ABSTRACT

Knowledge of the genetic variability among genotypes is important for the transfer of useful genes and to maximize the use of available germplasm resources. This study was carried out to assess the genetic variability of 14 elite Coffea arabica cultivars using random amplified polymorphic DNA (RAPD) associated with a prior digestion of genomic DNA with restriction endonucleases. The accessions were obtained from the Coffea collection maintained at the Instituto Agronômico do Paraná (IAPAR), located in Londrina, Paraná, Brazil. Twenty-four informative RAPD primers, used in association with restriction enzymes, yielded 330 reproducible and scorable DNA bands, of which 224 (68%) were polymorphic. The amplified products were used to estimate the genetic variability using Dice's similarity coefficient. The data matrix was converted to a dendrogram and a three-dimensional plot using principal coordinate analysis. The accessions studied were separated into clusters in a manner that was consistent with the known pedigree. The associations obtained in the dendrogram and in the principal coordinate analysis plot suggest the probable origin of the Kattimor cultivar. The RAPD technique associated with restriction digestion was proved to be a useful tool for genetic characterization of C. arabica genotypes making an important contribution to the application of molecular markers to coffee breeding.

The genetic variability of 40 accessions of C. arabica was evaluated using a combination of the random amplified polymorphic DNA (RAPD

The RAPD technique associated with restriction digestion of genomic DNA was used to assess the genetic variability within and among nine populations of Coffea arabica, including six progenies belonging to the Sarchimor germplasm, the progeny PR 77054-40-10 (Catuaí Vermelho IAC 81 x Icatu), and two commercial cultivars (IAPAR 59 and Catuaí Vermelho IAC-81). These populations were evaluated using analysis of molecular variance (AMOVA), genetic similarity among progenies, and percentage of polymorphic loci. A total of 99 RAPD markers were evaluated of which 67 (67.67%) were polymorphic. AMOVA showed that 38.5% and 61.5% of the genetic variation was distributed among and within populations, respectively. The fixation index (F ST ) of the genotypes was 0.385. The mean genetic variability estimated within populations ranged from 15.58 (IAPAR 59) to 8.27 (Catuaí Vermelho IAC 81). A distinct level of genetic variability was revealed for each of the coffee progenies and varieties studied. The methodology used in this investigation was useful to determine the genetic variability within and among C. arabica L. populations providing significant information for coffee breeding.

The objective of this study was to identify molecular markers associated with the resistance to race 3 of the SCN. Two microsatellites (Satt187 and Satt309) and three RAPD markers (OPAG-05 946 , OPF-04 1038 , and OPAQ-01 1987 ) were found which explained 31.3%, 28.9%, 13.8%, 11.4% and 9.9%, respectively, of the phenotypic resistance variation to race 3 of the SCN. However, by multiple regression analysis, with the elimination of markers which least contributed to an explanation of the resistance, the most significant combination occurred with the inclusion of the markers Satt187 and Satt309, which together explained 75.2% of the resistance. These markers were mapped in two distinct regions. One located in the linkage group G with the markers OPAG-05 846, OPF-04 1038 , OPAQ-01 1987 and Satt309 at an interval of 34.7 cM, and another located in the group A 2 with the marker Satt187. Inheritance studies have shown those two dominant genes control resistance to SCN, in the population analyzed.