Floral visitor assemblages related to coriander genotypes and sowing dates: relationship with volatile signals

Abstract

Intraspecific diversity of crops producing volatile organic compounds could harbor different assemblages of flower visiting insects, improving agricultural landscape heterogeneity and thus, natural regulation of crop pests. In this context, the objectives of this work were i) to evaluate the composition, abundance and richness of floral visitor assemblages in different coriander crop genotypes and sowing dates and ii) to determine the relationship between insect assemblages and volatile signals emitted by the different coriander genotypes. Two field experiments (Exp. 1 and 2) were conducted in a completely randomized design with four replications, at the Faculty of Agronomy in the University of Buenos Aires, Argentina. Exp. 1 included early and late sowing dates while Exp. 2 included only late sowing date. Treatments were three coriander genotypes from different origins: Leisure 2008 (L) a variety from USA, GSN 2008 (G) a variety from France and a population from Argentina (A). At full flowering, floral visitor insects were sampled using an entomological net. The sampling units were the coriandeŕs umbels contained in squares of 40 × 40 cm. Two squares were randomly placed in each plot and several samplings were made in each of them, along 10 min-periods. Floral visiting insects were classified into pollinator, predator, parasite, herbivore and decomposer functional groups according to their habits and food preferences. Composition and abundance of floral visitor assemblages differed among genotypes, mainly for the early sowing date. Differences could be attributed to the intraspecific variability of volatile signals to which some insects were sensitive. Although richness was similar among assemblages related to each genotype, different species composition suggests that the combination of different coriander genotypes in cropping systems could enhance insect species diversity of the agricultural system and natural pest regulation.