Mapeamento físico de sequências satélite em espécies silvestres de solanum l. (seção petota, série commersoniana)

Abstract

In potato breeding, wild species can serve as a valuable source of alleles with desirable traits, including tolerance to abiotic stresses, such as the triploid) native to Brazil, Solanum calvescens. To shed light on the controversy surrounding its origin and taxonomic status, previous characterization of the repetitive fraction of its genome and that of related species revealed variation on composition and abundance of satellite DNA. This study aimed to locate these repetitive sequences on the chromosomes of wild species within the Commersoniana series: S. calvescens (2n=3x=36), Solanum chacoense (2n=2x=24), and Solanum commersonii (2n=2x=24). The investigation provided insights into their dynamics and on karyotypic evolution within this group. For slide preparation, root meristem cells were treated with an 8-hydroxyquinoline solution (2mM) and fixed in Carnoy solution (3:1). Enzymatic treatment (4%cellulase + 2% pectinase) followed, and the cells were further fixed in Carnoy (3:1) until use. Three satellite DNA probes were employed, each specific to its respective species: CA8 (for S. calvescens), CH11 (for S. chacoense), and CO1 (for S. commersonii). Additionally, telomericDNA and 5S rDNA probes were used. Hybridization occurred in a humid chamber at 37°C for 16 hours. Detection involved anti-digoxigenin and anti-biotin antibodies in 1x TNB buffer. Finally, the slides were mounted in Vectashield® medium containing DAPI. Signals of CA8 were detected in the subtelomeric regions of both S. calvescens and S. commersonii, but no signal was observed in S. chacoense. For CH11 signals of varying intensity were observed in all species. Notably, in S. commersonii, subterminal signals were located on nearly all chromosomes, distinguishing it from the other species. Repeat CO1 was observed in S. chacoense and S. commersonii, in interstitial and subterminal regions. Some blocks were observed in S. chacoense. Triploid species S. calvescens showed three 5S rDNA signals in the pericentromeric regions of the short arms of the chromosomes, while in diploid species only two signals were visualized in similar region of the chromosome. For the telomeric probe, in addition to the terminal signals, interstitial signals were observed in the three species, as already described in other Solanum species. The results indicate that S. calvescens differs from the other species in relation to the location pattern of the evaluated satellite sequences, whichcorroborates the hypothesis that it is a distinct species.