Evaluation and Genetic Analysis of Seed Vigor in Inbred Lines and Responding Hybrids in Shaan A and Shaan B Groups

Seed vigor is one of the key determinants of seed quality in maize, directly influencing emergence rate, seedling growth, and stand uniformity, thereby affecting final yield formation. This study aimed to identify high-vigor inbred lines and hybrids, uncover key genes involved in regulating seed germination, and provide a theoretical basis for breeding high-vigor maize varieties.

Twenty-two maize inbred lines from two heterotic groups, Shaan A Group and Shaan B Group, were used to produce 104 F₁ hybrids following an NC-Ⅱ mating design. Seed vigor was evaluated under both the standard germination test and the cold soaking germination test. Nine traits were recorded, including germination energy (GE), germination percentage (GP), germination index (GI), seedling length (SL), root length (RL), dry weight (DW), vigor index I (VIⅠ), vigor index Ⅱ (VIⅡ), and vigor index Ⅲ (VIⅢ). Genotypic and phenotypic data were combined to perform a genome-wide association study (GWAS) for major traits. Quantitative trait nucleotides (QTNs) significantly associated with seed vigor were identified. Public transcriptome data were further used to screen potential candidate genes and to predict their possible functions.

Significant genetic variation was observed for seed vigor–related traits in both inbred lines and hybrids. Compared with the standard germination test, cold soaking treatment reduced GE, GP, and GI, and increased the range of phenotypic variation among genotypes. Most traits showed significant effects of genotype, treatment, and their interaction, indicating that seed vigor is mainly controlled by genetic factors. Germination traits were positively correlated with seedling growth traits and vigor indices. Several materials showed stable performance under different germination conditions and low sensitivity to cold soaking. Hybrids derived from KA105, KA088, KA085, and KA205 of the Shaan A Group, and KB088, KB060, KB168, KB076, and KB021 of the Shaan B Group maintained relatively high seed vigor under cold soaking conditions. Some inbred lines with moderate seed vigor were able to improve hybrid performance in specific combinations. GWAS detected 43 QTNs significantly associated with seed vigor, including seven loci that were shared by two or more traits under cold soaking conditions. Based on transcriptome data, 11 candidate genes were identified, of which eight had functional annotation and were mainly related to stress response and transcription regulation.

Maize seed vigor is a quantitative trait under genetic control, and genetic variation is the main source of phenotypic differences. Seed vigor is regulated by multiple loci, with key genomic regions involved under low-temperature conditions. The accumulation of favorable alleles can improve seed vigor in hybrids, and hybrid performance is also influenced by specific genetic interactions between parents.