Caracterização citogenética e molecular em acessos do gênero Arachis

Abstract

The Arachis genus has been the target of several studies due to its importance in human and animal food and because its seeds are recognized as source of protein and oil of vegetal origin, besides its use as ornamental plants. Arachis breeding programs have as main objective the introduction of new varieties and increase of genetic variability through crosses and selection to obtain important agronomic characters. Cytogenetic techniques such as conventional staining, chromosome banding with fluorochromes and FISH were used to analyze four species of Heteranthae: Arachis pusilla, A. giacomettii, A. dardani and A. sylvestris. All species had a diploid chromosome number 2n = 20, A. pusilla and A. dardani presented a karyotypic formula 18m + 2sm and satellite type 2, while A. giacomettii and A. sylvestris had 16m + 4sm and satellite type 10. Flumachromes CMA and DAPI revealed in A. pusilla a large number of blocks rich in Guanine and Cytosine, located in eight chromosomal pairs in the pericentromeric position. DAPI + blocks were observed in the proximal region in most chromosomes of the analyzed accesses of this species after the FISH technique. Arachis dardani presented two large subterranean CMA + blocks. A. giacomettii and A. dardani presented only two CMA + blocks, in the terminal region of the satelite chromosome pair. In situ hybridization demonstrated in A. giacomettii two hybridization signals in the terminal region of a chromosomal pair and in A. pusilla four 45S rDNA sites in two chromosomal pairs and two adjacent 5S rDNA sites. In A. giacomettii, two hybridization signals were visualized in the terminal region of a chromosomal pair, coinciding with the CMA + blocks, but not visualized, but 5S rDNA sites. For the molecular technique, 35 oligonucleotide primers from legume expression libraries were used, which were applied in two contrasting peanut lines, "BR1" and "LVIPE-06" accessions, commonly used in the formation of segregating populations. Objective of obtaining a panel of endonucleases recommended to generate polymorphic markers useful for the genetic improvement of peanuts or for genetic mapping purposes. From the total of oligonucleotide primers, three generated polymorphisms directly from PCR between the accesses investigated. Of the monomorphic amplicons, ten were purified, sequenced and aligned for the identification of candidate SNPs for the generation of restriction and conversion maps in molecular tags.