Protocols for Micropropagation of Woody Trees and Fruits

3.3. Observations to be Recorded
IN VITRO MUTAGENESIS IN BANANA 555
3.3.1. Shoot-tip Cultures
For tissue culture experiments, data are scored on various traits such as number of
shoots (total number of scorable shoots per culture), shoot length (average length of
the shoots in the culture, cm), number of roots (total number of scorable roots per
shoot), root length (length of the longest root, cm), multiplication ratio (estimated by
dividing “number of cultures after subculturing” by “number of cultures before
subculturing” and shoot survival (proportion of shoots resuming growth upon gamma
irradiation, %). If deemed necessary, the post-irradiation in vitro rooting response
can also be determined by culturing the surviving shoots on SM4 medium and the
observations with respect to number of days for first root initiation, number of roots,
root length and shoot length are recorded.
3.3.2. Cell Suspension Cultures
Weight gain (final fresh weight/initial fresh weight of the cells), settled cell volume (can
be measured by transferring known volume of cell suspension into sterile graduated
tube and allowing to settle for 10 min), number of somatic embryos (total number of the
globular, torpedo or advanced stage somatic embryos obtained per ml of cells plated),
number of plantlets regenerated (total number of plantlets obtained per ml of cells
plated).
3.3.3. Plant Survival during Hardening
The proportion of surviving plants (%) for “shoot-tip multiplication” and “ECS” derived
plants in the greenhouse is recorded.
4. FIELD PLANTING AND EVALUATION
It would be desirable to evaluate maximum number of plants in the field; however,
banana field trials cannot be compared with the field crops requiring high planting
densities. It is also difficult to recommend any particular population size for field trial.
However, at least about 500 plants are field evaluated. It is strongly suggested that only
the standard cultivation practices shall be adopted based on the local conditions.
The greenhouse hardened non-irradiated (control) and irradiated populations are
field transferred for evaluation and screening for variants. The sources of variation
could be the individual effects or a combined effect of genetic causes, physiological
effect of irradiation, physiological effect of in vitro culturing and somaclonal variation.
4.1. Observations to be Recorded
As a guideline, the standard descriptors are to be referred for data scoring (INIBAP,
1996); however, data can also be recorded on any other traits of specific interest as well
(Kulkarni et al., 2002). At least 2 border rows of a phenotypically matching banana
genotype/s shall essentially be incorporated from all sides of the experimental block.
Data are scored as described above (excluding the border rows).