The improvement of maize (Zea mays L.) anthers tissue culture by the addition of free amino acids in the culture medium

Maize (Zea mays L.) anthers of the variety Zac.58-VO and the H-34 hybrid were cultivated in liquid and solid Murashigue-Skoog (MS) and Yu Pei (YP) media supplemented with one, three, 10, 30 or 100 times the original concentration of the five most abundant free amino acids previously found in the same maize anthers. These amino acids were alanine, asparagine, aspartic acid, and glutamic acid, as well as serine in Zac.58-VO and glutamine in H-34. The results indicate that free amino acid composition of anther-containing microspores in the mid-uninucleate stage of microsporogenesis show few significant differences between cultivars. Addition of the five most abundant free amino acids to the culture media improve anther viability, callus formation, and development of embryo-like structures. Both MS and YP liquid media, supplemented with three and 10 times the amino acid concentration, increased 12 and 20 days anther viability in Zac.58-VO and H-34, respectively. Callus induction and embryolike structures formation were 10% and 9.5% for the hybrid H-34 in YP liquid medium supplemented with three times the free amino acid concentration. In contrast, anthers of the landrace Zac.58-VO cultivated under the same conditions yielded only 4% and 3.5%, respectively. Therefore there exists a dose relationship between the degree of improvement of the cultivar and the expression of the androgenic character.