Petiole Bases Research Articles

Characterization of hemicellulose in sacred lotus (Nelumbo nucifera Gaetn.) petiole during xylogenesis

Hemicelluloses play a crucial role in connecting cellulose and lignin within the plant cell wall and find extensive biotechnological applications. There is a notable gap in research concerning the hemicellulose from Nelumbo nucifera, the basal eudicot adapted to aquatic environments. To fill this gap, hemicellulose characteristics from the apical to the basal segments of petioles from 4-month-old N. nucifera plants were examined. Results showed that during the initial phase of xylogenesis, xyloglucan predominated in the hemicellulose fraction, while later stages were gradually dominated by 4-O-methyl-D-glucurono-D-xylan (MGX). Having a typical tetrasaccharide reducing end, the glucuronoxylan in N. nucifera was also shown with a typical the MeGlcA on the C2 Xyl carbon sidechain. The total degree of acetylation increased from apex (0.45) to base (0.55) of petiole. Notably, no arabinosyl side-chains were detected in the N. nucifera xylan, suggesting that N. nucifera hemicellulose aligns most closely with dicot wood rather than the non-commelinid monocot (grass). Transcriptomic analysis also indicated that the middle and basal region exhibited higher xylan synthesis activity. This study contributes new evidence supporting the conservation of dicotyledonous hemicellulose during evolution.

First Report of Dickeya dadantii Causing Potato Blackleg in Fujian Province China.

Blackleg and soft rot are harmful diseases in potato (Solanum tuberosum) caused by Pectobacterium spp. and Dickeya spp. (Czajkowski et al. 2015). The occurrence of potato blackleg was serious in potato-producing areas around Xiapu County in Fujian Province, China, in 2021 (6 ha) and 2022 (7 ha), with an incidence of approximately 5%, which reached nearly 23%. Three diseased plants were collected to isolate the pathogen. Single colonies from each sampled plant were isolated and streaked onto fresh plates. DNA from three colonies from different plants was PCR amplified with primer pair 27F/1492R (Lane 1991) for the 16S rRNA gene. Since the sequences were identical, we selected strain M2-3 for further analysis. The strain M2-3 was gram-negative, pectolytic on CVP, grew at 37°C and 5% NaCl. The bacterium was positive for phosphatase activity, erythromycin sensitivity, indole production, gelatin liquefaction, malonic utilization, and acid production from, melibiose, raffinose, and arabinose. The bacterium was negative for sucrose, α-methyl glucoside, sorbitol, trehalose, lactose, and sodium citrate (Fujimoto et al. 2018;),although sucrose and lactose did not provide the expected results, there are exception in all species. The genome of strain M2-3 was sequenced and deposited in the NCBI database under accession numbers: CP077422. An Average Nucleotide Identity (ANI) analysis showed that M2-3 clustered with other D. dadantii strains and has a 98.39% identity with D. dadantii strain DSM 18020 (CP023467). The housekeeping genes (recA, dnaX, acnA, gapA, icd, mdh, mtlD and pgi) were amplified with primer pairs designed previously(Fujimoto et al. 2018; Ma et al. 2007) and sequenced. A multilocus sequence analysis (MLSA) was performed by concatenating the 8 gene sequences and constructing a maximum likelihood phylogenetic tree using PhyloSuite version 1.2.1 (Zhang et al. 2020) and IQ-tree version 1.6.8 (Nguyen et al. 2015) software. Strain M2-3 was clustered together with Dickeya dadantii. For the pathogenicity test, three plants per treatment, totaling nine plants, were used. Bacterial suspensions (1×10^8 CFU/mL) were made in a 10mM PBS buffer. 10 μL of M2-3, D. dadantii type strain 18020 (positive control), and buffer (negative control) were injected into the plant stems near the base. Water stains appeared at the site of inoculation after 2 days and they gradually became black and rotten. The leaves became yellow and wilted, and the petiole base rotted within 5 days of inoculation completing the Koch postulate. According to average nucleotide identity and housekeeping gene sequence analysis, strain M2-3 was identified as Dickeya dadantii. Previous studies have reported several pathogens that cause potato blackleg in China, including P. atrosepticum, P. carotovorum, P. brasiliense, P. parmentieri, P. polaris, and P. punjabense (Li-ping et al. 2020; Wang et al. 2021). To the best of our knowledge, this study is the first to report potato blackleg disease caused by Dickeya dadantii in Fujian Province, China. This finding suggests that this pathogen may cause a threat to potato production in Fujian Province.

Stipules in angiosperms

Abstract Stipules are generally regarded as the outgrowths of the leaf base in angiosperms. Other interpretations see stipules as independent organs comparable to leaves. Stipules have been recognized as an important trait for plant taxonomy and identification, and there has been great progress in the understanding of their morphology, development, origin, function, and gene regulation over time. Therefore, this review will briefly summarize past research and aims to clarify the occurrence, location, and morphology of stipules in the families recognized by APG IV and reconstruct their ancestral states. Additionally, the developmental morphology of different types of stipule is presented through scanning electron microcopy observations and a survey of the existing literature. The difference between stipules and ligules is discussed in relation to the occurrence of postgenitally or congenitally fused ‘continuous’ stipules. A distinction is made between ‘true’ stipules and ‘pseudostipules’. The origin of stipules at the base of the leaf is explained from different perspectives. About one-third of the families are reported to have stipules, mostly concentrated in the Rosid clade with the highest level of diversity. On the basis of the ancestral state reconstructions, stipules may be absent in the ancestors of angiosperms, but are present in the ancestor of Rosids, with a pair appearing on both sides of the petiole base. The transition between paired and annular stipules is discussed, the latter arising postgenitally or congenitally. Several hypotheses are discussed to explain the abundance of stipules in the Rosid clade and their limited presence in the Asterid clade.

Polystichum lionelii (Dryopteridaceae), a new Andean species from northwestern Argentina

Polystichum lionelii, a new fern species from the Andean mountain grasslands of northwestern Argentina, is described and illustrated. It is morphologically well differentiated from the other species occurring in the region, showing some relationships especially with P. pycnolepis particularly by the morphology of the pinnules. However, the new species differs from the latter in significant characters, the rhizome scales are ovate to ovate-lanceolate, the basal petiole scales are concolorous, and lamina with filiform scales and multicellular hairs on the abaxial side. An identification key to all Polystichum taxa currently known to occur in the northwestern Argentina is presented.

Arboreality in blindsnakes (Typhlopidae) and threadsnakes (Leptotyphlopidae) from Hispaniola

Scolecophidian snakes, which include the blind and thread snakes (Miralles et al. 2018), usually have fossorial or ground-dwelling life styles, although some are known to climb rocks or vegetation. Das and Wallach (1998) reviewed cases of arboreality in this group, and additional records have been published since (Bazzano 2007; Murphy et al. 2016; Harrington et al. 2018; Kraus 2017; Repp 2019; de Fraga and de Carvalho 2022). The natural history of these snakes on Caribbean islands is poorly known. Henderson and Powell (2009) compiled natural history information on Caribbean herpetofauna in which definite climbing behavior is mentioned only for three species of Typhlopidae. According to the current zoogeographical definition of the Caribbean region (Hedges et al. 2019), records of arboreality in scolecophidian species can be expanded. The new addition is for the leptotyphlopid Epictia tenella (Klauber), which was recorded 1.5 m high in a tangle of lianas lying against a trunk (Murphy et al. 2016). For Typhlopidae, Antillotyphlops catapontus (Thomas) was found climbing into big carton nests of termites (Lazell 2006), A. richardii (Duméril and Bibron) was found 1.5 m high in a tree (Metopium toxiferum; Tolson and Campbell 1989), and Typhlops lumbricalis Linnaeus was found 1 m above the ground in a rotting petiole base still attached to a fan palm (Schwartz and Henderson 1991). Arboreal or climbing behavior in scolecophidian snakes occurs when the snakes follow chemical cues left by their prey, which consist usually of ants and termites (Gehlbach et al. 1971; Webb and Shine 1992). Here, I report observations of scolecophidian snakes from Hispaniola that were actively exposed on plants or found within epiphytes in trees. Additionally, I include one observation on the diurnal activity of a leptotyphlopid snake. These records appear to be the first for any Hispaniolan scolecophidian. Specimens were collected and deposited in the Museo Nacional de Historia Natural Eugenio de Jesus Marcano (MNHNSD) of Santo Domingo, Dominican Republic.

Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics

Plants detect their neighbors via various cues, including reflected light and touching of leaf tips, which elicit upward leaf movement (hyponasty). It is currently unknown how touch is sensed and how the signal is transferred from the leaf tip to the petiole base that drives hyponasty. Here, we show that touch-induced hyponasty involves a signal transduction pathway that is distinct from light-mediated hyponasty. We found that mechanostimulation of the leaf tip upon touching causes cytosolic calcium ([Ca2+]cyt induction in leaf tip trichomes that spreads towards the petiole. Both perturbation of the calcium response and the absence of trichomes reduce touch-induced hyponasty. Finally, using plant competition assays, we show that touch-induced hyponasty is adaptive in dense stands of Arabidopsis. We thus establish a novel, adaptive mechanism regulating hyponastic leaf movement in response to mechanostimulation by neighbors in dense vegetation.

First report of Athelia rolfsii associated with southern blight disease of Amorphophallus muelleri in China.

Amorphophallus muelleri, known as konjac, is widely used in the biomedicine and food processing due to its richness in glucomannan. Between the years of 2019 to 2022, severe outbreaks of southern blight on Am. muelleri were observed during August and September in the main planting region of Mile city. The average disease incidence was 20%, resulted in 15.3% of economic losses in approximately 10,000 m2. Infected plants showed wilting and rotting and were covered with white dense mats of mycelia and sclerotia on both petiole base and tubers. Am. muelleri petiole base covered with mycelial mats were collected for pathogen isolation. The infected tissues (n=20) were washed with sterile water and surface disinfected with 75% alcohol for 60 seconds, rinsed three times with sterile water, cultured on rose bengal agar (RBA) and incubated at 27 ℃ for two days (Adre et al. 2022). Individual hyphae were transferred to new RBA plates and incubated at 27 ℃ for 15 days to obtain purified cultures. Five representative isolates were subsequently obtained and exhibited identical morphological characteristics. All isolates produced dense, cotton-white aerial mycelia and had a daily growth rate of 1.6 ± 0.2 mm (n=5). After 10 days, all isolates formed sclerotia in spherical (diameter range 1.1 to 3.5 mm, aver. 2.0 ± 0.5 mm; n=30) and irregular shapes. The number of sclerotia per plate ranged from 58 to 113 (aver=82; n=5). These sclerotia were initially white and gradually turned brown as they matured. A representative isolate (17B-1) was selected for molecular identification and the translation elongation factor (TEF, 480 nt.), internal transcribed spacer (ITS, 629 nt.), large subunit (LSU, 922 nt.), and small subunit (SSU, 1016 nt.) regions were amplified with the primers EF595F/EF1160R (Wendland and Kothe 1997), ITS1/ITS4 (Utama et al. 2022), NS1/NS4, and LROR/LR5 (Moncalvo et al. 2000), respectively. The ITS (GenBank accession no. OP658949), LSU (OP658955), SSU (OP658952), and TEF (OP679794) sequences were 99.19%, 99.78%, 99.31%, and 99.58% similar to those of At. rolfsii isolates (MT634388, MT225781, MT103059, and MN106270, respectively). Thus, the fungus represented by isolate 17B-1 was identified as At. rolfsii, corroborating the identification of Sclerotium rolfsii Sacc., the anamorph, based on cultural and morphological features. Pathogenicity tests were performed on six-month-old asymptomatic Am. muelleri plants (n=30) grown in pots with sterile soil in a greenhouse at 27 °C and 80% relative humidity. The petiole base was scratched with a sterile blade and 20 plants were inoculated by placing a 5 mm2 mycelial plug of five-day-old isolate 17B-1 on the wound. Sterile RBA plugs were used on 10 wounded control plants. After 12 days, all inoculated plants exhibited symptoms similar to those observed in the field, while the control plants showed no symptoms. The morphological and molecular identification of the fungus reisolated from inoculated petioles confirmed its identity as At. Rolfsii, fulfilling Koch's postulates. S. rolfsii was first reported on Am. campanulatus in India (Sarma et al. 2002). As At. rolfsii causes konjac diseases in all Amorphophallus growing areas (Pravi et al. 2014), the importance of At. rolfsii as an endemic pathogen of Am. muelleri in China needs to be recognized, and its prevalence should be determined as a first step to managing this disease.

First Report of Providencia rettgeri Causing Soft Rot on Calla lily in China.

Calla lily (Zantedeschia hybrida) is widely cultivated as an ornamental plant in China and commonly used as cut flower. Water soaked lesions on the tuber and petiole followed by collapse of entire plant along with foul smell were noticed in a 4-hectare calla lily plantation in the Yanqing District of Beijing, China during August 2022. It was revealed 20%-30% of the plants had these symptoms. Petiole (5 cm) and tuber (5 mm3) samples were collected from 10 plants randomly from fields. The samples were disinfected with 75% ethanol for 5 s, and then rinsed three times with distilled water (DW). Five small pieces for each collected petiole and tuber (about 0.25 cm2 in area) were ground in DW; the suspension was plated on Luria Bertani agar and incubated for 12 h at 28°C. Single colonies were picked and re-streaked three times to purify the bacterial culture. The colonies were creamy, short rod-shaped, gray translucent, and with shiny texture. Gram staining revealed red color, confirming it as Gram-negative bacteria (Werkman et al. 1932). For molecular analysis, DNA was directly extracted from single colony using FastPure Bacteria DNA Isolation Mini Kit (Vazyme Biotech Co., Ltd. Nanjing, China). Four gene-specific markers (16S rRNA, dnaJ, atpD, and ropB) were then amplified using their respective primer pairs (Monciardini et al. 2002). The sequences obtained from four strains, namely ZAPR22R, ZAPR22L, ZAPR22P and ZAPR22S, were submitted after editing to GenBank with accession numbers OP740771.1-OP740774.1 for 16S rRNA, OP759518.1-OP759521.1 for atpD, OP759514.1-OP759517.1 for dnaJ, and OP759510.1-OP759513.1 for ropB genes. All of these gene sequences have the highest BLAST hit to Providencia rettgeri with 94.8% to 99.8% sequence identity (expcept dnaJ, 88.3%) and 96% to 100% of coverage. Phylogenetic tree constructed based on sequences of all four genes using RAxML v8.2.12 (github.com/stamatak/standard-RAxML) showed that the calla lily bacterial strains were clustered with type strain of P. rettgeri). Koch's postulate was performed to confirm the pathogenicity of the bacterial strain ZAPR22R by inoculating petiole base of 20 seedlings of Zantedeschia cv. 'Jingcai Yangguang' with the classical injection procedure. Three sites 1-2cm above the petiole base of individual plant were injected with 100 µl of 108 CFU/ml bacteria, and each was spaced 1 cm apart. All samples were incubated with 16 h of light and 8 h of darkness in a culture chamber at 70-80% relative humidity and 30℃. Soft rot symptoms were developed at the inoculated site after twenty days of inoculation, while no symptoms appeared in the controls. Bacteria reisolated from the inoculated tissues had similar phenotypes and identical molecular characteristics as the original isolate. To our knowledge, this is the first report of the occurrence of P. rettgeri on calla lily in China. P. rettgeri was described as a rhizobacterium that promotes the growth of vegetable crops and lichens from Brazil (Cavalcante da Silva et al. 2020; Swamy et al. 2016). In contrast, it was recently identified as the pathogenic bacterium which cause brown slime flux on Populus tomentosa, a Chinese deciduous tree (Zhou et al. 2020). In the present study, the soft rot was identified as a major disease affecting the growth of calla lily and posing a great threat to commercial calla lily industry. It also provides insights that more studies should be performed on the epidemiology of the disease in different parts of China to establish effective disease management strategies.

First Report of Charcoal Rot Caused by Macrophomina phaseolina on Stevia rebaudiana in Arizona, USA.

Stevia (Stevia rebaudiana Bertoni) is an important medicinal crop grown worldwide. Leaves of stevia contain a non-caloric sweetener, stevioside, which is used as a substitute to artificial sweeteners. In August 2022, symptoms of chlorosis, wilting, and root rot were observed in about 30 % of stevia plants growing at the Agricultural Station at Yuma Agricultural Center, Yuma, AZ, USA (32.7125° N, 114.7067° W). Infected plants initially showed chlorosis and wilting, and the plants eventually died with foliage remaining intact to the plant. Cross sections of the crown tissue of affected stevia plants showed necrotic tissue and a dark brown discoloration in areas of the vascular and cortical tissues. Dark brown microsclerotia were observed on stem bases and necrotic roots of the infected plants. Five symptomatic plants were sampled to isolate the pathogen. Root and crown tissues (0.5 to 1 cm) were surface disinfested with 1% sodium hypochlorite for 2 min, rinsed three times with sterile water, and plated onto potato dextrose agar (PDA). All the five isolates displayed rapid mycelial growth on PDA at 28°C with a 12-h photoperiod. The mycelia were initially hyaline and turned from gray to black after 7 days. Masses of dark spherical to oblong microsclerotia were observed after 3 days on PDA, measuring an average of 75 µm width × 114 µm length (n=30). For molecular identification, genomic DNA was extracted from mycelia and microsclerotia of a representative isolate (Yuma) using the DNeasy Plant Pro kit (Qiagen, Hilden, Germany). The internal transcribed spacer (ITS), translation elongation factor-1α (TEF-1α), calmodulin (CAL), and β-tubulin (β-TUB) regions were amplified using the primer sets, ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), MpCalF/MpCalR (Santos et al. 2020), and T1/T22 (O'Donnell and Cigelink 1997), respectively. A BLAST search of sequences revealed 98.7 to 100% identity to Macrophomina phaseolina sequences (MK757624, KT261797, MK447823, MK447918). Both morphological and molecular characteristics confirmed the fungus as M. phaseolina (Holliday and Punithaligam 1970). Sequences were submitted in the GenBank under accession numbers OP599770 (ITS), OP690156 (TEF-1α), OP612814 (CAL), and OP690157 (β-TUB). Pathogenicity assay was performed on 9-week-old stevia plants (var. SW2267), grown in 4-inch planters in the greenhouse. The inoculum was made from a 14-day-old culture of M. phaseolina grown in conical flasks (250 ml) in potato dextrose broth at 28°C. Mycelial mats of the fungus were blended in 250 ml of sterile distilled water, filtered through four layers of cheesecloth, and then calibrated to 105 microsclerotia/ml using a hemocytometer. Twenty healthy plants were inoculated by soil drenching 50 ml of the inoculum per pot. Soil drenching using sterile distilled water was done on 5 non-inoculated control plants. Plants were maintained in the greenhouse at 28 ± 3°C with 12 h photoperiod. After 6 weeks, necrosis at the base of petioles and chlorosis of the leaves, followed by wilting were noticed on all 20 inoculated plants, whereas all the 5 control plants remained healthy. The fungus was reisolated and identified as M. phaseolina based on the morphology and sequences of ITS, TEF-1α, CAL and β-TUB regions. Although M. phaseolina has been reported earlier on stevia in NC, USA (Koehler and Shew 2018), this is a first report from AZ, USA. M. phaseolina is known to be favored by high soil temperatures (Zveibil et al. 2011), thus represents a potential threat to stevia production in AZ, USA in coming years.

New insights into the phylogenetic relationships of Japanese knotweed (Reynoutriajaponica) and allied taxa in subtribe Reynoutriinae (Polygonaceae).

Japanese knotweed (Reynoutriajaponica) is native to East Asia, but has been introduced to the West where it is a noxious invasive weed. Taxonomically, Japanese knotweed is placed within subtribe Reynoutriinae (Polygonaceae), which also contains the austral genus Muehlenbeckia (incl. Homalocladium) and north temperate Fallopia. In the current study, we conducted a phylogenetic analysis using sequence data from six markers, two nuclear (LEAFYi2, ITS) and four plastid (matK, rbcL, rps16-trnK and trnL-trnF) to further resolve the evolutionary relationships within this group, using the widest sampling of in-group taxa to date. The results of this analysis confirmed that subtribe Reynoutriinae is a monophyletic group, characterised by the presence of extra-floral, nectariferous glands at the base of leaf petioles. Within the subtribe, four main clades were identified: Reynoutria, Fallopiasect.Parogonum, Fallopia s.s. (including Fallopia sects. Fallopia and Sarmentosae) and Muehlenbeckia. The Fallopia s.s. and Muehlenbeckia clades are sister to one another, while the Fallopiasect.Parogonum clade is immediately basal to them and Reynoutria basal to all three. Fallopia, as currently circumscribed, is paraphyletic as Muehlenbeckia is nested within it. To resolve this, we propose that species of Fallopiasect.Parogonum should be treated as a new genus, Parogonum (Haraldson) Desjardins & J.P.Bailey, gen. et stat. nov. Within Reynoutria, the allied specific and infraspecific taxa that fall under the name Japanese knotweed s.l. form a monophyletic group and their taxonomic status is discussed.

Local light signaling at the leaf tip drives remote differential petiole growth through auxin-gibberellin dynamics

Although plants are immobile, many of their organs are flexible to move in response to environmental cues. In dense vegetation, plants detect neighbors through far-red light perception with their leaf tip. They respond remotely, with asymmetrical growth between the abaxial and adaxial sides of the leafstalk, the petiole. This results in upward movement that brings the leaf blades into better lit zones of the canopy. The plant hormone auxin is required for this response, but it is not understood how non-differential leaf tip-derived auxin can remotely regulate movement. Here, we show that remote signaling of far-red light promotes auxin accumulation in the abaxial petiole. This local auxin accumulation is facilitated by reinforcing an intrinsic directionality of the auxin transport protein PIN3 on the petiole endodermis, as visualized with a PIN3-GFP line. Using an auxin biosensor, we show that auxin accumulates in all cell layers from endodermis to epidermis in the abaxial petiole, upon far-red light signaling in the remote leaf tip. In the petiole, auxin elicits a response to both auxin itself as well as a second growth promoter; gibberellin. We show that this dual regulation is necessary for hyponastic leaf movement in response to light. Our data indicate that gibberellin is required to permit cell growth, whereas differential auxin accumulation determines which cells can grow. Our results reveal how plants can spatially relay information about neighbor proximity from their sensory leaf tips to the petiole base, thus driving adaptive growth.

CsIAGLU Regulates the Angle of Leaf Petiole by Affecting Endogenous Content of Auxin in Cucumber (Cucumis sativus L.).

The leaf angle is an important factor determining plant shoot architecture that may boost crop yield by increasing photosynthetic efficiency and facilitating high-density planting. Auxin is an important phytohormone involved in leaf angle regulation. Here, we identified two Single-Nucleotide Polymorphisms (SNPs) in the Indoleacetic Acid (IAA) glucosyltransferase gene CsIAGLU in 80 re-sequenced cucumber lines, of which the CsIAGLU717G,1234T is the dominant allele associated with a small leaf pedicle angle (LPA), whereas CsIAGLU717C,1234A is linked with a large LPA. CsIAGLU was highly expressed in leaves and petioles. In natural cucumber populations, the expression of CsIAGLU was negatively correlated with the LPA. The mutation of CsIAGLU induced by the CRISPR-Cas9 system resulted in elevated free IAA levels and enlarged cell expansion on the adaxial side of the petiole base, thus producing a greater LPA. Consistently, exogenous IAA treatment led to increased LPA and cell size. Therefore, our findings suggest that CsIAGLU functions as a negative regulator of LPA development via auxin-mediated cell expansion in cucumber, providing a valuable strategy for cucumber breeding with small LPAs.

The diversity of banana cultivars in East Kalimantan based on morphological characteristic

Banana is a plant with nutritious fruit and can help prevent stunting. Banana plants are widely cultivated in East Kalimantan, but the type characterization has not been identified. The purpose of this study was to determine the diversity of banana plants in East Kalimantan and to characterize banana plants based on morphology. This research is explorative in nature by identifying directly in the field the cultivated banana cultivars. Morphological characterization of stems, leaves and fruit was carried out based on the banana description contained in IPGRI-INIBAP/CIRAD. The research instrument is a banana morphology observation sheet which contains parameters: leaf habit, pseudostem color, predominant underlying color of the pseudostem, sap color, blotches at the petiole base, blotches color, petiole canal leaf III, color of leaf upper surface, color of midrib dorsal surface, color of leaf lower surface, color of midrib ventral surface, wax on leaves. The result shows that at East Kalimantan is found 12 types of banana cultivars were found, Talas bananas, Rutai bananas, Kepok bananas, Mas bananas, Morosebo bananas, Tanduk bananas, Susu bananas, Maulin bananas, Red bananas, Ambon bananas, Raja bananas, and Cavendish bananas.There are variations in the morphological characteristics of banana plants, leaves and fruit that can characterize each banana.

First report of Utah fragile fern (Cystopteris: Cystopteridaceae) from New Mexico, and new nomenclatural combinations in Cystopteris tenneseensis

Two recently analyzed collections of Cystopteris from New Mexico represent the first records of Utah fragile fern for the state. Our morphological reexamination of this taxon reveals a single character (the thickness of lateral cell walls in rhizome and petiole base scales) that consistently distinguishes it from tetraploid Cystopteris tennesseensis. Therefore, we propose the new combination C. tennesseensis subsp. utahensis to accommodate these disjunct, tetraploid populations of the southwestern United States. A second new combination, C. tennesseensis subsp. laurentiana, is provided for morphologically similar hexaploids from the northeastern U.S. and southern Canada.

First Report of Soft Rot Caused by Pectobacterium versatile on Hydrangea macrophylla in China.

Hydrangeas (Hydrangea macrophylla) are recognized for their abundant, showy inflorescences which possess sepal colors (Schreiber et al., 2011). In recent years, the shrubs are grown as potted plants and also for landscaping in China. During the spring of 2021 in seedling greenhouse located in Tonghai County, Yunnan province, China (102°73' N, 24°12' E), a severe bacterial disease was observed on 12-month-old potted plants of cv. Enziandom. Symptoms on Hydrangeas initially appeared as thick liquid produced on the surface of the infected petiole base and water soaking in the infected stems. With the development of the infection, the basal stem color was dark brown and the stem base rapidly turned to wet rot. Severely infected leaves exhibited soft rot symptoms, and the presence of soft rot on mature plants decreased ornamental and market value. This disease was found in 40% of 15 surveyed greenhouses, and the disease incidence ranged from 30 to 50% in different regions. To identify the causal agent, disease-health tissues from infected plants were surface sterilized using 75% ethanol for 30 sec, then soaked in sterile distilled water for three times. The exudate from sheared tissue was streaked onto nutrient agar plates, and plates were incubated at 28°C for 24 hours (Koike et al., 2002). Four representative bacterial isolates BXH21032401-BXH21032404 were selected for further analysis. Colonies on NA were white, small, round and translucent with smooth edges. All bacterial isolates were gram-negative, rod-shaped, with 2-4 circumferential flagella and no entrapment membrane. Physiological and biochemical test and 96 phenotypes screened using the BIOLOG GENIII microplate system (Biolog, Hayward, CA, USA), the test results of four isolated strains are consistent with those of the reported Pectobacterium versatile (Portier et al. 2019). Total genomic DNA was extracted from bacterial suspensions with TIANamp Bacteria DNA Kit (TIANGEN, China). PCR amplification assays were conducted with specially designed primers using extracted genomic DNA as a template. All sequences of the PCR products were deposited in GenBank with accession numbers MZ852237-MZ852240 (16S rRNA), MZ921938-MZ921941 (pmrA), MZ926722-MZ926725 (acnA), MZ926726-MZ926729 (icdA), MZ926730-MZ926733 (gapA), MZ852233-MZ852236 (mdh), MZ926718-MZ926721 (mtlD), MZ921934-MZ921937 (pgi), MZ926734-MZ926737 (proA) and MZ921942-MZ921945 (rpoS). Maximum Likelihood phylogenetic trees based on 16S rRNA, pmrA sequences, and multilocus sequence analysis of housekeeping genes (acnA, icdA, gapA, mdh, mtlD, pgi, proA and rpoS) (Xie et al., 2018), all clustered BXH21032401-BXH21032404 into a clade containing other confirmed strains of P. versatile (Kravchenko et al., 2021). Pathogenicity tests were performed by spraying leaves of healthy 6-month-old potted H. macrophylla (cv. Enziandom) plants with bacterial suspension (20 mL/plant, 108 CFU ml-1). Plants were inoculated with sterile distilled water as control. Soft rot symptoms appeared on inoculated petioles in 5 days after incubation in growth chamber at 28°C showed similar symptoms as observed initially in the greenhouse, and strains were re-isolated successfully from symptomatic hydrangea to complete Koch's postulates. The pathogenicity test was carried out twice. To our knowledge, this is the first time that P. versatile is reported to cause hydrangea soft rot disease in China.

First Report of Gnomoniopsis idaeicola Causing Cane Wilt and Canker in Commercial Blackberry Fields in Oregon.

Oregon is the leading producer of blackberries in the United States (USDA 2021). In November 2020, we visited a seven-year-old, 5.6 HA field of thornless trailing cultivar 'Columbia Star' in Marion County, Oregon in response to grower reports of rapid plant death that they called 'Blackberry Collapse.' The pattern of disease in the field was semi-circular patches of dead plants. We estimate that ca. 17% of the plants were killed. Symptoms included fewer and stunted primocanes, floricane reddening, premature floricane senescence, or elliptical or irregular brown to purple cane lesions often near the base of necrotic petioles clasping the cane. Twenty-two cane lesions were collected, surface-disinfested, and placed on potato dextrose agar with streptomycin. In addition to common Rubus cane pathogens (Kalmusia coniothyrium, Botrytis spp., Diaporthe spp., and Seimatosporium lichenicola), Gnomoniopsis idaeicola was isolated from 23% of the samples. After isolation of G. idaeicola from 'Columbia Star', we also isolated the pathogen from symptomatic 'Black Diamond' blackberry in fields in Washington and Linn Counties in Oregon. G. idaeicola grew as white- to cream-colored circular colonies on the agar surface with sparse to dense aerial hyphae. Some isolates produced cream-colored exudate from irregular conidiomata. Conidia were single-celled, hyaline, oval to ellipsoid, and ranged from 4.9 to 6.9 µm long and 1.2 to 2.5 µm wide (n = 100). Perithecia and ascospores were not seen on canes or in culture; molecular methods were used to identify the fungus. Genomic DNA was extracted from nine isolates and β-tubulin, ITS region, and tef-1α were amplified using the primers and conditions described by Walker et al. (2010). Amplicons were Sanger sequenced in both directions by the Core Facilities of the Center for Quantitative Life Sciences of Oregon State University, Corvallis, OR. Sequences were deposited in GenBank (β-tubulin OK539758-OK539766; ITS OK348854-OK348862; tef-1α OK539767-OK539775). β-tubulin sequences (737 bp) were 100% identical to sequence of G. idaeicola from Rubus procerus, Oregon (GU320783). ITS sequences (518 bp) were 99.2 to 100% identical to G. idaeicola CBS125674T (GU320796). tef-1α sequences (860 bp) were 99.9 to 100% identical with reference sequences of G. idaeicola. Phylogenetic analyses of concatenated sequences using Tamura-Nei neighbor-joining (Tamura et al. 2004) confirmed identity. Pathogenicity of G. idaeicola isolates was tested in repeated experiments on four to five detached 'Black Diamond' primocanes and potted 'Columbia Star' plants with 4 mm hyphal plugs placed on fresh wounds and wrapped in parafilm; controls were treated with sterile agar plugs (Ellis et al. 1984; Stevanović et al. 2019). By 14 days, in each experiment, expanding necrotic lesions were observed on canes inoculated with G. idaeicola, but not with sterile agar plugs. ITS-sequence of fungi isolated from lesions confirmed identity as G. idaeicola, fulfilling Koch's postulate. G. idaeicola was described as a new species by Walker et al. (2010) from perithecia collected from wild Rubus spp. in the Pacific Northwest. Despite its presence on native Rubus, G. idaeicola has not been reported in commercial blackberry fields in OR. Stevanović et al. (2019) identified G. idaeicola as an important pathogen causing canker, wilt, and death of blackberry in Serbia. Surveys of Oregon blackberry fields for G. idaeicola are ongoing, along with research on the epidemiology and management of this emerging pathogen.

GmPIN1-mediated auxin asymmetry regulates leaf petiole angle and plant architecture in soybean.

Crop breeding during the Green Revolution resulted in high yields largely due to the creation of plants with semi-dwarf architectures that could tolerate high-density planting. Although semi-dwarf varieties have been developed in rice, wheat and maize, none was reported in soybean (Glycine max), and few genes controlling plant architecture have been characterized in soybean. Here, we demonstrate that the auxin efflux transporter PINFORMED1 (GmPIN1), which determines polar auxin transport, regulates the leaf petiole angle in soybean. CRISPR-Cas9-induced Gmpin1abc and Gmpin1bc multiple mutants displayed a compact architecture with a smaller petiole angle than wild-type plants. GmPIN1 transcripts and auxin were distributed asymmetrically in the petiole base, with high levels of GmPIN1a/c transcript and auxin in the lower cells, which resulted in asymmetric cell expansion. By contrast, the (iso)flavonoid content was greater in the upper petiole cells than in the lower cells. Our results suggest that (iso)flavonoids inhibit GmPIN1a/c expression to regulate the petiole angle. Overall, our study demonstrates that a signal cascade that integrates (iso)flavonoid biosynthesis, GmPIN1a/c expression, auxin accumulation, and cell expansion in an asymmetric manner creates a desirable petiole curvature in soybean. This study provides a genetic resource for improving soybean plant architecture.

Assemblages of Myxomycetes associated with Cocos nucifera L. trees

Arecaceae plants provide favorable microhabitats for the development of myxomycetes, but researches focusing on myxomycetes associated with palm trees are scarce. The myxobiota present on Cocos nucifera L. was evaluated in coconut groves in the municipality of Bonito, Pernambuco, Brazil. The incidence of myxomycetes on coconut palms and substrates and their composition, richness, taxonomic diversity, constancy, abundance, and seasonality of sporulation were analyzed. During direct field collections, inspections were made of the stems, leaf sheaths, inflorescence bracts, and petiole bases of 60 adult individuals. Myxomycetes were present in 80% of the coconut palms and were more abundant during the rainy season (June). A total of 128 specimens were obtained (63% from leaf sheaths, 31% from stems, 4% from petiole bases, and 2% from bracts), representing 14 species, with species/genus ratio = 2.80. Hemitrichia serpula, Physarum decipiens and Diderma effusum characterize the myxobiota. This work presents the first record of Diderma chondrioderma, Didymium clavus, Physarum crateriforme and P. roseum on C. nucifera for Brazil. The ocurrence of Didymium megalosporum in Brazil is confirmed 107 years after its first and only record in ground litter in an undefined location.

Psyllid honeydew as a Bombus food source in the boreal landscape

Abstract Bumblebees are opportunistic resource consumers and have been known to visit extrafloral nectaries and harvest aphid and scale honeydew. We report the first observation of bumblebees foraging psyllid honeydew in a tritrophic system in the boreal forest of Yukon Territory, Canada. In this system, a willow (Salix alaxensis) develops bizarrely enlarged petiole bases which act as nursery cavities for large numbers of psyllid immatures of Cacopsylla macleani (Homoptera: Psyllidae), with later instars dispersing over the underside of the leaf. These immatures produced abundant honeydew which was vigorously and persistently foraged by several bumblebees of multiple species (we identified Bombus vancouverensis, Bombus melanopygus and Bombus mckayi). Ants and vespid wasps were also present but in lower numbers. Salix alaxensis and Salix‐feeding psyllids are common throughout arctic and boreal regions, so honeydew production is potentially a supplementary food source for Bombus when floral nectar flows are limited due to low temperatures or drought.

ACA pumps maintain leaf excitability during herbivore onslaught

Recurrent damage by lepidopteran folivores triggers repeated leaf-to-leaf electrical signaling. We found that the ability to propagate electrical signals-called slow wave potentials-was unexpectedly robust and was maintained in plants that had experienced severe damage. We sought genes that maintain tissue excitability during group insect attack. When Arabidopsis thaliana P-Type II Ca2+-ATPase mutants were mechanically wounded, all mutants tested displayed leaf-to-leaf electrical signals. However, when the auto-inhibited Ca2+-ATPase double-mutant aca10 aca12 was attacked by Spodoptera littoralis caterpillars, electrical signaling failed catastrophically, and the insects consumed these plants rapidly. The attacked double mutant displayed petiole base deformation and chlorosis, which spread acropetally into laminas and led to senescence. A phloem-feeding aphid recapitulated these effects, implicating the vasculature in electrical signaling failure. Consistent with this, ACA10 expressed in phloem companion cells in an aca10 aca12 background rescued electrical signaling and defense during protracted S.littoralis attack. When expressed in xylem contact cells, ACA10 partially rescued these phenotypes. Extending our analyses, we found that prolonged darkness also caused wound-response electrical signaling failure in aca10 aca12 mutants. Our results lead to a model in which the plant vasculature acts as a capacitor that discharges temporarily when leaves are subjected to energy-depleting stresses. Under these conditions, ACA10 and ACA12 function allows the restoration of vein cell membrane potentials. In the absence of these gene functions, vascular cell excitability can no longer be restored efficiently. Additionally, this work demonstrates that non-invasive electrophysiology is a powerful tool for probing early events underlying senescence.