Effects of cadmium stress on seed germination characteristics of 58 millet accessions

To evaluate and compare the cadmium (Cd) tolerance of foxtail millet (Setariaitalica) accessions from different origins during the germination period, in this study, 58 accessions of foxtail millet were employed as the subject of the experiment, 100 mg·L⁻¹ Cd solution was used to apply Cd stress, and distilled water was used as the control. The Cd tolerance of the millet germplasm was determined following a double-layer filter paper method in an artificial intelligence incubator. Through principal component analysis, the weight of each germination index in the evaluation of Cd resistance was elucidated, and the membership function and cluster analysis methods were used to comprehensively evaluate the Cd resistance via fuzzy mathematics. The results showed that the Cd tolerance of different millet varieties significantly differed, and the radicle was more sensitive to Cd stress than the germ. The relative root length, relative germination percentage, and relative germination potential of millet varieties were sensitive to Cd stress, and their coefficients of variation were 50.83%, 57.56%, and 57.80%, respectively. Principal component analysis showed that the germination percentage, germination potential, relative germination percentage, and relative germination potential could be used as the key indexes for evaluating the Cd tolerance of millet. According to the cluster analysis, the 58 millet germplasms could be divided into three types: tolerant, moderately tolerant, and sensitive. Among them, Cd-tolerant millet varieties accounted for 20.69%, and their relative germination percentage and relative germination potential were all ≥60.00%. Based on the membership function score in fuzzy mathematics, eight Cd-tolerant varieties with a comprehensive score of > 5 were selected, and their relative germination percentage and relative germination potential were ≥60.00%.