First Report of Leaf Spot Caused by Corynespora cassiicola on Viburnum odoratissimum Ker-Gawl. var. awabuki (K. Koch) Zabel ex Rumpl. (sweet viburnum) in China

Sweet viburnum [Viburnum odoratissimum Ker-Gawl. var. awabuki (K. Koch) Zabel ex Rumpl.] belonging to the family Adoxaceae, is a medical and landscape plant, native to Korea (Jeju Island), Taiwan, and Japan (Edita 1988). In June and September 2019, leaf spots were observed on approximately 65% to 80% of sweet viburnum plants in a hedgerow located in Fenghe Xincheng District (28°41'52.9"N 115°52'14.3"E) in Nanchang, China. Initial symptoms of disease appeared as dark brown spots surrounded by red halos (Figure 1 A), which expanded irregularly. Finally, the center of the lesions desiccated and became light-brown, surrounded by a deep-red halos (Figure 1 B). Ten leaf samples with typical symptoms were collected and washed with tap water for about 15 min. The tissue between the healthy and necrotic area (ca. 4 mm × 4 mm) was cut with a sterile scalpel and surface sterilized with 70% alcohol for 45 s, 2% NaClO for 2 min, washed in sterile deionized water three times, dried on sterilized filter paper, then placed in Petri dishes and incubated at 25℃ in the dark. After 3 to 5 days, the hyphal tips from the edges of growing colonies were transferred to fresh PDA dishes. Eventually, 54 fungal isolates were obtained and, of these, 39 isolates were identical in their morphological characteristics. Morphological analysis was performed according with Ellis (1971). The isolate S18, chosen as representative, formed a gray to grayish brown colony with concentric circleson PDA, and a diameter of 8.5 to 9 cm after 7 days incubation at 25℃ (Figure 1 G). Conidia were hyaline, straight or slightly curved, needle shaped, truncate at the base, and acuminate at the tip, with 2 to 6 pseudosepta, 18.90 to 38.38 µm (avg. = 27.51 µm) × 1.64 to 4.50 µm (avg. = 2.60 µm) (n = 36) (Figure 1 H). The genes of fungal isolates (i.e., ITS, tub2 and ACT) were amplified with ITS4/ITS5 for ITS (White, Bruns et al. 1990), Bt2a/Bt2b for tub2 (Glass and Donaldson 1995) and ACT783R/ACT512F for ACT (Carbone and Kohn 1999) and sequenced. The sequences were deposited in GenBank (MW165772 for ITS, MW175900 for ACT and MW168659 for tub2), which showing greater than 99.1% similarity to multiple C. cassiicola accessions, respectively. Pathogenicity tests were performed on healthy leaves in field by inoculating surface-sterilized mature leaves with puncture wound (Figure C) and non-wounded young leaves with 20 µL of a conidial suspension (105 conidia ml-1) (Figure F and G) at 26℃. After 4 to 7 days, all inoculated leaves reproduced similar symptoms as observed initially in the field (Figure 1 C, E and F). To fulfill Koch’s postulates, the fungus was isolated on PDA from the margins of leaf spots on inoculated leaves and confirmed as C. cassiicola by morphological characters and ITS gene sequencing. Previously, C. cassiicola was reported as an endophyte on Viburnum spp. and Viburnum odoratissimum (Alfieri et al. 1994). More recently, C. cassiicola has been reported as a pathogen of many plant species in China, such as kiwifruit (Cui, Gong et al. 2015), American sweetgum (Mao, Zheng et al. 2021), castor bean (Tang, Liu et al. 2020), and holly mangrove (Xie, He et al. 2020). To our knowledge, this is the first report of leaf spot disease on sweet viburnum caused by C. cassiicola in China and the precise identification of the causal agent will be useful for its management.

Use of Routine Leaching Fraction Testing to Guide Irrigation at a Container Nursery

Efficient irrigation during container plant production is difficult to achieve as irrigation is scheduled daily or multiple times per day to maintain an adequate supply of water in the limited substrate volume. Leaching fraction (container drainage/water applied) testing is one strategy to monitor and adjust irrigation to limit excessive container drainage. We compared an automated irrigation schedule based on routine leaching fraction testing and weather (LFI) with a nursery's traditional irrigation practice (TIP). Compared to TIP, LFI reduced water applied in four of five sprinkler-irrigated trials without a notable growth affect; LFI increased water applied in a fifth trial but plant growth was also increased. Compared to TIP, LFI reduced water applied in all three micro-irrigated trials but also reduced growth in one of the trials. LFI reduced water applied by an average of 21% [57.8 vs. 73.1 kL·ha−1· d−1 (15,300 gal/acre/day) or $3,000 ha−1yr−1 ($1,200/acre/year) at a pumping cost of $0.53/kL ($0.20/1000 gal). We concluded that the greater economic benefit of water savings was to provide increased capacity for additional production under consumptive water use limitations rather than to reduce the unit cost of production. Index words: automation, evapotranspiration, sprinkler, micro-irrigation, weather. Species used in this study: Leyland cypress, Cupressus × leylandii A.B. Jacks. and Dallim., Parson juniper, Juniperus squamata Gordon ‘Expansa Parsonii', crape myrtle, Lagerstroemia indica L. × fauriei Koehne ‘Natchez', Indian hawthorn, Raphiolepis indica (L.) Lindl., sweet viburnum, Viburnum odoratissimum Ker Gawl.

A test of the rapid measurement of leaf photosynthesis-intercellular CO2 concentration response curve of an evergreen shrub Viburnum Odoratissimum

<p>Plant photosynthetic physiology is a crucial process reflecting plant growth and productivity. The maximum rate of Rubisco carboxylation (<em>V<sub>c,max</sub></em>) and the maximum rate of electron transport (<em>J<sub>max</sub></em>) of plant leaves are the main limiting factors of photosynthetic capacity and indispensable parameters in ecosystem mechanism models. Accurate simulation of <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> is vital to improve the prediction precision of vegetation dynamics under the background of climate changes. However, using traditional CO<sub>2</sub> response curves to obtain <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> was time-consuming (about 30 to 60 minutes for each CO<sub>2</sub> response curve) and labor-intensive in the field. The rapid photosynthesis-intercellular CO<sub>2</sub> concentration (A-Ci) response technique (RACiR) provided a potential convenient way to obtain A-Ci curve in an open gas exchange system, which would greatly improve the measurement efficiency. Nevertheless, whether the RACiR detecting method verified by limited conifers and deciduous species (especially poplar trees) in previous studies could be generally used for other plant functional groups remains unclear.</p><p> </p><p>Therefore, here we selected <em>Viburnum Odoratissimum</em> as the target and used Li-cor 6800 to test the applicability of the rapid RACiR detecting method on evergreen species. As the changes of CO<sub>2</sub> ranges and rates are the most important parameters in the method, we set 10 different change ranges of reference [CO<sub>2</sub>] (i.e., 400-1500 ppm, 400-200-800 ppm, 420-20-620 ppm, 420-20-820 ppm, 420-20-1020 ppm, 420-20-1220 ppm, 420-20-1520 ppm, 420-20-1820 ppm, 450-50-650 ppm, 650-50-650 ppm) to verify the accuracy of traditional CO<sub>2</sub> response curves and RACiR and to explore suitable [CO<sub>2</sub>] change ranges for evergreen species.</p><p> </p><p>Finally, our results showed that <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em> calculated by 10 rapid A-Ci response curves except <em>J<sub>max</sub></em> calculated by 650-50-650 ppm [CO<sub>2</sub>] were not significantly different from those calculated by traditional A-Ci response curves. Moreover, 400-200-800 ppm [CO<sub>2</sub>] compared with the other [CO<sub>2</sub>] ranges was suitable for <em>V. Odoratissimum</em>. Our results indicated the advantage of RACiR method for evergreen species and implied that preliminary experiments should be carried out according to specific tree species to determine the most appropriate change range of [CO<sub>2</sub>] when using RACiR to calculate <em>V<sub>c,max</sub></em> and <em>J<sub>max</sub></em>.</p>

AVALIAÇÃO DE ESPÉCIES ARBÓREAS PARA COMPOSIÇÃO DE CORTINAS DE SEGURANÇA CONTRA INCÊNDIOS FLORESTAIS

Cortina de segurança é um plantio em faixas com espécies vegetais de menor combustibilidade do que as do cultivo principal, a fim de reduzir ou evitar a propagação do fogo. O presente trabalho teve por objetivo avaliar o potencial das espécies Magnolia grandiflora L., Michelia champaca L., Viburnum odoratissimum Ker Gawl., Casearia sylvestris Swartz e Bougainvillea glabra Choisy para compor cortinas de segurança. Para isso, as espécies foram analisadas em função do teor de umidade, altura de chama, velocidade de propagação do fogo, quantidade de material combustível consumido em queimas experimentais e intensidade do fogo. Foram realizadas 10 repetições por espécie e as queimas foram realizadas no Laboratório de Incêndios Florestais, do Departamento de Ciências Florestais, da Universidade Federal do Paraná, em parcelas de 1 m², com uma carga de 1 kg de material combustível fino seco em estufa. As espécies que se destacaram nas análises foram B. glabra e C. sylvestris, as quais indicaram baixa combustibilidade, apresentando assim potencial para uso em cortina de segurança na prevenção de incêndios florestais.Palavras-chave: barreiras verdes, prevenção de incêndios, altura de chama, proteção florestal. EVALUATION OF TREE SPECIES FOR THE COMPOSITION OF GREEN FIREBREAKS AGAINST FOREST FIRES ABSTRACT: Green firebreaks are vegetation stripes with a lower combustibility than that of the main crop and are intended to prevent or restrict the spread of fire. The present study aimed to evaluate the potential of the following tree species to compose firebreaks: Magnolia grandiflora L., Michelia champaca L., Viburnum odoratissimum Ker Gawl., Casearia sylvestris Swartz and Bougainvillea glabra Choisy. The species were analyzed according to their moisture content, flame height, fire spread rate, amount of fuel consumed in controlled burns, and fire intensity. There were ten repetitions per species and the burns were done at the wildfire laboratory, from the forest sciences department, of Universidade Federal do Paraná, on experimental plots of 1 m2, with 1 kg of thin fuel load, kiln-dried at 75 °C for 48 hours. The most notable species from the analyses were B. glabra and C. sylvestris, which indicated low combustibility, showing potential to compose green firebreaks and prevent forest fires.Keywords: green firebreaks, fire prevention, flame height, forest protection.