Changes of vigor, physiological characteristics and genetic diversities of artificially aged sweet corn seeds

Objective  To identify the effects of artificial aging on vigor, physiological characteristics and genetic diversities of sweet corn (Zea mays L. saccharata Sturt.) seeds, and provide a reference for sweet corn seed storage and field production.

Method  ‘Nongtian88’ and ‘Nongtian99’ were selected as experimental materials and their seeds were treated using the method of artificial aging. The germination potential, germination rate, germination index and vigor index were measured using the method of germination in sand bed. The dehydrogenase (DHA) activity, peroxidase (POD) activity, relative electrical conductivity (REC) and malondialdehyde (MDA) content of artificially aged seeds were measured. The genetic diversity of artificially aged seeds was detected using SRAP, and the relationships between physiological characteristics, genetic diversities and seed vigor were analyzed.

Result  With the increase of aging time, seed germination potentials, germination rates, germination indexes, vigor indexes, DHA activities and POD activities of two cultivars decreased gradually, while the RECs and MDA contents increased gradually. Compared to the control (CK), the germination potentials, germination rates, germination indexes, vigor indexes, DHA activities and POD activities of ‘Nongtian88’ and ‘Nongtian99’ seeds decreased by 18.32% and 43.15%, 10.73% and 15.38%, 19.43% and 23.60%, 41.85% and 45.70%, 69.78% and 71.74%, 52.02% and 71.60% respectively after aging treatment for six days. The RECs of ‘Nongtian88’ and ‘Nongtian99’ seeds after soaking for 24 hours increased by 33.68% and 27.68% respectively than that of CK, and MDA contents increased by 41.50% and 47.08% respectively than that of CK. Compared to CK, the seed genetic diversities decreased after artificial aging treatment, the allele numbers, effective allele numbers and gene diversities of ‘Nongtian88’ and ‘Nongtian99’ seeds decreased by 29.35% and 23.58%, 25.00% and 20.00%, 96.99% and 83.35% respectively after aging treatment for six days. The correlation analysis showed that the RECs and MDA contents of aged seeds of two cultivars were significantly or highly significantly negatively correlated with vigor indexes, while DHA and POD activities were significantly or highly significantly positively correlated with seed vigor indexes.

Conclusion  With the increase of artificially aging time, the seed vigor indexes, DHA and POD activities of two sweet corn cultivars decrease gradually, while the RECs and MDA contents increase gradually. Artificial aging results in the decrease of seed genetic diversity. ‘Nongtian88’ seed has stronger aging resistant ability than ‘Nongtian99’.