Abstract:
The Key component of weed management in direct seeded rice is early flooding, Therefore, this
study was conducted to understand the response of seed storage duration and storage
conditions on germination under flooding. The present study was carried out using 4 rice
genotypes such as KhaoHlanOn (KHO), Khaiyan, IR64 and IR42 with three different storage
durations: 5, 10 and 15 months and two storage conditions; controlled storage (Seal Jar ) at 25
°C and relative humidity of 60-70 % and ambient storage (uncontrol storage -27-35 °C). Dry
seeds were sown in dry soil in 1 cm soil depth and flooded to 5 cm water depth and 0 cm
(saturated soil) maintained as control. Germination %, seedling vigor, growth and seedling
survival were assessed at 21 d after sowing. Lipid peroxidation and total phenolic content were
assayed in dry seeds before sowing and amylase activity was assayed in germinating seeds at 4 d
after sowing. Flooding decreased germination, seedling vigor and survival in 15 months old
seeds; greater decreased was associated with the seeds stored at ambient conditions than
controlled storage conditions. Higher malondialdehyde (MDA) content, lower phenolic content
and lower amylase activity of age seeds were associated with their lower germination and
seedling survival. The prolong seed storage at ambient condition resulted in increased MDA
content and deceased amylase activity. MDA content of dry seeds which were stored at
controlled conditions before sowing negatively correlated with seedling survival (r = -0.75***)
under flooding condition at 21 d after sowing. Controlled storage seeds showed higher phenolic
content and which was positively correlated with seedling survival (r = 0.56**) under flooded
condition. Five months stored tolerant rice genotypes ((KHO) and Khaiyan) had lower MDA and
phenolic content, dry seeds before sowing and higher germination, seedling vigor, survival, and
higher amylase activity under flooding conditions. Seed storage time and ambient storage
condition negatively affects the seedling survival and amylase activity under flooding conditions.
Combination with flooding tolerant rice genotypes and pre- seed management are important to
achieve improved crop establishment, especially areas prone to early flooding condition.
