Divergência genética em acessos de Psidiumguajava e avaliação da resistência de híbrido interespecífico de Psidium ao nematóide Meloidogyne enterolobbi

Abstract

The objectives of this study were to obtain and evaluate interspecific hybrids of the genus Psidiumto resistance to M. enterolobii and analyze the genetic variability of accessions of guava and araçazeiros of the active germplasm bank of Embrapa Semi-Arid based on microsatellites, to guide genetic resources and breeding programs, emphasizing crosses of guava with other Psidium species.The crosses were performed when the calyx ruptured on the flower buds. When the plants reached15 to 20 cm tall, they were inoculated with a suspension containing 10,000 nematode eggs. Four months after inoculation, the soils were removed from the plants for individual evaluation of the number of galls, number of eggs and reproduction factor (RF). Genotyping was performed with two and 13 microsatellite loci in hybrids and Psidium accessions, respectively. Total DNA was extracted by the CTAB 2x method and PCR products were analyzed by denaturing polyacrylamide gel 6%, stained with silver nitrate. Interspecific hybrids between GUA 161 PE P guajava x ARA 138 RR P. guineensewere highly tolerant to nematodes, with growth similar to the guava, and demonstrated high compatibility when grafted with the cultivar 'Paluma'. The 61 accessionsPsidiumaccessions showed similarity coefficient ranging from 0.75 to 1.00 and the dendrogram presented co-phenetic value of 0.85. Genetic variability was considered high ΦST=0.238 and it was observed formation of five groups at a cutoff of 83% similarity. The genetic similarity among P.guineense and some guava accessions were above 80%, suggesting greater possibility to obtain interespecific hybrids among these two species.