Somatic embryogenesis and plant regeneration from fragments of immature inflorescences and coleoptiles of durum wheat

Somatic embryogenesis and plant regeneration were obtained from the culture of immature inflorescence and coleoptile fragments of ten durum wheat cult ivars. The explants were cultivated on Murashige and Skoog (MS) medium with various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), 2.3 mu M to 11.3 mu M. After four to six weeks, both types of explants produced emb ryogenic and non-embryogenic calli. Embryogenic calli developed somatic emb ryos which produced normal fertile plants without visible abnormalities. Fo r inflorescence fragments, the highest frequencies of embryogenic callus fo rmation (100% for most cultivars) and regeneration (100% for 'Massa' and 'I sly') were obtained from 0.5 or 1-cm-long fragments incubated on media cont aining 6.8 mu M of 2,4-D. For coleoptile explants, embryogenesis and especi ally regeneration, frequencies were generally lower than for inflorescence fragments. The results depended largely on the length of the coleoptile exp lant, where fragments of 1 mm were better than 2 to 4-mm-long segments. The 2,4-D concentration did not influence callus induction but, for regenerati on, 9 mu M was best. For both inflorescence and coleoptile explants, and in our culture conditions, a genotype effect on callus induction and plant re generation was observed.