In this work, an apparatus for irradiation of the rice seeds with
LASER beam. was developed .This apparatus design is described. Seeds of rice (Giza 159 cv.) were irradiated with LASER beam for different
periods (0, 15, 30, 45 and 60 s.). Irradiation of rice seeds resulted in
increasing of the seed germination percent; however, prolonging the
irradiation period to 60 s. had lethal effect on the seeds. Isolation of different
seed-borne fungi from irradiated and non-irradiated rice seeds showed
obvious differences either in total number or number of each fungus isolated
from the different treatments. Increasing the irradiation period was correlated
with decreasing of the seed-borne fungi. While 41 isolates were obtained
from untreated seeds, only 26 isolates were obtained from seeds treated with
LASER beam for 15 s. compared with 3 isolates obtained from seeds treated
for 30 s. Irradiation of the seeds for 45 s. resulted in complete disinfections of
the seeds. Trichoderma sp. and Peniclilium sp. were isolated from the surface of
the seeds. Trichoderma isolates were more sensitive to the irradiation than
the Penicillium isolates. Isolation from seed coat showed that the dominant fungi were
Pyricularia oryzae and Helminthosporium sp. while Fusarium sp. was found in
the endosperm. Irradiation period of 30 or 45 s. resulted in complete
elimination of these fungi. Under greenhouse conditions the plants, emerged from irradiated
and non-irradiated seeds, showed different disease severity, which was
correlated negatively with prolonging of the irradiation period: in contrary, the
height of plants and fresh weight of the foliage and roots were correlated
positively with prolonging of the irradiation ceriod