Abstract：
The western flower thrips, Frankliniella occidentalis, is a serious pest causing both direct feeding damage and indirect harm by transmitting the tomato spotted wilt virus. A spraying double-stranded RNA (dsRNA) targeted at the vacuolar-type ATPase (vATPase) gene was developed and demonstrated high insecticidal activity in the laboratory but less effective in field applications. To improve control efficacy under field conditions, three strategies were explored in this study. First, to identify a more efficient RNA interference (RNAi) target, dsRNA specific to the Snf7 gene was tested alongside dsRNA targeting vATPase, and both were found to be similarly effective in controlling the thrips. Second, to elucidate the factors contributing to dsRNA resistance, dsRNA-degrading enzymes were annotated and their physiological roles in diminishing RNAi efficacy were investigated. Third, to suppress the dsRNA degradation from the dsRNase activities and protect it in field conditions, the dsRNA was encapsulated with chitosan. This formulation enhanced the dsRNA\'s resistance to environmental stressors such as ultraviolet light and the digestive enzymes in the thrips\' gut. Additionally, the chitosan formulation specifically increased the RNAi efficacy, likely by facilitating more efficient entry into the target cells, thus bolstering the insecticidal activity of the dsRNA. The formulated dsRNA was applied on F. occidentalis infesting the hot peppers in a greenhouse at a concentration of 500 ppm, demonstrating an 82.4% control efficacy compared with 59.2% control efficacy observed with the application of naked dsRNA. This study further demonstrated an enhancement in the spectrum of control by combining dsRNAs specific to three distinct thrips species, while the mixture showed no adverse effects on non-target insects, such as the lepidopteran Spodoptera exigua. Collectively, these findings reveal that the chitosan formulation of dsRNA not only improves control efficacy under field conditions but also broadens the control spectrum against three different thrips pests.
摘要：
西花蓟马，西花Frankliniella,是一种严重的害虫，通过传播番茄斑萎病毒而引起直接摄食损害和间接损害。开发了靶向液泡型ATPase（vATPase）基因的喷雾双链RNA（dsRNA），并在实验室中显示出高杀虫活性，但在现场应用中效果较差。为了提高现场条件下的控制效果，本研究探讨了三种策略。首先,为了识别更有效的RNA干扰（RNAi）靶标，与针对vATPase的dsRNA一起测试了对Snf7基因特异性的dsRNA，发现两者在控制蓟马方面同样有效。第二,为了阐明导致dsRNA抗性的因素，注释了dsRNA降解酶，并研究了它们在降低RNAi功效中的生理作用。第三，抑制dsRNA降解从dsRNase活性和保护它在田间条件下，dsRNA用壳聚糖封装。这种配方增强了dsRNA对环境应激源的抵抗力，例如紫外线和蓟马肠道中的消化酶。此外,壳聚糖配方特别增加了RNAi功效，可能是通过促进更有效地进入靶细胞，从而增强dsRNA的杀虫活性。将配制的dsRNA以500ppm的浓度应用于温室中侵染辣椒的西洋F。与应用裸dsRNA观察到的59.2%的对照效力相比,证明了82.4%的对照效力。这项研究进一步证明了通过结合特定于三种不同的蓟马物种的dsRNA来增强控制谱。虽然混合物对非目标昆虫没有不良影响，如鳞翅目夜蛾。总的来说，这些发现表明，dsRNA的壳聚糖制剂不仅提高了田间条件下的控制效力，而且拓宽了针对三种不同蓟马害虫的控制范围。
