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

in the plant itself. After inoculation of the leaf No. 1, plants still remained
on the nursery until the inoculation of the subsequent leaves (No. 2 and 3).
Nursery conditions were different as compared with the open field resulting
in the variability of DDP-days. In contradiction, Mobambo et al. (1997)
with a hybrid progeny obtained by crossing resistant and susceptible
plantain cultivars reported that the disease assessment of subsequent leaves
on young plants could reflect host response to black Sigatoka dependent on
plant age. Symptom development on earlier produced leaves was faster
than on later emerged leaves. Also another factor could be due to the
inoculation method in the present study. As we mentioned above, the
second and third leaves were inoculated using diseased leaf-fragments that
could produce much inoculum capable to promote a fast DDP-days.
However; Leiva et al. (2002) reported that mycelial homogenate and
fragments of diseased leaves as types of inoculum of M. fijiensis, promoted
disease symptom development in both ‘Grande Naine’ and ‘FHIA-18’ in
greenhouse condition. Additionally, the susceptibility of ‘Grande Naine’
with respect to the partial resistances shown by ‘FHIA-18’ in greenhouse
condition was found to coincide with the response of both cultivars in
natural conditions.
4. 3. 2. 2. Infection index (II-%)
The results in this variable were from the regenerated plants
subjected to the first irradiation. II-% showed significant differences
between the cultivars and the evaluation periods (June 16, 27, July 10 and
24, 2006) by Tukey analysis (P≦0.05). ‘Williams’ possess highest II-%
than ‘Cavendish Enano’. The II-% was found higher in latest evaluations.
Figs. 44-B and 45-B are showing the II-% frequency distribution by class
limits of “Cavendish Enano’ and ‘Williams’, respectively. Lowest II-%
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