PWD (pine wilt disease) is a devastating forest disease caused by the Bursaphelenchus xylophilus, which is the major invasive species in Asian and European countries. To control this disease, fumigation, pesticide injection, and clear cutting of epidemic trees have been widely used. But these management strategies have many limitations in terms of the effectiveness and environmental impacts, especially for the overuse of chemical pesticides. Thus, PCs (phytochemicals), the various compounds extracted from plants, have drawn extensive attention owing to their special characteristics, including abundant sources, low toxicity, high efficacy, and easy degradation. This review provides an overview of the current status of using PCs as alternative approaches to manage PWD. It discusses the efficacy of various PCs, the factors influencing their nematicidal activity, and their mechanism of action against B. xylophilus. These results will reveal the application of PCs in combating these devastating diseases and the necessity for further research.

The weevil Curculio chinensis Chevrolat (Coleoptera: Curculionidae) is a major cause of economic losses to growers of Camellia oleifera in China, as females lay their eggs in developing fruits and the hatching larvae feed on their seed, aborting fruit growth. Olfactory cues play a key role in the host location of this weevil. The present study focused on identifying volatiles from different parts of the host plant Ca. oleifera, namely, the leaves, fruit peel, and seeds, and testing the antennal and behavioral responses of adult Cu. chinensis to those same volatiles. Methods relied on gas chromatography, electroantennograms, and Y-tube bioassays. The results included a total of twenty-five volatiles emitted by the three plant parts, among which eight elicited antennal responses in Cu. chinensis adults of both sexes. The behavioral bioassays indicated that 3-hexenal, trans-2-hexen-1-ol, methyl salicylate, geraniol, and phenethyl alcohol were attractive to Cu. chinensis, while trans-2-hexenal and 2-ethyl-1-hexanol were repellent. Tests with different concentrations indicated that the behavioral response could be dose-dependent. Future studies should focus on field tests with blends of the attractant compounds in order to develop novel, improved control methods for field applications.

Background: Adinandra nitida, commonly known as Shiya tea, is a healthcare drink enriched in several phenolic acids and flavonoids, with a purple-red leaf variety possessing a unique flavor and a higher economic value. However, the mechanisms underlying leaf coloration and senescence discoloration remain unknown. Methods: Here, we compared both varieties of A. nitida (purple-red leaf, RL, and green leaf, GL) at two stages of development. To make sure the difference in leaf color in these four groups, several indexes, leaf colorimetric differences, H2O2 content in leaf cells, and antioxidant enzymes activities (superoxide dismutase (SOD), catalase (CAT)) were measured. With the integration of metabolome and transcriptome becoming a trend, metabolites in four groups were detected using an Ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) system, and the transcriptome was performed after the extraction of RNA in samples. Afterward, the activities of laccase (LAC) and peroxidase (POD) were measured for further analysis. Results: The deeper or discoloration of leaf color was not caused by the reactive oxygen species (ROS) stress because the H2O2 content was similar for each group. And the SOD and CAT activities improved significantly in young leaves, especially RL_young. Metabolome data showed a large shift in four groups. By focusing on the variation of flavonoids and 1079 metabolites detected in both varieties, along with the accumulation of flavonoids and tannins, proanthocyanins (PAs) were mostly accumulated in young RL. Differential analysis of expressed genes (DEGs) revealed six genes associated with leaf discoloration as hub factors, of which ANRs (ANR1 and ANR2) were positively correlated with the accumulation of PA in RL. Conclusions: Using integrate analysis of metabolome and transcriptome, our results revealed that six structural genes found in proanthocyanin biosynthesis, two reductases (ANR), two oxidative polymerases (POD64, LAC17) and two TFs (bHLH3 and MYB4) related to biosynthesis and polymerization of proanthocyanins were associated with not only the difference of GL and RL but also the faded coloration in two RL groups (RL_young and RL_old), which provided a foundation for further research on an understanding of the regulatory genes and the enzymes specific for proanthocyanidin biosynthesis, facilitating the genetic engineering of crops for beneficial metabolite accumulation.

Sirex noctilio and Amylostereum areolatum form a highly specific mutualistic symbiosis. The growth and host-degrading activities of the symbiotic fungus are critical to the woodwasps, which directly influence the larval survival rate and adult body size of the woodwasps. Gene expression analysis has been extensively employed to decrypt the intricate growth patterns of symbiotic fungi and identify the associated functional genes underpinning their degradation pathways. Appropriate reference genes are crucial for enhancing the accuracy of studies on gene expression. In an effort to refine gene expression analysis in A. areolatum, our study cultivated the symbiotic fungi on the wood powder medium of Pinus sylvestris var. mongolica, aligning closer to its natural growth conditions. Thirteen reference genes underwent meticulous evaluation via algorithms such as delta Ct, geNorm, BestKeeper, RefFinder, and NormFinder, depending on their stability amidst diverse growth and developmental epochs of A. areolatum. α-TUB, P450, and the combination (α-TUB + P450) were distinguished as the most stable candidates for RT-qPCR analysis, confirmed through AaLac1 expression validation. These findings contribute significantly to the investigation of gene expression in A. areolatum and facilitate a deeper understanding of its symbiotic relationship with S. noctilio.

Pine wilt disease, which is induced by pine wood nematode (PWN, Bursaphelenchus xylophilus), has caused huge economic and ecological losses. To overcome the drawbacks of chemical control against PWN, twenty compounds were screened, and a synergistic botanical–chemical combination was identified. A proportion of abamectin to rotenone of 7:3 (5.73 and 1.78 mg/L, respectively) achieved the highest co-toxicity coefficient of 231.09 with a median lethal concentration of 3.18 mg/L. It revealed 0% mortality in Pinus massoniana seedlings at 60 days post-treatment when applied at 400 times the synergistic concentration (2.29 g/L abamectin + 0.71 g/L rotenone) at 7 days after PWN inoculation. Furthermore, the synergistic combination significantly affected the physiological activity and population dynamics of PWN. Female oviposition was reduced by 71.92%, the egg hatching rates declined to 13.09 ± 0.02%, and head thrashing frequency was inhibited by 99.23 ± 0.01%. The enzymatic activities of peroxidase, acetylcholinesterase, succinate dehydrogenase, and glutathione S-transferase were significantly increased, while the population size declined by 96.17%. Transcriptomic and gene expression analyses suggested a potential “Na⁺/Ca²⁺/Cl⁻ ionic storm,” since the synergistic combination significantly activated genes associated with voltage-gated calcium channels, glutamate-gated chloride channels, and amiloride-sensitive sodium channels. These findings provide an eco-friendly strategy for PWN management via chemical control.

The stem blight disease on Elaeocarpus spp. was newly identified in 2022 on E. rugosus and E. hain in Guangzhou, representing a serious stem disease that causes branch rot and cankers in Elaeocarpus species and can lead to whole-plant death in severe cases. Strain ZX-13 was isolated from Elaeocarpus rugosus stems and showed excellent antagonism against the Elaeocarpus stem blight pathogen Pseudocryphonectria elaeocarpicola. Based on morphological characteristics, physiological and biochemical results, and molecular biology analyses, the strain was identified as Erwinia phyllosphaerae. Whole-genome sequencing and annotation indicate that strain ZX-13 has a high-quality draft assembly of 4,686,433 bp, with a GC content of 53.85%, encoding 4189 genes, 86 tRNA, 22 rRNA, and 110 ncRNA. Eight antifungal enzymes from the GH family may be crucial factors to its antagonistic activity. Using antiSMASH 7.1.0, the ZX-13 genome predicted eight BGCs (RiPPs, NRPs, terpenes, etc.), with one showing 100% similarity to carotenoid biosynthesis. Novel candidates include an O-antigen, hassallidin C, and lankacidin C. The study identified Erwinia phyllosphaerae ZX-13 as an antagonistic bacterial strain for the first time, indicating substantial potential for biocontrol applications.