Intraespecific variability and maternal environment effects on sunflower (Helianthus annuus) dormancy traits

MAILEN RIVEIRA RUBIN; GONZALO ARATA; LOPEZ ESTEBAN; MARIA VERONICA RODRIGUEZ; BATLLA DIEGO

Conferencia; 12th Conference of the International Society for Seed Science; 2017

Although the presence of dormancy in sunflower fruits at harvest is an usual problem to the seedindustry, there is little information about intraspecific variability for this trait and the regulation by theenvironment during fruit development. The aim of the present work was to define dormancyphenotypes resulting from intraspecific variability, and their interaction with the maternal environment.To achieve these objectives 20 sunflower genotypes were sown under irrigated field conditions indifferent 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 differenttemperatures (10-30°C). In addition, in selected genotypes, achenes and embryo germination responseto ABA, GAs and their corresponding synthesis inhibitors was also evaluated. Two main groups wereobtained: HTED and LTED (High and Low temperature expressed dormancy), the first of whichincluded the wild relatives and two domesticated lines, and the rest belonged to the LTED group. Bothgroups were subdivided further according to the persistence of embryo dormancy, and coat-imposeddormancy. Interaction with the maternal environment was significant for most genotypes tested.Obtained results showed that fruits exposed to lower temperatures and shorter photoperiods duringdevelopment presented a lower achene and embryo dormancy level at harvest and a higher achenedormancy release rate during storage. These differences in dormancy level were mainly expressed atlow incubation temperatures (10°C); temperature at which dormancy was expressed more strongly inmost of the genotypes. In addition embryos excised from fruits matured under late sowingenvironments showed a significant lower inhibition of germination by ABA than those matured underearlier sowing date environments, indicating that observed dormancy level regulation by the maternalenvironment could be partially explained by differences in embryo sensitivity to ABA. Sensitivity ofisolated embryos to ABA appears as the main trait related to differences in dormancy level amonggenotypes, and in response to the maternal environment.