Integrating Ecogeographic, Bioclimatic and Phylogenetic Analyses for the Wild Relatives of Sunflower (Helianthus annuus L.).

As with most major crops, sunflower (H. annuus L.) production has benefited from the introgression of valuable traits from its wild relatives (CWR), such as pest and disease resistance as well as cytoplasmic male sterility. We examined 36 CWR taxa of relatively close relation to the crop, ranging from narrow endemics to widespread, ‘weedy’ species. We utilized a ‘gap analysis’ methodology (Ramírez-Villegas et al., 2010) to compare the taxonomic, geographic, and ecosystemic representativeness of genebank collections of sunflower CWR against their potential distribution models, which were created from species occurrence geographic presence points, using both climatic and soil data layers as inputs. The analysis permitted the estimation of the completeness of genetic diversity held in germplasm collections and identified priority species and geographic regions for further collecting. In order to identify taxa with potentially valuable attributes for adaptation to extreme climates, we performed a predicted niche occupancy analysis based upon climatic suitability with potential distributions. The phylogeny of the taxa (Timme et al., 2007) was further used to analyze ancestral climatic overlap models. Through the gap analysis we identified priority areas for further collection of sunflower wild relatives which are under-represented in germplasm collections, and highlighted particular species of interest for exploration of traits for adaptation to high temperature and other climatic extremes.

Ramírez-Villegas J., C. Khoury, A. Jarvis, D.G. Debouck, and L. Guarino. 2010. A gap analysis methodology for collecting crop genepools: a case study with Phaseolus beans. PLoS ONE 5(10):e1349.

Timme, R. E., B. Simpson, and C. Randal Linder. 2007. High-resolution phylogeny for Helianthus (Asteraceae) using the 18S-26S ribosomal DNA external transcribed spacer. Am. J. Bot 94:1837-1852; doi:10.3732/ajb.94.11.1837