IN VIVO BIOCONTROL ACTIVITY OF BACILLUS SPP. STRAINS ON ALTERNARIA TENUIS RODICA MATEESCU, CĂLINA PETRUŢA CORNEA, IRINA GREBENIŞAN, NARCISA BĂBEANU, G.CÂMPEANU Faculty of Biotechnology, UASVM Bucharest, 59 Bd. Marasti, Bucharest, Romania, Fax: +40.1.224.55.95, rodica_mateescu@k.ro Key words: biocontrol, antifungal compounds, Bacillus spp., phythopathogenic fungi, Abstract Alternaria diseases are among the most common diseases of many plants in the world [1]. They affect primarily the leaves, stems, flowers and fruits of annual plants, especially vegetables [2]. The overuse of chemical pesticides has caused soil pollution and harmful effects on human beings. Accordingly, biological control of soil-borne diseases has been attracting attention. Many reports or reviews in this area have already appeared [3, 4, 5, 6]. Biological control agents are potential alternatives for the chemical fungicides presently used in agriculture to fight plant diseases. Bacillus ssp, strains are an example of a promising safe fungal biological control agents. This paper, describes that B.subtilis B2, B. licheniformis B40, B.subtilis mB2.9, B.subtilis tB2.2, B. licheniformis mB40.5, B. licheniformis tB40.2, which showed in vitro antibiotic activities against two strains of Alternaria tenuis [7, 8], were subjected to a pot test to investigate their ability to protect the plant against fungal disease. INTRODUCTION Fungal diseases can have major constraints on crop production and, in conventional agriculture, chemical fungicides are routinely used to provide disease control. However, as these chemicals are often toxic and potentially harmful to man and the environment, alternative methods for control are needed. Biological control is a potential alternative approach to chemical treatment and there are a number of fungal biocontrol products commercially available in Europe, including some that are registered as biopesticides. These are likely to increase in number in the coming years. Our researches were focused primarily to select Bacillus strains with antifungal potential, to obtain improved strains with increased activity against the plant pathogen Alternaria tenuis, to optimize culture conditions for the production of antifungal compounds [7, 8]. The aim of our researches presented in this paper was to test in vivo biocontrol ability of our Bacillus strains on the phytopathogen Alternaria tenuis. On planta were tested both culture broth and antifungal compounds extracted in alcohol. MATERIAL AND METHODS Microbial strains: in the experiments were used two fungal strains: Alternaria tenuis alt a1, A.tenuis alt a2 and seven bacterial strains: B.subtilis B2, B.subtilis mB2.9, B.subtilis tB2.2, B. licheniformis B40, B.licheniformis mB40.5, B.licheniformis tB40.2, B.subtilis lob1(from Dr Flori Constantinescu, Institute of Plant Protection, Bucharest). Media: L agar (meat extract 10g; peptone 10g, NaCl 5g; agar 15 – 20g, water 1000ml, pH =7,2); medium for iturin production (polypeptone 1%; glucose 1%; KH 2 PO 4 ; MgSO 4 x 7H 2 O 0,05%; pH =7,0); Sabouraud medium (glucose 15g; peptone 5g; agar 10g; distilled water 1000 ml; pH = 5,5 – 5,7). Culture conditions were presented previously [7].