Abstract
Androgenic responsiveness in anther (AC) and isolated microspore cultures (MC) was analysed using 15 lines of Polish winter rye (Secale cereale L.). The effect of low temperature (LT) alone or in combination with osmotic stress induced by mannitol treatment (MAN) and/or with reduced glutathione (GSH) on the effectiveness of the process was studied. Interestingly, each treatment had a different effect on microspore (mcs) vitality and capability to divide symmetrically. The first criterion for successful embryogenesis was to exceed the threshold number of at least 25% dividing microspores, which determined ‘embryogenic suspension culture’. In some configurations a spectacular effect was achieved, especially in lines highly recalcitrant to androgenesis induction. Relatively high effectiveness of androgenesis induction (up to 4.58 AS per 105 mcs per spike in MC and 21.29 AS per spike in AC) showed that the developed protocol with GSH and/or MAN tiller pre-treatments overcomes the genotypic barrier for androgenesis initiation in rye. Moreover, relatively high, spontaneous genome diploidization (55%) of regenerated plants demonstrated that the described protocols could be effectively integrated into conventional rye breeding programmes.
Highlights
Due to low soil and climate requirements as well as low sensitivity to unfavourable environmental conditions, rye (Secale cereale L.) currently belongs to the most important crops in the EU cereals market
Microspore viability was significantly influenced by the genotype of donor plants (Table 2; Fig. 1b, c, S1, S2), tiller pre-treatments (Control, GSH, mannitol treatment (MAN), GSH/ MAN, MAN and its combination with GSH (MAN/GSH)) had a significant effect on the mean microspore vitality and the frequency of symmetric divisions leading to androgenic structure (AS) formation under in vitro conditions in all categories (Fig. 1, S3, S4)
Research focused on optimization of rye (S. cereale L.) doubled haploids (DHs) production protocols was performed in several national research centers without spectacular success (Zimny 1993; Immonen and Anttila 1996a, b; Szarejko 2003)
Summary
Due to low soil and climate requirements as well as low sensitivity to unfavourable environmental conditions (e.g. low temperatures, salinity, water deficit), rye (Secale cereale L.) currently belongs to the most important crops in the EU cereals market. Rye is the best crop for healthy human nutrition because of much higher levels of total antioxidants, carbohydrates, proteins, vitamins, and especially dietary fibers (https://www.openaccessgovernment.org/healthyminorcereals-project/43195/; Tenhola-Roininen 2009). Gametophytic self-incompatibility and cross pollination significantly slow down rye breeding progress (Lundqvist 1956). Improvement of this crop is possible by conventional population breeding or hybrid breeding. In both breeding systems the implementation of totally homozygous doubled haploids (DHs) can shorten the time needed for the production of a new variety and increase the efficiency of desired trait selection. As the process is controlled by a complex network of internal and environmental factors, the realisation of this theoretically huge embryogenic potential is quite unique in laboratory practise (Ferrie and Caswell 2011; Żur et al 2013)
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