Investigation of pesticide residues in Fragaria and Myrica rubra sold in Hangzhou

This study investigated the concentration of the pesticide residues found in Fragaria and Myrica rubra sold in the city of Hangzhou. From an analysis of 151 (77 Fragaria and 74 Myrica rubra ) samples using gas chromatography-tandem mass spectrometry (GC-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), a total of 41 different pesticide residues were found to be present. Of the 41 residues, 14 were found using GC-MS/MS and 27 using LC-MS/MS. Of the 151 samples, 10 (13.0%) of the 77 Fragaria and 5 (6.8%) of the 74 Myrica rubra samples were found to contain a specific pesticide residue, and only 4 Fragaria samples and 2 Myrica rubra samples were found to be without any pesticide residue. Eighteen of the 41 pesticides were not detected in either Fragaria or Myrica rubra samples. Of the 41 different residues, 10 were detected in Fragaria samples and 20 in Myrica rubra samples. In Fragaria , procymidone was the most commonly detected residue, with a detection rate of 88.3%, followed by prochloraz, with a detection rate of 53.2%. In Myrica rubra , prochloraz was the most commonly detected residue, with a detection rate of 71.6%, followed by carbendazim, with a detection rate of 68.9%. The pesticide residues in some of the samples exceeded the maximum residue limit (MRL) set in People’s Republic of China. The MRL of dimethomorph was exceeded in 3 of the Fragaria samples and that of dichlorvos was exceeded in 2 of the Myrica rubra samples.

First Report of Leaf Spot Caused by Colletotrichum fructicola on Myrica rubra in China

Myrica rubra is an important fruit tree with high nutritional and economic value, which is widely cultivated in multiple regions of China. In January 2021, an unknown disease which caused leaf spot with approximately 20% (n=100 investigated plants) of incidence was discovered on the leaves of M.rubra in Jiujiang City of Jiangxi Province (29.71° N, 115.97° E). The initial symptoms were small pale brown spots (1 to 2 mm diameter) on the leaves, which gradually expanded into round or irregular dark brown spots with the occurrence of the disease, and the lesion developed necrotic tissues in the center at later stages, eventually leading the leaves to chlorotic and wilted. Ten diseased leaves with typical symptoms were collected and the leaf tissue (5 × 5 mm) at junction of diseased and healthy portion were cut. The surfaces were disinfected with 75% ethanol for 45 s, 1% sodium hypochlorite for 1 min, and rinsed in sterile water for 3 times then transferred to potato dextrose agar (PDA) at 28 ± 1 ℃ for 3 days. Five fungal single isolates with similar morphology were purified from single spores. On PDA medium, the colonies initially appeared white with numerous aerial hyphae, and the center of the colony turned gray at later stages, less sporulation. While on modified czapek-dox medium (Peptone 3g, K2HPO4 1g, MgSO4·7H2O 0.5g, KCl 0.5g, FeSO4 0.01g, Maltose 30g, Agar 15g, Distilled water 1000 mL, pH=7.0), the mycelia of the colony were sparse and produced a large number of small bright orange particles (conidial masses). Conidia were single-celled, transparent, smooth-walled, 1-2 oil globule, cylindrical with slightly blunt rounded ends, 14.45-18.44 × 5.54-6.98 μm (av=16.27 μm × 6.19 μm, n=50) in size. These morphological characteristics of the pathogen were similar to the descriptions of Colletotrichum fructicola (Ruan et al, 2017; Yang et al, 2021). To further confirm the identity of the pathogen, genomic DNA from a representative isolate was extracted with DNA Extraction Kit (Yeasen, Shanghai, China), and the internal transcribed spacer (ITS), glyceraldehyde-3-phosphatedehydrogenase (GAPDH), calmodulin gene (CAL), actin (ACT) and chitin synthase 1 (CHS 1) were amplified by using the primers ITS1/ITS4 (Gardes et al, 1993), GDF/GDR (Templeton et al, 1992), CL1C/CL2C (Weir et al, 2012), ACT-512F/ACT-783R and CHS-79F/CHS-345R (Carbone et al, 1999), respectively. The PCR amplified sequences were submitted to GenBank (GenBank Accession No. ITS, MW740334; GAPDH, MW759805; CAL, MW759804; ACT, MW812384; CHS-1, MW759803) and aligned with GenBank showed 100% identity with C. fructicola (GenBank Accession No. ITS, MT355821.1 (546/546 bp); GAPDH, MT374664.1 (255/255 bp); CAL, MK681354.1 (741/741 bp); ACT, MT364655.1 (262/262 bp); CHS, MT374618.1 (271/271 bp)). Phylogenetic tree using the maximum likelihood methods with Kimura 2-parameter model and combined ITS-ACT-GAPDH-CHS-CAL concatenated sequences, bootstrap nodal support for 1000 replicates in MEGA7.0, revealed that the isolate was assigned to C. fructicola strain (ICMP 18581 and CBS 125397) (Yang et al. 2021) with 98% bootstrap support. Pathogenicities of were tested on fifteen healthy M. rubra plants (five for wounded inoculation, five for nonwounded inoculation, and five for controls) in the orchard. Twenty leaves were marked from each plant, and disinfected the surface with 75% ethanol. Ten μL spore suspension (1.0 × 106 conidia/ml) of each isolate from 7-day-old culture were inoculated on the surface of 20 needle-wounded and 20 nonwounded leaves, respectively. Healthy leaves were inoculated with sterile water as controls by the same method. All inoculated leaves were sprayed with sterile water and covered with plastic film to remained humidification. After 5 days, all the wounded leaves which were inoculated with C. fructicola showed similar symptoms to those observed on the original leaves. Symptoms of nonwounded leaves were milder than the wounded inoculated leaves, while control leaves remained healthy. Finally, the C. fructicola was re-isolated from the inoculated leaves. C. fructicola has been reported on Juglans regia, Peucedanum praeruptorum, Paris polyphylla var. Chinensis in China (Wang et al, 2017; Ma et al, 2020; Zhou et al, 2020). As far as we know, this is the first report of C. fructicola causing leaf spot on M.rubra in China. This result contributes to better understand the pathogens causing diseases of M.rubra in this region of China and develop effective control strategies.

The bayberry database: a multiomic database for Myrica rubra, an important fruit tree with medicinal value

Background Chinese bayberry (Myrica rubra Sieb. & Zucc.) is an important fruit tree in China, and has high medicinal value. At present, the genome, transcriptome and germplasm resources of bayberry have been reported. In order to make more convenient use of these data, the Bayberry Database was established. Results The Bayberry Database is a comprehensive and intuitive data platform for examining the diverse annotated genome and germplasm resources of this species. This database contains nine central functional domains to interact with multiomic data: home, genome, germplasm, markers, tools, map, expression, reference, and contact. All domains provide pathways to a variety of data types composed of a reference genome sequence, transcriptomic data, gene patterns, phenotypic data, fruit images of Myrica rubra varieties, gSSR data, gene maps with annotation and evolutionary analyses. The tools module includes BLAST search, keyword search, sequence fetch and enrichment analysis functions. Conclusions The web address of the database is as follows http://www.bayberrybase.cn/. The Myrica rubra database is an intelligent, interactive, and user-friendly system that enables researchers, breeders and horticultural personnel to browse, search and retrieve relevant and useful information and thus facilitate genomic research and breeding efforts concerning Myrica rubra. This database will be of great help to bayberry research and breeding in the future.

Construction of a High-Density Genetic Map and Identification of Leaf Trait-Related QTLs in Chinese Bayberry (Myrica rubra)

Chinese bayberry (Myrica rubra) is an economically important fruit tree that is grown in southern China. Owing to its over 10-year seedling period, the crossbreeding of bayberry is challenging. The characteristics of plant leaves are among the primary factors that control plant architecture and potential yields, making the analysis of leaf trait-related genetic factors crucial to the hybrid breeding of any plant. In the present study, molecular markers associated with leaf traits were identified via a whole-genome re-sequencing approach, and a genetic map was thereby constructed. In total, this effort yielded 902.11 Gb of raw data that led to the identification of 2,242,353 single nucleotide polymorphisms (SNPs) in 140 F1 individuals and parents (Myrica rubra cv. Biqizhong × Myrica rubra cv. 2012LXRM). The final genetic map ultimately incorporated 31,431 SNPs in eight linkage groups, spanning 1,351.85 cM. This map was then used to assemble and update previous scaffold genomic data at the chromosomal level. The genome size of M. rubra was thereby established to be 275.37 Mb, with 94.98% of sequences being assembled into eight pseudo-chromosomes. Additionally, 18 quantitative trait loci (QTLs) associated with nine leaf and growth-related traits were identified. Two QTL clusters were detected (the LG3 and LG5 clusters). Functional annotations further suggested two chlorophyll content-related candidate genes being identified in the LG5 cluster. Overall, this is the first study on the QTL mapping and identification of loci responsible for the regulation of leaf traits in M. rubra, offering an invaluable scientific for future marker-assisted selection breeding and candidate gene analyses.