Drought tolerance and recovery capacity of two ornamental shrubs: Combining physiological and biochemical analyses with online leaf water status monitoring for the application in urban settings.

When plants are transferred from nursery to urban environments, they often face drought stress due to inadequate maintenance, such as insufficient irrigation. Using drought tolerant species may help mitigate the adverse impact of drought stress in urban settings. Additionally, utilizing novel technologies for water status monitoring may help optimize irrigation schedules to prevent transplanting failures. This study investigated the physiological and biochemical responses of two ornamental shrubs, Photinia x fraseri and Viburnum tinus, subjected to water stress of increasing severity and rewatering. Water relations, gas exchanges, chlorophyll fluorescence and biochemical analyses were conducted alongside real-time monitoring of water status using leaf-water-meter sensors (LWM). The progression of water stress had a notable negative impact on leaf gas exchanges and water relations in both species. Notably, P. fraseri avoided photoinhibition by reducing chlorophyll content and actual efficiency of PSII. Adjustments in leaf phenolic compounds played a significant role in enhancing drought tolerance of both species due to their antioxidant and photoprotective properties. Upon rewatering, both species exhibited complete recovery in their physiological functions, underscoring their remarkable tolerance and resilience to drought stress. Additionally, LWM sensors efficiently tracked the dehydration levels, exhibiting a rising trend during the water stress progression and a subsequent decline after rewatering for both species. These findings confirm the reliability of LWM sensors in monitoring physiological status of plants in outdoor contexts, making them a suitable tool for use in urban settings.

First Report of Pseudopestalotiopsis ixorae Causing Leaf Spot of Photinia × fraseri in China.

Photinia × fraseri is a well-known ornamental shrub in southern China. In December 2021, we observed leaf spots that were circular to irregular, gray with dark red margins and violet brown with brownish violet edges on the leaves of Photinia × fraseri shrubs in the scenic area of Shenlongtan (28°46'10″N, 115°42'93″E), Jiangxi Province, China. Almost 15% of the leaves in the 1300 m2 Photinia × fraseri planting area were symptomatic. Thirty symptomatic leaves were randomly collected from different plants, and sectioned into 5-mm2 pieces, which were surface-sterilized using 1% NaOCl for 30 s. After rinsing thrice in sterile distilled water and drying, the pieces were transferred onto potato dextrose agar (PDA) and incubated at 28 ℃ for 5-7 days. A total of sixteen morphologically similar isolates were obtained. After incubation on PDA for 20 days, the fungi had irregular edges, were white to pale brown, and had spare aerial mycelium on the surface with irregularly distributed black, gregarious conidiomata. Conidia were fusoid, subcylindrical, straight to slightly curved, 4-septated, slightly constricted at the septa, and 23 to 36 × 6 to 10 µm (mean: 27.6 × 7.7 µm). The morphological characteristics were consistent with the features of Pseudopestalotiopsis species (Maharachchikumbura et al. 2014). The genomic DNA of two representative isolates (JFRL032 and JFRL033) was extracted for further identification. The internal transcribed spacer (ITS) region, translation elongation factor 1-ɑ (tef1-ɑ) and ß-tubulin (tub2) genes were amplified and sequenced using primers ITS5/ITS4, EF1-526F/EF1-1567R, and Bt2A/Bt2B, respectively (Maharachchikumbura et al. 2012). The sequences of the two representative isolates were 100% identical to each other. These nucleotide sequences were deposited in GenBank with accession numbers, ON342794 and ON342795 (ITS); ON375851 and ON375852 (tef1-ɑ); ON375853 and ON375854 (tub2). BLASTn searches of the obtained sequences revealed 99%-100% to ITS (MG816316, 478/478 nucleotides), tef1-ɑ (MG816336, 924/926 nucleotides), tub2 (MG816326, 441/442 nucleotides) sequences of the ex-type strain of Pseudopestalotiopsis ixorae (NTUCC17-001.1). Phylogenetic analysis was conducted using the concatenation of multiple sequences (ITS, tef1-ɑ and tub2) with the Maximum likelihood statistics in PhyloSuite v1.2.2 (Zhang et al.2020). The phylogenetic tree showed the two isolates clustered with P. ixorae in a clade with 100% bootstrap support. The isolates were identified as P. ixorae based on morphological and molecular data. To confirm pathogenicity, eight healthy leaves of 3-year-old Photinia × fraseri were surface sterilized, scratched with a pair of sterilized tweezers, and ten µl of conidial suspension (106 conidia/ml) was sprayed on the injured leaves and the control was sprayed with sterile distilled water. Then, All plants were potted in a climate chamber at 25℃ and 85% relative humidity. After 3 days, leaf spot symptoms similar to those described above were observed on inoculated leaves, while the non-inoculated leaves remained symptomless. The pathogen was reisolated from the inoculated leaves to fulfill Koch's postulates and confirmed as P. ixorae by morphological and molecular analysis. It has been reported that P. ixorae can infect the Ixora plant (Tsai et al., 2018). To the best of our knowledge, this is the first report of P. ixorae causing leaf spot on Photinia × fraseri in China. The study provides valuable information for identifying and controlling the leaf spot on Photinia × fraseri.

Significant correlation between leaf vein length per unit area and stomatal density: evidence from Red Tip and Chinese photinias.

The vascular veins in photosynthetic leaves play an important role in transporting water and sugars throughout the plant body, and their venation pattern and vein density determine the hydraulic efficiency of the leaf. Likewise, stomatal density (SD) can influence photosynthetic gas exchange. However, the correlation between leaf vein density and SD is seldom reported. Herein, we examined 16 leaves from the hybrid Photinia × fraseri and 16 leaves from one of its parents, P. serratifolia, to explore the correlation between leaf vein density and SD. For each leaf, equidistant lamina quadrats were excised along two longitudinal transects (one along the midrib and another along the leaf margin). For each quadrat, micrographs of 1.2 mm × 0.9 mm stomatal imprints, and 2.51 mm × 1.88 mm micrographs of leaf veins were used to measure total vein area per leaf unit area (VAA) and total vein length per unit area (VLA), as indicators of leaf vein density, to determine the correlation between SD and leaf vein density. For each taxon, there was no significant correlation between SD and VAA, but there was a significant correlation between SD and VLA. The data indicate that SD is not positively correlated with VAA but positively correlated with VLA for both the hybrid and the parent species. This study indicates that future work should focus on the relationships between SD and total vein length per unit area rather than on total leaf vein area per unit area within and across species.

First Report of Leaf Spots Caused by Pestalotiopsis nanjingensis on Photinia × fraseri in China.

Photinia × fraseri Dress, belonging to the Rosaceae family, is widely cultivated as an ornamental plant in China. In July 2022, the leaf spot symptoms were observed on over thirty P. × fraseri plants in an approximately 2-hectare park in Xinjian District, Nanchang City, Jiangxi Province, China (28°43'02″ N, 115°44'01″ E), with a disease incidences of roughly 10% . At first, small, grayish-white lesions appeared on the leaf edges, later expanding into 2 to 10 mm circular or irregular spots. These spots turned grayish-white to brown, with dark brown margins. Eventually, some lesions' centers dried and died. For fungal isolation, ten symptomatic leaves were randomly collected. The edges between the diseased and healthy tissues were cut into small pieces (4 × 4 mm). These pieces were then surface-sterilized by dipping in 70% ethanol for 30 s and 1% NaClO for 30 s. Subsequently, they were rinsed three times with sterile distilled water. Leaf pieces were then transferred to potato dextrose agar (PDA) medium and incubated at 25 °C for 3-4 days. Eight isolates with similar colony morphology were collected from diseased leaves. Colonies of this fungus on PDA were nearly round, white, and had sparse aerial mycelium on the surface with black, gregarious conidiomata. The conidia were nearly cylindrical, smooth, hyaline, and 4-septate, measuring 16.7 to 24.3 × 4.2 to 6.6 µm (mean 20.9 × 5.3 µm, n=50). The three middle cells were smooth, doliiform, and brown, with concolorous septa that were darker than the rest of the cell. They measured 11.8 to 17.0 µm long (mean 14.1 µm, n=50). The basal and apical cells were triangular and transparent. The basal cells had a mean length of 4.7 µm and were equipped with a basal appendage, while the apical cells had two appendages with a mean length of 17.7 µm(n=50). The characteristics of these isolates match those of Pestalotiopsis species (Maharachchikumbura et al. 2014). To identify them accurately, three representative isolates, namely JFRL 03-161, JFRL 03-162, and JFRL 03-226, were selected for further analysis. The internal transcriptional spacer (ITS) region, ß-tubulin (TUB2) and translation elongation factor 1-alpha (TEF1-α) gene were amplified and sequenced using primers ITS1/ITS4 (White et al. 1990), BT2a/BT2b (Glass and Donaldson 1995), and EF1-526F/EF1-1567R (Maharachchikumbura et al. 2012), respectively. All sequences (ITS: OR342044-OR342046, TUB2: OR343299-OR343301, and TEF1-α: OR343302-OR343304) were deposited in GenBank. A BLASTn homology search revealed 99-100% identity to Pestalotiopsis nanjingensis CSUFTCC16 (ex-type). The sequences included ITS (OK493602, 486/486 nucleotides), TUB2 (OK562377, 438/439 nucleotides), and TEF1-α (OK507972, 478/478 nucleotides). The maximum likelihood analyses were performed for the combined ITS, TUB2 and TEF1-α data sets using IQtree web server (Trifinopoulos et al. 2016). The resulting phylogenetic tree demonstrated a strong association: the three isolates clustered tightly with P. nanjingensis forming a clade with robust 99% bootstrap support. This clustering, consistent with both morphological and molecular characteristics, confirmed the identity of the fungus as P. nanjingensis. To evaluate its pathogenicity, we obtained 3-year-old P. × fraseri 'Red Robin' plants, which were purchased then potted in a controlled climate chamber. We surface sterilized six healthy leaves of P. × fraseri with 70% ethanol and created wounds using a sterile needle. Subsequently, we inoculated a 50 µL conidial suspension (1 × 106 conidia/mL) of the isolate JFRL 03-161 on these wounded leaves. In parallel, another six leaves from P. × fraseri were inoculated with sterile distilled water, serving as the control group. All potted plants were incubated under conditions of 26 °C and 80% humidity. After seven days, all leaves inoculated with isolate JFRL 03-161 displayed symptoms similar to those observed in the field, whereas the control leaves remained unaffected. To fulfill Koch's postulates, we re-isolated P. nanjingensis plants from the symptomatic leaves and identified it based on morphological and molecular characteristics. It has been reported that two species of Pestalotiopsis, namely P. microspora and P. trachicarpicola can caused damage to the leaves of P. × fraseri in China (Xu et al. 2022; Zhu et al. 2021). However, to our best knowledge, this is the first report on leaf spot caused by P. nanjingensis on P. × fraseri in China. Therefore, it is necessary to pay more attention to the leaf spot disease of P. × fraseri caused by Pestalotiopsis species and develop appropriate control strategies.

An Inverse Scaling Relationship between Stomatal Density and Mean Nearest Neighbor Distance: Evidence from a Photinia Hybrid and One of Its Parents.

Stomata are involved in transpiration and CO2 uptake by mediating gas exchange between internal plant tissues and the atmosphere. The capacity for gas exchange depends on stomatal density (SD), stomatal size, and pore dimensions. Most published work on stomatal quantification has assumed that stomatal distribution and stomatal density are spatially homogeneous across the leaf, but this assumption has been seldom tested. We selected 32 leaves from a Photinia hybrid, Photinia × fraseri 'Red Robin', and one of its parents, P. serratifolia. For each leaf, the leaf surface was divided into three or four equidistant layers along the apical-basal axis, and, in each layer, two positions, one closer to the midrib and the other closer to the leaf margin, were further selected. We calculated SD and mean nearest neighbor distance (MNND) for each lamina section and tested the scaling relationship between SD and MNND of the sampled stomatal centers using reduced major axis protocols. In addition, we calculated the stomatal aggregation index (SAI) for each lamina section to examine the spatial arrangement of stomata at the given size of field of view of 1.2 mm × 0.9 mm. We observed that SD decreased from the lamina apex towards the base for central lamina areas but varied little at leaf margins. An inverse scaling relationship between SD and MNND was observed for both species. This relationship could be used for SD estimation using the rapidly estimated trait, MNND. SAI did not vary significantly throughout leaf lamina, and the numerical values of SAI for all fields of view were greater than one, which indicates significant spatial repulsion between stomata. The study suggests that SD varies across leaf lamina to fine-tune plant water use and maximize carbon gain. However, spatial structures of stomata from different lamina sections exhibit similar patterns (i.e., spatial inhibition between stomata at small scales), probably due to hierarchical leaf vein patterns.

Physiological responses of typical subtropical landscape shrubs to artificial light at night.

Artificial light at night is rapidly spreading and has become an important component of global change. Although numerous studies have focused on its potential ecological impacts, the physiological response mechanisms of landscape plants to artificial light at night have rarely been quantified. With common landscape shrubs in subtropical regions of China, Hydrangea paniculata, Photinia fraseri and Ligustrum japonicum, as test materials, we exa-mined the responses of antioxidant enzyme system and biomass in the light environment at night under different light quality (yellow light, white light) with different light intensities (20, 40, 60 lx) . The results showed that artificial light at night significantly increased the membrane peroxidation, stimulated plant antioxidant protection systems and raised the antioxidant enzyme activities of the three species. The effects of light quality on plant antioxidant enzymes varied across dspecies. The peroxidase (POD) and catalase (CAT) activities of H. paniculata under white light were 1.5 and 1.3 times as that under yellow light, respectively. Both enzyme activities of P. fraseri were 1.1 times as that under white light than under yellow light. The activities of two enzymes in L. japonicum under white light were 88.6% and 99.5% of those under yellow light, respectively. The antioxidant enzyme activities of the three species increased with increasing light intensity at night, whereas the contents of malondialdehyde increased rapidly and the antioxidant enzyme activities decreased when beyond a certain light intensity threshold (at 120 d, the threshold was about 40 lx). The protective enzymes that played the major role under nighttime light stress were different among the three species. For H. paniculata, POD and CAT complemented each other to resist stress-induced oxidative damage, while the main enzyme of L. japonicum was POD. The biomass of the three species increased significantly under artificial light at night. H. paniculata was the most sensitive to nighttime light stress, while L. japonicum had the strongest resistance to the stress. The deciduous shrub H. paniculata could tolerate the white night light lower than 40 lx, while the evergreen shrubs P. fraseri and L. japonicum could tolerate the yellow night light lower than 40 lx.

Antibacterial and anticancer activities of green-synthesized silver nanoparticles using Photinia glabra fruit extract.

Aims: We prepared Photinia glabra (PG) aqueous fruit extract, utilized it to synthesize silver nanoparticles (PG-Ag NPs) and evaluated the antibacterial and anticancer activities of the nanoparticles (NPs). Materials & methods: Silver nitrate aqueous solution was reduced to PG-Ag NPs using aqueous PG fruit extract. NP shape, size, composition and functionalization were determined using transmission electron microscopy, x-ray photoelectron spectroscopy, Fourier transform infrared and x-ray diffraction. Results & conclusions: PG-Ag NPs were spherical, approximately 39-77 nm-sized, functionalized surfaces with notable antibacterial activity against both Escherichia coli and Staphylococcus aureus, with an MIC <30 ug/ml and cytotoxicity toward esophageal cancer cells, with IC50 values less than 20 ug/ml. PG-Ag@rt NPs have been shown to be a potent antibacterial and anticancer agent, and their enriched particle surfaces can be conjugated with other compounds for multibiomedical applications.

The present study reports for the first time the preparation of Photinia glabra (PG) aqueous fruit extract and its use for the synthesis of smaller silver particles (PG-Ag NPs) from bulk aqueous silver nitrate solution (AgNO₃). The preparation followed the reduction ability of PG fruit extract phytochemical under different preparation conditions: at room temperature (PG-Ag@rt), at 70°C (PG-Ag@70) and in the presence of cerium oxide at 70°C (PG-Ag+CeO₂@70). The prepared smaller particles were found using transmission electron microscopy to be spherical in shape with sizes 39, 77 and 44 nm for PG-Ag@rt, PG-Ag@70 and PG-Ag+CeO₂@70, respectively. The NPs contained different functional groups on their surfaces due to the capping ability of PG fruit extract components. Among all, PG-Ag@rt NPs showed strongest antibacterial activity against Escherichia coli and Staphylococcus aureus with MIC 7.0 µg/ml and 28.0 µg/ml, respectively, and commendable anticancer activity toward Eca-109 cancer cells with IC₅₀ less than 20 ug/ml.

First report of Neopestalotiopsis clavispora causing leaf spot on Photinia bodinieri in China.

Photinia bodinieri Lévl. is an evergreen broadleaf species widely cultivated in subtropical China as an ornamental value (Zhang et al. 2018). In July 2021, leaf spot symptoms were observed on the campus of Jiangxi Agricultural University (28°45'56″N, 115°50'21″E), Jiangxi province, China. The spots were circular to irregular, gray in the center, and dark brown on the lesion margin. The disease incidence was estimated 15%. Leaf pieces (5 × 5 mm) from the lesion borders were surface-sterilized in 70% ethanol for 30 s, followed by 2% NaOCl for 1 min, and then rinsed three times with sterile water. Tissues were placed on potato dextrose agar (PDA) and incubated at 25°C in the dark. Pure cultures were obtained by monosporic isolation, and the representative isolates, SN-3, SN-7, and SN-11 were used for morphological studies and phylogenetic analyses. The colonies of three isolates grown on PDA were white, cottony, and exhibited flocculent, contained undulate edges with dense aerial mycelium on the surface. Conidia were 5-celled, clavate to fusiform, smooth, 18.2-24.3 × 5.5-8.4 µm (n = 100). The 3 median cells were dark brown to olivaceous, central cell was darker than other 2 cells, and the basal and apical cells were hyaline. Conidia developed filiform appendages; one basal appendage (3.3-8.2 µm long; n = 100), and 2-3 apical appendages (16-29 µm long; n = 100). Morphological features were similar to Neopestalotiopsis sp. (Maharachchikumbura et al. 2014). Portions of internal transcribed spacer (ITS) regions, ß-tubulin 2 (TUB2) and translation elongation factor 1-alpha (TEF1-α) genes were amplified from genomic DNA for the three isolates using primers ITS1/ITS4, T1/Bt-2b, EF1-728F/EF-2 (Maharachchikumbura et al. 2014), respectively. All sequences were deposited into GenBank (ITS, OQ572345 - OQ572347; TUB2, OQ597847 - OQ597849; TEF1-α, OQ597844 - OQ597846). A maximum likelihood and Bayesian posterior probability analyses using IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 with the concatenated sequences placed SN-3, SN-7, and SN-11 in the clade of N. clavispora. Based on the multi-locus phylogeny and morphology, three isolates were identified as N. clavispora. Pathogenicity of the three isolates was verified on nine disease-free 7-year-old Photinia bodinieri plants, which were grown in the field. Two healthy leaves per plant were wounded with two pricks using a sterile needle (Φ=0.5 mm) and inoculated with 20 µL conidial suspension per leaf (106 conidia/mL). Another nine control plants were inoculated with sterile water. 36 leaves were used for the pathogenicity test of three isolates. All leaves were covered with plastic bags to maintain a humid environment for 2 days. The inoculated leaves showed similar symptoms to those observed in the field, whereas control leaves were asymptomatic after 10 days. The fungi were consistently reisolated only from the inoculated and symptomatic leaves, fulfilling Koch's postulates. N. clavispora can cause leaf diseases in a variety of hosts, including Kadsura coccinea (Xie et al. 2018), Photinia serratifolia (Yang et al. 2018), Camellia chrysantha (Zhao et al. 2020). Photinia spp. is an excellent landscape gardening plant, threatened with grey blight (Pestalotiopsis microspore) (Ye et al. 2022), anthracnose (Colletotrichum sp.) (Guan et al. 2013). However, this is the first report of N. clavispora infecting Photinia bodinieri in China. This work provided crucial information for epidemiologic studies and appropriate control strategies for this newly emerging disease.

First Report of Powdery Mildew on Photinia × fraseri Caused by Podosphaera leucotricha in Guizhou Province, China.

The evergreen shrub Photinia × fraseri is a Photinia glabra × Photinia serrulata hybrid belonging to the family Rosaceae that is widely used in ornamental landscaping. In March 2022, severe powdery mildew symptoms were observed on shrubs of Photinia × fraseri in Huaxi University Town, Guiyang, Guizhou Province, China. All observed Photinia × fraseri plants in the green belts of both roads and parks in University Town showed powdery mildew symptoms. Almost all young branches of each Photinia × fraseri individual was infected. Powdery mildew colonies covered twig tips entirely, including the stems, petioles, and the adaxial and abaxial surfaces of leaves. Infected leaves were rolled up and had irregular, dark red spots. Fungal hyphae were straight to flexuous, branched, septate, 3 to 6 µm in width, and had nipple-shaped appressoria. Conidiophores were erect, straight or somewhat flexuous, and measured 90 to 300 µm × 7 to 10.5 µm (n = 30). Foot-cells were cylindrical or subcylindrical, straight or somewhat flexuous, and measured 25 to 50 × 7 to 9.5 µm (n = 30). Foot-cells were followed by one to two shorter cells, these being 10 to 16 × 7 to 9.5 µm in size (n = 50). Shorter cells were followed by one to six conidia (most often five conidia). Conidia formed in chains, ellipsoid to ovoid in shape, having dimensions of 22.5 to 30 × 12.5 to 16 µm (n = 50), and containing fibrosin bodies. No chasmothecia (fruiting bodies) were observed. Based on these morphological characteristics, the pathogen was identified as Podosphaera leucotricha (Ellis & Everh.) E.S. Salmon (Braun & Cook 2012). To confirm this species-level identification, the ribosomal DNA internal transcribed spacer (ITS) was amplified using the primers ITS1/ITS4 (White et al. 1990). The resulting sequence was deposited in GenBank (Accession No. ON325389). When the query coverage is 100%, the obtained ITS sequence showed 99.8% identity with P. leucotricha (AB027231, MT180425, MZ298746, KX842350, and KY661036) and 100% with P. leucotricha (HM242221, KY661017, KY661028, KY661050, KY661076, KR048110, MW364489, MW364490, MZ343479, OM022112, ON073894, and ON325389), respectively. Based on the ITS sequences of Podosphaera spp., phylogenetic tree was constructed with MEGA7.0 using the Maximum Likelihood method. The ML analysis supported our isolate's putative identification as P. leucotricha. To fulfill Koch's postulates, pathogenicity testing was conducted by gently pressing naturally diseased leaves onto young leaves of three healthy, potted 1-year-old Photinia × fraseri plants; three non-inoculated healthy plants served as control. Powdery mildew symptoms were observed on 100% inoculated Photinia × fraseri plants after 12 days (in a growth chamber at 21°C under a 12 h/12 h light/dark cycle), whereas the control plants remained symptomless. The powdery mildew colonies on inoculated leaves were morphologically identical to those observed on the original diseased leaves. It is known that P. leucotricha causes powdery mildew on Photinia × fraseri in Italy (Garibaldi et al. 2005). Moreover, this fungus reportedly infected Photinia serrulata in New Zealand, Ukraine, Italy, the United States, Japan, and in East China's Shandong Province (Liang et al. 2012). To the best of our knowledge, this is the first report of powdery mildew caused by P. leucotricha on Photinia × fraseri in Southwest China's Guizhou Province. This finding is significant as P. leucotricha is the causal agent of powdery mildew on apple and pear (Strickland et al. 2021). The occurrence of said disease on Photinia × fraseri could pose a potential disease threat to these fruit crops if nearby ornamental shrubs were able to act as reservoirs for the fungus, and a means to escape agricultural management efforts.

Leaf spot on Photinia × fraseri caused by Neopestalotiopsis asiatica in China.

Photinia × fraseri is a well-known evergreeen ornamental tree. Owing to its flower-like red leaves and its ability to tolerate stressful environments, P. fraseri is widely cultured as a fast-growing hedge in southern China. From July to September in 2021, a disease with symptoms similar to leaf spot was extensively observed on P. fraseri in Daozhen county (28° 51 'N, 107° 57 'E), Zunyi, Guizhou province, China. About 500 plants were surveyed and the incidence of leaf spot on P. fraseri leaves was 35% to 70%, significantly reducing the ornamental and economic value. The symptomatic leaves displayed irregular, watery dark brown lesions with black conidiomata in gray centers, and 10 symptomatic leaves were collected from 10 trees. After surface sterilization (0.5 min in 75% ethanol and 2 min in 3% NaOCl, washed three times with sterilized distilled water) (Fang 2007), small pieces of symptomatic leaf tissue (0.2 × 0.2 cm) were plated on potato dextrose agar (PDA) and incubated at 25°C for about 7 days. Three single-spore isolates, GZAAS 21-0327, GZAAS 21-0328 and GZAAS 21-0329, were obtained, which were identical in morphology and molecular analysis. Therefore, the representative isolate GZAAS 21-0328 was used for further study. The pathogenicity of GZAAS 21-0328 was tested through a pot assay. Ten healthy plants were scratched with a sterilized needle on the leaves. Plants were inoculated by spraying a spore suspension (106 spores mL-1) of GZAAS 21-0328 onto leaves until runoff, and the control leaves sprayed with sterile water. The plants were maintained at 28°C with high relative humidity (95%) in a growth chamber. The pathogenicity test was carried out three times (Fang 2007). The symptoms developed on all inoculated leaves but not on the control leaves. The lesions were first visible 72 h after inoculation, and typical lesions similar to those observed on field plants appeared after 15 days. The same fungus was reisolated and identified based on the morphological characterization and molecular analyses (ITS, TUB and TEF) from the infected leaves but not from the noninoculated leaves. Results of pathogenicity experiments of isolated fungi fulfilled Koch's postulates. Fungal colonies on PDA were villiform, creamy-white and sparse aerial mycelium on the surface with black, gregarious conidiomata. The conidia were fusoid, ellipsoid, straight to slightly curved, 4-septate, septa darker than the rest of the cell, and 23.0 (21.0 to 27.0) × 6.0 (5.0 to 7.0) µm (n=50). The morphological features were consistent with the descriptions of Neopestalotiopsis asiatica Maharachch. & K.D. Hyde (Maharachchikumbura et al. 2012; Maharachchikumbura et al. 2014; Farr et al. 2022). The pathogen was confirmed to be N. asiatica by amplification and sequencing of the internal transcribed spacer region (ITS), the partial ß-tubulin (TUB) and partial translation elongation factor 1-alpha (TEF) genes using primers ITS4/ITS5, T1/Bt-2b and EF1-728F/EF-2, respectively (Maharachchikumbura et al. 2014). The sequences of PCR products were deposited in GenBank with accession numbers OK563071 (ITS), OK584020 (TUB) and OK663023 (TEF). BLAST searches of the obtained sequences revealed 100% (482/482 nucleotides), 99.05% (419/421 nucleotides), and 99.33% (891/897 nucleotides) homology with those of N. asiatica in GenBank (JX398983, JX399018 and JX399049, respectively). Phylogenetic analysis (MEGA 6.0) using the maximum likelihood method placed the isolate GZAAS 21-0328 in a well-supported cluster with N. asiatica. The pathogen was thus identified as N. asiatica based on the morphological characterization and molecular analyses. To our knowledge, this is the first report of leaf spot on P. fraseri caused by N. asiatica in China. This study provides valuable information for the identification and control of the leaf spot on Photinia × fraseri.

[Arbuscular mycorrhizal fungi enhanced cadmium uptake in Photinia frase through altering root transcriptomes and root-associated microbial communities].

As a non-essential metal, cadmium (Cd) pollution poses severe threats to plant growth, environment, and human health. Phytoextraction using nursery stocks prior to their transplantation is a potential useful approach for bioremediation of Cd contaminated soil. A greenhouse pot experiment was performed to investigate the growth, Cd accumulation, profiles of transcriptome as well as root-associated microbiomes of Photinia frase in Cd-added soil, upon inoculation of two types of arbuscular mycorrhizal fungi (AMF) Sieverdingia tortuosa and Funneliformis mosseae. Compared with the control, inoculation of F. mosseae increased Cd concentrations in root, stem and leaf by 57.2%, 44.1% and 71.1%, respectively, contributing to a total Cd content of 182 µg/plant. KEGG pathway analysis revealed that hundreds of genes involved in 'Mitogen-activated protein kinase (MAPK) signaling pathway', 'plant hormone signal transduction', 'biosynthesis of secondary metabolites' and 'glycolysis/gluconeogenesis' were enriched upon inoculation of F. mosseae. The relative abundance of Acidobacteria was increased upon inoculation of S. tortuosa, while Chloroflexi and Patescibacteria were increased upon inoculation of F. mosseae, and the abundance of Glomerales increased from 23.0% to above 70%. Correlation analysis indicated that ethylene-responsive transcription factor, alpha-aminoadipic semialdehyde synthase, isoamylase and agmatine deiminase related genes were negatively associated with the relative abundance of Glomerales operational taxonomic units (OTUs) upon inoculation of F. mosseae. In addition, plant cysteine oxidase, heat shock protein, cinnamoyl-CoA reductase and abscisic acid receptor related genes were positively associated with the relative abundance of Patescibacteria OTUs upon inoculation of F. mosseae. These finding suggested that AMF can enhance P. frase Cd uptake by modulating plant gene expression and altering the structure of the soil microbial community. This study provides a theoretical basis for better understanding the relationship between root-associated microbiomes and root transcriptomes of P. frase, from which a cost-effective and environment-friendly strategy for phytoextraction of Cd in Cd-polluted soil might be developed.

A comprehensive checklist of the deciduous photinia genus Pourthiaea (Maleae, Rosaceae), with emphasis on their validity and typification.

Due to the complicated evolutionary history in Pourthiaea, ninety-seven taxa have been described since 1784, and ninety-one of them are validly published taxa, five are naked names, and one is an invalid name. After a comprehensive and critical evaluation, 213 names have been published, including new combinations, new status, and new names; this may be due to the controversial taxonomic position of Pourthiaea in the apple tribe, Maleae. We herewith provide a taxonomic checklist of Pourthiaea for further taxonomic and evolutionary studies. We also lectotypify two taxa: Photiniaamphidoxavar.stylosa and P.glabravar.fokienensis.

The complete chloroplast genome sequence of Photinia × fraseri, a medicinal plant and phylogenetic analysis.

Photinia × fraseri is a common ornamental arbor in the genus Photinia (family Rosaceae), which complete chloroplast (cp) genome was sequenced, assembled and annotated. The chloroplast genome of P. fraseri was 160,184 bp in length, including a large single copy (LSC) region of 88,121, a small single copy (SSC) region of 19,295 bp, and two inverted repeat (IR) regions of 26,384 bp. The GC contents of LSC, SSC, IR and whole genome are 36.5%, 34.1%, 30.3%, and 42.7%, respectively. There are 131 genes annotated, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The phylogenetic analysis revealed that P. fraseri was most related to Photinia serratifolia as a sister group with 100% bootstrap support. The complete chloroplast genome sequences of P. fraseri will provide valuable genomic information to further illuminate phylogenetic classification of Photinia genus.

The complete chloroplast genome of Photinia davidsoniae: molecular structures and comparative analysis.

Photinia davidsoniae is a common ornamental arbor in the genus Photinia (family Rosaceae). Here, we sequenced and assembled the complete plastome of P. davidsoniae using the next-generation DNA sequencing technology. And we then compared it with nine Photinia species using a range of bioinformatics software tools. The ten plastomes had sizes ranging from 159,230 bp for P. beckii to 160,346 bp for P. davidsoniae. They all had a conservative quartile structure. It contained two single-copy regions: a large single-copy (LSC) region, a small single-copy (SSC) region, and a pair of inverted repeat (IR) regions. Each of the plastomes encoded 113 unique genes, including 79 protein-coding genes, four rRNA genes, and 30 tRNA genes. Furthermore, we detected six hypervariable regions (matK-rps16, rpoB-trnC, trnT-psbD, ndhC-trnV, psbE-petL, ndhF-rpl32-trnL), which could be used as potential molecular markers. We constructed two phylogenetic trees with plastomes or concatenated protein sequences of 25 species of 8 genera of Rosaceae. The tree constructed with complete plastomes has much stronger support. The results placed P. davidsoniae in the upper part of the phylogenetic tree. It shows that P. davidsoniae and P. lanuginosa are closely related. In summary, the plastomes of Photinia are conserved overall but carry significant minor variations, as expected. The results will be indispensable for distinguishing species, understanding the interspecific diversity, and elucidating the evolutionary processes of Photinia species.

Identification and Characterization of Nothophoma quercina Causing Bud Blight on Photinia × fraseri in China.

Photinia (Photinia × fraseri Dress) is a well-known green plant that has high ornamental value and is widely distributed around the world. An outbreak of typical bud blight disease was observed between May and August in photinia in 2017 in Qingdao, China. The causal agent for this blight was subsequently isolated from symptomatic samples and identified as Nothophoma quercina based on morphological characterization and molecular analyses (ITS, LSU, RPB2, and TUB2). Results of pathogenicity tests on isolated fungi also supported the conclusion that N. quercina is the pathogen responsible for this condition. To our knowledge, this is the first report of bud blight on P. fraseri caused by N. quercina in China.

First Report of the Colletotrichum siamense species complex causing Anthracnose on Photinia × fraseri Dress in China.

Photinia × fraseri Dress is mainly distributed in the southeast and east of Asia and North America and has been widely cultivated in China. In summer 2018, an anthracnose disease of P. × fraseri Dress was found in a park in Nanjing City, China. Disease leaves showed small, round, light reddish brown spots in the early stage of infection that gradually expanded into round spots, with light gray in centers and brown edges. Fresh lesions were cut into 2-3 mm2 sections, sterilized with 75% ethanol for 30 s, followed by 1% NaClO for 90 s, washed with sterile water 3 times, and placed on potato dextrose agar (PDA) with 0.1 mg/mL ampicillin at 25°C. Colonies of a representative strain "HDSN2-1" were white to greenish grey, and the daily growth rate was 9.5 to10.5 mm/day. Aerial mycelium was grayish white, dense, and cottony, with visible conidial masses at the inoculum point. Conidia were one-celled, smooth-walled, hyaline, with obtuse to rounded ends, with a size of 12.8 to 18.4 × 4.5 to 6.8 µm. Appressoria were one-celled, brown, thick-walled, ellipsoidal, and 7.3 to 10.3 × 5.4 to 6.97µm. The morphological characteristics of HDSN2-1 matched those of the Colletotrichum gloeosporioides species complex (Weir et al. 2012). For further identification, DNA was extracted from HDSN2-1 mycelium and the internal transcribed spacer (ITS) region and partial sequences of ß-tubulin (TUB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase (CHS-1) and calmodulin genes(CAL) were amplified by PCR, and sequenced with primers ITS1/ITS4, TubF1/TubR1, GDF/GDR, CHS-79F/CHS-345R, and CAL1C/CAL2C, respectively(Weir et al. 2012). The sequences were deposited in GenBank [Accession nos: MN889417, MN894596, MN894597, MN894598, MN894599]. A phylogenetic tree was constructed using the maximum likelihood/span>method with concatenated sequences (ITS, TUB2, GAPDH, CHS and CAL) (Zhu et al. 2019). Analyses conducted in MEGA7 placed HDSN2-1 in the C. siamense clade, which includes ex-type ICMP 18578. Pathogenicity of HDSN2-1 was verified on leaves from 7 healthy 8-year-old P. × fraseri and inoculated with either 5-mm mycelial plugs from the edge of 5-day old cultures on PDA or 10 µL of spore suspension (106 conidia/mL),15 healthy plants（8-year-old）were used in 5 repetitions (5 for control, and 10 for the pathogenicity test) in the same way. Controls were treated with PDA plugs or sterile dH2O. The leaves were incubated at 25 ℃ and the inoculated plants were kept in a greenhouse (relative humidity > 85%, 25 ± 1°C). Symptoms were not observed on control plants. Fungal isolates from the symptomatic plants showed the same morphological characteristics with HDSN2-1. C. siamense is a common fungal pathogen of many plants. For example, it was previously reported infecting apples and citrus fruits ( Abirammi et al. 2019). This is the first report of anthracnose of P. × fraseri caused by C. siamense in China. References: Weir B.S., et al. 2012. Stud. Mycol. 73:115. https://doi.org/10.3114/sim0011 Zhu, L. H. et al. 2019. Plant Dis.103: 1431. https://doi.org/10.1094/PDIS-12-18-2265-PDN. Abirammi, K., et al. 2019. Plant Dis.103:768. https://doi.org/10.1094/PDIS-09-18-1489-PDN Funding: This research was financially supported by the National Key Research and Development Programme of China (2017YFD0600104).

Deciphering the chemical origin of the semen-like floral scents in three angiosperm plants.

The chemical origin and biological role of distinct semen-like odor occasionally found in some flowers are very curious but remain scarcely studied. Here, we used direct ambient corona discharge ionization mass spectrometry (MS) to study the volatile chemical composition behind the semen-like odor emitted by the fresh flowers of Photinia serrulata, Castanopsis sclerophylla and Stemona japonica without any chemical pretreatment. Chemical identification was performed using high-resolution MS analysis in combination with tandem MS analysis and whenever possible was confirmed by the analysis of standard reference compounds. A total of 19 compounds, mostly belonging to nitrogenous volatiles, were identified in P. serrulata, C. sclerophylla, and S. japonica flowers, 1-pyrroline, 1-piperideine, 2-pyrrolidone, and phenethylamine being common in all the three studied species. Several lines of evidence indicate that the major component responsible for the semen-like odor is most likely 1-pyrroline. 1-Pyrroline is most probably formed via the oxidative deamination of putrescine, as indicated by the observation of signal from 4-amino-butanal intermediate. Flower visitation observations suggest that the released volatiles serve to attract dipterans, including Syrphidae, Calliphoridae, and Muscidae. On the analytical side, the comparison of our results to earlier studies also indicate that compared to the traditional GC-MS approach the direct corona discharge ionization mass spectrometry provides more sensitive detection of VOCs with high proton affinity, in particular volatile amines, and therefore can be used to complement traditional GC-MS approach for the highest chemical coverage of VOC analysis.

Physiological and Biochemical Responses in Two Ornamental Shrubs to Drought Stress.

Drought stress is one of the most important abiotic stress limiting the plant survival and growth in the Mediterranean environment. In this work, two species typically grown in Mediterranean areas with different drought responses were used. Two shrubs, with slow (Photinia × fraseri Dress 'Red Robin') or fast (Eugenia uniflora L. 'Etna Fire') adaptation ability to drought, were subjected to three water regimes: well-watered (WW), moderate (MD), and severe (SD) drought stress conditions for 30 days. Net photosynthetic rate, stomatal conductance, maximum quantum efficiency of PSII photochemistry (Fv/Fm), relative water content (RWC), chlorophyll content, proline, malondialdehyde (MDA), and antioxidant enzyme activities (superoxide dismutase, catalase, and peroxidase) were measured. Results showed that RWC and proline were higher in Eugenia than in Photinia, demonstrating the greater tolerance of the latter to the water stress. The drought stress levels applied did not compromise photosynthetic efficiency through stomatal regulation, while a reduction of Fv/Fm ratio was observed at the end of the experimental period. MDA significantly increased after 30 days in both species. The antioxidant enzyme activities showed different responses to water stress conditions. In both species, the water stress scores showed positive, while proline content showed negative correlations with all physiological parameters.