INTRAESPECIFIC VARIABILITY AND MATERNAL ENVIRONMENT EFFECTS ON SUNFLOWER (Helianthus annuus) DORMANCY TRAITS

ARATA GONZALO JOAQUÍN; RIVEIRA RUBIN MAILÉN; BATLLA DIEGO; RODRIGUEZ MARÍA VERÓNICA

Monterrey, California USA

Conferencia; 12th Triennial International Society for Seed Science Conference; 2017

International Society for Seed Science

Although the presence of dormancy in sunflower fruits at harvest is a usual problem to the seed industry, there is little information about intraspecific variability for this trait and the regulation by the environment during fruit development. The aim of the present work was to define dormancy phenotypes resulting from intraspecific variability, and their interaction with the maternal environment. To achieve these objectives 20 sunflower genotypes were sown under irrigated field conditions in different planting dates during two consecutive years. Genotypes were classified according to i) dormancy expression along the thermal range ii) rate of dormancy release during storage, iii) contribution of the fruit components to dormancy, and iv) embryo sensitivity to GA and ABA. At harvest, and at regular times during storage, achene, seed and embryo germination was evaluated at different temperatures (10-30°C). In addition, in selected genotypes, achenes and embryo germination response to ABA, GAs and their corresponding synthesis inhibitors was also evaluated. Two main groups were obtained: HTED and LTED (High and Low temperature expressed dormancy), the first of which included the wild relatives and two domesticated lines, and the rest belonged to the LTED group. Both groups were subdivided further according to the persistence of embryo dormancy, and coat-imposed dormancy. Interaction with the maternal environment was significant for most genotypes tested. Obtained results showed that fruits exposed to lower temperatures and shorter photoperiods during development presented a lower achene and embryo dormancy level at harvest and a higher achene dormancy release rate during storage. These differences in dormancy level were mainly expressed at low incubation temperatures (10°C); temperature at which dormancy was expressed more strongly in most of the genotypes. In addition embryos excised from fruits matured under late sowing environments showed a significant lower inhibition of germination by ABA than those matured under earlier sowing date environments, indicating that observed dormancy level regulation by the maternal environment could be partially explained by differences in embryo sensitivity to ABA. Sensitivity of isolated embryos to ABA appears as the main trait related to differences in dormancy level among genotypes, and in response to the maternal environment.