Microsatellite Analysis Reveals Genetic Variation in 'Yerba Mate' Trees from Argentina.

Ilex paraguariensis A. St. Hil. is a perennial, dioecious tree native to southern South America. It has great socio-economic importance in the region due to its use for the preparation of 'mate' beverages. In this study, individuals from a remnant of subtropical forest held in the Campo Anexo Manuel Belgrano (CAMB, San Antonio, Misiones, Argentina) were genetically characterised. Leaves from 113 adult plants from 11 subpopulations were collected, covering a total area of 15.5 km², aiming to represent the potential variability within it. Subpopulations are, on average, 1.5 km apart from each other, and plants within each subpopulation are separated by at least 5 metres. Total genomic DNA was extracted using commercial kits, and six nuclear microsatellite loci were PCR-amplified under optimised conditions. Allele sizing was accomplished by automated fragment analysis and comparison with molecular weight standards. The frequency data matrix was analysed in GenAlEx. Genetic distances were obtained using Nei's index with the poppr library within the R environment; a Neighbour-Joining (NJ) network was generated using the ape library. The distribution of allelic variation showed 53 alleles (average: 8.83 alleles per locus). The average heterozygosity values were Ho = 0.541 and He = 0.604, Shannon's information index resulted in 1.303, on average, and the Fixation Index was 0.097. These values are comparable to those reported for natural populations from southeastern Brazil and 1.96 times higher than those recorded for Uruguayan populations, which represent the southernmost species distribution tail. There was no clustering of individuals according to the sampled subpopulation in the NJ network. The study results reveal intermediate genetic variability in CAMB wild 'yerba mate' plants, but this was similar to that reported for the 'yerba mate' centre of diversification.