Two possible sources of resistance to pre-harvest sprouting were evaluated in quinoa. They showed dormancy at harvest and significant variations in dormancy level in response to environmental conditions experienced during seed development. The aims of this work were to evaluate the importance of seed coats in the regulation of dormancy in this species, to investigate possible mechanisms of action and to assess association of seed coat properties with changes in dormancy level caused by the environment. Accessions Chadmo and 2-Want were grown under field conditions on different sowing dates during 2 years. Seed coats were manipulated and seed germination was evaluated at different temperatures. Seed coat perforation before incubation led to faster dormancy loss in both accessions. This effect decreased with delayed sowing date, and seeds expressed a level of dormancy not imposed by coats. This suggests the presence of embryo dormancy in the genus Chenopodium. Seeds of the accession 2-Want had a significantly thinner seed coat at later sowing dates, associated with a decreasing coat-imposed dormancy, but this pattern was not detected in Chadmo. The seed coat acts as a barrier to the release of endogenous abscisic acid (ABA) in quinoa, suggested by the increase in germination and a higher amount of ABA leached from perforated seeds. ABA is able to leach from seeds with an intact seed coat, suggesting that differences in seed coat thickness may allow the leakage of different amounts of ABA. This mechanism may contribute to the observed differences in dormancy level, either between sowing dates or between accessions.

Pre-harvest sprouting (PHS) is a serious risk when adapting quinoa (Chenopodium quinoa) seed production to different temperate environments. Two quinoa accessions, ‘2-Want’ and ‘Chadmo’ were evaluated under field conditions in the Argentinean pampas over 2 years on five different sowing dates, to explore a range of climate conditions under which seed filling is manageable in this region. Both accessions exhibited dormancy during seed development and maturation under the conditions examined; however, dormancy expression was restricted to low temperatures in 2-Want, while seeds of Chadmo, originating from the humid island of Chiloe, southern Chile, expressed a high level of dormancy at all examined temperatures. Dormancy release was observed as a reduction in the lowest temperature permissible for seed germination, which broadened the optimal germination temperature window. Higher storage temperature increased the rate of dormancy release. The environment during seed development on the mother plant affected the levels and patterns of seed dormancy, with higher temperatures and longer photoperiods promoting dormancy. As dormancy was released before the next production period, the levels of dormancy observed in the accession would allow timely planting and uniform germination, while dormancy during seed maturation ensures the prevention of PHS. Chadmo showed deeper dormancy levels in all situations, compared with 2-Want, therefore greater PHS tolerance under various conditions in the pampas region can be expected for Chadmo, which makes this accession a better candidate to be included in adaptive breeding programmes for quinoa.

Quinoa (Chenopodium quinoa Willd.) is a staple food crop for millions of impoverished rural inhabitants of Andean South America where it has been cultivated for millennia. Interest in quinoa, due largely to its superior nutritional characteristics, is fuelling a growing export market and has led to an increased focus on genetic research and the development of quinoa breeding programmes throughout South America. The success of these breeding programmes will rely heavily on the development of core germplasm collections and germplasm conservation. We report the development of a set of fluorescence-tagged microsatellite molecular markers that can be used to characterize genetic diversity within quinoa germplasm and we use this set of 36 microsatellites markers to genetically characterize the diversity of 121 accessions of C. quinoa held in the USDA germplasm bank, 22 accessions from the CIP-FAO international nursery collection and eight accessions representing parents from genetic mapping populations. A total of 420 alleles were detected among the quinoa accessions with an average of 11 alleles detected per microsatellite locus. Genetic heterogeneity was observed in 32% of the quinoa accessions at a given locus and suggests that many of these accessions represent heterogeneous seed lots or landraces. Both unweighted pair-group method with arithmetic averages (UPGMA) and principle components analysis (PCA) analyses partitioned the quinoa accessions into two main clusters. The first major cluster consisted of accessions from the Andean highlands of Peru, Bolivia, Ecuador, Argentina and extreme northeastern Chile. The other main cluster contained accessions from both the lowlands of Chile and a set of USDA accessions with no known passport data, collected by Emigdio Ballón. Using the patterns of genetic diversity detected within the C. quinoa accessions we discuss hypotheses regarding quinoa's centre of diversity, including highland and lowland ecotype clustering patterns, origin of lowland varieties, origin of domestication, and diversity levels in the USDA and CIP-FAO collections.