Genetics and epigenetics instabilities in hybrids and wild populations of Solanum species.

MASUELLI, R.W.

Foz Iguazú, Brasil

Simposio; 52º Congreso Brasilero de Genética; 2006

Sociedad Genética de Brasil

Interspecific hybridization and polyploidization are considered major factors in the origin and evolution of plants. Although hybridization is frequent in nature, new species form only when reproductive barriers arise between the hybrids and its parents. Reproductive barriers could be produce by fertility reduction due to chromosome differences or external isolation between hybrids and the parental species. The evolution of Solanum species has been principally explained  by polyploid speciation. However, more than 70% of the tuber-bearing Solanum species are diploid that exhibit little chromosomal differentiation and asexual propagation.  These characteristics of the Solanum species are basic condition for diploid hybrid speciation. In 2x S. tuberosum x 2x S. kurtzianum hybrids we found floral abnormalities that reduce fertility and constitute an internal reproductive barrier. The hybrids did not show cytological abnormalities but novel RAPD and AFLP fragments were observed. We found that DNA methylation changes could be the cause of the genomic and phenotypic instabilities observed. Similarly, floral abnormalities were observed in a diploid species S. ruiz-lealli, a putative hybrid between S. chacoense and S. kurtzianum.   We discuss an alternative model of homoploid hybrid speciation involving, among others, genetic and epigenetic changes as internal reproductive barriers.