Induction and development of anther-derived gametic embryos in cucumber (Cucumis sativus L.) by optimizing the macronutrient and agar concentrations in culture medium

Anther culture response of a cucumber cultivar (Beta Alpha) and three Iranian landraces of cucumber (Basmenj, Isfahani, and Korki) on MS culture media with an altered macronutrient strength (half, full, 1.5-fold, and double-strength) or various concentrations of agar (0, 3.5, 7, and 14 g L-1) was evaluated in two separate experiments. The effect of different concentrations of agar on the development of callus-derived embryos was also assessed. The androgenic potentials of various cucumbers were significantly (P < 0.01) influenced by the different macronutrient strengths and agar concentrations, although anther culture responses could vary according to the cucumber type. A doubled strength of macronutrients in culture medium resulted in the highest percentage of callogenesis (100%) in Isfahani cucumber, while use of full strength of macronutrients produced the highest percentage of embryogenic calli (83.33%) in the mentioned landrace compared to other tested forms. The maximum number of gametic embryos (1.26 and 1.23 embryos/anther) differentiated from Isfahani anther cultures on full-and half-strength MS medium, respectively. In the second experiment, the highest percentages of callogenesis were obtained in MS culture media solidified with 14 g L-1 and 7 g L-1 agar for Basmenj, with 3.5 g L-1 agar or liquid medium for Isfahani, with 7 g L-1 agar for Beta Alpha, and with 14 g L-1 agar for Korki. Culture media solidified with 7 g L-1 agar produced the highest percentage of embryogenic calli compared to other treatments. Anther culture of Korki cucumber on culture medium with 14 g L-1 agar produced the maximum number of embryos per anther compared to other cucumbers. Improved production of mature somatic embryos (torpedo and cotyledonary embryos) was achieved with higher agar concentrations (7 and 14 g L-1) for the cucumber cultivar and all landraces.