Gamma Rays and CarbonIon-Beams Irradiation for Mutation ...

3. 2. 1. 3. Chronic irradiation ( 137 Cs) at the “Gamma Greenhouse” in
banana plants
Chronic irradiation of banana plants was done in “Gamma
Greenhouse” facility. Banana plants were irradiated for a 9-month duration,
from September 2002 until the end of June 2003 (Fig. 3, C). In this case the
source of gamma rays was 137 Cs. Plantlets were irradiated in three doses:
0.25, 0.50 and 0.75 Gy (20 hours/day). Unique characteristics observed in
the mutants were evaluated.
3. 2. 2. Juglone toxin screening
The materials from three multiplications after irradiation at
“Gamma Room”, and “Gamma Field” (“Gamma Greenhouse” irradiated
plants were not screened) were acclimated under greenhouse conditions at
the University of Tsukuba. The plantlets were transplanted into the small
plastic pots with organic soils. When the plants reached 15-20 cm height
and 4-6 leaves, inoculations were made with juglone as host-specific toxin.
Leaf-discs were obtained from the second expanded leaf with a
6 mm of radius (113.09 mm 2 ). ‘FHIA-01’ (black Sigatoka resistant) was
included as resistance indicator (10.79±2.13 mm 2 ) as criteria to compare
the irradiated susceptible cultivars (‘Cavendish Enano’, ‘Williams’ and
‘Orito’). Ten mL of juglone solution-150 ppm (Reyes-Borja et al., 2005)
were placed in a 30 mm Petri dish, embedding 12 leaf discs and kept for 24
hours in an incubator at 26 o C under light conditions. Leaf discs photos
were obtained using a Camedia Digital Camera C-5050 Zoom (Olympus).
Necrotic area was measured with the GIMP 1.2 software by counting the
number of pixels per mm 2 of the full disc (113.09 mm 2 ) and number of
pixels of the green area by selecting hand-draw regions, obtaining the value
of necrotic area by difference. A total of 208, 179 and 307 plants were used
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