Development of typical staining patterns of soybean seed by the tetrazolium test for evaluation of seed viability and vigor

It was noted that with light staining, 0.1 percent tetrazolium solution (2,3,5-Triphenyl Tetrazolium Chloride or TZ), soybean seed could partly survive. From this fact, single seed comparison of TZ staining patterns to normal and abnormal structures of seedlings can lead to more accurate and concrete evaluation of viability and vigor by the TZ test of soybean seed. Ten soybean seed lots of various varieties were treated and tested through the standard germination test (sand), field emergence test, and vigor tests by the seedling classification test and the seedling growth rate test. The seed treatments included, T1: dry seed (control) T2: soak imbibed seed in distilled water for 1 min. 30 sec. at 40 deg C T3: stain imbibed seed with 0.1 percent TZ solution for 1 min. 30 sec. at 40 deg C Dry and soaked seed treatments were statistically non-significant in percentages of standard germination, field emergence, strong seedlings determined by seedling classification test and seedling dry weight. Standard germination, field emergence and strong seedling (seedling classification test) percentages of TZ stained seed were 7, 12 and 11 percent, respectively decreased from dry seed and statistically different. However, they were not statistically different in seedling dry weight identified by the seedling growth rate test. Continuing the study, the light staining technique by 0.1 percent TZ was used to maintain soybean seed viability. The staining pattern on a cotyledon surface with seed coat removed of an individual seed was observed closely and photographed under the stereomicroscope before sand germination. The normal and abnormal structures of the seedling were inspected to compare with staining patterns in the photographs. The experience gained from this practice was used to evaluate viability and vigor of 37 soybean seed lots of various common varieties. Statistical methods, the T-Test and the correlation, were used to identify the accuracy of TZ results against the results observed through the standard germination test, field emergence test and the accelerated aging test. It was found that the viability estimated by the TZ test and the standard germination was not different statistically. Close correlation were also found between the TZ test results and the accelerated aging and field emergence test results in estimating vigor.