Early-Stage Phenotypic Variation and NaCl Tolerance in Native Mexican Maize Accessions

Salinity is a major constraint on maize establishment, yet the extent of early-stage variation among native Mexican maize accessions remains insufficiently characterized. This study evaluated the in vitro response of 130 native maize accessions (Zea mays L.) to saline stress in order to identify promising materials for early-stage salinity tolerance.

Seeds were germinated under control and saline conditions (150 mM NaCl), and early seedling traits were recorded, including germination, coleoptile length, mesocotyl length, radicle length, seminal root number, and seedling biomass. Univariate analyses were used to identify contrasting accession responses, whereas principal component analysis, Ward's hierarchical clustering, and optimized stratification were applied to classify phenotypic patterns under saline stress.

Salinity reduced germination and early seedling growth overall, but the magnitude of these effects varied markedly among accessions, revealing substantial phenotypic variation at the earliest developmental stages. Several accessions maintained favourable performance under saline stress. In particular, CIMMYT 433 combined stable germination with superior radicle length and seminal root number, whereas CIMMYT 658 showed favourable coleoptile and mesocotyl elongation. Multivariate analysis based on accession-specific NaCl-response differences identified four contrasting response groups. Cluster 1 showed the lowest overall NaCl-induced reduction and therefore grouped accessions with greater early-stage stability, whereas Cluster 2 showed the greatest reductions and represented the most affected response group. Tuxpeño and Olotillo related materials were prominent among the accessions with favourable early-stage responses.

Native Mexican maize harbours substantial early-stage variation in response to salinity, and this variation can be effectively captured through integrated seedling traits and multivariate classification. The accessions identified here represent promising germplasm for further physiological, genetic, and breeding studies aimed at improving salinity tolerance.