NÚMERO MÍNIMO AMOSTRAL PARA OBTENÇÃO DE DADOS GENÉTICOS POPULACIONAIS EM PLANTAS UTILIZANDO MARCADORES ISSR

Abstract

Deciding how many individuals should be sampled in order to have a sample that is representative of the genetic variability of the real population is one of the great questions of population genetics. In order to answer this question, we used data from ISSR (Inter-Simple Sequence Repeat) markers of populations of 60 or 59 individuals from five plant species Achyrocline flaccid (Weinm.) DC., Campomanesia xanthocarpa O. Berg, Eugenia uniflora L., Psidium guajava L. and Solanum mauritianum Scop. From the original population, subpopulations of sample sizes of 5, 10, 15, 20, 25, 30, 35, 40, 45 and 58 individuals were obtained by random sampling. Each subpopulation was assayed 50-fold, consisting of 50 replicates. For each of the 2500 subpopulations obtained, the Shannon diversity index (I), Nei genetic diversity (h), Nei genetic distance (D) and genetic differentiation coefficient (GST) were calculated. The values obtained were evaluated by the normality test, analysis of variance and pairwise comparison. The results showed that in all species and indices the amplitude of the data was inversely proportional to the sample size. However, this amplitude was minimal when compared to sample sizes higher than 30 individuals. In this sense, a sample size of 30 individuals is sufficient for reliable estimation of population genetic indexes with ISSR markers in plants. The sample effort beyond this number would imply in the increase of the costs without change in the interpretation regarding the genetic status of the species under study.