CAPACIDADE DE COMBINAÇÃO, HETEROSE E DIVERGÊNCIA GENÉTICA DE TOMATEIROS

Abstract

Two experiments were conducted, the objectives of this study were (a) to estimate general the combining ability (GCA), specific combining ability (SCA), heterosis in tomato commercial hybrids of single cross and assessing the genetic variation of tomato by ISSR markers; (b) determinating the genomic variation from wild ancestors to contemporary tomato variety. This experiment was conducted a total of twenty three genotypes (six commercial hybrids single crosses, fifteen double crosses derived from a partial diallel and two commercial hybrids) in a randomized block design with three replications. It evaluated traits were total production (TP) and commercial production (YC), fruit average mass (MM), fruit width (FW), fruit lenght (FL), and fruit stalk diameter (FSD). To identify and estimate the genetic diversity of plants was used nine ISSR primers and were based on the on Jaccard’s coefficient. There were significant differences between for all traits of estimates for GCA. The SCA were significant differences between treatments for the TP, YC and FSD demonstrating non-additive genes are importante on genetic control of these traits. The best double cross hybrid according to SCA was (Dominador x Compack) for presenting an increase of this ratio in hybrid for TP, YC, MM and FW in GCA. The average heterosis have indicated a much lower expression of heterosis in the double crosses hybrids. The dendrogram revealed difference and separate in three: A-Dominador, Aguamiel, Plutão and Pietra; B-The Compack and more distant the Forty-C. The results suggested significanting between molecular data and GCA, SCA and heterosis, indicating that marker ISSR can be exploited in breeding plant programs targeting superior tomato hybrids and high genetic divergence between the commercial hybrids was observed for the hybrid ‘Forty’. The plant material to estimate genomic variation in tomato consisted at thirty one accessions in the germplasm bank of ‘núcleo de pesquisas em hortaliças (NUPH) – UNICENTRO’. Ten accessions of Solanum lycopersicum var. cerasiforme, nine of Solanum lycopersicum, six of Solanum pimpinellifollium and six of Solanum peruvianum. The dendrogram evidenced that S. lycopersicum and S. pimpinellifolium was closer genetically. Already, S. lycopersicum var. cerasiforme was the more distant from all other genetic groups. Principal Coordinate Analysis (PCoA) also showed high genetic variability in genotypes collection with emphasis for the commercial hybrids. The Bayesian analysis evidenced that this genetic variability can be explained by the formation of three genetic groups. The group comprising S. lycopersicum and S. pimpinellifolium is that strongly supported by literature where the contemporary tomato cultivars were nearest to S. pimpinellifolium due to events of gene introgression. S. peruvianum formed a separate group due the characteristics involving specifically the specie, but the introgressive hybridizations of genes begin to configure an constitutive part in tomato contemporary. The genetic distance between S. lycopersicum var. cerasiforme to S. lycopersicum may be due that it isn't used intensively as source to introgression of genes, as well as, S. pimpinellifolium and S. peruvianum don't have participated the introgression of genes this specie.