoids formed when cultures were incubated under diffuse light (16-h photoperiod). Casein hydrolysate (200 mg 1 -t) or L-arginine (0.23 mM) had no effect on numbers of embryoids formed, whereas L-tryptophan (0.20raM) enhanced such formation with 2,4-D and decreased such formation with dicamba. Two additional experiments generally demonstrated that response to auxin source in the genotypes ND 7532, PCYT 20, Yaqui 50, and Oasis was similar to that in PCYT 10. The higher molar concentration of dicamba required to induce embryogenic callus coupled with more evident embryoid precocious germination and a more rapid rate of tissue necrosis upon extended incubation without subculture suggests that dicamba is metabolized more rapidly than 2,4-D in T. aestivum callus cultures.

Somatic embryo (embryoid) formation from immature-embryo-derived caUi was quantified in replicated experiments involving 10 Triticum aestivum L. genotypes. Several published media formulations, which had previously been optimized for wheat tissue culture, were tested for each genotype. Embryos from each plant were randomly assigned to each medium. Percentage precocious germination of immature embryos and mean percentage scutellar callus per explant were recorded. Embryoids per callus were determined by microscopic examination at 28 and 56 days. There were highly significant differences among genotypes, media, and individual plants from which explants were taken. A medium based on double the Murashige and Skoog (MS) inorganic salt concentration was significantly better than other media. Inclusion of all MS vitamins appeared essential for optimal response. Two genotypes were tested in a second experiment where both 3,6-dichloro-o-anisic acid (9.05/aM) and 6-furfurylaminopurine (0.46 #M) were substituted for 2,4-dichlorophenoxyacetic acid (4.52 pM) in either double or normal MS medium. This substitution significantly increased embryoid formation at 28 days. Additions of either 6-furfurylaminopurine or coconut water increased precocious germination of both embryo explants and embryoids.