Cancan Zhu

Carya illinoinensis is an economically important nut tree, and its chloroplast (cp.) genome has been reported; however, its mitochondrial (mt) genome remains unknown. In the present study, we assembled the first mt genome of C. illinoinensis. The circular mt genome of C. illinoinensis is 495,205 bp long, with 37 protein-coding genes(PCGs), 24 tRNA genes, and 3 rRNA genes. All the tRNAs could be folded into typical cloverleaf secondary structures, with lengths of 58–88 bp. A conserved U-U-C-x-A-x2 consensus nucleotide sequence was discovered in the Ψ–loops of tRNA sequences. In addition, 447 dispersed repeats were detected, as well as found 482 RNA editing sites and 9,960 codons in the mt genome. Furthermore, a total of 27 DNA sequences with a length of 43,277 bp were transferred from the cp. to the mt genome, and eight integrated cp-derived genes (trnL-CAA, trnV-GAC, trnD-GUC, trnW-CCA, trnN-GUU, trnH-GUG, trnM-CAU, and rps7) were identified. We also obtained 1,086 hits, including 364.023 kp of nuclear genome sequences, that were transferred to the mt genome. To determine the evolutionary position of C. illinoinensis, we conducted a phylogenetic analysis of the mitogenomes of C. illinoinensis and 14 other taxa. The results strongly suggested that C. illinoinensis and Fagus sylvatica formed a single clade with 100% bootstrap support. This study sequenced comprehensive data on the C. illinoinensis mitochondrial genome and provided insights into the conserved sequences of tRNA genes, which could facilitate evolutionary research in other Carya trees in the future.

Pecan forests (Carya illinoinensis) are significant contributors to both food and oil production, and thrive in diverse soil environments, including coastal regions. However, the interplay between soil microbes and pecan forest health in coastal environments remains understudied. Therefore, we investigated soil bacterial and fungal diversity in coastal (Dafeng, DF) and inland (Guomei, GM) pecan plantations using high-throughput sequencing. The results revealed a higher microbial diversity in the DF plantation than in the GM plantation, significantly influenced by pH and edaphic factors. The dominant bacterial phyla were Proteobacteria, Acidobacteriota and Bacteroidota in the DF plantation, and Acidobacteriota, Proteobacteria, and Verrucomicrobiota in the GM plantation. Bacillus, Nitrospira and UTCFX1 were significantly more abundant bacterial genera in DF soil, whereas Candidatus Udaeobacter, HSB_OF53-F07 and ADurbBin063-1 were more prevalent in GM soil. Basidiomycota dominated fungal sequences in the GM plantation, with a higher relative abundance of Ascomycota in the DF plantation. Significant differences in fungal genus composition were observed between plantations, with Scleroderma, Hebeloma, and Naucoria being more abundant in DF soil, and Clavulina, Russula, and Inocybe in GM soil. A functional analysis revealed greater carbohydrate metabolism potential in GM plantation bacteria and a higher ectomycorrhizal fungi abundance in DF soil. Significantly positive correlations were detected between certain bacterial and fungal genera and pH and total soluble salt content, suggesting their role in pecan adaptation to coastal environments and saline–alkali stress mitigation. These findings enhance our understanding of soil microbiomes in coastal pecan plantations, and are anticipated to foster ecologically sustainable agroforestry practices and contribute to coastal marshland ecosystem management.

Pecan (Carya illinoinensis) is an important economic forest crops widely cultivated in China. From June to September in both 2021 and 2022, severe leaf disease resembling anthracnose was observed in 6.6-ha pecan orchard in Jintan (31°42'23.84″ N, 119°21'22.90″ E), Jiangsu Province. The disease severity was about 15 to 25% with 5 to 12% incidence on 100 surveyed trees of the orchard in 2022. Symptoms initially appeared as small gray-bark sunken lesions, which gradually developed to big sunken lesions with brown edges and irregular-shaped. Small fragments (4 × 4 mm) from the necrotic borders of infected leaves were surfaced sterilized, plated on potato dextrose agar (PDA) and then incubated in darkness at 25°C for 3 days. Pure cultures were obtained by monosporic isolation. Twenty-one isolates with similar characteristics were obtained from the infected leaves (isolation frequency about 90%). The upper side of colonies on the PDA plates was milky, and the reverse side was pale yellow at the center and pale white at the margin. After 10 days of growth on the PDA medium, these isolates produced spores separately. . Through electron microscopic observation, conidia were smooth walled, hyaline, aseptate, guttulate, cylindrical with rounded ends with 15 to 20.5 × 5.3 to 6.7 μm (mean 18.5 × 5.8 μm, n = 50) in size. These morphological characteristics were similar to those of the species of Colletotrichumspp (Weir et al. 2012, Fu et al. 2019). To further identify the isolates, the regions of internal transcribed spacer (ITS), actin (ACT), calmodulin (CAL), chitin synthase (CHSI), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and beta-tubulin 2 (TUB2) loci of the three representative isolates (JSJT-1, JSJT-2, and JSJT-3) were amplified and sequenced with the primer pairs ITS-1F/ITS-4, ACT-512F/ACT-783R, CL1/CL2A, CHS-79F/CHS-345R, GDF/GDR and T1/T2 primers, respectively (Weir et al. 2012). Sequences of them were deposited in GenBank under nos. OR214960 to OR214962 (ITS), OR228543 to OR228545 (ACT)，OR228546 to OR228548 (CAL), OR228549 to OR228551 (CHSI), OR228552 to OR228554 (GAPDH), and OR228555 to OR228557 (TUB2). Multilocus phylogenetic analysis revealed that the three isolates and C. aenigma were clustered in the same clade. Based on the results of morphological and molecular analysis, these isolates were identified as C. aenigma. The pathogenicity of three isolates was tested on leaves of pecan seedlings. Suspensions of conidia were obtained by scraping the surface of a 10-day-old sporulated petri dish PDA cultures into sterile water. Suspensions were adjusted to a density of 2 × 106 conidia/ml with a hemocytometer.The conidial suspension of each isolate was sprayed evenly on the surface of leaves from three healthy pecan seedlings. Sterilized distilled water was used for negative controls. The pathogenicity experiment was repeated three times. Finally, all inoculated plants were kept in a light-incubator at 28°C under 100% relative humidity and 12 h photoperiod. Two weeks after inoculation, the inoculated plants developed symptoms similar to those of the original diseased plants, while controls remained asymptomatic. C. aenigma were re-isolated from from inoculated leaves. C. aenigma has been reported as the causal agent of anthracnose on several economically important plants, such as grape ( Kim et al. 2021), tree peonies (Wang et al.2023), chili (Diao et al. 2017), and pear (Fu et al. 2019), but this is the first report of C. aenigma causing anthracnose on pecan in China. Identification of C. aenigma as a pathogen of pecan is important for implementing control management strategies for pecan disease. References: Diao, Y. Z., et al. 2017. Persoonia. 38:20. Fu, M., et al. 2019. Persoonia. 42:1. Kim, J. S., et al. 2021. Plant Dis. 105:2729. Weir, B. S., et al. 2012. Stud. Mycol.. 73:115. Wang, Y. L., et al. 2023. Plant Dis. 107(4):1242. The author(s) declare no conflict of interest. Keywords: Colletotrichum aenigma, Anthracnose, Carya illinoinensis, Pathogenicity.

Chaste-tree (Vitex agnus-castus Linn.) is a perennial ornamental shrub that is native to Europe, which has been widely distributed in China. Since 2021, a serious leaf spot on chaste-tree leaves was observed in Nanjing Botanical Garden, Jiangsu Province, China (31°14'6″N, 118°22'12″E). The disease incidence on the leaves ranged from 20 to 40%. The disease symptom initially appeared as irregular small gray spots on leaves that gradually coalesced into larger lesions with diseased leaves turning black and withering. From August of 2021 to 2022, small pieces of leaf tissues (5×5mm) from the necrotic borders of five typical symptomatic infected leaves were collected and surface sterilized (with 75% ethanol), then incubated in darkness at 25°C for 7 days. A total of fifteen isolates were obtained by monosporic isolation (isolation frequency of 76%). The fungal colonies were initially grayish-white and turned into dark gray with abundant cotton-like aerial hyphae. Microscopic observations revealed light-brown conidia that were obclavate or obpyriform (inversely pear-shaped) with length between 10 and 20 µm (mean 13.3 ± 2.4 µm) and widths between 5 and 10 µm (mean 7.8 ± 1.2 µm), 2 to 4 transverse septa and 0 to 2 longitudinal septa per conidium (n=30) were observed. The fungus was identified as Alternaria alternata based on the colony characteristics (Simmons 2007) and the representative isolate Aa1 was used for further studies. To further identify Aa1, the region of internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (EF-1a) and RNA polymerase second largest subunit (RPB2) genes were amplified from genomic DNA and sequenced with the primer pairs ITS1/ITS4 (Jayawardena et al. 2019), EF-728F/EF-986R (Carbone and Kohn 1999), Gpd1/Gpd2 (Berbee et al. 1999) and RPB2-5F/RPB2-7cR (Liu et al. 1999) respectively. Sequences were deposited into GenBank (Accession No. OQ626644 and OQ630494-OQ630496), which showed 99.2 to 100% sequence homology with those A. alternata strains in GeneBank (ITS, MN394880; GAPDH, MN410920; EF-1a, MN410916; RPB2, MN410918). The multigenes phylogenetic analysis revealed that isolate Aa1 and Alternaria alternata TCS3002 + CBS 916.96 clustered within the same clade with 99% bootstrap support. To test pathogenicity, conidial suspension (1×106 spores/ml) of Aa1 was sprayed uniformly across the leaves of three 1-year-old healthy chaste-tree seedlings; sterilized distilled water sprayed on other trees were used as negative control and the experiment was repeated three times. All inoculated plants were kept in same condition (25°C, under a 16 h/8 h photoperiod and 70% relative humidity). One week later, black/gray spots were observed on the leaves of inoculated plants, similar to the symptoms that were observed on the original diseased plants, while controls remained asymptomatic. Cultures were re-isolated from the infected leaves and were again identified as Aa1 by both morphological characteristics and DNA sequence analysis. The pathogen reported here has a broad host range, and has also been reported on Magnolia grandiflora L. (Liu et al. 2019), Kalanchoe pinnata (Sanahuja et al. 2018) and Kadsura coccinea (Zhang et al. 2020) to cause leaf spot. To our knowledge, this is the first report of A. alternata causing leaf spot disease on chaste-tree and provides an important reference for further biology and epidemiology research.

Carya illinoinensis, is a highly valuable nut plant that is cultivated worldwide. As a precious pecan pollination resource, C. illinoinensis cv. Xinxuan-4 is protandrous, with a very early bud break in China. In this study, the chloroplast (cp) genome of 'Xinxuan-4' was sequenced and compared with closely related cultivars. The cp genome was found to be 160,819 bp in length, and it had a common quadripartite architecture with one large single copy (LSC; 90,022 bp), one small single copy (SSC; 18,791 bp), and two inverted repeats (IRs; 26,003 bp). The genome contained 132 genes, including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes, with a GC content of 36.1%. Furthermore, 278 simple sequence repeats and 59 long repeat sequences were identified, and the genome comparisons revealed that there was a greater divergence in the noncoding regions than in the coding regions. According to the gene selective pressure analysis, five genes (petD, rpl16, rps12, rpoC2, and rpoC1) were identified to be potentially under positive selection when contrasted with the other Carya genotypes. Phylogenetic analysis of the cp genome of 'Xinxuan-4' and 17 other species inferred that Carya is monophyletic and that the genetic relationship between 'Xinxuan-4' and 'Pawnee' is quite close from an evolutionary perspective. The currently characterized cp genome of 'Xinxuan-4' offers useful data for subsequent research on this pecan species.

Pecan (Carya illinoinensis) is one of the important economic forest crops widely cultivated in Jiangsu Provinces, China. From August to September in both 2021 and 2022, a foliar blight was observed in 7-ha and 6-ha pecan orchards in Changzhou (31°58'9.6″ N, 119°48'33.84″ E), and Jurong (31°52'15.46″ N, 119°9'24.62″ E), Jiangsu Province. The disease severity was about 32% with 8% incidence on 120 surveyed trees of the two orchards. Typical symptoms were lesions with a dark-brown color, which later became brown. We collected eighteen pecan leaves with typical symptoms in the surveyed pecan orchards and took them back to the laboratory for identification. Small fragments (approximately 9 mm2) from the necrotic borders of infected leaves were surfaced sterilized, plated on potato dextrose agar (PDA) and then incubated in darkness at 25°C. Pure cultures were obtained by single-spore culture. Thirty-three isolates with similar characteristics were obtained from the infected leaves (isolation frequency 85%), and the colonies surface on PDA was ochreous with patchs of olivaceous-yellow and sparse aerial mycelium. Observing from the back of the plate, the colonies were cream-yellow. Two types of single-cell conidia were produced on PDA. Alpha-conidia were 7.4 (range, 5.9 to 8.8) × 2.1 (range, 1.6 to 2.8) μm (n = 100), aseptate, smooth, fusiform, straight and tapering towards both ends. Beta-conidia were 25.1 (range, 19.1 to 36.2) × 1.3 (range, 1.0 to 2) µm (n = 100), filiform, hyaline, aseptate and curved at one end. The morphological features of these isolates agreed with those of Diaporthe sp. (Gomes et al. 2013; Gao et al. 2017). To further identify the isolates, the regions of internal transcribed spacer (ITS, OR214967 to OR214969), calmodulin (CAL, OR228558 to OR228560), translation elongation factor 1-α (EF1a, OR228561 to OR228563), histone H3 (HIS, OR228564 to OR228566), and beta-tubulin 2 (TUB2, OR228567 to OR228569) were amplified and sequenced from genomic DNA for the three representative isolates (LSM1, LSM2 and LSM3), respectively (Gomes et al. 2013). Multilocus phylogenetic analysis revealed that the three isolates and D. pseudophoenicicola were clustered in the same clade. Based on the results of morphological and molecular analysis, these isolates were identified as D. pseudophoenicicola. The pathogenicity of three isolates were tested on leaves of pecan seedlings. The conidial suspension (1 × 105 conidia/ml) of each isolate was sprayed evenly on the surface of leaves of three healthy seedlings. Sterilized distilled water was used for negative controls. Finally, all inoculated plants were kept in a greenhouse at 28°C under 100% relative humidity. Two weeks after inoculation, the inoculated plants developed symptoms similar to those of the original diseased plants, while controls remained asymptomatic. D. pseudophoenicicola were re-isolated from from inoculated plants. The pathogenicity experiment was repeated three times. Previously, D. pseudophoenicicola has been reported to cause stem-end browning disease in ripe mango (Takushi et al. 2016; Xu et al 2022). To our knowledge, this is the first report of D. pseudophoenicicola causing leaf blight on pecan . This study provides important information for developing effective pecan disease management practices.

Pecan (Carya illinoinensis) is one of the important economic forest crops which has been widely cultivated in Anhui and Jiangsu Provinces, China. Since 2019, symptoms resembling anthracnose disease...

Pecan (Carya illinoinensis) is a world-famous nut tree that is widely cultivated in China, especially in Jiangsu Province (Zhang et al. 2015). In April 2022, cankers on trunks were recorded in peca...

Pecan (Carya illinoinensis) is a world-famous nut tree which widely cultivated in China. Quanjiao County, located in Anhui province, is reputed to be the capital of pecan production in China. Since...