Aims One of the major limitations to the production of alfalfa (Medicago sativa) is the fungus Phoma medicaginis, which infects alfalfa and causes leaf spots. This study aims to understand alfalfa’s response to P. medicaginis infection, the colonization of arbuscular mycorrhizal fungus (AMF) and the effect of AMF on plant–pathogen interactions. Methods and Results Transcriptome analysis (RNA‐seq) was used to identify differentially expressed genes (DEGs) in alfalfa infected by P. medicaginis and colonized by AMF Rhizophagus intraradices. AMF ameliorated the effects of P. medicaginis infection on alfalfa by reducing leaf spot incidence and disease index by 39·48 and 56·18% respectively. Inoculation with pathogen and AMF induced the activity of defence pathways, including peroxidase (POD), polyphenol oxidase activities and jasmonic acid (JA), salicylic acid concentration. Plants showed differential expression of P. medicaginis resistance‐related genes, including genes belonging to pathogenesis‐related (PR) proteins, chitinase activity, flavonoid biosynthesis, phenylpropanoid biosynthesis, glutathione metabolism, phenylalanine metabolism and photosynthesis. Inoculation with AMF led to changes in the expression of genes involved in PR proteins, chitinase activity, phenylalanine metabolism and photosynthesis. Conclusion The physiological and transcriptional changes caused by P. medicaginis infection in non‐mycorrhizal and mycorrhizal alfalfa provides crucial information for understanding AMF’s association with pathogenic systems. Significance and Impact of the Study This study showed that AMF alleviated alfalfa leaf spots demonstrating that AMF can serve as a biocontrol strategy for alfalfa disease management.

Spring black stem and leaf spot of lucerne (alfalfa, Medicago sativa L.), caused by Phoma medicaginis, is an important disease in temperate regions of the world. It is now a serious disease threatening global lucerne production. This experiment was designed to test the combined effects of the arbuscular mycorrhizal (AM) fungus Funneliformis mosseae and the rhizobium Sinorhizobium medicae on growth, nutrient uptake and disease severity in lucerne. The results showed that F. mosseae increased plant phosphorus and nitrogen uptake and plant dry weight, and this beneficial effect was enhanced when in association with S. medicae. Rhizobial and AM fungal effects were mutually promoting; inoculation with AM fungus significantly increased the formation of root nodules, and inoculation with rhizobium increased the percentage of root length colonised by AM fungus (P < 0.05). After infection with P. medicaginis, typical leaf spot symptoms with the lowest disease incidence and disease index occurred on plants that were host to both F. mosseae and S. medicae. Plants with both symbiotic microorganisms had higher activities (concentrations) of phenylalanine ammonia-lyase, chitinase, β-1,3-glucanase, lignin, hydroxyproline-rich glycoprotein and jasmonic acid. Therefore, the tested AM fungus (F. mosseae) and rhizobium (S. medicae) have the potential to reduce damage and yield loss in lucerne from spring black stem and leaf spot caused by P. medicaginis.

No abstract

No abstract

No abstract

No abstract

No abstract

The thermoelectric (TE) properties of n-type polycrystalline YbBaGaGe bulks can be optimized by high-pressure and high-temperature (HPHT) sintering. After HPHT sintering, abundant nanograins are randomly distributed in the sample. Grains are refined by HPHT, with the grains being smaller with higher pressure. In comparison with the arc-melted sample, the samples obtained by quenching under high pressure possess a great number of nanograins and lattice structural disorders. Lower thermal conductivity is benefited by our deliberately engineered microstructures via HPHT, and the minimum thermal conductivity is 0.86 W m K at 773 K. The thermal conductivity and electrical properties are optimized simultaneously by raising the reactive sintering pressure. In comparison with the arc-melted sample (0.56), a maximum zT value of 1.13 at 773 K is obtained for the YbBaGaGe sample fabricated at 5 GPa. This demonstrates that HPHT provides an effective strategy to improve TE performance through simultaneously enhancing electrical and thermal transport properties and should be applicable to other thermoelectric materials.