Studies of intraplant pollen supply in modern and wild genotypes of sunflower

ASTIZ, V., A.C. FERNÁNDEZ , P.A. MARINANGELI, A. FLEMMER Y L.F. HERNÁNDEZ

Simposio; X Internationtal Symposium of Pollination; 2011

Sunflower plants grown under optimal conditions alwaysform incomplete developed fruits (IDF). Our objective was to identify,qualitatively and quantitatively, the intraplant pollen supply and its possiblerelationship with the generation of fully developed fruits (FDF) and IDF. Sunflower plants were grown under irrigation and fertilization in the Agronomy Dept.-UNS (Bahía Blanca, Argentina: 38º 45´ S., 62º 11´ W.)in a factorial combination of two hybrids and three planting dates (PD). Closeto anthesis, pollen grains per flower (P/F) were counted. Postanthesis viability was assessed using Alexanderstain. At harvest, FDF and IDF were counted. In the first and third PD, thestudy was done in capitulum sectors (external [ES], medium [MS] and internal[IS]). Both hybrids showed similar results. In the two extreme PD there weredifferences in the IS: Number of IDF (higher in the third) and number of (P/F) (higherin the first). Considering the whole capitulum, the number FDF was higher inthe first and second PD, while the number of (P/F) was higher the in the secondPD. In all cases the higher number of FDF were observed in the ES and MS andthe higher number of FDI predominated in the IS. Pollen viability of the twohybrids in the three PD was not significantly different between capitulumsectors. The formation of FDI would not depend on pollen intraplant supply as both, pollenavailability and itsquality, was not limiting in thetwo genotypes. It is not known whether failure of pollen germinationcould occur. The highest number of (P/F) observed in the IS of the capitula inboth genotypes may respond to a legacy of the species strategy to invest resourcesin the sporophytic generation during the late stages of anthesis for thepurpose of not competing with photoassimilate supply in the proximal regions ofthe capitulum which has ovaries in active development at that stage. Our preliminaryresults also indicate that in wild and inbred lines of sunflower, thedistribution of the amount of P/F in the capitulum would be similar.