Crop gene editing against biotic stresses via CRISPR/Cas9 tools: a review

Prokaryotic type II CRISPR/Cas9 (clustered regularly interspaced short palindromic repeat/CRISPR-associated protein9) adaptive immune system has been applying in many plants for editing target gene(s). The CRISPR/Cas9 technology is superior to other programmable nucleases, such as ZFNs (zinc finger nucleases) and TALENs (transcription activator-like effector nucleases), for its fast activating, simplicity, high efficiency, and economically feasibility. Thus, the current study have mainly focused on the study of CRISPR/Cas9 technology against plant biotic agents like fungus, bacteria, virus, and insect pests. Though this technology is highly applicable against all biotic agents but the success rate based on the previously published papers clarified that it is more effective towards to viruses and fungi. This technology may be used in editing both the target sites either of plants or biotic agents. In both the cases it produces desirable modification in the target sites, makes this technology more applicable to produce biotic agent resistant crop variety. So this editing technology is considered not only a powerful tool for genome editing in both plant and biotic agent but also for developing non-transgenic biotic stress resistant crop variety. The current review may explore the role of CRISPR/Cas9 technology in introgression of QTL, deletion of unwanted genes for crop plants resistant against specific pests and environmental stresses.