Influence of seed maturity stages on germinability and seedling vigor in groundnut

Summary Groundnut (Arachis hypogaea) seeds lose their germinability more rapidly in seed lots harvested in summer season than those harvested in rainy season. The present study was initiated to understand the possible causes of rapid loss of germinability in two contrasting seasons. The study was conducted with five groundnut cultivars, varying in several physical, morphological and chemical characteristics of seed. Seeds before storage and after 12 months were shelled and categorized based on the “shell-inside” color, ie, over mature (OVM), optimally mature (OPM) and immature (IMM), and a natural seed lot (NTL) was considered as control. The trend of loss of germinability and seedling vigor in seeds of different maturity stages was similar in both the seasons, except that germinability and seed vigor decreased more rapidly in the seed lots obtained in summer than in rainy season. Among various maturity stages, the overall germinability and seedling vigor was higher in OPM than in NTL and IMM seeds. The cultivars Kadiri 3 and ICGS 11 showed least influence of seed maturity stages and storage period on seed vigor, whereas GG 2 showed highest influence, indicating wide genetic variability in seedling vigor. However, IMM seed percentage was higher in Virginia (15%) as compared to the Spanish market types (10%). In addition, analysis of total sugars in seeds of different maturity stages showed that higher sugars in IMM seeds may be responsible for imbibitional injury due to absorption of excessive water resulting in poor germination. On the other hand, seed calcium (Ca) content was higher in OVM (0.040 ppm) and OPM (0.039 ppm) seeds. The cultivars Kadiri 3 and ICGS 11 (both 0.040 ppm Ca) showed higher Ca content and GG 2 (0.034 ppm) least. In addition, relationships between seed Ca and germination percentage (r=0.79**) and seed Ca and seedling vigor (r=0.84**) were positive. Thus, Kadiri 3 and ICGS 11 were identified with higher seed Ca and GG 2 with lower seed Ca content. If these results are confirmed in large number of genotypes, seed Ca content could be used as an index of seed and seedling vigor in groundnut.