02565naa a2200229 a 450000100080000000500110000800800410001902400250006010000240008524501670010926000090027652018060028565000230209165000240211465000260213870000240216470000190218870000220220770000210222970000210225077300640227119038012025-02-20       2011    bl uuuu     u00u1 u    #d7 a10.1002/ps.22062DOI1 aARGOLO FILHO, R. C.  aGrowth variation among Bacillus thuringiensis strains can affect screening procedures for supernatant-secreted toxins against insect pests.h[electronic resource]  c2011  aBACKGROUND: Supernatant-secreted proteins in Bacillus thuringiensis (Berliner) (Bt) with insecticidal activity provide an important source of information for discovery of new useful strains and/or entomotoxins. However, physiological variation among isolates might interfere in the detection efficiency of screening procedures on Bt collections. The aim of this study was to assess the magnitude of this variation in a sample of isolates from a tropical Bt collection, which was gauged through the assessment of their temporal patterns of growth and protein secretion in culture supernatants (SNs), as well as of the corresponding toxicity against fall armyworm(Spodoptera frugiperda, JE Smith). Feedingbioassays were performed, with larvae being treated with heated and non-heated total protein extracted from SNs collected at different culture times. Larvamortality and reduction in pupa formation were observed. RESULTS: Intra- and interisolate variations were observed in the temporal patterns of growth, quality and quantity of protein secreted, aswell as in insecticidal activity of these SNs, based on larvaemortality and pupation rates. These results suggest that the insecticidal potential of certain isolates can be hidden if comparisons are done on the basis of the same number of cells in the culture and/or the same culturing time. CONCLUSIONS: Methods of screening Bt collections on the basis of feeding bioassays can be misleading with regards to identifyingmore promising isolates for biocontrol purposes if physiological differences are not considered. The consequences and implications of these findings for the development of experimental systems that depend on toxicity bioassays to identify alternative Bt strains and entomotoxins with practical applicability have been discussed.  aBiological control  aControle biológico  aSpodoptera Frugiperda1 aGOMES JUNIOR, R. A.1 aBARRETO, M. R.1 aLANA, U. G. de P.1 aVALICENTE, F. H.1 aLOGUERCIO, L. L.  tPest Management Science, Sussexgv. 67, p. 1184-1192, 2011.