STRIGOLACTONES AND BRASINOESTEROIDS AND THEIR INTERACTION WITH ABSCISIC ACID IN THE BREAKING OF SEED DORMANCY OF SUNFLOWER (Helianthus annuus L.)

M. DELLA MADALLENA; ALEMANO S.; A. ANDRADE; DEL BEL Z.; A. VIGLIOCCO

Otro; IV Reunión Conjunta de Sociedades de Biología de la República Argentina; 2020

In agriculture, the successful and uniform seed germination is important to avoid problems in the establishment of seedlings that ultimately impact on the crop yield. Thus, dormancy is an undesirable trait, for this reason different treatments have been implemented to overcome this problem. Germination and dormancy are processes modulated mainly by the abscisic acid (ABA)/gibberellin (GAs) balance, but other hormonal groups such as strigolactones (SLs) and brassinosteroids (BRs), also participate in its regulation. The objective of this investigation was to elucidate the hormonal changes that occur in the embryonic axis in response to exogenous treatments with growth regulators that also impact on the breaking of seed dormancy in sunflower seeds. Cypsels of Xi3 line, characterized as dormant at harvest, were supplied by the Argentine Cooperatives Association (ACA) and used in this research study. Treatments with GA3 and Ethephon, both effective in the sunflower dormancy release, were applied alone or in combination. Endogenous hormonal determinations were performed in the embryonic axis of control and treated seeds at 0 (dry seed), 3, 6, and 12 h of imbibition. ABA, BRs (Castasterone ?CS?) and SLs (deoxystrigol ?DS?) were extracted twice with diethyl ether and identified and quantified by Liquid Chromatography-Tandem Mass Spectrometry (LC?ESI/MS?MS). Regarding ABA, during the imbibition all treatments reduced their endogenous level respect to 0 h, but no differences were observed between treatments and control condition. It is widely accepted that not only endogenous levels of ABA and GAs but also the ABA/GAs ratio constitutes a central mechanism in the regulation of seed germination and dormancy. In this sense, the ABA/GA1 ratio showed a significant decrease at 12 h for all treatments in comparison to the control. Respect to DS, at 12 h of imbibition reached relatively lower endogenous levels in the embryonic axis treated with respect to the control condition, which suggests that DS should not exceed a threshold level of approximately 40,000 pmol/g PS to trigger germination. In relation to CS, a notable increase was registered at 12 h imbibition, which would indicate its participation in germination. In conclusion, it is necessary that endogenous levels of ABA and DS remain low and DS level increase in the embryonic axis during imbibition for the germination takes place successfully.