Enhancement of embryogenesis in freshly isolated microspore cultures of ornamental kale through direct cold shock treatment

Abstract

Heat shock treatment of isolated microspore cultures (IMCs) at 32–33 °C for 1–3 days is almost the rule to induce microspore embryogenesis in most Brassica species. In this study, the effect of cold shock treatment of fresh IMCs on embryogenesis in ornamental kale was investigated. The open field-grown ‘Songbird Red’ F1 cultivar was used as donor plant. The microspores at mostly late unicellular stage were cultured in NLN - 15 % sucrose medium containing activated charcoal. As shock treatment (T), the fresh IMCs were subjected to either 32 °C for 2 days (T1) or 4 °C for 1 (T2), 2 (T3), and 3 days (T4). The highest embryo yield (37.75 mean embryos/Petri dish) occurred for cold shock at 4 °C for 1 day in T2. This application produced 7.7-fold more embryos than the common heat shock of 32 °C for 2 days in T1. Cold shock also affected the embryogenesis pathway. While filamentous suspensor-like structures were observed only in T2, embryo growth without suspensor was observed in both T1 and T2. In conclusion, the exposure of IMCs to 32 °C for 2 days is not a prerequisite for induction of microspore embryogenesis in ornamental kale.