Resistance to Insects

Widespread outbreaks of insect pests do not occur very frequently in Triticeae cereals, yet they can cause substantial crop losses. In order to enhance the insect resistance (see also Chap. 10) of wheat, Stoeger et al. (1999) generated transgenic lines which expressed the insecticidal lectin-encoding GNA gene from snowdrop (Galanthus nivalis). The transgene was directed either by the ubiquitous maize Ubi-1 promoter or by the phloem-specific sucrose synthase 1 promoter of rice. By means of an infestation bioassay using the grain aphid Sitobion avenae under glasshouse conditions, they showed that the generative reproduction of aphids on GNA-expressing plants was significantly reduced.

The barley trypsin inhibitor BTI-CMe, encoded by the HvITR1 gene, is a protease inhibitor putatively involved in defence against herbivores. Purified gene product was shown to reduce the in vitro activity of trypsin and trypsin-like proteases of fall armyworm (Spodoptera frugiperda) gut extracts (Alfonso et al. 1997). Ubiquitous expression of the ITR1 gene in wheat significantly inhibited the development and reduced the survival rate of Angoumois grain moth (Sitotroga cerealella) neonate larvae reared on mature grains. In contrast, survival or weight gain of the grasshopper Melanoplus sanguinipes, which is another important pest in cereals, was not significantly reduced upon feeding on CMe-expressing wheat leaves compared to administration of non-transgenic control leaves (Altpeter et al. 1999).

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