Do native and invasive herbivores have an effect on Brassica rapa pollination?

• Mutualistic (e.g. pollination) and antagonistic (e.g. herbivory) plant–insect interactions shape levels of plant fitness and can have interactive effects.
• By using experimental plots of Brassica rapa plants infested with generalist (Mamestra brassicae) and specialised (Pieris brassicae) native herbivores and with a generalist invasive (Spodoptera littoralis) herbivore, we estimated both pollen movement among treatments and the visiting behaviour of honeybees versus other wild pollinators.
• Overall, we found that herbivory has weak effects on plant pollen export, either in terms of inter‐treatment movements or of dispersion distance. Plants infested with the native specialised herbivore tend to export less pollen to other plants with the same treatment. Other wild pollinators preferentially visit non‐infested plants that differ from those of honeybees, which showed no preferences. Honeybees and other wild pollinators also showed different behaviours on plants infested with different herbivores, with the former tending to avoid revisiting the same treatment and the latter showing no avoidance behaviour. When taking into account the whole pollinator community, i.e. the interactive effects of honeybees and other wild pollinators, we found an increased avoidance of plants infested by the native specialised herbivore and a decreased avoidance of plants infested by the invasive herbivore.
• Taken together, our results suggest that herbivory may have an effect on B. rapa pollination, but this effect depends on the relative abundance of honeybees and other wild pollinators.

     

Identification and functional characterization of doublesex gene in the testis of Spodoptera litura

Fusion of the testis occurs in most Lepidoptera insects, including Spodoptera litura, an important polyphagous pest. Testicular fusion in S. litura is advantageous for male reproduction, and the molecular mechanism of fusion remains unknown. Doublesex influences the formation of genitalia, the behavior of courtship, and sexually dimorphic traits in fruit-fly and silkworm, and is essential for sexual differentiation. However, its purpose in the testis of S. litura remains unknown. The doublesex gene of S. litura (Sldsx) has male-specific SldsxM and female-specific SldsF isoforms, and exhibits a higher expression level in the male testis. At the testicular fusion stage (L6D6), Sldsx attained the highest expression compared to the pre-fusion and post-fusion periods. Moreover, Sldsx had a higher expression in the peritoneal sheaths of testis than that of germ cells in the follicle. CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/Cas9) was applied to S. litura to determine the role of Sldsx. A mixture of single guide RNA messenger RNA and Cas9 protein (300 ng/μL each) was injected into eggs within 2 h following oviposition. CRISPR/Cas9 successfully induced genomic mutagenesis of Sldsx at Go generation. The mutant males had smaller testis surrounded by less tracheae. Moreover, the mutant males had abnormal external genitalia and could not finish mating with wild-type females. Additionally, testes were fused for almost all mutant males. The results showed that Sldsx was not related to testicular fusion, and is required for both testis development and the formation and function of external genitalia in S. litura. The main roles of doublesex on the male are similar to other insects.     

首次入侵广东的草地贪夜蛾迁入路径及天气背景分析

草地贪夜蛾 Spodoptera frugiperda (J. E. Smith)是联合国粮农组织全球预警的超级害虫,2019年1月入侵我国云南,并随季风远距离迁飞扩散,4月23日,广东省广州市增城区首次发现并确认该虫幼虫发生为害,对当地玉米等粮食作物构成严重威胁。本研究运用基于WRF模式的昆虫三维轨迹分析程序和GrADS气象图形软件,模拟了入侵广东的草地贪夜蛾的迁飞路径及天气背景场。结果表明:按照幼虫发育历期推算,首批草地贪夜蛾成虫迁入广东的时间可能为4月8日~13日;在此期间,越南北部及华南地区的西南低空急流可为草地贪夜蛾的迁飞提供运载气流,而风切变、降雨和下沉气流为草地贪夜蛾的迫降提供便利条件;4月9-10日存在草地贪夜蛾的有效迁飞路径,入侵广东省增城区草地贪夜蛾种群的有效虫源地分布在越南及老挝北部。本研究为华南地区草地贪夜蛾春季迁入种群的监测预警及防控提供了科学依据。     

草地贪夜蛾首次入侵广东地区发生为害调查

草地贪夜蛾Spodoptera furgiperda(J.E.Smith)是一种新的重要农业入侵害虫,目前已侵入我国云南、广西、广东等地。本研究调查了草地贪夜蛾首次入侵成虫后代幼虫在珠三角和粤北地区的种群密度和为害情况。结果表明:本次调查珠三角和粤北地区均已出现草地贪夜蛾取食为害,所调查的10种作物中,仅在玉米上发现取食为害;其中草地贪夜蛾幼虫在从化地区为害最重(虫口数量222头/百株、为害率80%),其次是连平(虫口数量98头/百株、为害率68%)、英德(虫口数量76头/百株、为害率62%)、增城(虫口数量66头/百株、为害率20%)和珠海(虫口数量46头/百株、为害率30%),新丰最低(虫口数量6头/百株、为害率3%)。本研究为监测草地贪夜蛾首次入侵的发生和为害提供依据,并为通过调查田间种群密度指导幼虫防治工作提供技术支持。     

甲维盐对斜纹夜蛾幼虫肠道细菌的影响

【目的】斜纹夜蛾幼虫属杂食性、高食量的害虫,通过分子生物学手段对经甲维盐处理后的斜纹夜蛾幼虫肠道微生物进行比对,研究肠道共生菌群受毒剂刺激后的代谢变化,探讨菌株的自身代谢与甲维盐的作用受体的相关性。【方法】基于Illumina MiSeq技术测序平台,对取食甲维盐和未取食甲维盐的斜纹夜蛾幼虫中肠细菌的16S rRNA可变区进行高通量测序,分析对比细菌群落结构多样性。【结果】肠杆菌属、根瘤菌属在斜纹夜蛾的肠道中占优势地位,经过甲维盐处理后两者的丰度大幅下降。沙雷氏菌属和黄单胞杆菌属在处理后减少到几乎为零,相反,原先不占据优势的棒状杆菌属和甲醇杆菌属,处理后丰度明显上升。【结论】甲维盐处理后的优势菌群以及丰富度均发生变化,表明斜纹夜蛾的肠道菌群结构可能与甲维盐毒理机制有关。     

狗牙根、白三叶草对淡剑纹灰翅夜蛾生长发育和繁殖的影响

利用室内饲喂法,以高羊茅分别为对照,研究狗牙根(Cynodon dacyton)、白三叶草(Trifolium repens)对淡剑纹灰翅夜蛾Spodoptera depravata(Butler)存活、生长发育及繁殖的影响。结果表明,用狗牙根、白三叶草饲喂淡剑纹灰翅夜蛾的化蛹率、幼虫成蛾率均显著低于对照组。幼虫历期显著长于对照组。用狗牙根、白三叶草饲喂幼虫时,淡剑纹灰翅夜蛾的蛹期、产卵前期、产卵期、产卵量、♀成虫寿命与对照组均无显著差异,但幼虫龄期明显增加。狗牙根、白三叶草饲喂的淡剑纹灰翅夜蛾种群增长参数与对照组相比存在明显差异:(1)世代净生殖率(R0);(2)内禀增长率(rm);(3)周限增长率(λ);(4)种群数量趋势指数(I)明显降低;世代平均周期(T)和种群加倍时间(DT)明显延长。由此可见,狗牙根和白三叶草并不是淡剑纹灰翅夜蛾喜好的寄主植物。     

甜菜夜蛾抗药性研究现状

就有关甜菜夜蛾Spodoptera exigua(Hbner)对常用杀虫剂的抗药性现状作综述。甜菜夜蛾对拟除虫菊酯类、有机磷类、氨基甲酸酯类杀虫剂已产生了较高水平的抗药性,其中山东泰安抗性种群对氯氟氰菊酯的抗性高达2445.5倍;对多杀菌素等生物杀虫剂产生了中低水平的抗性;对昆虫生长调节剂如虫酰肼的敏感性也有所降低,但昆虫生长调节剂依然是比较理想的防治药剂。对交互抗性及抗性治理也作了阐述。     

斜纹夜蛾Cecropin D成熟肽的原核表达及活性检测

采用RT-PCR方法从斜纹夜蛾Spodoptera litura脂肪体组织中扩增得到了Cecropin D成熟肽基因序列,分析发现Cecropin D成熟肽与斜纹夜蛾Cecropin B之间存在2个氨基酸残基的差异。将获得的基因序列连接入原核表达载体pGEX-4T-1,并在原核细胞中实现了该蛋白的融合表达。SDS-PAGE结果表明,诱导后的宿主菌比未诱导菌中多出了一条融合蛋白表达带,诱导后1 h就可以检测到该蛋白,从诱导后1 h到5 h该蛋白在表达量上没有明显的差异。生长曲线显示在IPTG诱导后宿主菌的生长受到明显的抑制,纯化后的蛋白对细菌具有一定的抑制作用。     

Efficacy of Spodoptera exigua multiple nucleopolyhedrovirus as a biological insecticide for beet armyworm control in greenhouses of southern Spain

Chemical control measures targeted at Spodoptera exigua in greenhouse sweet pepper crops in Spain have resulted in pest resistance to virtually all commercially available insecticidal products. A multicapsid nucleopolyhedrovirus (SeMNPV), isolated from diseased S. exigua in Spain, was produced in laboratory reared larvae, tested for insecticidal activity in a laboratory bioassay, and was then applied in eleven commercial greenhouses planted with sweet pepper. Virus occlusion bodies (OBs) were applied on two occasions, at an interval of ～7 days, at a rate of 5×10⁸ OBs/L of spray in a volume of ～600 L/ha, depending on crop phenology and greenhouse area. The percentage of plants showing recent (<48 h old) feeding damage fell dramatically in greenhouses with high infestations of S. exigua; the same pattern was observed, although less dramatically, in greenhouses with low infestations. Average mortality of larvae collected from treated plants at 4 days after each application, and reared in the laboratory until death, was high (70–89%) and was not significantly affected by the degree of crop infestation. In a separate trial, the rate of acquisition of infection was examined in larvae that fed on plants treated with 1×10⁸ or 5×10⁸ OBs/L of spray. Of the 27 and 60% of larvae, respectively, that acquired infection in the 48 h period after spraying, about half became infected in the first 6 h post-application, irrespective of application rate. Acquisition of infection proceeded more slowly during the night-time compared to the daytime period, underlining the advantages of early morning applications of the virus. We conclude that the Spanish SeMNPV isolate merits registration as a biological insecticide for use in greenhouse crops in this region.