Estudos moleculares, anatômicos e expressão gênica de genótipos de bananeira contrastantes quanto ao despencamento dos frutos

Abstract

The finger drop of banana is closely related to the maturation process and involves the softening and weakening of the pedicel. The aim of this study was to evaluate the genetic diversity of banana genotypes with contrasting levels of fruit finger drop by means of molecular markers and evaluate the susceptibility and resistance to finger drop from anatomical studies and analysis of gene expression via real-time quantitative PCR.The genotyping data generated by microsatellites was carried out based on the number of base pairs of each fragment and dendrogram cluster calculated by UPGMA method. Of the 30 microsatellite primer evaluated, 139 alleles were obtained, with the average of 4.66 alleles per locus. No relationship was found between the polymorphism detected by microsatellite markers and the degree of finger drop fruit. For the anatomical characterization, genotypes in the maturation stages 4, 5 and 6, and from different ploidy levels and finger drop resistance patterns, were used. In genotype 017041-01, susceptible, the presence of air parenchyma, was observed, a feature which was not evidenced in the resistant genotypes genotypes BB France, Khai Nai and BRS On Preciosa. Higher values of variable AF and increased deposition of lignin in the vascular bundles, were related to finger drop resistance. The values of Ct (cycle threshold) were used to determine the gene expression difference on cell wall modifier genes (PEL1, EXP1 and XTH4) between different stages of maturation in the finger drop zone (ZD) and in the middle of the fruit (control zone-ZC). To perform the analysis of relative expression, the 2− ΔΔ CT method, was used. RT-qPCR analysis showed that there was a differential expression between the stages of maturation. Ploidy levels and resistance patterns, did not show correlation with the results of the expression. Genes XTH4 and PEL1 showed expression profiles related to finger drop in fruits in different genotypes being good candidates for functional studies in bananas, and may be useful in strategies of genetic improvement aiming the production of banana fruits with resistance to finger drop.