| Sumario: | Identification of gene analogs for resistance to cassava (Manihot esculenta Crantz) Diseases, and their relationship to resistance to three Phytophthora species. Two strategies were used to find resistance genes in cassava. The first through hybridizing probes from maize and rice, using RFLP. The second strategy consisted of amplifying conserved regions of DNA, with degenerated NBS and Pto kinase primers, in three cassava genotypes resistant to Phytophthora tropicalis and P. palmivora, obtaining clones that were sequenced and compared with known resistance genes. Specific primers were designed from the sequences, allowing DNA regions of parental material and resistant and susceptible individuals, to be amplified. Bands were separated by denaturing polyacrylamide gel electrophoresis, and non-denaturing polyacrylamide gel (SSCP - single strand conformation polymorphism-). Five QTLs associated to Phytophthora spp resistance were identified. Cassava has a very low homology with the genes of the monocotyledons tested. A total of 28 NBS and 2 Pto kinase clones were obtained; of these, 5 showed homologous sequence with NBS-LRR RGAs (resistance gene analogs). Four of them had open reading frames with conserved motifs of the NBS region, and were considered as RGAs. Three different RGAs classes were identified. It remain to be shown if there are association to resistance to Phytophthora.
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