Strawberry Fusarium wilt, mainly caused by Fusarium oxysoporum f. sp. Fragariae (Fof), seriously threatens the yield and quality of strawberry. Piriformospora indica is an endophytic fungus that can colonise the roots of a wide range of plants, promoting plant growth and enhancing plant resistance. Against this background, the positive effects of P. indica on the growth of the daughter plants of ‘Benihoppe’ strawberry (Fragaria × ananassa Duch.) under Fof stress were investigated in this study. The study began by examining the inhibitory effect of P. indica on Fof growth through dual culture on agar plates. Subsequently, a symbiotic system between P. indica and strawberry plantlets was established, and the impact of P. indica on Fusarium wilt resistance and related physiological and biochemical indexes of the plantlets were evaluated. The results indicate that fungus colonization with P. indica significantly enhances the growth indices of strawberries, including plant height, petiole length, petiole diameter, and leaf area. Additionally, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves of P. indica were increased, and the content of malondialdehyde (MDA) was decreased compared to those without colonization. Under the stress from Fof, the growth indexes of plant height, stem diameter, leaf area, petiole diameter, and root length of strawberry plants colonization with P. indica were significantly higher than those without colonization and the symptoms of wilting were relatively mild. The activities of SOD, POD, and CAT in roots and leaves of plants colonized with P. indica were significantly increased compared to those without colonization. Furthermore, the content of MDA in roots was decreased. These results suggested that P. indica could increase resistance to Fusarium wilt in strawberry by increasing the activity of antioxidant enzymes and reducing the content of MDA.

Canarium album fruit has great potential to be consumed as a raw material not only for food but also medicine. The diverse active metabolites composition and content of C. album fruits greatly affect their pharmacological effects. However, up to now, there has been no report on the global metabolome differences among fruits from distinct C. album cultivars. In our present study, by using non-targeted metabolomics techniques, we identified 87 DAMs (differentially accumulated metabolites) including 17 types of flavonoids from fruits of four different C. album cultivars. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis revealed that the flavone and flavonol biosynthesis- and flavonoid biosynthesis-related DAMs were major factors determining their metabolome differences. Comparative transcriptomic analysis revealed that 15 KEGG pathways were significantly enriched by genes of the identified 3655 DEGs (differentially expressed genes) among different C. album cultivars. Consistent with the metabolome data, flavonoid biosynthesis-related DEGs, including eight key structural genes (such as FLS, CCoAOMT, CHI, C4H, DFR, LAR, and C3′H, etc.) and several regulatory transcription factor (TF) genes (including 32 MYBs and 34 bHLHs, etc.), were found to be significantly enriched (p < 0.01). Our study indicated that the differential expression of flavonoid biosynthesis-related genes and accumulation of flavonoids played dominant roles in the various metabolome compositions of fruits from different C. album cultivars.

Kiwifruit (Actinidia spp.) is susceptible to waterlogging stress. Although abundant wild germplasm resources exist among Actinidia plants for improving the waterlogging tolerance of kiwifruit cultivars, the underlying mechanisms remain largely unknown. Here, a comparative study was undertaken using one wild germplasm, Maorenshen (A. valvata Dunn, MRS), and one cultivar, Miliang-1 (A. chinensis var. deliciosa (A.Chev.) A.Chev. cv. Miliang-1, ML). Under stress, the ML plantlets were seriously damaged with wilted chlorotic leaves and blackened rotten roots, whereas the symptoms of injury in the MRS plantlets were much fewer, along with higher photosynthetic rates, chlorophyll fluorescence characteristics and root activity under stress conditions. However, neither aerenchyma in the root nor adventitious roots appeared in both germplasms upon stress exposure. The activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), as well as their transcript levels, were constitutively higher in MRS than those in ML under both normal and stress conditions. Waterlogging stress significantly enhanced the PDC and ADH enzyme activities in both germplasms, which were 60.8% and 22.4% higher in the MRS roots than those in the ML roots under waterlogging stress, respectively. Moreover, MRS displayed higher activities of antioxidant enzymes, including SOD, CAT, and APX, as well as DPPH-radical scavenging ability, and decreased H₂O₂ and MDA accumulation under both normal and stress conditions. Our findings suggest that the waterlogging tolerance of the wild A. valvata germplasm was associated with high PDC and ADH, as well as antioxidant ability.

Actinidia chinensis Planch. is a fruit tree originating from China that is abundant in the wild. Actinidia eriantha Benth. is a type of A. chinensis that has emerged in recent years. The shape of A. eriantha is an elongated oval, and the skin is covered with dense, non-shedding milk-white hairs. The mature fruit has flesh that is bright green in colour, and the fruit has a strong flavour and a grass-like smell. It is appreciated for its rich nutrient content and unique flavour. Vitamin C, sugar, and organic acids are key factors in the quality and flavour composition of A. eriantha but have not yet been systematically analysed. Therefore, we sequenced the transcriptome of A. eriantha at three developmental stages and labelled them S1, S2, and S3, and comparisons of S1 vs. S2, S1 vs. S3, and S2 vs. S3 revealed 1218, 4019, and 3759 upregulated differentially expressed genes and 1823, 3415, and 2226 downregulated differentially expressed genes, respectively. Furthermore, the upregulated differentially expressed genes included 213 core genes, and Gene Ontology enrichment analysis showed that they were enriched in hormones, sugars, organic acids, and many organic metabolic pathways. The downregulated differentially expressed genes included 207 core genes, which were enriched in the light signalling pathway. We further constructed the metabolic pathways of sugars, organic acids, and vitamin C in A. eriantha and identified the genes involved in vitamin C, sugar, and organic acid synthesis in A. eriantha fruits at different stages. During fruit development, the vitamin C content decreased, the carbohydrate compound content increased, and the organic acid content decreased. The gene expression patterns were closely related to the accumulation patterns of vitamin C, sugars, and organic acids in A. eriantha. The above results lay the foundation for the accumulation of vitamin C, sugars, and organic acids in A. eriantha and for understanding flavour formation in A. eriantha.

Chinese olive (Canarium album), a characteristic fruit tree in tropical and subtropical areas, suffers greatly from low-temperature stress (LTS). The regulatory roles of microRNA (miRNA) in plant LTS responses have been confirmed in many plant species but not in C. album. In this study, a cold-tolerant cultivar ‘Rui’an 3′ (RA) and a susceptible cultivar ‘Qinglan 1’ (QL) treated at 25 °C (control, CK) and −3 °C (cold temperature treatment, CT) were subjected to small RNA (sRNA) and transcriptome sequencing for the exploration of the cold responses of C. album. Comparative sRNA sequencing analysis identified much fewer LTS-responsive, differentially expressed miRNAs (DEMs) in RA (4 DEMs) than in QL (23 DEMs). Cal-miR482-22 was found to be specifically induced by LTS in RA. Cal-miR397-3 was upregulated, while cal-miR398_2-3 and cal-undef-190 were downregulated after LTS only in QL. However, when compared with QL, a higher basic expression of cal-miR397-3, and lower expression of cal-miR398_2-3 and cal-undef-190 were found in RA, suggesting that they may contribute to the cold tolerance of RA. Comparative transcriptome analysis showed that the number of LTS-responsive differentially expressed genes (DEGs) identified in QL was larger than that in RA, and some DEGs were also predicted as the target genes of the identified DEMs, forming multiple differentially expressed miRNA–target gene pairs, such as cal-miR397-3_laccase 2, 4, 17, cal-miR482-22_suppressor of npr1-1, etc. Quantitative real time PCR results showed that the expression changes of DEGs and DEMs in different samples were generally consistent with the sequencing results. Our study indicated that the basic expression levels of some miRNAs (especially the cal-miR397-3, cal-miR398_2-3, and cal-miR482-22), and their target genes contribute greatly to the cold-tolerance characteristics of C. album. Our study is helpful for understanding the roles of miRNAs in the cold resistance and responses of C. album.

In recent years, kiwifruit (Actinidia chinensis cv. Hongyang) was introduced into Fujian Province as an economically important fruit. During 2016 and 2017, symptoms of bacterial canker were observed on kiwifruit in an approximately 15-ha orchard with 3-year-old plants in Fuan city, Fujian Province of China. The orchard exhibited 70 to 80% incidence. Symptoms on leaves began as brown angular spots surrounded by chlorotic margins that later became dark brown spots surrounded by yellow halos, and occasionally red-rusty cankers with reddish exudates were observed on the stems (e-Xtra, Figure 1). Two representative strains, FJ-21a and FJ-21d, were isolated onto Luria-Bertani medium (LB) from stems showing typical symptom of red-rusty cankers with reddish exudates, which were randomly selected from two different plants. These two strains were gram-negative, aerobic, rod shaped, and nonfluorescent on KB or LB; positive for carbohydrates utilization, levan production, and hypersensitive on tobacco and tomato; and...