Aspectos fisiológicos e morfológicos de progênies de meios-irmãos de milho submetidos ao estresse salino

Abstract

Soil salinization is one of the main limiting factors for agriculture, particularly in semi-arid regions, where inadequate irrigation and management practices exacerbate salt accumulation in the soil. Maize (Zea mays L.), a crop of great socioeconomic importance in Brazil and worldwide, exhibits moderate sensitivity to salinity, which adversely affects its growth and productivity in salt-affected areas. In this context, the identification and selection of salt-tolerant genotypes is a key strategy for cultivation under saline conditions. Therefore, the objective of this study is to evaluate the morphophysiological performance of half-sib maize progenies under salt stress during the juvenile phase, and to identify the most promising genotypes using multivariate statistical tools. The experiment was conducted in a greenhouse using a randomized block design in a 21 (genotypes) × 2 (salinity levels) factorial arrangement, with three replications. Twenty half-sib progenies and one commercial hybrid (GNZ-7788) used as a check were evaluated under two salt concentrations: 0.14 dS m−1 and 3.0 dS m−1. The measured variables included plant height at the V3 and V6 stages (ALT_V3 and ALT_V6), number of live and dead leaves (FVI and FMO), biomass of fresh and dry leaves, stem, and roots (MF_F, MF_C, MF_R, MS_F, MS_C, and MS_R), relative water content (RWC), chlorophyll a fluorescence parameters (Fo, Fm, Fv, and Fv/Fm), SPAD index, total chlorophyll content (TOTCH), and electrolyte leakage (EL). The data were subjected to Analysis of Variance (ANOVA), Principal Component Analysis (PCA), and the Multi-Trait Genotype-Ideotype Distance Index (MGIDI) to enable the simultaneous selection of genotypes based on multiple traits. Results showed significant effects of salinity on most variables, notably reductions in biomass and changes in physiological efficiency under stress. The genotype × salinity interaction was significant for leaf, stem, and root biomass, as well as for RWC, indicating genetic variability among genotypes in their response to salt stress. Genotypes G2 and G6 stood out by maintaining high biomass levels, higher relative water content, and membrane integrity under salinity, demonstrating greater morphophysiological stability. PCA and MGIDI identified two main components associated with biomass production (FA1) and water retention capacity (FA2). Both tools were effective in distinguishing and selecting superior genotypes. We conclide that integrating morphophysiological data with multivariate analyses is an efficient strategy for the early selection of salt-tolerant maize genotypes. Progenies G2 and G6 showed promising potential for use in breeding programs aimed at improving adaptation to salt-affected semi-arid environments.