Capturing heterosis on the basis of a CMS system in Chenopodium quinoa

The world faces a series of challenges in the agri-food sector e.g. providing enough food for a growing world population of 9 billion in 2050 while simultaneously mitigating the effects of climate change. A part of the strategy to increase food production worldwide is the introduction of new robust crop species, adapted to adverse conditions like drought and salinity. The transition to a more plant-based protein production would result in more efficient use of natural resources. Quinoa (Chenopodium quinoa) has gained popularity in the past decades due to its high quality protein, composed of all essential amino acids. In addition, quinoa can withstand adverse conditions, it can tolerate salinity levels higher than 20ds/m. This crop has been cultivated for over 5000 years in a wide range of environments in the Andes, varying from moderate climates in the coastal lowlands of Chile and the marginal soils of the Andean highlands of Peru and Bolivia, up to 4000 meters above sea level. Quinoa breeding efforts are in its infancy and were mostly aimed to allow cultivation in Western Europe and North-America by selecting day-length insensitive varieties with shorter crop cycle length and the removal of saponins from the seed coat. Despite breeding efforts, yield has remained low in these regions, averaging 1.8 tons/hectare with regional and seasonal exceptions reaching 3.5 tons / hectare. Current breeding goals are strongly focused on improving yield. A major development in plant breeding was the introduction of hybrid varieties for crops like maize, wheat and rice, resulting in higher yields by making use of heterosis. Creating hybrid varieties reliably and on a large scale is currently impossible for quinoa due to it being a self-pollinator and having small hermaphrodite and female flowers bundled in dense clusters, making complete and large-scale emasculation unfeasible. The overall aim of this project is to develop F1 hybrid varieties by using a genetic source of male sterility (cytoplasmic male sterility). The first objective is to understand the genetics behind our source of male sterility, in particular identifying how many restorer/maintainer alleles are interacting with the sterility factors encoded by the mitochondrial genome. The second objective is to test if F1 hybrid varieties have the potential to outperform inbred lines by testing combining ability of several parental lines. Quinoa is an allotetraploid species with an A and a B genome, resulting in a fixated heterosis coming from the complementarity of both ancestors. Expected heterosis might therefore be lower compared to that of diploid species. On the other hand, quinoa knows five distinct ecotypes covering a wide range of genotypes with significant genetic distance. The potency of F1 hybrids has not yet been explored in quinoa. If both objectives are achieved, it will be a major progress towards the development of the first hybrid varieties.