Aphids are major insect pests of cereal crops, acting as virus vectors as well as causing direct damage. The responses of wheat to infestation by cereal aphid (Sitobion avenae) were investigated in a proteomic analysis. Approximately, 500 protein spots were reproducibly detected in the extracts from leaves of wheat seedlings after extraction and 2-DE. Sixty-seven spots differed significantly between control and infested plants following 24 h of aphid feeding, with 27 and 11 up-regulated, and 8 and 21 down-regulated, in local or systemic tissues, respectively. After 8 days, 80 protein spots differed significantly between control and aphid treatments with 13 and 18 up-regulated and 27 and 22 down-regulated in local or systemic tissues, respectively. As positive controls, plants were treated with salicylic acid or methyl jasmonate; 81 and 37 differentially expressed protein spots, respectively, were identified for these treatments. Approximately, 50% of differentially expressed protein spots were identified by PMF, revealing that the majority of proteins altered by aphid infestation were involved in metabolic processes and photosynthesis. Other proteins identified were involved in signal transduction, stress and defence, antioxidant activity, regulatory processes, and hormone responses. Responses to aphid attack at the proteome level were broadly similar to basal non-specific defence and stress responses in wheat, with evidence of down-regulation of insect-specific defence mechanisms, in agreement with the observed lack of aphid resistance in commercial wheat lines.
With a projected increase in world population to 10 billion over the next four decades, an immediate priority for agriculture is to achieve maximum production of food and other products in a manner which is environmentally sustainable and cost effective. Despite the synthesis of improved pesticides, and integrated pest management strategies, yield losses due to insects have actually increased slightly for most crops over the last two decades.
The concept of utilising a transgenic approach to host plant resistance was realised in the mid 1990s with the commercial introduction of genetically modified crops expressing genes encoding the entomocidal d‐endotoxin from
Bacillus thuringiensis
(
Bt
). More recently this strategy has been extended to include the pyramiding (stacking) of genes encoding different Bt toxins for greater levels of pest control. Although not as yet a commercial reality, other strategies based on the use of plant derived genes (enzyme inhibitors, lectins) and those from animal sources, including insects (biotin‐binding proteins, neurohormones, enzyme inhibitors), are being developed. The use of fusion proteins to increase the spectrum and durability of resistance is also actively being pursued. However, if transgenic insect‐resistant crops are to play a useful role in crop protection, it is apparent that they must be compatible with the other components of integrated pest management (IPM).
The current chapter addresses the role of insect‐resistant transgenic crops in agriculture and discusses both their current status and future developments. Given the importance of natural enemies in controlling pest populations, the potential impact of such crops on predators and parasitoids is also addressed.
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