Novel Environmentally Friendly RNAi Biopesticides: Targeting V-ATPase in Holotrichia parallela Larvae Using Layered Double Hydroxide Nanocomplexes.

RNA interference (RNAi)-based biopesticides offer an attractive avenue for pest control. Previous studies revealed high RNAi sensitivity in Holotrichia parallela larvae, showcasing its potential for grub control. In this study, we aimed to develop an environmentally friendly RNAi method for H. parallela larvae. The double-stranded RNA (dsRNA) of the V-ATPase-a gene (HpVAA) was loaded onto layered double hydroxide (LDH). The dsRNA/LDH nanocomplex exhibited increased environmental stability, and we investigated the absorption rate and permeability of dsRNA-nanoparticle complexes and explored the RNAi controlling effect. Silencing the HpVAA gene was found to darken the epidermis of H. parallela larvae, with growth cessation or death or mortality, disrupting the epidermis and midgut structure. Quantitative reverse transcription-polymerase chain reaction and confocal microscopy confirmed the effective absorption of the dsRNA/LDH nanocomplex by peanut plants, with distribution in roots, stems, and leaves. Nanomaterial-mediated RNAi silenced the target genes, leading to the death of pests. Therefore, these findings indicate the successful application of the nanomaterial-mediated RNAi system for underground pests, thus establishing a theoretical foundation for developing a green, safe, and efficient pest control strategy.

Potent insecticidal activity of Eleocharis dulcis (Burm. f.) Trin peel extract and its main components against aphids.

BACKGROUND: Aphids are significant pests of cash crops and food farm crops. Botanical insecticides are safe for aphid control, especially for organic farming. In this study, Eleocharis dulcis (Burm. f.) Trin. peel extract (EDPE), a new botanical insecticide, was investigated for its active compositions against several agricultural aphids. RESULTS: The results showed that the EDPE had high insecticidal activity against Sitobion avenae Fabricius, Aphis gossypii Glover, Megoura crassicauda Mordvilko, and Acyrthosiphon pisum Harris, with half-lethal concentration (LC50 ) values of 95.92, 81.04, 140.31, and 255.73 mg/L after 48 h of treatment. In the pot culture assay, the aphicidal effects of 25% EDPE soluble liquid (SL) at a concentration of 0.016% were 68.98 ± 5.61%, 79.33 ± 8.27%, and 88.82 ± 3.91% after the first, third, and seventh days of treatment, respectively. Nine compounds were identified by bioactivity-directed fractionation: 4',5'-dimethoxy-6,6-dimethylpyranoisoflavone (1), 3-methoxy-4-hydroxylonchocarpin (2), 4-hydroxylonchocarpin (3), 4-methoxylonchocarpin (4), barbigerone (5), lonchocarpusone (6), 6a,12a-dehydrodeguelin (7), 13-homo-13-oxa-6a, 12a-dehydrodeguelin (8) and deguelin (9). Among them, 4-hydroxylonchocarpin (3) showed the highest aphidicidal activity against M. crassicauda, S. avenae, and A. pisum, with LC50 values of 97.24, 140.63, and 112.31 mg/L, respectively. CONCLUSION: These data contribute to a better understanding of the aphicidal activity of EDPE and its main component, 4-hydroxylonchocarpin. This will help to develop new botanical insecticides to contro aphids. © 2022 Society of Chemical Industry.

Design, Synthesis, and Herbicidal Activity of Naphthalimide-Aroyl Hybrids as Potent Transketolase Inhibitors.

Transketolase (TK) was identified as a new target for the development of novel herbicides. In this study, a series of naphthalimide-aroyl hybrids were designed and prepared based on TK as a new target and tested for their herbicidal activities. In vitro bioassay showed that compounds 4c and 4w exhibited stronger inhibitory effects against Digitaria sanguinalis (DS) and Amaranthus retroflexus (AR) with the inhibition over 90% at 200 mg/L and around 80% at 100 mg/L. Also, compounds 4c and 4w exhibited excellent postemergence herbicidal activity against DS and AR with the inhibition around 90% at 90 g [active ingredient (ai)]/ha and 80% at 50 g (ai)/ha in the greenhouse, which was comparable with the activity of mesotrione. The fluorescent quenching experiments of At TK revealed the occurrence of electron transfer from compound 4w to At TK and the formation of a strong exciplex between them. Molecular docking analyses further showed that compounds 4w exhibited profound affinity with At TK through the interaction with the amino acids in the active site, which results in its strong inhibitory activities against TK. These findings demonstrated that compound 4w is potentially a lead candidate for novel herbicides targeting TK.

Design, Synthesis, Herbicidal Activity, and Molecular Docking Study of 2-Thioether-5-(Thienyl/Pyridyl)-1,3,4-Oxadiazoles as Potent Transketolase Inhibitors.

Transketolase (TK) has been regarded as a new target for the development of novel herbicides. In this study, a series of 2-thioether-5-(thienyl/pyridyl)-1,3,4-oxadiazoles were designed and synthesized based on TK as the new target. The preliminary bioassay results indicated that compounds 4l and 4m displayed the best herbicidal activities against Amaranthus retroflexus (AR) and Digitaria sanguinalis (DS), with the inhibition exceeding 90% at 100-200 mg/L in vitro. Moreover, they also displayed higher postemergence herbicidal activities (90% control) against AR and DS than all of the positive controls at 45-90 g [active ingredient (ai)]/ha in a greenhouse. Notably, compounds 4l and 4m showed a broad spectrum of weed control at 90 g ai/ha. More significantly, compound 4l exhibited good crop selectivity against maize at 90 g ai/ha. Both fluorescent binding experiments and molecular docking analyses indicated that compounds 4l and 4m exhibited strong TK inhibitory activities with superior binding affinities than the others. Preliminary mechanism studies suggested that they might exert their TK inhibitory effects by occupying the active cavity of At TK and forming more strong interactions with amino acids in the active site. Taken together, these results suggested that compound 4l was a potential herbicide candidate for weed control in maize fields targeting TK.

Design, Synthesis, and Herbicidal Activity of Thioether Containing 1,2,4-Triazole Schiff Bases as Transketolase Inhibitors.

Transketolase (TK) represents a potential target for novel herbicide development. To discover novel TK inhibitors with potency against resistant weeds, 36 thioether compounds containing 1,2,4-triazole Schiff bases were designed and synthesized for herbicidal activity evaluation. The results demonstrated that compounds 5av and 5aw provided excellent weed control with inhibition of over 90% against the tested weeds, even at concentrations as low as 100 mg/L in vitro. In addition, compounds 5av and 5aw exhibited higher postemergence herbicidal activity than all of the positive controls against the tested weeds at 50-90 g [active ingredient (ai)]/ha in a greenhouse, while being safe for crops of maize and wheat at 90 g (ai)/ha. Fluorescent binding experiments of At TK indicated that compounds 5av and 5aw had strong TK inhibitory activity and could tightly bind with the enzyme At TK. Also, molecular docking analyses revealed that the structures of compounds 5av and 5aw were suitable for TK inhibitory activity. Taken together, these results suggested that compounds 5av and 5aw were promising herbicide candidates for weed control in wheat and maize fields targeting TK.

Identification of Wheat Leaf Rust Resistance Genes in Chinese Wheat Cultivars and the Improved Germplasms.

Leaf rust is an important wheat disease that is a significant hindrance for wheat production in most areas of the world. Breeding resistant cultivars can effectively and economically control the disease. In the present study, a wheat collection consisting of 100 cultivars from China and 18 improved germplasms from global landrace donors together with 36 known single Lr gene lines were tested with 20 strains of Puccinia triticina Eriks. in the seedling stage to postulate the Lr gene in the cultivars and germplasms. In addition, 12 diagnostic molecular markers specific to 10 Lr genes were used to detect the presence of the Lr genes in the wheat collection. Resistance to leaf rust of these cultivars at the adult plant stage was tested in fields under natural infection during the 2016 to 2018 cropping seasons in Baoding, Hebei Province. The gene postulation combined with molecular marker detection showed that six Lr genes (Lr1, Lr26, Lr33, Lr34, Lr45, and Lr46) were identified in 44 wheat accessions, including 37 cultivars and seven improved germplasms. Among the 44 wheat accessions postulated with Lr genes, Lr1 was present in four accessions, Lr26 in 12 accessions, Lr33 in two accessions, Lr34 in 14 accessions, Lr45 in three accessions, and Lr46 in 16 accessions. In the collection of 118 cultivars/germplasms, 34 wheat lines displayed adult-plant resistance carrying Lr34, Lr46, and/or underdetermined genes. Therefore, a high level of leaf rust resistance can be achieved through the combination of all-stage resistance and adult-plant resistance genes together in wheat cultivars.