Environmental control of dormancy in quinoa (Chenopodium quinoa) seeds: two potential genetic resources for pre-harvest sprouting tolerance

Abstract

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.

Structural aspects of dormancy in quinoa (Chenopodium quinoa): importance and possible action mechanisms of the seed coat

“…1B with D for Chadmo). Under low incubation temperatures (5 and 108C) the expression of dormancy is stronger in quinoa seeds (Ceccato et al, 2011). Under low incubation temperatures (5 and 108C) the expression of dormancy is stronger in quinoa seeds (Ceccato et al, 2011).…”

“…Similar results were reported previously in the genus Chenopodium for C. polyspermum, C. album and C. bonus-henricus (Jacques, 1968;Karssen, 1970;Pourrat andJacques, 1975, Dorne, 1981). Temperatures and photoperiods experienced during this period are associated with seed dormancy level in quinoa (Ceccato et al, 2011). However, the fact that Chadmo seeds did not respond in that way to sowing date is a warning against generalizations of these patterns to the whole species.…”

“…In seeds belonging to the late sowing date a significant level of coat-imposed dormancy was still expressed in 2-Want at 10 and 58C, overcome by perforation (Fig. The fact that dry afterripened seeds of both accessions achieve maximum germination at 10 and 58C (Ceccato et al, 2011), indicates that the observed reduction in germination was due to dormancy expression, and not a consequence of nonoptimal temperatures for germination. Chadmo seeds expressed strongly reduced germination under low incubation temperatures, which was not overcome by coat perforation (Fig.…”

“…Briefly, two quinoa accessions, Chadmo and 2-Want, both presenting dormancy at harvest, were cultivated in the field (34860 0 S, 58865 0 W, Hurlingham, Buenos Aires, Argentina) on three sowing dates during the first experimental year (2 November, 27 December and 13 March) and on two sowing dates during the second experimental year (7 November and 8 February) during 2005-2006 and 2006-2007. Furthermore, random samples of the same seed lot, taken months later, had 100% germination (Ceccato et al, 2011). Environmental data were obtained from a conventional meteorological station located about 300 m from the experimental site [Instituto de Clima y Agua, Instituto Nacional de Tecnología Agropecuaria (INTA)].…”

Seeds of future past: climate change and the thermal memory of plant reproductive traits

“…In terms of thermal time, the rate of dormancy change is a function of exposure to post-dispersal temperatures (Pritchard et al, 1996). The rate of dormancy loss is proportional to the difference between the actual temperature and a thermal threshold for dormancy change (Ceccato, Daniel Bertero & Batlla, 2011), and thus can be incorporated into the model by considering a separate set of dormancy-change thermal traits.…”