Abstract
Laboratory experiment was conducted to examine the effects of soil reduction and inoculation of Pythium spp. on seedling emergence and establishment of rice using 8 varieties including foreign varieties. Two types of soil were prepared, i.e., dry oxidized soil (OS) obtained from paddy field, and reduced soil (RS) with powdered rice straw added. Each soil type was inoculated with Pythium spp. (IP) or not inoculated (NP). Oxidation-reduction potential at one day after seeding was -136 mV in RS, while 400 mV in OS. Emergence percentage was 75% in RS, while 94% in OS. Emergence percentages of “Alborio-J1”, ”Kitaake” and “Iburiwase” were significantly lower in RS than in OS. On the other hand, “Italica Livorno” and ”Arroz da Terra” showed less reduction of emergence percentage in RS relative to OS, suggesting their tolerance to soil reduction. The inoculation of Pythium spp. to soil significantly reduced the establishment percentage in all varieties; it was 14% in IP and 80% in NP. However the reduction in “Dunghan Shali” was relatively small. In addition, the establishment rate was lower in RS/IP than in RS/NP, but higher in RS/IP than in OS/IP, suggesting that infection of seedlings with Pythium spp. may be inhibited by the reduction of dissolved oxygen concentration after the inoculation.
