Número de cloroplastos como indicador estável para inferência de ploidia em portulaca spp.

Abstract

The success of breeding programs for ornamental plants such as purslanes (Portulaca spp.) is closely linked to the correct identification of ploidy levels. Polyploidization is a technique that generates new genetic combinations and phenotypic variations, making it useful in the improvement of Portulaca spp. due to their ornamental, medicinal, and nutritional value. This study aimed to determine the ploidy level of Portulaca spp. accessions by counting the number of chloroplasts per guard cell, providing support for breeding programs of the species. Leaf samples from 15 genotypes cultivated in a greenhouse were collected and analyzed under an optical microscope (40×). Three stomata from each of five random fields of the leaf were analyzed, and the data were subjected to ANOVA, the Scott–Knott mean test, and Tocher clustering. The observed means varied widely, from 4.93 to 24.65 chloroplasts per guard cell, indicating the presence of different ploidy levels, ranging from diploids to hexaploids. Analysis of variance confirmed significant differences among genotypes (p < 0.001). Tocher clustering classified the accessions into four distinct groups and revealed high genetic divergence between

the most contrasting accessions (PU0010 with 24.65 chloroplasts and PU001 with 4.93). Broad- sense heritability was high (98.56%), indicating strong genetic control of the trait. The results

confirm that chloroplast counting is an efficient primary tool with high selective accuracy (99.3%), useful for selecting genotypes and guiding crosses for the subsequent development of promising hybrids with desirable characteristics such as vigor, resistance, and ornamental value.