Adaxial Leaf Surface Research Articles

Pilot Evaluation of Field Pea Accessions Under Water Deficit Conditions

Field pea, a key pulse crop for sustainable agriculture, faces significant production challenges due to drought, exacerbated by extreme climatic changes. This study evaluated 17 field pea plant introductions (PIs) and two commercial varieties under greenhouse conditions to assess their performance, determine the relationships between agronomic traits and grain yield (GY), and identify genotypes with stable yields under drought stress. Two water treatments were applied: 100% field capacity for well-watered (WW) and 60% field capacity for water deficit (WD) conditions, with drought stress imposed 21 days after planting. Significant genotypic variation was observed under both conditions. Water deficit significantly reduced GY, the number of pods per plant (NPP), plant height (PH), aboveground dry vegetative biomass (ADVB), and days to maturity (DTM) while increasing stomatal density on both adaxial (SD.ADX) and abaxial leaf surfaces (SD.ABX). Traits associated with GY in WW, such as NPP, PH, ADVB, and SD.ADX, showed stronger correlations under WD, with DTM being significantly associated with GY only in WD. Top-performing genotypes in both conditions exhibited higher pod numbers, increased aboveground dry vegetative biomass, late maturity, and lower adaxial stomatal density. Notably, PI 272215 was identified as a top performer under both conditions, with an 88% yield stability index. PI 180702 demonstrated comparable performance to PI 272215 but with no yield loss under the same conditions. These findings can be used for future field pea breeding programs aimed at developing drought-tolerant field pea varieties.

Foliar solution hydrophobicity influenced by plant species, product, and concentration

AbstractFoliar application of nutrients and pesticides is a popular practice for plant maintenance and weed control. Understanding how different products and adjuvants interact with the intended plant leaf surface will improve uptake and decrease losses. Various fertilizer, adjuvant, and pesticide solutions were tested to determine solution hydrophobicity on St. Augustinegrass, tall fescue, and white clover. A 1 µL droplet of each solution was placed on the adaxial leaf surface and imaged with a stereomicroscope to determine average solution contact angle. For all solutions groups, plant species had the most consistent effect, with white clover having the highest average contact angle followed by St. Augustinegrass and tall fescue, respectively. All product solutions significantly reduced the average contact angle compared to water. The urea solution resulted in the largest decrease for the fertilizer group at 7.6%. The largest decrease was found with the siloxane nonionic surfactant, which resulted in a decrease of 87.5% compared to water alone. Significant interactions were found between plant species and product solutions, indicating product solutions interact differently dependent upon the leaf surface characteristics. The results suggest that plant leaf surface, product solution and concentration, and their combination should be accounted for to increase wettability of a foliar application and improve product absorption.

Phyllanthus prancei sp. nov. (Phyllanthaceae), a new species from Brazilian Amazon based on specimens collected by G. T. Prance and collaborators over 50 years ago

A new species of Phyllanthus, collected by Sir Ghillean Tolmie Prance in Amazonas State, northern Brazil, is described. Phyllanthus prancei is the second known species in Phyllanthus subg. Conami sect. Calodictyon. It differs from the congeneric species P. tuerckheimii Webster by having tomentose branches, stipules and petioles, midrib tomentose only on the adaxial leaf surface, three free styles, and glandular, cupuliform, foveolate disc. A detailed description, photographs, an illustration, and comments on the distribution, habitat, phenology and preliminary conservation status are provided for the species.

First Report of Powdery mildew Caused by Golovinomyces ambrosiae on Verbena × hybrida in the U.S.

Verbena × hybrida, also known as common garden verbena, has an important ornamental value for their wide range of flower colors and for attracting hummingbirds and butterflies. During the winter of 2021-2022 (December through February), more than 50% pot-grown verbena plants showed symptoms of powdery mildew in a field trial at a Syngenta Crop Protection research facility in Vero Beach, FL. Symptoms were characterized by the development of white, superficial mycelium on the adaxial side of leaves which, eventually, progressed to covering the whole surface of leaves, causing leaf discoloration, shoot distortion, and eventual plant death. Morphological characterization was carried out by observing powdery mildew colonies under the microscope. This powdery mildew forms dense patches of white mycelia, mainly on the adaxial leaf surfaces. The mycelium was a mat of hyphae with septa. Conidiophores were erect. The foot cells were straight, followed by one to three short cells bearing short chains of up to four conidia. The conidia were hyaline and ellipsoidal to doliiform in shape. Conidial germination is of the Eudoidium type. The conidia ranged from 25 to 32 μm long by 12 to 16 μm wide. The length to width ratio ranged between 1.6 and 2.3, but most were between 2.0 and 2.2. This is further verification of its identity as Golovinomyces ambrosiae and not Golovinomyces latisporus, because the length to width ratio of the latter species is consistently less than 2.0 (Qiu et al. 2020). Chasmothecia were not observed. Additionally, the ITS, GAPDH, and IGS regions were sequenced using the primer pairs ITS4/ITS5 (White et al. 1990), PMGAPDH1/PMGAPDH3R (Bradshaw et al. 2022a), and IGS-12a/NS1R (Carbone and Kohn 1999), respectively. The ITS region (GenBank number=PP924119) cannot distinguish between G. latisporus and G. ambrosiae and as such aligned 100% with both species on GenBank. However, the GAPDH and IGS regions can be used to distinguish G. ambrosiae from G. latisporus (Bradshaw et al. 2022b). The GAPDH (GenBank number=PP931995) and IGS (GenBank number=PP931996) regions aligned 100% with multiple G. ambrosiae sequences from GenBank including ON360708 and MK452567, respectively. The specimen was deposited in the Larry F. Grand Mycological Herbarium (NCSLG 24479). To confirm pathogenicity, 'Tuscany® Pink Picotee' and 'Quartz XP Violet with Eye' plugs were transplanted to 10-cm diameter pots containing ProMix potting mix and maintained in a greenhouse (± 26 °C). Inoculation was carried out 21 days after transplanting by touching infected leaves onto healthy leaves of 15 disease-free plants of each variety. Fifteen non-inoculated plants of each variety were used as controls. Typical powdery mildew symptoms and signs were first observed ten days after inoculation and the pathogen was more aggressive on 'Tuscany® Pink Picotee'. Symptoms were not observed on non-inoculated plants. The fungus was morphologically identical to the one originally recovered from infected plants in the field. There have been many reports of Golovinomyces spp. affecting Verbena spp. worldwide; however, this is the first report of G. ambrosiae causing powdery mildew on Verbena × hybrida in the U.S. (Braun and Cook, 2012, Choi et al., 2021; Bradshaw et al. 2024). Powdery mildews reduce plant quality and decreases the aesthetics value of infected plants, causing great losses to the ornamental industry. Correct identification of the causal agent is crucial to recommend appropriate control methods, as they may differ according to the pathogen species.

First Report of Powdery Mildew on Vitis bryoniifolia Caused by Erysiphe necator in China.

Grapes, belonging to the genus Vitis, are one of the world's most economically valuable fruit crops, which are widely used as the source of wine, raisins, and juice. The genus Vitis contains about 60 species mainly distributed in Asia, Europe, and North America to northern South America (Wan et al. 2013). In May 2022, severe powdery mildew symptoms were found on wild Vitis bryoniifolia plants at Guizhou Normal University, Guiyang, China. The incidence observed was approximately 85% among 50 V. bryoniifolia plants. Infected leaves appear white powdery patches, eventually leading to chlorosis to necrosis. Mycelia occurred on adaxial and abaxial leaf surfaces, petioles and young shoots. Upon microscopic observation hyphae were hyaline and 3.5-6 μm wide. Hyphal appressoria were solitary and lobed to multilobed. Conidiophores were erect, straight to somewhat flexuous and 80-130 µm long (n = 30). Foot cells were subcylindrical to curved-sinuous at the base, followed by 2-4 cells. Conidia formed singly (occasionally 2-6 in a chain) and were ellipsoid to ovoid in shape with dimensions of 22.5-38 × 12-19.5 µm (n = 50). No fibrosin bodies were observed on conidia. Based on these morphological characteristics, the powdery mildew fungus strongly resembled Erysiphe necator (Braun and Takamasu 2000; Zheng et al. 1987) that has been shown to cause powdery mildew on Vitis (Gadoury et al. 2012; Gaforio et al. 2011; Qiu et al. 2015). To confirm the identification, the ribosomal DNA internal transcribed spacer (ITS) and the ribosomal large subunit (LSU) region were amplified and sequenced using the ITS1/ITS4 primer pair (White et al. 1990) and the NL1/NL4 primer pair (Ziemiecki et al. 1990), respectively. The spliced 1250-bp ITS-LSU sequence (GenBank accession no. PP188565) shared 99.84-100% identity with ITS-LSU sequences of E. necator (LC028995, LC028996, ON073862, LC777882, and OM033353). Based on the phylogenetic analysis of the combined ITS-LSU dataset of Erysiphe species (Takamasu et al. 2015), PP188565 was grouped in a clade with E. necator strains MUMH530, MUMHs141, and VPRI19719. To perform pathogenicity analysis, leaves of three healthy, potted 1-year-old V. bryoniifolia plants were inoculated by gently pressing with diseased leaves. Three non-inoculated healthy plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Powdery mildew symptoms, similar to field conditions were observed on inoculated plants 13 days after inoculation, whereas control plants remained symptomless. Fungus reisolated from inoculated V. bryoniifolia plants was morphologically identical to that on originally diseased plants, and the spliced ITS-LSU sequence of reisolated fungus shared 100% identity with PP188565, fulfilling Koch's postulates. Based on the morphological and molecular characterizations, the powdery mildew fungus was identified as E. necator. To our knowledge, this is the first report of powdery mildew caused by E. necator on V. bryoniifolia in China. This work further expands the host range of Erysiphe necator on Vitis species.

Stomatal patterning is differently regulated in adaxial and abaxial epidermis in Arabidopsis.

Stomatal pores in leaves mediate CO2 uptake into the plant and water loss via transpiration. Most plants are hypostomatous with stomata present only in the lower leaf surface (abaxial epidermis). Many herbs, including the model plant Arabidopsis thaliana, have substantial numbers of stomata also on the upper (adaxial) leaf surface. Studies of stomatal development have mostly focused on abaxial stomata and very little is known of adaxial stomatal formation. We addressed the role of leaf number in determination of stomatal density and stomatal ratio, and studied adaxial and abaxial stomatal patterns in mutants deficient in known abaxial stomatal development regulators. We found that stomatal density in some genetic backgrounds varies between different fully expanded leaves and recommend using defined leaves for analyses of stomatal patterning. Our results indicate that stomatal development is at least partly independently regulated in adaxial and abaxial epidermis, as i) plants deficient in ABA biosynthesis and perception have increased stomatal ratios, ii) the epf1epf2, tmm and sdd1 mutants have reduced stomatal ratios, iii) erl2 mutants have increased adaxial but not abaxial stomatal index, and iv) stomatal precursors preferentially occur in abaxial epidermis. Further studies of adaxial stomata can reveal new insights into stomatal form and function.

Contributing to the knowledge of Pantanal Flora: a new endemic species of Dimerostemma (Asteraceae: Heliantheae) from Mato Grosso do Sul, Brazil

Dimerostemma pantanalense is a new species, which is described, illustrated, and discussed in this paper. The species can only be found in the municipalities of Ladário and Corumbá, Mato Grosso do Sul state, Pantanal, Brazil. It is preliminarily categorized as Critically Endangered (CR) due to the advance of urbanization and the risk of fires in the Pantanal. It is morphologically similar to D. annuum but differs by its life-cycle perennial (vs. annual), leaves opposite and alternate (vs. only opposite), sessile (vs. subsessile with petiole up to 5 mm long), lanceolate (vs. linear), venation suprabasal acrodromous imperfect (vs. hyphodromous), adaxial and abaxial leaf surfaces strongly villous to estrigose and glandular (vs. only nearly glabrous), receptacle convex to conical (vs. only convex), phyllaries 3-seriate (vs. 2-seriate), conduplicate palea carinate-alate (vs. not carinate-alate), cypselae oblanceolate to obovate (vs. subquadrangular) and pappus coroniform with two slightly developed awns (vs. coroniform with two well-developed awns). We present photographs and line drawings of the new species, along with discussions on its geographical distribution, habitat, phenology, and conservation status. Additionally, we provide an identification key for species of the genus in the Brazilian Pantanal.

First Report of Powdery Mildew on Sophora flavescens Caused by Erysiphe diffusa in China.

Sophora flavescens (Fabaceae) is a deciduous subshrub which has been used in Chinese popular medicine for a long history (He et al. 2015). In June 2023, severe powdery mildew symptoms were observed on wild S. flavescens plants on Longwen hill of Guizhou Normal University, Guiyang, China. The incidence was approximately 80% among 100 S. flavescens plants observed. Almost all leaves were infected. Mycelia occurred on both adaxial and abaxial leaf surfaces, petioles, and stems, forming small-to-large patches. Hyphae were hyaline, 5 to 7 μm wide. Hyphal appressoria were solitary. Conidiophores were erect, straight to somewhat flexuous, and 45 to 120 µm long (n = 50). Foot cells were subcylindrical to slightly curved, followed by 2 to 3 shorter cells. Conidia formed singly, were ovoid to cylindrical, 26 to 42 × 12 to18 µm (n = 50). Based on these morphological characteristics, the powdery mildew fungus was tentatively identified as Erysiphe diffusa (Braun and Cook 2012). To confirm the identification, the ribosomal DNA internal transcribed spacer (ITS) and the ribosomal large subunit (LSU) region were amplified and sequenced using primer pairs ITS1/ITS4 (White et al. 1990) and NL1/NL4 (Ziemiecki et al. 1990), respectively. The obtained 647-bp ITS sequence (GenBank accession no. PP130131) displayed 100% identity with the ITS sequences of E. diffusa. The obtained 618-bp LSU sequence (GenBank accession no. PP693303) displayed 100% identity with the ITS sequences of E. diffusa (MT325922 and MT628019) and E. manihoticola (MT106658 and MT106660). Using a phylogenetic tree based on the combined ITS-LSU data, the isolate was grouped in a clade with the E. diffusa strain (GenBank accession no. LC777871). To fulfill Koch's postulates, leaves of three healthy potted S. flavescens plants were inoculated by gently pressing with diseased leaves. Non-inoculated plants were used as controls. All plants were incubated in a greenhouse at 25 ± 2°C, 80% relative humidity. After 15 days, typical powdery mildew symptoms were observed on the inoculated plants, whereas no symptoms were found on the control plants. The reisolated fungus from the inoculated S. flavescens was morphologically identical to that on naturally diseased plants, and the ITS sequence of the reisolated fungus showed 100% identity with PP130131. As the causal fungus of soybean powdery mildew, E. diffusa is known to infect papaya and other legumes, including Lens culinaris and Mimosa caesalpiniifolia (Attanayake et al. 2009; Luz et al. 2019). Particularly, E. diffusa has been previously reported to infect S. flavescens in the United Kingdom (Jones and Baker 2007; Bradshaw et al. 2023), but this is the first report of S. flavescens powdery mildew caused by E. diffusa in China. This work further expands the geographical range of E. diffusa-infected S. flavescens plants.

Amphistomy: stomata patterning inferred from 13C content and leaf-side-specific deposition of epicuticular wax.

The benefits and costs of amphistomy (AS) vs. hypostomy (HS) are not fully understood. Here, we quantify benefits of access of CO2 through stomata on the upper (adaxial) leaf surface, using 13C abundance in the adaxial and abaxial epicuticular wax. Additionally, a relationship between the distribution of stomata and epicuticular wax on the opposite leaf sides is studied. We suggest that the 13C content of long-chain aliphatic compounds of cuticular wax records the leaf internal CO2 concentration in chloroplasts adjacent to the adaxial and abaxial epidermes. This unique property stems from: (1) wax synthesis being located exclusively in epidermal cells; and (2) ongoing wax renewal over the whole leaf lifespan. Compound-specific and bulk wax 13C abundance (δ) was related to amphistomy level (ASL; as a fraction of adaxial in all stomata) of four AS and five HS species grown under various levels of irradiance. The isotopic polarity of epicuticular wax, i.e. the difference in abaxial and adaxial δ (δab - δad), was used to calculate the leaf dorsiventral CO2 gradient. Leaf-side-specific epicuticular wax deposition (amphiwaxy level) was estimated and related to ASL. In HS species, the CO2 concentration in the adaxial epidermis was lower than in the abaxial one, independently of light conditions. In AS leaves grown in high-light and low-light conditions, the isotopic polarity and CO2 gradient varied in parallel with ASL. The AS leaves grown in high-light conditions increased ASL compared with low light, and δab - δad approached near-zero values. Changes in ASL occurred concomitantly with changes in amphiwaxy level. Leaf wax isotopic polarity is a newly identified leaf trait, distinguishing between hypo- and amphistomatous species and indicating that increased ASL in sun-exposed AS leaves reduces the CO2 gradient across the leaf mesophyll. Stomata and epicuticular wax deposition follow similar leaf-side patterning.

Hyperspectral and Chlorophyll Fluorescence Analyses of Comparative Leaf Surfaces Reveal Cellular Influences on Leaf Optical Properties in Tradescantia Plants.

The differential effects of cellular and ultrastructural characteristics on the optical properties of adaxial and abaxial leaf surfaces in the genus Tradescantia highlight the intricate relationships between cellular arrangement and pigment distribution in the plant cells. We examined hyperspectral and chlorophyll a fluorescence (ChlF) kinetics using spectroradiometers and optical and electron microscopy techniques. The leaves were analysed for their spectral properties and cellular makeup. The biochemical compounds were measured and correlated with the biophysical and ultrastructural features. The main findings showed that the top and bottom leaf surfaces had different amounts and patterns of pigments, especially anthocyanins, flavonoids, total phenolics, chlorophyll-carotenoids, and cell and organelle structures, as revealed by the hyperspectral vegetation index (HVI). These differences were further elucidated by the correlation coefficients, which influence the optical signatures of the leaves. Additionally, ChlF kinetics varied between leaf surfaces, correlating with VIS-NIR-SWIR bands through distinct cellular structures and pigment concentrations in the hypodermis cells. We confirmed that the unique optical properties of each leaf surface arise not only from pigmentation but also from complex cellular arrangements and structural adaptations. Some of the factors that affect how leaves reflect light are the arrangement of chloroplasts, thylakoid membranes, vacuoles, and the relative size of the cells themselves. These findings improve our knowledge of the biophysical and biochemical reasons for leaf optical diversity, and indicate possible implications for photosynthetic efficiency and stress adaptation under different environmental conditions in the mesophyll cells of Tradescantia plants.

First Report of Powdery Mildew on Quercus fabri and Q. robur Caused by Erysiphe quercicola in China.

Quercus (Fagaceae) is a genus of ecologically and economically important shrub and tree species (Yin et al. 2018). In April 2022, powdery mildew symptoms were observed on Quercus fabri and Quercus robur leaves on Longwen hill, Guizhou Normal University, Guiyang, China. The incidence was 30% (Q. fabri, n = 50) and 20% (Q. robur, n = 30), respectively. Powdery mildew fungi from these two Quercus species shared similar morphological characteristics. Mycelia occurred on adaxial and abaxial leaf surfaces, forming small to large patches; hyphae were hyaline, 3-7 µm wide; hyphal appressoria were lobed to multilobed, solitary; conidiophores were erect, straight, 36-80 µm long (n = 30); foot cells were followed by 1-2 shorter cells; conidia formed singly, obovoid to ellipsoid, 24-38 × 12-27 µm (n = 50), without fibrosin bodies; no chasmothecia were observed. Based on these characteristics, powdery mildew fungi on both Q. fabri and Q. robur were identified as Erysiphe quercicola (Takamatsu et al. 2007). To confirm the identification, ribosomal DNA internal transcribed spacer (ITS) sequences of two fungal samples from Q. fabri and Q. robur were separately amplified and sequenced using primer pair ITS1/ITS4 (White et al. 1990). The obtained ITS sequences (GenBank accession nos. QR414372 and QR414373, respectively) shared 100% identity, and 99.38-99.84% identity with diverse ITS sequences of E. quercicola (Takamatsu et al. 2015). In a phylogenetic tree based on ITS sequences of Erysiphe species (Takamatsu et al. 2007), QR414372 and QR414373 were grouped in a clade with ITS sequences of E. quercicola. To fulfil Koch's postulates, leaves of three healthy potted Q. fabri plants and three healthy potted Q. robur plants were inoculated by gently pressing diseased Q. fabri and Q. robur leaves onto healthy leaves. Non-inoculated healthy Q. fabri and Q. robur plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Typical powdery mildew symptoms were observed on all inoculated plants 15 days after inoculation, whereas no symptoms were observed on control plants. Fungi separately reisolated from inoculated Q. fabri and Q. robur were morphologically identical to those on their originally diseased plants, and ITS sequences of reisolated fungi shared 100% identity with QR414372 and QR414373. E. quercicola has previously been reported to infect Quercus species, including Q. robur in Australia, Q. crispula, Q. phillyraeoides and Q. serrata in Japan, and Q. phillyraeoides in Korea (Lee et al. 2011). In China, Q. fabri and Q. robur may be infected by E. alphitoides and E. hypophylla, respectively (Zheng et al. 1987). To our knowledge, this is the first report of powdery mildew caused by E. quercicola on Q. fabri and Q. robur in China. This work provides a foundation to protect Quercus plants against this fungal pathogen.

Southern blight of water lily: The first host record of Agroathelia rolfsii on Nelumbo nucifera discovered in Florida, USA.

Nelumbo nucifera Gaertn. (Nelumbonaceae, Eudicots), also known as water lily or sacred lotus, is a nonnative and invasive plant commonly found in artificial ponds and natural lakes throughout Florida (UF-IFAS 2023; Wunderlin et al. 2023). In August 2020, a single sample of water lily plants showing large leaf spots were collected at a residence in Dunnellon, Marion County, Florida (80% disease prevalence with 40% leaf coverage). Symptoms and signs of the disease were necrotized adaxial leaf spots only, bordered by whitish mycelia and hyphae with clamp connections, and whitish to light brown sclerotia formed in the center (<0.7 mm diameter). Symptomatic tissue was plated on acid potato dextrose agar (APDA) amended with chloramphenicol (100 mg/L) and ampicillin (30mg/L), and incubated at 20 °C for one week. Data supporting the molecular identification of this putative pathogen were gathered by PCR amplification and Sanger sequencing of the complete internal transcribed spacer (ITS) and a fragment of the large subunit (LSU) of the rRNA gene (~1.5 kb) using primers ITS1F and LR5 (FDACS-DPI PPST 2020-105211, GenBank OR492009) (White et al. 1990). The identification of the host was confirmed by Sanger sequencing of three plant barcode fragments: ITS2 (ITS2-S2F/ITS4, OR492008), ribulose 1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) (rbcLa-F/rbcLa-R, GenBank OR502388), and Maturase K (matK) (matK-KIM1R/matK-KIM3F, GenBank OR502389) (Fazekas et al. 2012). MegaBLAST queries of the ITS/LSU sequence obtained here recovered a 99.61% match to the fungal pathogen Agroathelia (=Athelia) rolfsii (Sacc.) Redhead & Mullineux. (Redhead and Mullineux 2023) (Amylocorticiaceae, Agaricomycotina) strain GP3 (GenBank JABRWF010000005) (Yan et al. 2021). MegaBLAST queries of three host plant DNA barcodes recovered matches of greater than 99.62% similarity to N. nucifera sequences. After diagnosis, symptomatic dried leaf samples were deposited at Plant Industry Herbarium Gainesville (PIHG 17807) and an axenic culture was deposited at the Agricultural Research Services Culture Collection (NRRL 66964). Koch's postulates were fulfilled by the inoculation of sclerotia (as in Terrones-Salgado et al. 2022) on adaxial leaf surface of four-week- old water lily transplants obtained from an artificial pond on campus (two plants with five leaves each). One additional transplant was not inoculated and served as a control; this plant remained asymptomatic during the experimentation period. Each transplant was kept in a 27-gallon plastic container (21W × 30L × 14H in) filled with tap water containing one tablespoon of 20-20-20 all-purpose-water-soluble plant fertilizer (VPG, TX, USA) in a plant biosafety level 2 greenhouse (23 °C, >50% relative humidity, and a 12-h/12-h photoperiod). All inoculated leaves showed necrotized areas after one week and new sclerotia were observed floating on the water surface after three weeks. Fungal pathogen was reisolated and reidentified subsequently. Agroathelia rolfsii is the causal agent of southern blight, also known as grey rot, and is reported from at least in 260 plant genera, including specialty crops such as citrus, cucumber, pepper, peanuts, pumpkin, and strawberry (Farr and Rossman 2018). Agroathelia rolfsii usually causes lower stem, crown, and root rots; consequently, leaf spots are a noteworthy presentation of symptoms for this fungus.

First Report of Rust Disease on Alcea rosea caused by Puccinia modiolae in China.

Alcea rosea, belonging to the Alcea genus in the Malvaceae family, originated from China, but it is now grown worldwide. A. rosea has been widely used in traditional Chinese medicine to alleviate constipation, pain, swelling, and sores. In February 2023, typical symptoms of fungal infection were observed on A. rosea at Guizhou Normal University in Guiyang, Guizhou Province, China. The disease incidence was over 90% (n = 100) for the surveyed A. rosea plants, and the disease severity range from 30% to 90%. The initial symptoms of A. rosea rust were the appearance of chlorotic spots on the leaves. Subsequently, numerous reddish to dark-brown erumpent pustules (telia) were observed. Gradually, the entire plant was covered by rust and the center of each lesion turned brown, necrotic, and ruptured over times, eventually causing defoliation. Voucher specimens of infected A. rosea leaves as representative samples have been deposited at Guizhou Normal University (GNU2023LS008). Telia are round in shape, mostly aggregated in mass, with a diameter of 0.28-0.78 mm (0.46 mm, n = 20). They range in color from reddish-brown to dark brown, and are mainly hypophyllous but occasionally formed on the adaxial leaf surface. The teliospores are fusoid with dimensions of 31.3-93.8 × 10.9-21.3 μm (57.5 × 15.1 µm average, n = 50), hyaline or yellowish to light-brown in color, mostly two-celled, with a smooth wall (1.5-3.0 µm) and a thickened apex (3.0-9.0 µm). However, teliospores which are one-, three-, or four-celled with a notch at the apex, are rarely observed. The morphological characteristics of host symptoms and teliospores were similar to those of Puccinia modiolae (Aime and Abbasi 2018; Albu et al. 2019). For phylogenetic analysis, genomic DNA was extracted from the teliospores of infected leaves. To confirm the species-level identification, PCR was performed on the extracted DNA to amplify the ribosomal DNA internal transcribed spacer (ITS) and large subunit (LSU) regions using primer pairs ITS1/ITS4 (Schoch et al. 2012) and NL1/NL4 (Ziemiecki et al. 1990), respectively. The resulting ITS DNA sequence (GenBank accession no. OR607960) showed 100% identity with P. modiolae sequences (OP369291.1), when the query coverage was 100%. The LSU DNA sequence obtained (OR607961.2) shared 99.85% similarity with P. modiolae (MK458702.1). A phylogenetic tree was constructed using MEGA7.0 and the maximum likelihood method based on the ITS and LSU sequences. The fungal isolates collected in this study and several reference sequences of P. modiolae were grouped within a clade that included the isolates reported on A. rosea in Korea (Ryu et al. 2023), with 100% bootstrap support. Pathogenicity testing was conducted by gently pressing spore powder of naturally diseased leaves onto young leaves of three healthy A. rosea plants, with three noninoculated healthy plants serving as controls. The inoculated and noninoculated plants were kept in a growth chamber at the 26°C with a 12 hour light/dark cycle and 80% humidity. After 2 weeks, all inoculated A. rosea plants showed characteristic disease symptoms of rust infection and telia of P. modiolae, while control plants remained symptomless. The pathogen was identical to that observed on the original diseased leaves. The study results indicate that the causal fungus responsible for the disease is P. modiolae, which has been previously reported on Malvaceae plants (Farr and Rossman 2022). To the best of our knowledge, this is the first report of P. modiolae on A. rosea in China. This study will contribute to an increased understanding of the host range of Puccinia modiolae.

First report of Puccinia xanthii causing rust disease on Xanthium orientale in Korea.

Puccinia xanthii Schw. is a microcyclic rust fungus, first found on Xanthium strumarium Lour in North Carolina, the United States. This rust fungus is native to the continental United States, Hawaii, Mexico, and the West Indies (Arthur 1934). It has become notoriously invasive and is now distributed in the Europe (Bulgaria, France, Hungary, Italy, Romania, Spain, and the former Yugoslavia), India, Indonesia, Australia, and South Africa (Parmelee 1969; Alcorn 1976; Wahyuno 2012). In East Asia, the fungus has been reported in Japan (Hiratsuka et al. 1992) and China (Zhao et al. 2014) but not in Korea. It has been reported mainly on the invasive weeds Xanthium and Ambrosia species. In addition, it rarely occurs on sunflowers (Helianthus spp.) in Australia (Alcorn 1976), South Africa (Pretorius et al. 2000), and North America (Gulya and Charlet 2002). In Korea, rust disease symptoms caused by a Puccinia fungus were first found on X. orientale L. at the roadside of Okcheon-gun, Chungcheongbuk-do (36 27'95.428"N 127 66'26.378"E) in October 2021 and were repeatedly observed in the same site in 2022. The similar symptom was additionally found on X. orientale in Yesan-gun, Oct. 2022. The symptoms were brown spots on round chlorotic haloes on the adaxial leaf surface and dark brown pustules on the abaxial leaf surface. Telia were brown to dark brown, round, mostly grouped, 0.28-0.61 mm in diameter, and mainly formed on the abaxial leaf surface but sometimes on the adaxial leaf surface. Teliospores were two-celled, pedicellate, and measured 37.6-110 × 12.4-21.5 μm in size; the wall was yellowish or almost colorless, smooth, 1.2-2.6 μm thick at the sides, and up to 7.4 μm thick at the apex. The morphological characteristics of the teliospores were identical to those of P. xanthii described by Arthur (1934) and Parmelee (1969). Based on phylogenetic analyses (e-Xtra 2) of the internal transcribed spacer (ITS) and partial large subunit (LSU) rDNA extracted from the teliospores, they were identified as P. xanthii. BLAST analysis showed that the sequences had high homologies (over 99.82%) with the reference strains of P. xanthii (EF635903 and KX999896). The representative specimens were preserved at the Animal and Plant Quarantine Agency Herbarium (PQK211005 for Okcheon-gun isolate and PQK220913 for Yesan-gun) and the sequences were deposited in GenBank (OR958716 and OR958692). A pathogenicity test was performed by dropping a suspension of germinating teliospores and basidiospores onto the adaxial leaf surfaces of apparently healthy X. orientale plants in Oct. 2022, using the isolate PQK220913 (OR958692). The three inoculated plants were placed together with three controls treated with only distilled water, in the dark at saturated humidity for 24 hours in an isolated greenhouse. After two weeks, typical rust symptoms were observed in the three infected plants, whereas no symptoms appeared in the control plants (e-Xtra 1). The causal fungus was identified as P. xanthii based on host relationships, successful experimental inoculation, morphological characteristics, and sequence similarity of partial DNA fragments. To our knowledge, this is the first report of P. xanthii on X. orientale in Korea. P. xanthii was additionally confirmed on X. orientale in Gumi-si, Boeun-gun, Seongju-gun, Naju-si, and Gunsan-si in 2023, indicating its wide distribution in Korea. It is expected that P. xanthii could be a candidate as a biological agent for controlling the invasive weed, X. orientale.

Occurrence of Powdery Mildew Caused by Erysiphe corylacearum on Hazelnuts in Israel

Hazelnut (Corylus avellana L) is an emerging crop in Israel, primarily cultivated as a host plant to establish truffle plantations through symbiosis with ectomycorrhizal fungi. A significant damage and yield reduction is caused by the prevalent occurrence of powdery mildew in hazelnut trees (Sezer et al., 2017). Until recently, Phyllactinia guttata was considered the primary pathogen in Western Asia, the Caucasus region, and Europe (Abasova et al. 2018; Arzanlou et al. 2018; Mezzalama et al. 2021). However, in the last years, a new destructive species Erysiphe corylacearum has been identified as the pathogen of powdery mildew on hazelnuts in these regions (Meparishvili et al. 2019; Mezzalama et al. 2021; Kalmár et al. 2022; Zajc et al. 2023). In May 2022, powdery mildew symptoms were observed on hazelnut plants in the Ein-Zivan truffle plantation, gardens of Merom-Golan, and the adjacent garden of the packing house Pri-Beresheet in the northern Golan region of Israel. Symptoms were observed on the abaxial and adaxial leaf surfaces, fruits, and husks. Disease incidence and severity ranged between 30-70% and 5-90%, respectively. Disease severity was significantly greater on the leaves of the offshoots compared to those on the tree canopy. Morphological characterization of leaf samples from ten different trees showed the following characteristics: hyphal appressoria were lobed, solitary, 1–4 μm in diameter; mycelium was amphigenous, hyaline, and septate; conidiophores vertically elevated from the mycelium 50– 80 μm long. Conidia (n= 30) on conidiophores were hyaline, ellipsoid to ovoid, 24 – 34 μm long and 15.5 – 23 μm wide. Chasmothecia in several maturation degrees appeared in October on both sides of the leaves. They were spherical (n= 30) 86 – 125 μm in diameter, with 7 - 14 aseptate straight appendages, 67 - 96 μm long, 4.9 - 7.1 μm wide, dichotomous branched at the end 42 - 56 μm wide. In each chasmothecia, there were 3-5 asci (n=30) with a width of 38 – 43 μm and a length of 48–64 μm of oval-ellipsoid shape. Asci contained 4-8 ascospores (n=30), 18 - 26 μm long and 11 - 15.5 μm wide. A pathogenicity test was conducted to fulfill Koсh’s postulates. Both detached leaves and plants of C. avellana were artificially infected by brushing conidia from infected leaves. Inoculated leaves in Petri dishes on 2% water agar (n= 5), and plants (n= 5) were incubated under 25°C and 12-h photoperiod/day. Untreated leaves and plants served as control. Typical symptoms appeared on the upper surface of the leaves within 7-10 days after inoculation. No symptoms were found on untreated control plants or detached leaves. The fungus isolated from the inoculated leaves was morphologically identical to the original isolates from natural diseased plants. DNA was extracted and the rDNA internal transcribed spacer region of five isolates originated from leaves of the tree canopy and offshoots was amplified using primers ITS1 and ITS4, and sequenced. BLAST analysis of 595 bp fragments (all identical and represented by isolate Cora1, GenBank Accession No. OR752437) showed 99% identity to ITS rDNA sequences of E. corylacearum from Georgia (MK157199) and 100% identity to isolates from Azerbaijan, Turkey and Italy (LC270863, KY082910 and MW045425, respectively) and only 83% similarity to P. guttata (accession number AB080558). To the best of my knowledge this is the first report on E. corylacearum causing powdery mildew in Israel. Future control measures to manage the disease on hazelnuts in truffle plantations in Israel should be considered.

New findings of gymnosperms in the Middle Jurassic of the East European platform

The plant-bearing layers in the Stoilensky open mine (Belgorod Region, Russia) are dated to the middle Bathonian–early Callovian based on the dinoflagellate cysts and spore-pollen assemblages, and in the Mikhailovsky open mine (Kursk Region, Russia) – to the middle–late Bathonian based on palynological data. Representatives of Pseudotorellia are recorded in the Middle Jurassic of the Belgorod and Kursk regions for the first time. A new species, Pseudotorellia oskolica, is described from the Stoilensky open mine based on the unique morphological and epidermal features. Leaves of this species are very narrow, they are characterized by the presence of stomata on the adaxial leaf surface. The type material of Czekanowskia europea from the Middle Jurassic of the Pripyat depression in Belarus was restudied. The diagnosis for C. europea is provided, since only a description of this species was given in the original publication. Czekanowskia leaves are recorded from the Belgorod and Kursk regions for the first time. They are determined as C. europea based on the similar epidermal features as in the type leaves. A shoot of Pagiophyllum sp. and numerous leaf fragments of Podozamites sp. were found in association with C. europea in the Pripyat depression. These genera are recorded in Belarus for the first time. Findings of Pseudotorellia, Czekanowskia and Podozamites leaves in the Middle Jurassic floras of the East European platform are discussed.

A new Begonia species (sect. Baryandra, Begoniaceae) from Batangas Province, Luzon Island, Philippines

Begonia tanauanensis is a newly described endemic species in B. sect. Baryandra from Tanauan City, Batangas, southern Luzon, Philippines. Morphological data shows this species resembles B. chingipengii, a species from eastern Luzon as both species have light pink flowers, fleshy green lamina, and boat-shaped bracts. However, B. tanauanensis does not have the prominent white midrib and veins in the adaxial leaf surface, ciliate hairs on leaf margin, strongly keeled stipules and tomentose hairs on the abaxial leaf surface and petioles of B. chingipengii. The plants were observed to have a restricted and severely fragmented distribution. Unfortunately, these observed populations are also affected by human activities and threat of volcanic activity of the nearby Taal Volcano. Because of these threats, we provisionally assess the species as “Critically Endangered” (CR) following the IUCN Red List Categories and Criteria.

The leaf micromorphology and anatomy of gamba grass, Andropogon gayanus Kunth (Poaceae: Panicoideae)

Context Andropogon gayanus, commonly known as gamba grass, is one of the declared weeds of national significance in Australia. Past studies have focused on gross morphology of root structures, biogeochemical behaviour, and ecology, but there has been limited work on comparative descriptions of leaf micromorphology and anatomy. Aims We investigated and described its leaf micromorphology and anatomy to understand weed biology and ecophysiology. Methods Optical and scanning electron microscope examination of the adaxial and abaxial leaf surfaces of A. gayanus was carried out. We identified and generated a list of morphological characters that were used to compare several dried herbarium specimens of A. gayanus. Key results The leaf characters were consistent across all specimens examined, with minor differences in leaf pubescence, indicating this could be a plastic trait. Conclusions Andropogon gayanus leaves are well adapted to wet and dry tropical conditions. Plasticity in leaf surface pubescence possibly enhances its adaptability, increasing its success as a weed in Australian ecosystems. The success of A. gayanus in Australia could be because the environment compares favourably with the native environment of the species in Africa, where it has adapted to extremes of wet and dry conditions over a large geographical range. Implications Plant morphological and taxonomic studies of A. gayanus focused on describing characters of spikelets and caryopses are recommended to understand how reproductive structures aid in its successful proliferation.

Morphology and excreting-function of microhairs in salt-tolerant Zoysia japonica, comparing adaxial and abaxial leaf surfaces

Bicellular trichomes called ‘microhairs’ are known as ‘salt glands’ in some Chloridoideae in the Poaceae. The adaxial leaf surface of Zoysia japonica, a salt-tolerant grass, excretes salts, whereas the abaxial leaf surface does not. In this study, we investigated the morphology and excreting-function of the microhairs of Z. japonica, comparing the adaxial and abaxial leaf surfaces. Scanning electron microscopy of the leaf surfaces showed the distribution of microhairs on both sides and revealed significant excretion on the adaxial side but a small excretion on the abaxial side. Energy-dispersive X-ray spectrometry revealed that microhairs on the adaxial side excrete sodium, magnesium, and chlorine, whereas those on the abaxial side excrete or secrete insoluble substances, which sometimes contain silicon. Transmission electron microscopy was used to clarify the ultrastructure of microhairs, as in the first detailed report on Zoysia spp.; however, the microhairs on both leaf sides showed typical structures of bicellular salt glands reported in Chloridoideae. The cap cells of the microhairs had smooth surfaces without epicuticular wax structures. These results indicate that the ultrastructural features of Z. japonica microhairs are important for understanding physiological mechanisms in common with salt-excretion and the excretion or secretion of other substances.

Analogous Charging Effect of Surfactant-Pesticide Spray Jet on Droplet Characteristics and Deposition on Hydrophobic Leaf Surfaces

An induction charging principle had been applied to enhance spray droplet characteristics and quantity deposition on hydrophobic abaxial-adaxial leaf surfaces from pesticide EC Glyphosate [C3H8NO5P] and surfactant Silwet L-77 [C13H34O4Si3] formulations. A nozzle cap containing two electrodes (spacing at 9 mm apart) was used to superpose charges to spray droplets under applied voltages of 2–12 kV in an electric field (E) of 8.9 × 105 V/m. From a tee-jet flat fan (TP11004VS) nozzle tip fitted into the electrode cap and positioned at 60 cm high above targeted Brassica campestris leave surfaces, the spray droplets were directed onto the leaves at a liquid flow pressure of 4 bar and travelling speed of 2 m/s. The measurements were done using Keithsley picoammeter to quantify spray chargeability (CMR), droplet sizes by lesser particle size analyzer (LPSA) and deposition on leaf surfaces by high-speed camera. In effect, droplet sizes of EC, L-77 and EC + L-77 decreased with an increasing applied voltage. The CMR of L-77 was lower than EC and highest for EC + L-77 composite solution. Based on Image analysis of droplets density per leaf area, maximum exposure of adaxial leaf surfaces intercepted many charged spray droplets than abaxial surfaces. As regressed, the quantity of charged spray deposition from EC + L-77 formulation was highest at both adaxial (approx. 27.44 Qd/cm2) and abaxial (approx. 5.57 Qd/cm2) hydrophobic leaf surfaces than EC of 26.12: 3.19 Qd/cm2 and L-77 of 24.80: 2.53 Qd/cm2, respectively. Also, contact angle, Theta E, of charged spray droplets was smaller than Theta C on adaxial than abaxial leave surfaces, a phenomenon attributed to high chemo-electrical properties of formulations that aided the direct flight, coiling and deposition of droplets in order of EC &gt; EC + L-77 &gt; L-77. Generally, there was no observable droplet rebound; hence, surfactant-pesticide composite spraying is considered suitable for electrostatic application in plant protection technology. Therefore, for effective application, charged droplets from glyphosate EC in silwet L-77 solution should be recommended, as it provides optimum droplet sizes, chargeability, contact angle and deposition on hydrophobic leave surfaces.