Agriculture Reference
In-Depth Information
Tetrazolium (Tz) Vigor Test
The TZ viability test can be modiied and used as a vigor test by separating all normal viable seeds into
different vigor categories. One approach is to separate seeds into three categories such as high, medium,
and low which are given indices of 3, 2 and 1, respectively (Figure 8.8). Each vigor category is based on
the pattern and intensity of coloration, as well as location and extent of various mechanical and structural
defects (Figure 8.9). A similar but expanded approach for some crops is described in the AOSA Vigor
Testing Handbook. Based on tetrazolium staining patterns, individual seeds are placed in one of several
main classes of viability and vigor. Within each of the classes, a seed is assigned to one of several sub-
classes. This approach provides a wider range of classiication and higher precision for estimating vigor.
For example, dry beans are irst placed in one of eight viability/vigor classes.
1. High vigor with no damage.
2. High vigor with minor damage.
3. Medium vigor.
4. Low vigor.
5. Very low vigor.
6. Very low vigor with high degree of damage.
7. Nonviable seeds with extensive damage to plumule/cotyledon junction.
8. Dead seeds.
Within those classes, a seed can be assigned to one of several subclasses. For instance, there are 5
subclasses within class 3 (medium vigor) for beans:
1. Mechanical damage on the two cotyledons with internal lesions.
2. Fractures at the radicle tip not extended into stele.
3. Damaged radicle tip with deteriorated tissue not extending to stele.
4. Supericial striations on hypocotyl, but not extending to stele.
5. Stink bug damage on the lower region of one cotyledon affecting the internal surface.
This approach is described in detail in the 2009 AOSA Vigor Testing Handbook for corn, soybean,
cotton and peanut.
This test is especially suitable for large-seeded legumes and results are often correlated with those
of other vigor tests. It provides the advantage of a quick turnaround time compared to two or three weeks
required for other seed vigor tests. The AOSA Vigor Testing Handbook (2009) has more details about using
the TZ test as a vigor test.
