The North Central Regional Plant Introduction Station maintains more than 300 accessions of Echinochloa representing 15 species from a diverse cross-section of nations and growing conditions from around the world. With such a diverse collection, no single germination-testing protocol was adequate for accurately assessing their viability. By manipulating light conditions, we determined that some accessions were lightrequiring and others were dark-requiring. However, no pattern was found for this response based on taxonomy or improvement status. Most accessions tested showed optimal germination when tests were conducted between 25 to 30°C, but both positive and negative photoblastic responses were sometimes expressed, even at lower temperatures. A sequential treatment of darkness followed by light revealed that skotodormancy (dormancy caused by darkness) was being induced in light-requiring seeds. Similarly, a sequential treatment with light followed by darkness revealed that photodormancy (dormancy caused by light) was being induced in dark-requiring seeds. Thus, without prior knowledge of the light requirements of a particular accession, we conclude that a side-by-side germination test where two replicates receive periodic light (12 hours at 30°C / 12 hours dark at 20°C) and the other two are tested in darkness (12 hours at 30°C / 12 hours at 20°C) is best for Echinochloa. This approach is recommended for germplasm centers, seed-testing laboratories, and others working with genetically and geographically diverse Echinochloa seed lots.
SummaryThe North Central Regional Plant Introduction Station maintains more than 300 accessions of Echinochloa representing 15 species from a diverse cross-section of nations and growing conditions from around the world. With such a diverse collection, no single germination-testing protocol was adequate for accurately assessing their viability. By manipulating light conditions, we determined that some accessions were light-requiring and others were dark-requiring. However, no pattern was found for this response based on taxonomy or improvement status. Most accessions tested showed optimal germination when tests were conducted between 25 to 30°C, but both positive and negative photoblastic responses were sometimes expressed, even at lower temperatures. A sequential treatment of darkness followed by light revealed that skotodormancy (dormancy caused by darkness) was being induced in light-requiring seeds. Similarly, a sequential treatment with light followed by darkness revealed that photodormancy (dormancy caused by light) was being induced in dark-requiring seeds. Thus, without prior knowledge of the light requirements of a particular accession, we conclude that a side-by-side germination test where two replicates receive periodic light (12 hours at 30°C / 12 hours dark at 20°C) and the other two are tested in darkness (12 hours at 30°C / 12 hours at 20°C) is best for Echinochloa. This approach is recommended for germplasm centers, seed-testing laboratories, and others wor...