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Effects of Genotype and Pretreatment on the Pollinic Embryogenesis of Spring Triticale (X Triticosecale Wittmack)

Ali Ltifi, Faouzi Haouala

Abstract


The aim of this work was to obtain haploid plants of spring triticale through pollinic embryogenesis and to study the genotype and pretreatment effects on the anther culture response. Microspore embryogenesis represents a unique system of single cell reprogramming in plants and the microspore, by specific pretreatments, switches towards an embryogenesis pathway. The study was carried out on 3 varieties (Tcl82, Tcl83, Bienvenu) and 7 lines (Liron, Dix, Pollmer, Sardev, Sphd, Copi and Ardi) of triticale. Seedlings were cultivated in an open field and spikes were removed when the microspores were at the mid to late uninucleate stage. Spikes containing microspores were subjected to different pretreatments: cold, cold combined with thermal shock, and cold combined with osmotic shock. Anthers were cultured then in three induction media: M1 is the medium 190-2 of Wang and Hu (1984) modified, M2 is the medium M1 in which the agar has been substituted by the ficoll, and M3 is the medium BAC3 of Szarejko and Kasha (1991) modified by the substitution of ficoll by agar. They were placed in an incubator in dark at 28°C during 30 to 40 days until the embryos and calli of pollen origin appeared. Embryos and calli were transferred after in the regeneration medium 190-2 without hormones. Seedling regeneration occurred at 24°C with 16-hour of light photoperiod. In vitro androgenesis for the genotypes Tcl1 (recalcitrant to anther culture), Tcl2, and Tcl4 (respond well to anther culture) was induced with all pretreatments. However, the treatments T1 and T3 gave the better induction of androgenesis and were more favorable to the regeneration of green plants. Production of embryos was the highest on the semi-liquid medium (M2) and the number of embryos per 100 anthers was 32.0, 33.3, and 11.5 for the genotypes Tcl1, Tcl2, and Tcl4, respectively. The number of embryos formed per 100 cultured anthers varied from 3.4 for genotype 'Ardi' to 50.6 for the genotype 'Copi'. The genotypes 'Copi', 'Tcl3', 'Liron' and 'Tcl83' showed a good regeneration capacity with 3.5, 2.7, 2.7, and 2.2 plants per 100 cultured anthers, respectively. Cold at 4°C for 3 weeks applied alone or in combination with mannitol was the most favorable treatment for the induction of embryos and the regeneration of green plants. The semi-liquid medium containing ficoll was more favorable to the induction of embryos than the solid medium containing agarose. However, the semi-liquid and solid media had equivalent effects on plant regeneration.


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