Table 2.
Application of external RNAs for plant insect pest resistance.
| Target | RNA Type and Origin | RNA Amount | RNA Application and Feeding Assays | Plant Host | Effect | Effect Maintenance | Reference |
|---|---|---|---|---|---|---|---|
| Cyp18A1 and Ces genes of BPH; KTI gene of ACB | In vitro synthesized dsRNA | Rice—1 mL of dsRNA (1.0 mg/mL); maize—10 mL of dsRNA (0.5 mg/mL) | Root or seed soaking; larvae feeding 24 hpt | Rice, maize | Increased insect mortality rate | At least for 3–7 dpt | Li et al. (2015) [20] |
| Actin gene of CPB | In vitro transcribed dsRNA (50, 102, 208, 266, and 297 bp) | 5 μg of actin-dsRNA (200 µL) per single leaf of one plant | RNA coated over the leaf surface by the side of a 200 μL pipette tip; larvae feeding from 0.5 hpt for 7 days | potato | Lowered biological activity of CPB (monitored weight, instar stage, and mortality) | At least for 28 dpt | San Miquel and Scott (2016) [19] |
| HC-Pro gene of ZYMV | In vitro transcribed dsRNA (588 bp) | 10.5 µg (10 µL) of dsRNA onto the upper side per leaflets (of a single leaf) | Mechanical inoculation (gently rubbing the surface of carborundum-dusted leaves) | tomato | dsRNA detection in tomato (local and systemic leaves) and in insects (aphids, whiteflies, and mites) | Detection at 3, 10, and 14 dpt | Gogoi et al. (2017) [21] |
| JHAMT and Vg genes of BMSB | In vitro synthesized dsRNA (200–500 bp) | 5 µg or 20 µg in 300 µL of water (0.067 µg/µL or 0.017 µg/µL) | Immersion of the green beans in the dsRNA solution (3 h) | common bean | Decreased expression of JHAMT and Vg genes in BMSB | Ghosh et al. (2018) [22] | |
| AK gene of ACP | In vitro synthesized dsRNA (200–500 bp) | 200 mL of dsRNA (0.5 mg/mL); | RNA spraying; | citrange | Detection of the dsRNAs in the citrus plants; increased ACP mortality | dsRNA detection in plants 49 dpt | Ghosh et al. (2018) [22]; Hunter et al. (2012) [55] |
| 1 L (0.2 mg/mL), 100 mL (1.33 mg/mL), or 10 mL (1 mg/mL) of dsRNA | Soil/root drench application (soaking for 0.5 h); | citrange | |||||
| 6 mL (1.7 mg/mL) of dsRNA | trunk injections | citrange |
Cyp18A1—a cytochrome P450 enzyme; Ces—carboxylesterase; KTI—kunitz-type trypsin inhibitor; BPH—the brown planthopper (Nilaparvata lugens); ACB—Asian corn borer (Ostrinia furnacalis); CPB—Colorado potato beetle; hpt—hours post-treatment; dpt—days post-treatment; HC-Pro—the helper component-proteinase; ZYMV—zucchini yellow mosaic virus; BMSB—brown marmorated stink bug; JHAMT—juvenile hormone acid O-methyltransferase; Vg—vitellogenin; AK—arginine kinase; ACP—Asian citrus psyllid.