Early Sowing Approach for Developing Climate Resilient Maize: Cold Stress Impact on Germination of Adapted Inbred Lines with High Nutritive Value

Abstract

In temperate regions, early sowing of high nutritive genotypes could support maize production sustainability by avoiding warming-related unfavorable environment conditions during flowering. Seven standard maize (SM) lines and their nine quality protein maize (QPM) counterparts were evaluated for cold tolerance during germination. Cold stress (13°/6 °C) was applied for five days, after a 48 h imbibition period under optimal temperature (25°/22 °C). Germination, physiological parameters, and some primary and secondary metabolites in the seeds were analyzed. No significant differences (p > 0.05) were observed in cold tolerance between SM and QPM. Cold stress significantly reduced germination energy (SM-p < 0.05, QPM-p < 0.001) and physiological traits (p < 0.001), with shoot traits being most severely affected. The potentially high impact of gallic (p < 0.001), protocatechuic (p < 0.05), and p-coumaric (p < 0.001) acids on germination under stress and negative effect of lutein + zeaxhantin and β-cryptoxhantin (p < 0.05) on root length was revealed. Among all lines, L3QPM excelled under stress, with unchanged germination energy and the lowest fold change in vigor indices (0.35 for VI1, 0.45 for VI2). Also, β + γ-tocopherol and gallic and caffeic acids were significantly higher (p < 0.05) compared to its SM original. Lines L1QPM2, L3QPM, and L7QPM, combining improved nutritional quality with high cold tolerance, will be incorporated in further early sowing research and breeding programs.