Caracterização morfológica de subamostras de quiabo-de-metro (Trichosanthes cucumerina L.) procedentes da Amazônia.

Abstract

Studies on genetic diversity are an important tool for the use and conservation of plant genetic resources. One of the main reasons for the limited use of new germplasm is the lack of adequate documentation, characterization and evaluation of the material. Using this argument the objective of this study was to characterize morphological subsamples of snake gourd (Trichosanthes cucumerina L.), as well as develop a list of descriptors for the species and determine the genetic divergence among subsamples. The subsamples were collected in seven cities of Amazonas state Parintins (PIN I), Urucará (URU), Apuí (APU), Urucurituba (UTB), Itacoatiara (ITA), Manaus (MAO) and Iranduba (Ilha da Marchantaria - IMI), and one city of Pará state Terra Santa (TSA). Parintins was the only subsample that provided two subsamples (PIN II). The establishment of morphological characteristics that define the descriptors and the proposed methodology was made using lists for others cucurbits and adapted for the characteristics of snake gourd. Genetic variability was verified by multivariate analysis techniques expressing the multiples information in measures of similarity, thus the subsamples were grouped by the hierarchical method of average distances called UPGMA and graphic dispersion made by the method of principal coordinates analysis (PCO). The characterization of subsamples allowed establishing a list of 39 descriptors for Trichosanthes cucumerina referring to the flower, fruit and seed. The list was divided into characteristics (descriptors), classes, ranges and codes. The descriptors that exhibited the greatest variation were immature fruit color and shape of the ripe fruit, and the descriptors that not varied were number of flowers per raceme and shape of the seed. Analyze of genetic variability selected 14 descriptors that showed greater variation. The subsamples were more divergent APU and URU, and more similar were UTB and PIN I. The information from UPGMA and PCO showed the same results indicating no relationship between geographic distance and phenotypic similarity of snake gourd subsamples. The characterization and analysis of genetic variability indicated the existence of variability among the accessions evaluated of Trichosanthes cucumerina.