Crossing methods and cultivation conditions for rapid production of segregating populations in three grain amaranth species

Abstract

BackgroundGrain amaranths (Amaranthus sp) have been cultivated for thousands of years in Central and South America. Their grains are of high nutritional value, but the low yield needs to be increased by selection of superior genotypes from genetically diverse breeding populations. Amaranths are adapted to harsh conditions and can be cultivated on marginal lands although little is known about their physiology. The development of controlled growing conditions and efficient crossing methods is important for research on and improvement of this ancient crop. Grain amaranth was domesticated in the Americas and is highly self-fertilizing with a large inflorescence consisting of thousands of very small flowers. We evaluated three different crossing methods (open pollination, hot water emasculation and hand emasculation) for their efficiency in amaranth and validated them with genetic markers. ResultsWe identified cultivation conditions that allow an easy control of flowering time by manipulating day length manipulation and achieved flowering times of four weeks and generation times of two months. All three different crossing methods successfully produced hybrid F 1 offspring, but with different success rates. Open pollination had the lowest (10%) and hand emasculation the highest success rate (74%). Hot water emasculation showed an intermediate success rate (26%) with a maximum of 94% success. It is simple to perform and suitable for a more large-scale production of hybrids. We further evaluated 11 single nucleotide polymorphism (SNP) markers and found that they were sufficient to validate all crosses of the genotypes used in this study for intra-and interspecific crosses. Conclusions Despite its very small flowers, crosses in amaranth can be carried out efficiently and evaluated with inexpensive SNP markers. Suitable growth conditions strongly reduce the generation time and allow the control of plant height, flowering time and seed production. In combination, this enables the rapid production of segregating populations which makes amaranth an attractive model for basic plant research but also facilitates further the improvement of this ancient crop by plant breeding.

Speed breeding: a powerful tool to accelerate crop research and breeding

“…Speed breeding methods have already been successfully applied to accelerate breeding objectives for amaranth (Amaranthus spp.) [17] and peanut (Arachis hypogaea) [18]. For species that require short days to trigger the reproductive phase, such as rice (Oryza sativa) and maize (Zea mays), the speed breeding technique could be used to promote rapid vegetative growth prior to reducing the photoperiod.…”