ENVIRONMENTAL DISTRIBUTION AND DIVERSITY OF BACILLUS-THURINGIENSIS INSPAIN

Bacillus thuringiensis was isolated from 301 our of 1,005 samples coll ected in Spain from agricultural and non-cultivated soils, dust from s tored products, and dead insects. Based on the production of para spor al crystals, 1,401 isolates were identified as B. thuringiensis after examining 11,982 B. thuringiensis-like colonies. Vile found a greater presence of B. thuringiensis in dust from grain storages than in other habitats. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis o f the spore-crystal mixtures revealed diverse populations of B. thurin giensis which were differentiated in at least 92 distinct protein prof iles. Serological identification also showed great diversity among the Spanish isolates which were distributed among 38 of the 58 known sero vars. The most frequently found serovars were aizawai, kurstaki, konku kian, morrisoni, and thuringiensis. which together represented more th an 50% of the serotyped isolates. In preliminary toxicity assays, a nu mber of isolates were found to show significant insecticidal activity against the lepidopterans Heliothis armigera (76.1% of the assayed iso lates), Spodoptera exigua (50.5%), and Plutella xylostella (19.7%). Th irty five isolates were toxic to both H. armigera and S. exigua, and e ight were toxic to S. exigua and P. xylostella. Four and one isolates were toxic to the coleopterans Leptinotarsa decemlineata and Colaspide ma atrum, respectively, and three to the dipteran Tipula oleracea. The electrophoretic pattern and serovar of most of the isolates with toxi c activity were consistent with those reported in the literature, alth ough other isolates revealed unusual protein profiles, were assigned t o new H serovars, or were included in H serovars nor previously report ed within such pathotypes.