Can the Tetrazolium Test be Used as an Alternative to the Germination Test in Determining Seed Viability of Grass Species?

Currently, the standard germination test (SGT) is the official test for evaluating seed viability in seed testing laboratories around the world. The SGT takes 3 to 4 wk to complete for most grasses, including the dormancy breaking treatment period. The tetrazolium test (TZT), however, offers quick viability determination within 24 to 48 h, even for dormant seeds. This study was conducted to compare SGT and TZT results for tall fescue (TF), annual and perennial ryegrass (ARG and PRG), orchardgrass (OG), bentgrass (BG), Kentucky bluegrass (KBG), and fine fescues (FF). A total of 3432 samples representing the seven species were evaluated for viability by SGT and TZT during 2009 to 2013 at the Oregon State University Seed Laboratory (OSUSL). According to the germination tolerance table of the Association of Official Seed Analysts (AOSA), both SGT and TZT results were within tolerance in 94.2% of TF samples, 95.2% of ARG samples, 90.4% of PRG samples, 93.7% of OG samples, 90.8% of FF samples, 83.9% of BG samples, and 42.4% of KBG samples. Dormancy was the main reason for higher viability by TZT results than by SGT in the same sample, causing the two test results to be out-of-tolerance. Based on these results, it can be concluded that the TZT can be used as an alternative viability test to the SGT for TF, ARG, PRG, OG, FF, and possibly for BG. However, the KBG has higher levels of dormancy, which brings the SGT below the TZT results, especially for freshly harvested seeds. [ABSTRACT FROM AUTHOR]