Divergência genética em progênies de Mimosa caesalpiniifolia Benth. via análise digital de imagens e estresse salino em sementes

Abstract

Mimosa caesalpiniifolia Benth., Popularly known as thrush in northeastern Brazil, is a forest species native to the Caatinga and belonging to the Fabaceae family. It has multiple uses for the semiarid region, however, there are few studies on variation in genetic diversity through seed morphometric analysis and adaptability of the species to different saline stresses, since the soils in this region have a high amount of salts. Thus, the objective of the present work was to characterize morphometrically and to identify genotypes tolerant to salt stress in Mimosa caesalpiniaefolia seeds from different origins, aiming to apply genetic divergence in characters, with a view to the selection of seed producing matrices. For this, four progenies from four different origins were selected, from the states of Ceará, Paraíba, Pernambuco and Rio Grande do Norte, totaling 16 progenies. From the seed morphometry, genetic diversity was evaluated by two methods, digital caliper (length, width and thickness) and the ImageJ® program (area, perimeter, circularity, width, roundness and solidity). For the induction of saline stress (Step I). initially a sample of the seeds was taken, to join the four sources in order to obtain a representative sample and later knowledge about the average point of tolerance of the seeds. As a solute, sodium chloride (NaCl), calcium chloride (CaCl2) and potassium chloride (KCl) were used. In osmotic potentials 0.0; -0.2; -0.4; -0.6; -0.8 and -1.0 MPa. The germination%, germination speed index, length of the main root and aerial part and dry mass of the root and aerial part were evaluated. After carrying out the evaluations, the solutes and the defined dose were reapplied in each matrix of each source, to identify tolerance to salt stress at the matrix level (Step II). Subsequently, the correlation analyzes between the methods (Pachymeter x ImageJ®), phenotypic and genotypic correlation between the morphometric variables and univariate and multivariate analysis of variance were performed. For the salinity experiment, analyzes of genetic correlations, multivariate analyzes and evaluation of productivity, stability and adaptability were performed using the MHPRVG method. Digital image processing proved to be efficient to discriminate the morphometric differences between the studied origins, thus, the image analysis presents itself as a useful tool for morphometric differentiation and selection of seed producing genotypes in studies of divergence and genetic breeding of this species. Mimosa caesalpiniifolia Benth seeds. are sensitive to salinity caused by the reduction of water potential, in which the average ranking index made it possible to select PG6, PG15, PG8, PG5 and PG14 as the progenies that present the best productivity, adaptability and stability performances in all evaluated environments.