Abstract

Thanawan Kantha, Chaiyavat Chaiyasut*, Duangporn Kantachote, Suchada Sukrong and Amorntip Muangprom

Soil samples from organic saline paddy fields from 14 provinces of the northeast region of Thailand were collected and used for isolating photosynthetic bacteria (PB) prepared as a Soil and Straw Products (SSPs). PB from these SSPs were further grown in double strength G5 broth under microaerobic-light conditions before purification. A total of 130 isolates were then screened for growth in G5 broth under microaerobic-dark conditions for 24 h and 15 isolates were further selected by secondary screening in G5 broth under microaerobic-light conditions for 24 h. Four isolates (tk35, tk85, tk103 and tk123) were selected and all were identified as Rhodopseudomonas palustris based on their 16S rRNA gene. After incubation in SSP for 4 weeks with microaerobic-dark conditions, all SSPs had pH values in a range of 5.33 -7.17 and electrical conductivity (EC) values were between 3.02-12.93 dS/m. It was also found that the 5-aminolevulinic acid (ALA) content increased with time to achieve levels of 2.95, 2.94, 2.95 and 2.96 mM, from strains tk35, tk85, tk103 and tk123, respectively. The results indicate that SSP containing selected PB could produce ALA and this could be practically applied to organic saline paddy fields and increase growth and yields of rice.