Variabilidade cariotípica em acessos de batata-doce (Ipomoea batatas (L.) Lam., Convolvulaceae)

Abstract

Sweet potato (Ipomoea batatas (L.) Lam., Convolvulaceae) is a hexaploid species (2n=6x=90), originated in the American continent, its tuberous root is highly appreciated in human consumption. Its cultivation is among the ten most important food crops in the world and genetic improvement is essential to increase productivity and improve root quality. For this, there is a wide genetic variability for characters of agronomic interest that is maintained in germplasm banks. Considering the importance of cytogenetic characterization of these genotypes, especially because it is an asexually reproducing hexaploid species, the objective of this work is to characterize the karyotype of sweet potato accessions from the Germplasm Bank of the UFLA Breeding Program. Branches from four accessions (Ligeirinha, UFVJM-61, 1153 e 666) were collected in the experimental fields of the Center for Development and Technology Transfer/DAG/ESAL/UFLA and cultivated to obtain roots. Meristems pretreated with 2mM 8-hydroxyquinoline for 4h at room temperature and fixed in methanol:acetic acid (3:1) were used to prepare slides. The cell wall was submitted to enzymatic digestion (100 U pectinase: 200 U cellulase, pH 4.8), for 1h and 20min to 1h and 40min. Slides were prepared using the flame-drying technique and used for fluorescent in situ hybridization to locate the 5S and 35S rDNA loci. The best metaphases of each accession were used for karyotype description, determination of number and location of rDNA sites. Three accessions had 90 chromosomes and the “1153” genotype was aneuploidy (2n=6x=90-1). Six 5S rDNA sites were observed for all accessions, showing variation in the location in the chromosomes (proximal and some in the entire arm). The 35S sites were located in the terminal region of the chromosomes in all accessions, but in different numbers (12, 14 and 16). The karyotypic variability observed in the four accessions of Ipomoea batatas L. indicates that it is essential to expand the detailed description of the karyotype of the accessions from the UFLA sweet potato germplasm bank, to guide conservation and the choice of parents for controlled crosses.