Whitefly (Bemisia tabaci) damages field crops by sucking sap and transmitting viral diseases. None of the insecticidal proteins used in genetically modified (GM) crop plants to date are effective against whitefly. We report the identification of a protein (Tma12) from an edible fern, Tectaria macrodonta (Fee) C. Chr., that is insecticidal to whitefly (median lethal concentration = 1.49 μg/ml in in vitro feeding assays) and interferes with its life cycle at sublethal doses. Transgenic cotton lines that express Tma12 at ∼0.01% of total soluble leaf protein were resistant to whitefly infestation in contained field trials, with no detectable yield penalty. The transgenic cotton lines were also protected from whitefly-borne cotton leaf curl viral disease. Rats fed Tma12 showed no detectable histological or biochemical changes, and this, together with the predicted absence of allergenic domains in Tma12, indicates that Tma12 might be well suited for deployment in GM crops to control whitefly and the viruses it carries.
The cabbage maggot, Hylemya brassicae (Bouché), had three generations per year from 1970 to 1973 inclusive, a partial fourth was noted in most years. A small proportion of first generation pupae entered aestivation in 1971.Thermal units required for fly emergence from overwintered pupae fell within a narrow range (174 to 199), but there was little correlation between thermal units and fly emergence in subsequent generations. Lack of adequate moisture delayed establishment of larvae in roots in some generations. Lack of adequate soil moisture delayed establishment of larvae in roots in some generations, and this appeared to be the chief reason for the lack of correlation between thermal units and fly peaks.Throughout this investigation the over-all population remained remarkably constant. Parasitism by a staphylinid, Aleochara bilineata Gyll., and a fungus, Strongwellsea castrans Batko and Weiser, and soil moisture were the most important biological and climatic factors affecting survival. Parasitism of the adult by a nematode, Heterotylenchus sp., was recorded for the first time.Although large numbers of seed maggot adults, Hylemya florilega (Zett.) and H. platura (Meig.), were recorded, few infested rutabaga. Other species trapped included Euxesta notata (Weid.) and Muscina spp.
In Hylemya brassicae (Bouché) little oviposition occurred when access to host plant material was denied. The mustard oil, allyl isothiocyanate (AITC), stimulated the flies into greater activity and attracted them to its source. Sinigrin and four other glucosinolates (mustard oil glucosides) tested induced oviposition. AITC by itself did not induce, oviposition, but in the presence of a glucosinolate, small concentrations of AITC caused an increase in the number of eggs laid. Glucose, sucrose, casein, wheat germ oil, and a mixture of B-vitamins did not influence oviposition at the concentrations tested, but casein hydrolysate inhibited it. The role of glucosinolates and common nutrients in host selection by H. brassicae is discussed.
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