Development of insect pests resistance is a common problem causing high yield losses. Different modes of insecticidal actions have been proposed to overcome this problem. Pyramiding Bt-gene into one plant, can delay evolution of resistance, under condition that Bt-proteins express low level of similarity. In case of very similar proteins, insects might exhibit cross-resistance. To avoid this, various Bt- toxins expressing genes or synthetic genes (Syn-vip3BR), chimeric (Cry2aX1) or Cry and Vip toxins that are sufficiently different in comparison to those currently used (Cry1I, Cry2Af2). Another approach, RNA interference, can be used as another pest control in plants. Insects that absorb long double stranded RNA and have specific cell machineries to activate the RNAi process, get target gene silenced. Consequences can be: growth inhibition or abnormal growth, higher sensitivity to external factors or death. This paper also describes studies, in which both approaches: Bt-toxins and RNAi, were combined.
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