Hydrotime Model Parameters Estimate Seed Vigor and Predict Seedling Emergence Performance of Astragalus sinicus under Various Environmental Conditions

Abstract

Seed vigor is an important aspect of seed quality. High-vigor seeds show rapid and uniform germination and emerge well, especially under adverse environmental conditions. Here, we determined hydrotime model parameters by incubating seeds at different water potentials (0.0, −0.2, −0.4, −0.6, and −0.8 MPa) in the laboratory, for 12 seed lots of Chinese milk vetch (Astragalus sinicus) (CMV), a globally important legume used as forage, green manure, and a rotation crop. Pot experiments were conducted to investigate the seedling emergence performance of 12 CMV seed lots under control, water stress, salinity stress, deep sowing, and cold stress conditions. Meanwhile, the field emergence performance was evaluated on two sowing dates in June and October 2022. Correlation and regression analyses were implemented to explore the relationships between hydrotime model parameters and seedling emergence performance under various environmental conditions. The seed germination percentage did not differ significantly between seed lots when seeds were incubated at 0.0 MPa, whereas it did differ significantly between seed lots at water potentials of −0.2, −0.4, and −0.6 MPa. The emergence percentage, seedling dry weight, and simplified vigor index also differed significantly between the 12 seed lots under various environmental conditions. Ψb(50) showed a significant correlation with germination and emergence performance under various environmental conditions; however, little correlation was observed between θH or σφb and germination and emergence. These results indicate that Ψb(50) can be used to estimate seed vigor and predict seedling emergence performance under diverse environmental conditions for CMV and similar forage legumes. This study will enable seed researchers, plant breeders, and government program directors to target higher seed vigor more effectively for forage legumes.

Siberian Wildrye (Elymus sibiricus) Seed Vigor Estimation for the Prediction of Emergence Performance under Diverse Environmental Conditions

“…Thus, any differences in their germination and emergence patterns and stress resistance were not due to their genotype. Therefore, the differences in the lag period of delay to germination are most likely due to their actual vigor level caused by seed aging or deterioration [9]. We noticed that in our study, among all seed lots, as expressed by seedling emergence under field and pot conditions, seed lots 6, 10, and 11 had relatively high vigor and were also the youngest of all seed lots (stored one or two years before the experiment); on the other hand, seed lots 8 and 13, had the lowest vigor level (longer MGT or lower seedling emergence under different conditions) and was also the oldest of all seed lots (stored five years before the experiment).…”

“…Despite SWR's valuable agricultural and ecological uses and economical importance, its low seed yield and quality have become one of the major constraints encountered by farmers, herders, and agricultural companies. Previous research suggested that poor establishment of small-seeded forage species is common, and weak seedlings produced by forage seeds also reduce the possibility of survival [7,8], especially under adverse environmental conditions, such as drought, salinity, and alkalinity stresses [9]. Thus, improving stand establishment in unfavorable environmental conditions is a critical determinant of SWR cultivation and utilization.…”

“…Previously, many researchers the presence of a positive linear relationship between seed vigor and seedling emergence under different conditions [13][14][15][16]. High-vigor seeds show rapid and uniform germination and emergence performance, especially under stressful environmental conditions [9,10]. In contrast, low-vigor seeds generally caused poor seedling emergence and resulted in serious yield and economic losses, as previously found for alfalfa (Medicago sativa L.) [17], white clover (Trifolium repens L.) [18], Festuca sinensis [19], and many other plant species [20][21][22].…”

“…However, seed vigor describes the comprehensive characteristics of the seeds beyond SG, and seeds from different commercially available sources may have similarly high levels of SG in the laboratory. Nevertheless, under more unpredictable conditions experienced in the field, these seeds may have strikingly contrasting abilities to establish normal plants due to differences in their vigor [9,12]. Accordingly, there is an imperative need to develop more feasible and precise approaches to test SWR seed vigor.…”

Assessment of Germination Response to Salinity Stress in Castor through the Hydrotime Model

“…The hydrotime model provides useful information on seed germination characteristics under stress conditions, defining the tolerance or sensitivity of a variety to salt stress [43]. Its parameters are hydrotime requirements (θ H ), which define the speed of germination, and base water potential (Ψ b ), which indicates the minimum potential (Ψ) of a seed lot to reach germination.…”