Evaluating the relationship of pollinator attractiveness to floret length in inbred sunflower (Helianthus annuus, Asteraceae) lines

Abstract

<p>The objective of this study was to examine the relationships between sunflower (Helianthus annuus L.) floret length and the visitation rates of pollinators and determine whether floret length could be used to predict pollinator attractiveness. This study characterizes inbred attractiveness to bees, the impact of floret lengths, and examines the relationship between the two. In 2019, 79 male fertile inbreds and 59 male sterile inbreds were planted in a small plot research study at the Corteva™ Agriscience location in Woodland, California, USA. Bee visits to each genotype were recorded during the bloom period. Floret lengths were measured from each genotype using photometry methods. Bee visitation rates are used to measure the attractiveness of a genotype to bees. Bee visitation rates were significantly affected by floret length (p-value = 0.0049), genotype (p-value = 1.092e-13) and observation date (p-value = 1.697e-10). A general linear mixed model was constructed and predicted mean values for bee visits for each genotype were generated. Least squares mean values were generated for each genotype for floret length. Regression of bee visitation rates onto floret lengths reveals little correlation between the two factors, R2 = 0.025. Correlation slightly improves for male sterile genotypes alone R2 = 0.058 but declines for male fertile genotypes alone R2 = 0.002. These results suggest that for the group of inbreds studied, floret length is not a good predictor of pollinator attractiveness.</p>