The diversity of soil microorganisms in mulberry root rot disease infesting fields was investigated from The Queen Sirikit Sericulture Center at Kanchanaburi Khon Kaen Sisaket and Ubon Ratchathani provinces. Isolation of the soil microorganisms was performed on four media as nutrient agar (NA) potato dextrose agar (PDA) rose bengal agar (RBG) and modified selective fusarium agar (SFA). Twenty-four bacterial isolates were arisen from NA including gram positive endospore forming rod gram negative rod gram positive cocci and Actinomycetes. Similarly 75 isolates of fungi were gained from PDA RBG and SFA and could be defined to be Aspergillus sp. Chaetomium sp. Curvularia sp. Fusarium sp. Penicillium sp. Phytophthora sp. and Rhizopus sp. by their morphological characteristics. Verification of the causal pathogen of mulberry root rot disease could be accomplished using specific primers for F. solani in which a DNA band at approximately 300 bp was revealed.

The objective of this research was to isolate plant growth promoting rhizobacteria from Wedelia trilobata (L.) A.S. Hitchcock rhizosphere and preliminarily test their plant growth promoting properties such as nitrogen fixation siderophore production phosphate solubilization and indole-3-acetic acid production. Forty-seven bacterial isolates were obtained including 26 isolates of gram positive 18 isolates of gram negative and 3 isolates of actinobacteria. After that 8 isolates (including BWTM1_MSU BWTM2_MSU BWTM5_MSU BWTM6_MSU BWWM6_MSU BWWM8_MSU BWWM9_MSU and BWWM16_MSU) were selected for studying on root colonization and plant growth promoting properties under aseptic condition. The results showed that BWTM5_MSU had the evident on the promotion of plant growth with the most percentage of rice seed germination (63.33%) high level of root and shoot length with 6.11 cm and 3.89 cm respectively. As a result the root and shoot fresh weight was as high as 9.56 mg and 11.33 mg respectively. It also correlated with the highest production of indole-3-acetic acid up to 421.29 ug/ml. The root colonization was studied by counting rhizobacteria isolate BWTM5_MSU from rice rhizoplane and rhizosphere with presented bacterial number at 9.67x106 CFU/g root and 1.64x10 10 CFU/g soil respectively.