An attempt was made to study the effect of biological seed treatment on the
viability and keeping quality of B. rapa and incidence of Pythium damping-off.
Trichoderma virens (UPM 23) and Trichoderma harzianum (UPM 29) were used
as the microbial inoculants in bio-pelleting of the seeds. UPM 23 produced greater
antagonistic activity against Pythium splendens, the causal pathogen of dampingoff
of B. rapa, based on the in vitro dual culture and colony degradation tests.
Percentage inhibition of radial growth (PIRG) of P. splendens was 83.8% and
94.0% when co-inoculated on Potato Dextrose Agar (PDA) and Corn Meal Agar
(CMA) respectively. Parasitized hyphae failed to regenerate when plated on fresh
CMA medium. UPM 23 was as effective as Captan® in protecting the B. rapa
seeds against Pythium pre-emergence damping-off, due to its ability to colonize
the germinating seed, compete for sites and nutrients and directly parasitizing
Pythium. Percentage reduction in seedling emergence was 7.0%, 14 days after sowing, as compared to the control (80.6%). There was no significant difference in
percentage post-emergence damping-off of seedlings between bio-pelleted seeds
or controL However, number of surviving plants at harvest was higher for UPM 23
bio-pelleted seeds relative to the other treatments. Measurement of seed viability
based on germination test, electrical conductivity test, accelerated aging test and
tetrazoliwn staining, showed that B. rapa seeds either Trichoderma bio-pelleted or
rice flour pelleted with 10% moisture content bas better keeping quality when
stored at 10°C ± 2°C, until week 24 of storage. Seed viability and quality was
further improved by reducing the moisture content to 4%. Incorporation of
biocontrol agents such as UPM 29 and UPM 23 in hio-pelleting, regardless of seed
moisture content required low storage temperature to ensure the survival and
proliferation of these inoculum on the seed surface
