In vitro morphogenesis and plant regeneration from seed and leaf explants of four Agropyron species

The study investigated the effects of growth regulators, supplemented to semi-solid or liquid variants of MS medium, on in vitro callogenesis and morphogenesis from seeds and leaf explants of four Agropyron species, native of Iran and used also in gardening, i.e., A. cristatum, A. desertorum, A. intermedium and A. trichophorum. Experiments were conducted both in darkness and under a 16 h photoperiod, however no significant difference was observed between them as for callus induction. For all the species, callus (embryogenic and/or organogenic) formation on semi-solid medium was better (up to 40% of callusing seeds) when MS medium was supplemented with 5 or 10 mu M 2,4-D. Shoot development from those organogenic calluses was easily obtained by transferring them on semi-solid MS medium, supplemented with 2.7 mu M NAA, 6.7 mu M BAP and 2.3 mu M kinetin. Elongated shoots were rooted on semi-solid MS medium, containing 5 mu M NAA and 0.5 mu M kinetin. However, further development of embryogenic calluses was not possible, unless callus induction was obtained in liquid MS medium. On the contrary, embryogenic masses of A. cristatum and, to a less extent, A. trichophorum developed further and gave rise to plantlet regeneration when those masses were induced in liquid MS medium, supplemented with 5 mu M 2,4-D, and then transferred in liquid growth regulator-free MS medium under continuous agitation. Plantlets from both organogenesis (all four species) and somatic embryogenesis (A. cristatum) were easily acclimatized in pots under greenhouse conditions. As regards leaf explants, callus induction was maximum when MS medium was supplemented with 5 mu M 2,4-D; however, plant regeneration was never observed from leaf-derived calluses, neither via organogenesis nor via somatic embryogenesis.