Non-host plants:Are they mycorrhizal networks players?

Common mycorrhizal networks(CMNs)that connect individual plants of the same or different species together play important roles in nutrient and signal transportation,and plant community organization.However,about 10%of land plants are non-mycorrhizal species with roots that do not form any wellrecognized types of mycorrhizas;and each mycorrhizal fungus can only colonize a limited number of plant species,resulting in numerous non-host plants that could not establish typical mycorrhizal symbiosis with a specific mycorrhizal fungus.If and how non-mycorrhizal or non-host plants are able to involve in CMNs remains unclear.Here we summarize studies focusing on mycorrhizal-mediated host and non-host plant interaction.Evidence has showed that some host-supported both arbuscular mycorrhizal(AM)and ectomycorrhizal(EM)hyphae can access to non-host plant roots without forming typical mycorrhizal structures,while such non-typical mycorrhizal colonization often inhibits the growth but enhances the induced system resistance of non-host plants.Meanwhile,the host growth is also differentially affected,depending on plant and fungi species.Molecular analyses suggested that the AMF colonization to non-hosts is different from pathogenic and endophytic fungi colonization,and the hyphae in non-host roots may be alive and have some unknown functions.Thus we propose that non-host plants are also important CMNs players.Using non-mycorrhizal model species Arabidopsis,tripartite culture system and new technologies such as nanoscale secondary ion mass spectrometry and multiomics,to study nutrient and signal transportation between host and non-host plants via CMNs may provide new insights into the mechanisms underlying benefits of intercropping and agro-forestry systems,as well as plant community establishment and stability.

Effects of Microtubule Polymerization Inhibitor on the Hypersensitive Response of Wheat Induced by the Non-Host Pathogen Sphaerotheca fuliginea

The plant cytoskeleton is a highly dynamic and versatile intracellular scaffold composed of microtubules and microfilaments, serving a multiplicity of functions in plant cells. To reveal the relationship between the cytoskeleton in wheat （Triticum aestivum L.） cv. Suwon 11 attacked by the non-host pathogen Sphaerotheca fuliginea and the initiation of the hypersensitive response, the microtubule inhibitor oryzalin was injected into the wheat leaves immediately prior to inoculation. The incidence of hypersensitive cell death was significantly lower than that in water-treated control. In addition, the occurrence of hypersensitive cell death was also delayed and S. fuliginea was able to penetrate and form haustoria in epidermal tissues of wheat. All the results above indicated that hypersensitive cell death was associated with depolymerisation of microtubules, suggesting that microtubules might play an important role in the expression of non-host resistance of wheat.

Differential Responses of Phytophthora sojae to Seed Exudates of Host Soybean and Non-host Maize

In order to clarify the differential response of Phytophthora sojae to the seed exudates of host soybean and non-host maize and understand the relationship between seed exudates and host selectivity of Phytophthora sojae, non-host maize Suiyu 23 and susceptible host soybean Sloan seed exudates were collected to measure their influence on mycelial growth, formation and germination of oospores, chemotaxis, encystment and germination of zoospores of Phytophthora sojae. The results showed that nonhost maize seed exudates exhibited repellency to zoospores of Phytophthora sojae, it also could significantly inhibited Phytophthora sojae mycelial growth, formation of oospores compared with the control;compared with host soybean, non-host maize seed exudates could significantly inhibited Phytophthora sojae mycelial growth, formation and germination of oospores, germination of cysts, which indicated that the seed exudates was the critical factor to host selectivity of Phytophthora sojae and the maize seed exudates was closely related to its non-host resistance.

A review： chemical ecology of Ips typographus （Coleoptera, Scolytidae）

Chemical ecology of the spruce bark beetle lps typographus （L.） was reviewed. The outbreak of 1.typographus in central Europe triggered extensive research on chemical ecology, Males initiate host location and produce semiochemicals which attract both males and females, A successful mass attack must first overcome the resistance of the host tree. Pioneer I. typographus evolved to use the resin flow of host trees as kairomones in host location, and synthesized semiochemicals initially to detoxify the resin. If small bark beetle populations infest healthy trees, mass attack is prevented by host resistance, Nine monoterpene alcohols were found in male hind-guts, including cis-verbenol （cV） and 2-methyl-3-buten-2-ol （MB） which are regarded as primary aggregation pheromones, and a low proportion of lpsdienol （ld） which increases attractiveness of cV and MB, Verbenone （Vn） and Ipsenol （le） are anti-aggregation pheromones, that play important roles in adjusting attack density and insect density under the bark. Non-host volatiles are repellent to L typographus, so that beetles do not waste energy boring into non-host trees. The relationship between host resistance, pheromone compounds and behavior, non-host volatiles, bioassays and mass trapping are reviewed, Results of field bioassays stressed that traps baited with specific pheromones could be used as a reasonable protection measure.

Rhizophagus irregularis influences As and P uptake by alfafa and the neighboring non-host pepperweed growing in an As-contaminated soil

It was documented that arbuscular mycorrhiza fungi（AMF） play an important role in protecting host plants against arsenic（As） contamination. However, most terrestrial ecosystems contain a considerable number of nonmycorrhizal plants. So far little information is available for the interaction of such non-host plants with AMF under As contaminations. By using a dual compartment cultivation system with a plastic board or a nylon mesh separating roots of non-host pepperweed from roots of the AM-host alfafa plants, avoiding direct root competition, the two plant species were grown separately or partially separated（with rhizosphere effects） in the presence or absence of the AMF Rhizophagus irregularis in As-contaminated soil. The results indicated that mycorrhiza caused phosphorus（P） concentration decrease in the non-host pepperweed, but promoted the P concentration of the AM host alfafa. Mycorrhiza is potentially helpful for non-host pepperweed to adapt to As contamination by decreasing root As concentration and showing no suppressing effect on biomass production. The study provides further evidence for the protective effects of AMF on non-host plants against As contamination, and improved our understanding of the potential role of AMF for non-host plant adaptation to As contaminated soils.

Unconventional routes to developing insect-resistant crops

Concerns over widespread use of insecticides and heightened insect pest virulence under climate change continue to fuel the need for environmentally safe and sustainable control strategies. However, to develop such strategies, a better understanding of the molecular basis of plant-pest interactions is still needed. Despite decades of research investigating plant-insect interactions, few examples exist where underlying molecular mechanisms are well characterized, and even rarer are cases where this knowledge has been successfully applied to manage harmful agricultural pests. Consequently, the field appears to be static, urgently needing shifts in approaches to identify novel mechanisms by which insects colonize plants and plants avoid insect pressure. In this perspective, we outline necessary steps for advancing holistic methodologies that capture complex plant-insect molecular interactions. We highlight novel and underexploited approaches in plant-insect interaction research as essential routes to translate knowledge of underlying molecular mechanisms into durable pest control strategies, including embracing microbial partnerships, identifying what makes a plant an unsuitable host, capitalizing on tolerance of insect damage, and learning from cases where crop domestication and agronomic practices enhance pest virulence.