CRISPR/Cas biosensing for plant pathogens and engineered crops

Plant pests (pathogens, insects and weeds together) remove up to 40% of global crop production every year, and plant diseases alone cost more than USD 220 billion, yet outside certification, quarantine and seed-testing schemes most infections are confirmed only after symptoms appear, when the epidemic has already outrun the intervention. Closing this lag requires assays combining reference-method specificity with a portable, instrument-light format. CRISPR/Cas biosensing addresses this requirement: once a Cas effector binds its programmed target, Cas12 and Cas13 enter a collateral trans -cleavage state that cleaves labeled reporters in large molar excess, converting sequence recognition into a fluorescent, colorimetric or lateral flow signal typically within 15 to 60 min and reaching attomolar sensitivity with pre-amplification. Depending on the ortholog, guide design and conditions, recognition can resolve single-nucleotide differences. This review traces the toolkit from genome editor to field diagnostic across two applications usually treated separately: detection of plant pathogens and pests, and surveillance of transgenic and genome-edited crops. We compile disease-resolved performance data for assays spanning fungi, oomycetes, bacteria, phytoplasmas, viruses, viroids, nematodes and insect vectors, with explicit attention to horticultural and agronomic systems from tomato and cucumber to potato, brassicas, rice, wheat and sugarcane, and to engineered crops in which a single-nucleotide edit leaves no transgenic signature. Engineering advances that narrowed the laboratory-to-field gap (protospacer adjacent motif relaxation, one-pot and amplification-free chemistry, multiplexing, nanozyme transduction and smartphone integration) are appraised alongside the constraints of sampling, quantification, stability and validation that still separate field-compatible prototypes from validated, certified diagnostics.