Arbuscular Mycorrhizal Fungus Alters Alfalfa (Medicago sativa) Defense Enzyme Activities and Volatile Organic Compound Contents in Response to Pea Aphid (Acyrthosiphon pisum) Infestation

Pea aphid (Acyrthosiphon pisum) infestation leads to withering, reduced yield, and lower quality of the host plant. Arbuscular mycorrhizal (AM) fungi have been found to enhance their host plants’ nutrient uptake, growth, and resistance to biotic stresses, including pathogen infection and insect pest infestation. Therefore, we evaluated the effects of AM fungus Rhizophagus intraradices on alfalfa defense responses to pea aphid infestation. Aphid infestation did not affect the colonization of AM fungus. The inoculation of AM fungus, on average, enhanced alfalfa catalase and the contents of salicylic acid and trypsin inhibitor by 101, 9.05, and 7.89% compared with non-mycorrhizal alfalfa, respectively. In addition, polyphenol oxidase activities significantly increased by six-fold after aphid infestation in mycorrhizal alfalfa. Moreover, the fungus significantly (p < 0.05) improved alfalfa shoot N content, net photosynthetic and transpiration rates, and shoot dry weight in aphid infected treatment. The aphid infestation changed the total volatile organic compounds (VOCs) in alfalfa, while AM fungus enhanced the contents of methyl salicylate (MeSA). The co-expression network analysis of differentially expressed genes (DEGs) and differentially expressed VOCs analysis showed that three DEGs, namely MS.gene23894, MS.gene003889, and MS.gene012415, positively correlated with MeSA both in aphid and AM fungus groups. In conclusion, AM fungus increased alfalfa’s growth, defense enzyme activities, hormones, and VOCs content and up-regulated VOC-related genes to enhance the alfalfa’s resistance following aphid infestation

Analysis of Key Technologies for New Green Marine Propulsion Systems

The new green Marine propulsion system, as a new generation of marine propulsion, has advantages of strong mobility, low fuel consumption, low noise, safety and comfort. Three green propulsion solutions for different ship types are proposed, including pure electric propulsion system, compound energy storage electric propulsion system and diesel-electric hybrid propulsion system. The structure features and performance advantages are introduced and the key technologies such as new energy storage, DC network and shaft generator/motor are discussed. The related research achievements and typical project cases are also introduced

Patterning single-layer materials by electrical breakdown using atomic force microscopy

The development of nanoelectronics and nanotechnologies has been boosted significantly by the emergence of 2D materials because of their atomic thickness and peculiar properties, and developing a universal, precise patterning technology for single-layer 2D materials is critical for assembling nanodevices. Demonstrated here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores, nanostrips, and other nanostructures on demand. This can be achieved by voltage scanning or applying a constant voltage while moving the tip. By measuring the electrical current, the formation process on single-layer materials was shown quantitatively. The present results provide evidence of successful pattern fabrication on single-layer MoS2, boron nitride, and graphene, although further confirmation is still needed. The proposed method holds promise as a general nanomachining technology for the future

Screening and Analysis of Antifungal Strains <i>Bacillus subtilis</i> JF-4 and <i>B. amylum</i> JF-5 for the Biological Control of Fusarium Wilt of Banana

Purpose: This study aimed to identify the antagonistic bacteria from the rhizosphere of healthy bananas that can effectively suppress the Fusarium wilt of banana, and to further investigate the inhibitory mechanism. Method: The primary and secondary screening techniques were implemented using the double-plate and fermentation antagonism methods. The strain was identified based on physiological and biochemical tests, 16S rRNA gene sequencing, and specific gene amplification. The effects of crude extract on the protein content, lipid peroxidation, and pectinase activity of mycelia were determined from the identified isolates. Results: Two antagonistic bacteria, JF-4 and JF-5, were screened and initially identified as Bacillus subtilis (GenBank: OR125631) and B. amylum (GenBank: OR125632). The greenhouse experiment showed that the biological control efficiency of the two antagonists against the Fusarium wilt of banana was 48.3% and 40.3%, respectively. The catalase content produced by lipid peroxidation increased significantly after treatment with the crude extracts of JF-4 and JF-5 at concentrations of 0.69 μmol/L and 0.59 μmol/L, respectively. The protein and ergosterol content and pectinase activity decreased significantly. The two antagonistic bacteria might inhibit the growth of pathogens by enhancing lipid peroxidation and decreasing the synthesis of cell metabolites. Twenty compounds were identified by gas chromatography–mass spectrometry (GC-MS). B. subtilis JF-4 was further sequenced and assembled to obtain a complete circular chromosome genome of 681,804,824 bp. The genome consisted of a 4,310,825-bp-long scaffold. Conclusion: The findings of this study may help elucidate the mechanism behind this biocontrol isolate