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

‘Williams’ (93%), the necrotic area values ranged from 15 mm 2 to 30 mm 2 ,
except in Orito (95% of the evaluated plants) that varied from 10 mm 2 to 30
mm 2 (Fig. 15-A, -B and -C). A few plants among the three susceptible
irradiated cultivars were observed showing a low value of necrotic area
ranging from 5.97 mm 2 to 9.92 mm 2 . The values in these plants were lower
than the resistance indicator value (10.79±2.13 mm 2 ) which was selected in
this study (Table 5).
Different screening methods have been mentioned by different
authors (Harelimana et al., 1997; Molina and Krausz, 1988; Lepoivre et al.,
2002). The leaf puncture bioassay has been widely used to assess host-
tolerance/resistance to black Sigatoka or juglone; however, detached
banana leaves or the injection of crude toxic extract into the leaves is easy
but neither sensitive nor quantitative.
Clear variation between a black Sigatoka-susceptible cultivar
‘Grand Naine’ and the line ‘IV-9’ reported as highly resistant were
observed using the needle-piercing method with a phytotoxic extract to
measure the diameter of the area of necrotic tissue (Molina and Krausz,
1988). The toxic activity of the extracts apparently can be used to screen
banana and plantain breeding materials rapidly even at very young stage of
plant growth. This should prove very useful to hasten the resistance
screening process (Molina and Krausz, 1988).
In the present study, irradiated plants from “Gamma Room” and
“Gamma Field” were screened. 208, 179 and 307 plants were screened in
‘Cavendish Enano’, ‘Williams’ and ‘Orito’, respectively. Plants containing
low values (5-10 mm 2 of necrosis produced by using 150 ppm of juglone
on the leaf discs) were selected. 5, 8 and 20 plants were selected in
‘Cavendish Enano’, ‘Williams’ and ‘Orito’, respectively. In studies
mentioned by FAO/IAEA (2002) it was also found that from around 4,000
irradiated ‘Grande Naine’ plants screened, 19 putative mutants were
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