KELIMPAHAN BAKTERI RIZOSFER PADA SISTEM PHT-BIOINTENSIF SERTA KEMAMPUAN ANTAGONISMENYA TERHADAP SCLEROTIUM ROLFSII PADA KEDELAI

Abundance of beneficial microorganisms in the soil is one of the active soil indicators the success of integrated pests management (IPM) system. Some beneficial groups of microorganisms can be used as biocontrol agents. This experiment was conducted to evaluate the effects of IPM-Biointensive by integrated application of resistant varieties, rice-straw mulch, and biocontrol agents on the abundance of rizospheric bacteria of soybean, also to evaluate the suppressiveness of the bacteria to the mycelial growth of S. rolfsii in vitro. Abundance of the bacteria was determined by isolation using serial dilution and plate-count techniques. Suppression to the fungus was evaluated using dual culture technique. Heat tolerant bacteria had the highest abundance (ranged 10¹¹-10¹² cfu/g soil), followed by non-fluorescence bacteria (10¹¹ cfu/g soil), chitinolytic bacteria (10⁶-10⁹ cfu/g soil), and fluorescence bacteria with population range was 10³-10⁸ cfu/g soil. Gepak kuning variety grown with application of rice-straw mulch and PGPR (V₂ M₁ P₁) caused the highest abundance of rizosphere bacteria. One of the heat tolerant bacteria, i.e. TP32, caused the highest suppression to the mycelial growth of S. rolfsii in vitro. Based on the morphology, physiology, and biochemical properties, the isolate was identified as Bacillus sp.