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

ASTIZ, VALENTINA; FERNÁNDEZ, ANA CLARA; MARINANGELI PABLO; FLEMER, ANDREA; LUIS HERNÁNDEZ

Cholula

Simposio; X International Symposium of Pollination; 2011

International Commission for Plant-Bee Relation-ships Statutes

Sunflower plants grown under optimal conditions always form incomplete developed fruits (IDF). Our objective was to identify, qualitatively and quantitatively, the intraplant pollen supply and its possible relationship 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). Close to anthesis, pollen grains per flower (P/F) were counted. Postanthesis viability was assessed using Alexander stain. At harvest, FDF and IDF were counted. In the first and third PD, the study was done in capitulum sectors (external [ES], medium [MS] and internal [IS]). Both hybrids showed similar results. In the two extreme PD there were differences in the IS: Number of IDF (higher in the third) and number of (P/F) (higher in the first). Considering the whole capitulum, the number FDF was higher in the first and second PD, while the number of (P/F) was higher the in the second PD. In all cases the higher number of FDF were observed in the ES and MS and the higher number of FDI predominated in the IS. Pollen viability of the two hybrids in the three PD was not significantly different between capitulum sectors. The formation of FDI would not depend on pollen intraplant supply as both, pollen availability and its quality, was not limiting in the two genotypes. It is not known whether failure of pollen germination could occur. The highest number of (P/F) observed in the IS of the capitula in both genotypes may respond to a legacy of the species strategy to invest resources in the sporophytic generation during the late stages of anthesis for the purpose of not competing with photoassimilate supply in the proximal regions of the capitulum which has ovaries in active development at that stage. Our preliminary results also indicate that in wild and inbred lines of sunflower, the distribution of the amount of P/F in the capitulum would be similar.