Responses of explant type of wheat (Triticum aestivum L.) genotypes to different tissue culture media

Abstract

Wheat recalcitrance to in vitro culture is one of the most important and crucial steps for its genetic transformation, and is directly associated with the ability of the explant to regenerate, composition of the media and genotype. Callus induction and regeneration potential of various explants, viz, mature embryo, immature embryo, endosperm supported (ES) mature embryo and shoot apical meristem, taken from the same plants of two wheat genotypes (AS-2002 and GA-2002) were investigated using Murashige and Skoog (MS) basal callus induction medium supplemented with 2, 4, 6 or 8 mg/L of 2,4-dichlorophenoxyacetic acid (2,4-D) and regeneration media comprising various combinations of auxins and cytokinins. In vitro culture response of the explants taken from the same plant varied from each other and was influenced by the genotype and media composition. Immature embryo culture of genotype AS-2002 exhibited the highest callusing ability (84.75 %) followed by the mature embryo culture of genotype GA-2002 (78.50 %). Similarly, immature embryos cultured on MS basal medium supplemented with 4 mg/L 2,4-D and mature embryos cultured on MS basal medium supplemented with 6 mg/L 2,4-D exhibited the highest callusing ability of 90.83 and 88.33 %, respectively. Immature embryos of genotype GA-2002 cultured on MS based regeneration medium supplemented with 0.2 mg/L 2,4-D, 0.5 mg/L zeatin and 0.5 mg/L benzylaminopurine (BAP) showed a significantly higher regenerating potential. ES mature embryos of genotypes GA-2002 and AS-2002 cultured on regeneration medium comprising 0.4 mg/L 2,4-D, 1.0 mg/L zeatin and 1.5 mg/L BAP showed maximum regeneration potentials of 59.67 and 59.0 %, respectively. Appraisal of the responses of the four explants used showed that endospermsupported mature embryo is the most suitable explant for plant regeneration in wheat.