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Agnieszka Płażek and Franciszek Dubert

Improvement of Medium for Miscanthus x Giganteus Callus Induction and Plant Regeneration

Miscanthus x giganteus tissue cultures brown quickly and strongly, probably as an effect of oxidation of phenolics produced by plant tissue. The aim of the work was to improve the medium composition for callus induction and plant regeneration of M. giganteus, with two experiments. The first one was aimed at developing a protocol to inhibit biosynthesis and oxidation of phenolics. Callus was induced from immature inflorescences on basal MS medium with 6.5 mg · dm-3 2,4-D, 0.25 mg · dm-3 BAP, 500 mg · dm-3 casein hydrolysate and 30 g · dm-3 sucrose (control medium), and this medium supplemented with one of the following: 200 mg · dm-3 chitosan, 65 g · dm-3 banana pulp (BP), 100 mg · dm-3 cysteine, or 30 g · dm-3 honey instead of sucrose. Plant regeneration used basal MS medium supplemented with 30 g · dm-3 sucrose and 0.2 mg · dm-3 BAP or 0.05 mg · dm-3 KIN. The second experiment was to verify whether BP and honey increase callus production and plant regeneration. For callus induction the explants were put on the control medium and medium supplemented with one of these: 65 g · dm-3 BP, 30 g · dm-3 honey instead of sucrose, or 65 g · dm-3 BP + 30 g · dm-3 honey instead of sucrose. The regeneration medium was basal MS medium supplemented with 0.05 mg · dm-3 KIN and 30 g · dm-3 sucrose or 30 g · dm-3 honey. Tissue browning was independent of medium content, but there was less browning on medium supplemented with honey. In the first experiment, regenerated plants were obtained only on basal MS medium with 30 g · dm-3 sucrose and 0.05 mg · dm-3 KIN. In the second experiment, MS medium containing BP and honey instead of sucrose was the best medium for callus induction, and regeneration from these calli was highest on basal MS with KIN and honey.

Open access

Aneta Słomka, Elżbieta Kuta, Agnieszka Płażek, Franciszek Dubert, Iwona Żur, Ewa Dubas, Przemysław Kopeć and Grzegorz Żurek

Miscanthus ×giganteus Greef et Deu. (Poaceae), a hybrid of Miscanthus sinensis and M. sacchariflorus native to Japan, is an ornamental and a highly lignocellulosic bioenergy crop, cultivated in the European Union as an alternative source of energy. This grass reproduces exclusively vegetatively, by rhizomes or via expensive in vitro micropropagation. The present study was aimed at finding the barriers that prevent sexual seed production, based on detailed embryological analyses of the whole generative cycle, including microsporogenesis, pollen viability, megasporogenesis, female gametophyte development, and embryo and endosperm formation. Sterility of M. ×giganteus results from abnormal development of both male and female gametophytes. Disturbed microsporogenesis (laggard chromosomes, univalents, micronuclei) was further highlighted by low pollen staining. The frequency of stainable pollen ranged from 13.9% to 55.3% depending on the pollen staining test, and no pollen germination was observed either in vitro or in planta. The wide range of pollen sizes (25.5-47.6 μm) clearly indicated unbalanced pollen grain cytology, which evidently affected pollen germination. Only 9.7% of the ovules developed normally. No zygotes nor embryos were found in any analyzed ovules. Sexual reproduction of M. ×giganteus is severely hampered by its allotriploid (2n=3x=57) nature. Hybrid sterility, a strong postzygotic barrier, prevents sexual reproduction and, therefore, seed formation in this taxon.