Differences in insect resistance between tomato species endemic to the Galapagos Islands
1 Wageningen UR Plant Breeding, Wageningen University and Research, Centre, P.O. Box 386, Wageningen, AJ 6700, The Netherlands
2 Graduate School Experimental Plant Sciences. Wageningen Campus. Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
3 Plant Research International, Business Unit Bioscience, Wageningen University and Research Centre, P.O. Box 619, Wageningen, AP 6700, The Netherlands
4 Centre for BioSystems and Genomics, P.O. Box 98, Wageningen, AB 6700, The Netherlands
5 Netherlands Metabolomics Centre, Einsteinweg 55, 2333 CC, Leiden, The Netherlands
BMC Evolutionary Biology 2013, 13:175 doi:10.1186/1471-2148-13-175Published: 24 August 2013
The Galapagos Islands constitute a highly diverse ecosystem and a unique source of variation in the form of endemic species. There are two endemic tomato species, Solanum galapagense and S. cheesmaniae and two introduced tomato species, S. pimpinellifolium and S. lycopersicum. Morphologically the two endemic tomato species of the Galapagos Islands are clearly distinct, but molecular marker analysis showed no clear separation. Tomatoes on the Galapagos are affected by both native and exotic herbivores. Bemisia tabaci is an important introduced insect species that feeds on a wide range of plants. In this article, we address the question whether the differentiation between S. galapagense and S. cheesmaniae may be related to differences in susceptibility towards phloem-feeders and used B. tabaci as a model to evaluate this.
We have characterized 12 accessions of S. galapagense, 22 of S. cheesmaniae, and one of S. lycopersicum as reference for whitefly resistance using no-choice experiments. Whitefly resistance was found in S. galapagense only and was associated with the presence of relatively high levels of acyl sugars and the presence of glandular trichomes of type I and IV. Genetic fingerprinting using 3316 SNP markers did not show a clear differentiation between the two endemic species. Acyl sugar accumulation as well as the climatic and geographical conditions at the collection sites of the accessions did not follow the morphological species boundaries.
Our results suggest that S. galapagense and S. cheesmaniae might be morphotypes rather than two species and that their co-existence is likely the result of selective pressure.