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

class limits values are clearly separated from the lower as is indicated
between dotted vertical lines. In ‘Cavendish Enano’ highest DDP-days
values ranged from 52.0 to 59.9 days and in ‘Williams’ varies from 50.0 to
54.9 showing quite different reaction expression against to black Sigatoka
comparing with the lowest values in both cultivars.
All these values gave a sign that there exist great inter-
individual variations of the DDP-days due probably to variable
mutagenesis caused by the ion-beam irradiation. Molina and Castaño
(2003) found in their results on inoculation methods using young plants
with both resistant and susceptible cultivars to black Sigatoka, which the
DDP-days in the resistant cultivar ‘FHIA-01’ was 77.5 days and the
susceptible cultivar ‘Gros Michel’ was 31.2 days. In the present study, the
high range of DDP-days demonstrated that there was a reaction of this
group of plants against to the fast development of the disease. Additionally,
Mobambo et al. (1997) reported differences of the DDP-days (identical
with DDT by Mobambo et al.) between young and mature plants in a
hybrid progeny of plantain. DDT of the hybrids were 7-16 and 28-36 days
longer in young and mature plants, respectively. This variable allowed
segregation between susceptible and resistant clones and also between
different levels of resistance among the hybrids. These authors also
mentioned that the similarity in ranking and response levels as shown by
the high correlations between clones of mature and young plants indicate
reliable and efficient evaluation in germplasm at young plants phase on
response to black Sigatoka. However, agronomic traits like yield
performance cannot be predicted by early evaluation for disease response
of a clone.
In the present experiment, the variation of the DDP-days in each
inoculated leaf could be due probably to the high inoculum pressure
existing in the open field or the inoculum produced by the diseased leaves
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