PJ-160:

Determination of a suitable condition for Azospirillum sp. B510 infection and colonization in rice plant and observation of the colonization

The use of microorganisms with the aim of improving crop production is one of the important practices for sustainable agriculture. Azospirillum sp. B510 is a promising nitrogen (N)-fixing endophytic bacteria for rice. It is known that inoculation of this bacterium increases growth and yield of rice plants and also enhances disease resistance. However, the effect of B510 inoculation is unstable and varies by fields, probably because of unstable colonization of the strain in rice. The objectives of this study were to establish a suitable condition for B510 infection in rice plant and observe the colonization using fluorescent protein expression technique. In this study, we evaluated 2 types of plant growth media [rice growth (RG) and murashige and skoog (MS), with and without N, potassium nitrate (KNO₃) and ammonium nitrate (NH₄NO₃)] to determine a suitable condition for B510 infection and colonization in rice (Oryzae sativa cv. Nipponbare). Dehulled, surface-sterilized rice seeds were inoculated with B510 and grown in Agri-pots (with 0.4% agar) in a growth chamber for 10 days (25℃, 16:8h light:dark). Plant growth (fresh weight, root and leaf length and plant height) and colonization rate of the bacterium inside the surface sterilized plant were examined. Colonization of DsRED expressing B510 was observed in the plant under fluorescent microscope. From the study we found a suitable condition for the colonization of B510 and observed the colonization of B510 in rice plant.

keywords:*Azospirillum*,endophytic bacteria,colonization,fluorescence microscope,rice