Transgenic approaches to improve resistance to nematodes and weevils

Abstract

Banana and plantain are important staple crops for Africa and important fruit crops for Asia, Latin America and Caribbean islands. Several nematode species and rhizome weevil (Cosmopolites sordidus) are major pests in banana that cause heavy damage and revenue loss. Pesticides and biocontrol agents control the pests, but pesticide residues pose severe environmental problems. Conventional breeding is a difficult and slow process due to the limited sources of resistance, sterility of cultivated banana varieties, polyploidy levels, long cropping cycle and the lack of rapid screening methods. Genetic engineering is considered as one of the eco-friendly and safer methods to control these pests. This review discusses the seriousness of the problem, the status and source of pest resistance and the mechanisms involved. The availability of various genes with potential to control nematodes and weevils is discussed. Further, current efforts and future prospects for identifying natural resistance genes and RNAi-based defences with potential to control nematode and banana weevil in a transgenic approach are outlined and discussed. Nematode-resistant transgenic banana cultivars expressing rice or maize cystatin genes and peptides evaluated under field conditions and those weevil-resistant cultivars developed using papaya cystatin gene with enhanced inhibitory potential are discussed in the light of biosafety concerns.