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

4. 2. 2. Assessment of banana plantlets at the nursery and at field
conditions
A soil bed was constructed inside a greenhouse and the plantlets
were transferred on a soil substrate (soil : vermiculite = 1:1) and covered
with a plastic sheet to avoid dehydration (Fig. 25). Factors such as
transportation conditions, disease attack, or some abnormal behavior
caused by the irradiation could bring about the high mortality (Fig. 26).
Surviving plants were transplanted to bags and covered by using a cotton
sheet and spraying water for three times a day to avoid plantlets
dehydration (Fig. 27). Only 87 plants survived the nursery acclimatization.
Plants were kept in a nursery plot until May 2006 and the bags were
changed for a bigger one to recover vigor (Fig. 28). Fortunately, plants
from every dose for the two cultivars survived except in the dose of 2 Gy of
the ‘Cavendish Enano’. Using these materials (height of plant around 35
cm) the experiments for black Sigatoka inoculation in nursery plot and later
on at the field conditions were conducted.
4. 2. 2. 1. Disease development period (DDP-days) and infection index
(II-%)
Three banana leaves per plant were inoculated. Plants were
about 30 cm height and the younger expanded leaf was marked as the first
leaf for inoculation by a conidial solution. Second and third successive
young emitted leaves were inoculated by fragments of the diseased banana
leaves. Prior to inoculation of the first leaf, a solution containing a M.
fijiensis conidial was prepared. The cultures were provided by the
Laboratory of Pathology of the Estación Experimental Tropical Pichilingue,
INIAP (Fig 29, A). The colonies for inoculation were cut in small pieces
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