First report of Diplodia mutila causing leaf blight on Magnolia grandiflora in China

Magnolia grandiflora is a widely cultivated ornamental tree in China. In June 2020, a leaf blight disease was observed on M. grandiflora in Guizhou University (26° 44' 57'' N, 106° 65' 94'' E) in Guiyang, China. The initial symptoms on leaves were expanding round necrotic lesions with a grey center and dark brown edge, and twigs were withered when the disease was serious. Of the 100 plants surveyed 65% had symptoms. To isolate the potential causal pathogen, diseased leaves were collected from an M. grandiflora tree at Guizhou University. Isolations from made form the junction between healthy and symptomatic tissue and disinfested by immersing in 75% ethanol for 30 seconds, 3% NaOCl for 2 minutes, and then washed 3 times in sterile distilled water. Symptomatic tissue was then plated on potato dextrose agar (PDA) and incubated at 25ºC with 12-hour light for 3–5 days. Three isolates (GUCC 21235.1, GUCC 21235.2 and GUCC 21235.3) were obtained. Colonies on PDA after 7 d were dark brown, pycnidia embedded in the mydelium were dark brown to black, single and separated. Conidiophores were transparent measuring 7–12.5 × 2.5–4.5 µm (mean = 9.5 × 3.6 µm, n = 30) in length. Conidia were transparent becoming brown when mature with a diaphragm, with round ends measuring, 21–27 × 10–15 µm (mean = 23.6 × 12.6 µm, n = 30). To confirm the pathogen by molecular characterization, four genes or DNA fragments, ITS, LSU, tef1 and β-tubulin, were amplified using the following primer pairs: ITS4-F/ ITS5-R (White et al., 1990), LR0R/ LR5 (Rehner & Samuels, 1994), EF1-688F/ EF1-986R (Carbone & Kohn, 1999) and Bt2a/ Bt2b (O'Donnell & Cigelnik, 1997). The sequences of four PCR fragments of GUCC 21235.1 were deposited in GenBank, and the accession numbers were MZ519778 (ITS), MZ520367 (LSU), MZ508428 (tef1) and MZ542354 (β-tubulin). Bayesian inference was performed based on a concatenated dataset of ITS, LSU, tef1 and β-tubulin gene using MrBayes 3.2.10, and the isolates GUCC 21235.1 formed a single clade with the reference isolates of Diplodia mutila (Diplodia mutila strain CBS 112553). BLASTn analysis indicated that the sequences of ITS, LSU, tef1 and β-tubulin revealed 100% (546/546 nucleotides), 99.82% (568/569 nucleotides), 100% (302/302 nucleotides), and 100% (437/437 nucleotides) similarity with that of D. mutila in GenBank (AY259093, AY928049, AY573219 and DQ458850), respectively. For confirmation of the pathogenicity of this fungus, a conidial suspension (1×105 conidia mL-1) was prepared from GUCC 21235.1, and healthy leaves of M. grandiflora trees were surface-disinfested by 75% ethanol, rinsed with sterilized distilled water and dried by absorbent paper. Small pieces of filter paper (5 mm ×5 mm), dipped with 20 µL conidial suspension (1×105 conidia mL-1) or sterilized distilled water (as control), were placed on the bottom-left of the leaves for inoculation. Then the leaves were sprayed with sterile distilled water, wrapped with a plastic film and tin foil successively to maintain high humidity in the dark dark. After 36 h, the plastic film and tin foil on the leaves was removed, and the leaves were sprayed with distilled water three times each day at natural condition (average temperature was about 25 °C, 14 h light/10 h dark). After 10 days of inoculation, the same leaf blight began to appear on the leaves inoculated with conidial suspension. No lesion was appeared on the control leaves. The fungus was re-isolated from the symptomatic tissue. Based on the morphological information and molecular characterization, the isolate GUCC 21235.1 is D. mutila. Previous reports indicated that D. mutila infects a broad host range and gives rise to a canker disease of olive, apple and jujube (Úrbez-Torres et al., 2013; Úrbez-Torres et al., 2016; Feng et al., 2019). This is the first report of leaf blight on M. grandiflora caused by D. mutila in China.

The influence of edaphic factors on the vital state of large-flowered magnolia (Magnolia grandiflora L.). in the Nikitsky Botanical Gardens

The most widespread magnolia on the Southern coast of the Crimea and, in particular, in the Arboretum of the Nikitsky Botanical Gardens is the evergreen Magnolia grandiflora L., introduced in 1817. Currently, 28 generative specimens of Magnolia grandiflora of different ages grow in the Arboretum, including garden forms with different vital state. There are very few data on the relation of this species to soil conditions. For this reason, we have studied the influence of edaphic factors on the vital state of Magnolia grandiflora growing in the Arboretum of the Nikitsky Botanical Gardens. A number of limiting edaphic factors have been identified, the main of which is the high skeletal structure of the soil. The humus reserves in the soil have a positive effect on the vital state of trees. A high level of agricultural technology is the main method of improving the vital state of Magnolia grandiflora .

First Report of Leaf Spot Caused by Colletotrichum siamense on Magnolia grandiflora in China

Magnolia grandiflora (Southern magnolia) is a popular evergreen tree, planted especially as an ornamental for landscaping. In September 2019, leaf spots were observed on M. grandiflora at the campus of Jiangxi Agricultural University (28°45′56″N, 115°50′21″E). Approximately 64% (23 out of 36) M. grandiflora trees (most 24-year-old) occurred leaf spot disease at the campus. On average, 40% of the leaves per individual tree were affected. Foliar symptoms began as small dark brown lesions formed along the leaf margins. As the disease developed, the lesions’ center was sunken with a dark brown border. Symptomatic leaves were collected and cut into 5 × 5 mm pieces. Leaf pieces from the margin of the necrotic tissue were surface sterilized in 70% ethanol for 30 s followed by 2% NaOCl for 1 min and then rinsed in sterile water three times. Tissues were placed on potato dextrose agar (PDA) and incubated at 25°C. Of more than 35 isolates, most shared a similar morphology, with an isolation rate of 85%. Three isolates (JNG-1, JNG-2, and JNG-3) were chosen for single-spore purification and used for morphological characterization and identification. Colonies on PDA of the three isolates were white, cottony, and grayish-white on the undersides of the culture. Conidia were single-celled, straight, hyaline, cylindrical, clavate, and measured 4.4-5.6 × 13.2-17.8 µm (4.7 ± 0.3 × 14.6 ± 1.0 µm, n = 100). Appressoria were brown to dark brown, ovoid to clavate, slightly irregular to irregular, and ranged from 5.5-9.2 × 4.6-6.5 µm (7.3 ± 0.4 × 5.4 ± 0.3 µm, n=100). Morphological features were similar to Colletotrichum siamense as previously described (Weir et al. 2012). The internal transcribed spacer (ITS) regions, actin (ACT), calmodulin (CAL), beta-tubulin 2 (TUB2), chitin synthase (CHS-1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were amplified from genomic DNA for the three isolates using primers ITS1/ITS4, ACT-512F/ACT-783R, CL1/CL2, T1/Bt2b, CHS-79F/CHS-345R and GDF/GDR (Weir et al. 2012), respectively and sequenced. All sequences were deposited into GenBank (ITS, MZ325948-MZ325950; ACT, MZ461477 - MZ461479; GAPDH, MZ461483 - MZ461485; TUB2, MZ461486 - MZ461488; CHS-1, MZ441182 - MZ441184; CAL, MZ461480 - MZ461482). A neighbor-joining phylogenetic tree was constructed with MEGA 7.0 using the concatenation of multiple sequences (Kumar et al. 2016). According to the phylogenetic tree, all three isolates fall within the C. siamense clade (boot support 96%). The pathogenicity of three isolates were tested on M. grandiflora plants, which were grown in the field. Healthy leaves were wounded with a sterile needle and then inoculated with 10 µL of spore suspension (106 conidia/mL). Controls were treated with ddH2O (Zhu et al. 2019). All the inoculated leaves were covered with black plastic bags to keep a high-humidity environment for 2 days. All the inoculated leaves showed similar symptoms to those observed in field, whereas control leaves were asymptomatic for 10 days. The infection rate was 100%. C. siamense was re-isolated from the lesions, whereas no fungus was isolated from control leaves. It was confirmed that C. gloeosporioides is the causal agent of leaf spot on Magnolia virginiana in America (Xiao et al. 2004). However, this is the first report of C. siamense causing leaf spot on M. grandiflora in China. This study provided crucial information for epidemiologic studies and appropriate control strategies for this newly emerging disease.

Hydraulic segmentation does not protect stems from acute water loss during fire

The heat plume associated with fire has been hypothesized to cause sufficient water loss from trees to induce embolism and hydraulic failure. However, it is unclear whether the water transport path remains sufficiently intact during scorching or burning of foliage to sustain high water loss. We measured water uptake by branches of Magnolia grandiflora while exposing them to a range of fire intensities, and examined factors influencing continued water uptake after fire. Burning caused a 22-fold mean increase in water uptake, with greatest rates of water loss observed at burn intensities that caused complete consumption of leaves. Such rapid uptake is possible only with steep gradients in water potential, which would likely result in substantial cavitation of xylem and loss of conductivity in intact stems. Water uptake continued after burning was complete, and was greatest following burn intensities that killed leaves but did not consume them. This post-fire uptake was mostly driven by rehydration of the remaining tissues, rather than evaporation from the tissues. Our results indicate that the fire-plume hypothesis can be expanded to include a wide range of burning conditions experienced by plants. High rates of water loss are sustained during burning, even when leaves are killed or completely consumed.

The antibacterial effect of Magnolia mouthwash on the levels of salivary Streptococcus mutans in dental plaque: a randomized, single-blind, placebo-controlled trial

Background and Objectives: Dental caries is one of the most common chronic diseases around the world. Inhibitory effects of Magnolia Grandiflora bark extract has been proved on tooth decay both in vitro and by using free sugar chewing gum. This research aimed to examine the effect of Magnolia Grandiflora bark mouth-wash on the prevalence of Streptococcus mutans in dental plaque. Materials and Methods: This crossover, placebo-controlled, clinical trial study, was performed on a total of twenty participants (aged 18 to 35 years) in both control and intervention groups and four phases. The prevalence of S. mutans was measured in a certain volume of volunteer’s dental plaque at the beginning of the project (phase 1), after the first prescription (phase 2), following the washout period (phase 3) and finally after the second prescription (phase 4) by culture on bacteriology medium. Plaque index and saliva sampling were carried out in follow-up visits by a dentist. The data were analyzed using T-Test (paired and independent) quantitatively. Results: There was a significant difference in S. mutans frequency in dental plaque between when the participants used Magnolia mouthwash and when they washed out or used a placebo (p<0.005). Results also showed a significant difference between Magnolia and Placebo groups in the mean count of saliva bacterial colony counts after oral administration in the first and second time (P<0.001 and P<0.004, respectively). Conclusion: The current trial showed that Magnolia Grandiflora %0.3 mouthwash tends to decrease the number of S. mutans in dental plaque significantly. Therefore, its mass production and release to the oral health community are suggested. However, further studies with larger sample sizes and varying treatment are required to substantiate the findings of this study.

Seed Reproduction technology of the Magnolia grandiflora from seeds

This article highlights the results obtained on the basis of scientific research carried out in 2019-2020 on the technology of reproduction from the seeds of Magnolia grandiflora plant in the farmer’s farm named “Saydullo Temirov” specialized in the cultivation of landscape trees and shrubs located in the Uighur village of Pakhtaobod District of Andijan region. As a result of the study, determination of seed stratification time, planting time and methods, as well as maintenance work were determined, and conclusions were made.