SUSCEPTIBILITY OF THE COFFEE LEAF MINER (PERILEUCOPTERA SPP.) TO BACILLUS-THURINGIENSIS DELTA-ENDOTOXINS - A MODEL FOR TRANSGENIC PERENNIALCROPS RESISTANT TO ENDOCARPIC INSECTS

Binding of several Bacillus thuringiensis delta-endotoxins was studied on histological midgut sections of larvae of coffee leaf miner Perile ucoptera coffeella from Brazil and Perileucoptera sp from Madagascar. CryIA(a), CryIA(b), CryIA(c), CryIB, CryIE, and CryIIA were tested for binding, and only CryIA(c), CryIB, and CryIE yielded a positive respo nse. The toxins bound to the whole midgut, and the result was identica l on both insect populations. The same toxins, to the number of which CryIC was added, were tested on larvae of P. coffeella. CryIA(c) and C ryIB were toxic with an LC50 of 1.47 mu g/ml and 21.93 mu g/ml, respec tively. CryIE was not toxic to P. coffeella. CryIA(c) and CryIB were t ested for synergistic activity and were shown to act by cumulative eff ect when delivered to the insect larvae as a mixture.