Guava culture stands for an important fruit-growing business in Brazil, with a greater and greater market. But, since 1989 severe damages to the culture caused by the nematode Meloidogyne enterolobii, have been reported. One the alternatives to solve this problem is the use of rootstocks with resistance to this nematode. This research aimed at the molecular characterization, with RAPD markers, of Psidium accessions susceptible to be utilized as rootstocks for the commercial guava trees. 30 primers were tested, from which 19 supplied distinct results for the amplification. The primers generated 163 polymorphic marks, resulting into a mean of 8,6 polymorphic bands per primer. The cluster analysis was performed per species, the accessions of Psidium sp presented the formation of two groups, one formed by A-UFLA accession and the other subdivided into four subgroups, that is, the accession with increased genetic distances, A-Ufla, resistant to M. enterolobii, A-Ufla4 and A-Ufla5, both susceptible to the nematode in issue, all collected in Lavras-MG with a similarity of about 66%. In the cluster analysis of the thirteen accessions of P.cattleyanum, it was possible to found the formation of two great groups. One made up by three accessions susceptible to M. enterolobii (A-20.2, A-10.1 and A-9.2) and the other group formed by ten accessions. The accessions grouped together according to the region of origin in six groups, the most divergent being that native to region of Lavras - MG, with 0.65 of similarity, where the genetic distances ranged from 0.88 to 0.65. The thirteen accessions of P. guineense, all susceptible to M. enterolobii, namely, 12 coming from Recife and one proceeding from Pelotas (A-14.1), grouped themselves together and two groups with similarity ranging from 0.59 to 0.83. As to the diversity study among the guava tree accessions, the greatest genetic distances were detected between the accessions G.P.S and G-Ufla with 0,71 Lavras-MG.
plant resistance to diseases; root-not nematode; genetic markers
