MARGINAL CROSS-RESISTANCE TO MOSQUITOCIDAL BACILLUS-THURINGIENSIS STRAINS IN CRY11A-RESISTANT LARVAE - PRESENCE OF CRY11A-LIKE TOXINS IN THESE STRAINS

Culex quinquefasciatus mosquito larvae resistant to the Cry11A toxin s howed marginal cross-resistance to the multiple toxin crystals from B. thuringiensis subsp. israelensis and also to toxin crystals from thre e other mosquitocidal strains, i.e. B. thuringiensis subsp. fukuokaens is, subsp. jegathesan, and subsp. kyushuensis. Cross-resistance patter ns of the Cry11A-resistant larvae to mosquitocidal strains of B, thuri ngiensis together with the immunological screening using antisera rais ed against Cry11A indicated the presence of Cry11A-like toxins in thes e strains and could be used as a screening tool for the identification of novel toxins. The Cry11A-resistant larvae had significantly less r esistance to the Cry11B toxin from B. thuringiensis subsp. jegathesan. The occurrence of cytolytic toxins in all of these mosquitocidal stra ins partially explains the marginal cross-resistance observed with mul tiple toxin crystals since each of these crystals also contains cytoly tic toxins.