TRAP and SRAP markers to find genetic variability in complex polyploid Paullinia cupana var. sorbilis

Abstract

The guarana plant (Paullinia cupana var. sorbilis) is a polyploid rich in natural caffeine, used as a source for producing industrial soft drinks. Embrapa Western Amazon maintains an Active Germplasm Bank (BGA) with 270 clones, which represents the genetic basis of the species conservation and breeding programs. The BGA evaluations conducted using phenotypic traits and Random Amplified Polymorphic DNA (RAPD) markers indicated low genetic variability. Therefore, the objective of this study was to analyze the genetic diversity of the clonal germplasm of the guarana plant using Target Region Amplification Polymorphism (TRAP) and Sequence-Related Amplification Polymorphism (SRAP) markers. Sixty clones of the guarana plant were analyzed; 18 were cultivars, eight were similar clones according to morpho-agronomic traits, and 34 were clones of a different origin. The percent polymorphism found was 79% for TRAP and 74.5% for SRAP. The Polymorphic Information Content (PIC) values for both markers ranged from 0.29 to 0.37, with an amplified fragment size between 100 and 800bp. No genotypes with genetic similarity of one were found in the three germoplasm samples analyzed, which ruled out the possibility of the occurrence of duplicates. In the cluster analysis, the dendrogram generated by the SRAP marker added three additional groups when compared with TRAP and distinguished two genotypes in the sample comprising morpho-agronomically similar clones. The TRAP and SRAP markers yielded complementary information on the genetic variability of the guarana germplasm. Therefore, the combination of the two markers has the potential to broaden genetic characterizations and facilitate parental selection in breeding programs.