scholarly journals Heat Treatment Effects on Strawberry Plant Survival and Angular Leaf Spot, Caused by Xanthomonas fragariae, in Nursery Production

Plant Disease ◽  
2009 ◽  
Vol 93 (3) ◽  
pp. 299-308 ◽  
Author(s):  
William W. Turechek ◽  
Natalia A. Peres
Keyword(s):  
Heat Treatment ◽  
Leaf Spot ◽  
Plant Protection ◽  
Angular Leaf Spot ◽  
Bacterial Cells ◽  
Heat Treated ◽  
Nursery Stock ◽  
Xanthomonas Fragariae ◽  
Nursery Production ◽  
Plastic Bag

Angular leaf spot is an important disease in strawberry nursery production. The European and Mediterranean Plant Protection Organization (EPPO) lists Xanthomonas fragariae as an A2 quarantine pathogen. Therefore, nurseries wishing to export plants to European countries must maintain phytosanitary standards to exclude X. fragariae. To help nurseries achieve these standards, heat treatment for killing or reducing the number of viable bacterial cells in strawberry crown tissue was investigated. First, the sensitivity of bacteria to heat was determined by dispensing 1-ml aliquots of standardized cell suspensions in microcentrifuge tubes for each of four isolates of X. fragariae, including the type culture, and submerging the tubes in water at 36, 40, 44, 48, 52, and 56°C for 0, 1, 2.5, 5, 10, 15, 30, 60, 120, 240, 360, and 480 min. Bacteria were transferred to growth medium to determine the proportion surviving heat treatment. Two trials were conducted in a greenhouse to determine the sensitivity of bare-root plants to heat treatment. In the first trial, plants of cvs. Camarosa and Diamante from two different nurseries were heat treated as follows: (i) plants placed in metallic mesh cages and immersed directly into water (industry standard, direct dip); (ii) plants sealed in a plastic bag and the bag immersed in water (bagged dry); or (iii) plants wetted in warm water, sealed in a plastic bag, and then immersed in water (bagged wet). Plants were treated at 44 or 48°C for 0, 60, 120, 180, and 240 min. In the second trial, plants of cvs. Camarosa, Camino Real, Diamante, Oso Grande, Strawberry Festival, and Ventana from a single nursery were subjected to the same treatments. In both trials, plants were potted after treatment and rated for growth characteristics. Results showed that populations of bacteria exposed to 56 and 52°C were killed completely after 15 and 60 min of exposure, respectively; both treatments killed plants. Bacterial populations exposed to 44°C for 4 h or 48°C for 2 h were reduced by 105 or 106 CFU/ml. The same treatments minimally affected vegetative growth of plants bagged dry or wet, but flowering was adversely affected. These heat treatments were selected for testing of nursery stock of several cultivars in field trials established at two locations in successive years. The survival rate among cultivars was similar to that observed in greenhouse trials, and angular leaf spot developed appreciably only in non-heat-treated control plots. Heat treatment of strawberry nursery stock is feasible and can be used to supplement standard production practices for producing pathogen-free nursery stock.

scholarly journals First Report of Xanthomonas fragariae Causing Angular Leaf Spot on Strawberry (Fragaria x ananassa) in Taiwan

Plant Disease ◽  
2020 ◽  
Author(s):  
Hung-Yi Wu ◽  
Qiao-Juan Lai ◽  
Yi-Mei Wu ◽  
Chia-Lin Chung ◽  
Pei-Che Chung ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Plant Protection ◽  
Management Strategies ◽  
Sprinkler Irrigation ◽  
Angular Leaf Spot ◽  
Windward Side ◽  
Bacterial Disease ◽  
Specific Primers ◽  
First Report ◽  
Xanthomonas Fragariae

Angular leaf spot of strawberry, considered an A2 quarantine pest by the European and Mediterranean Plant Protection Organization (EPPO 2019), is an important bacterial disease in many regions. Since 2017, symptoms similar to angular leaf spot were observed in several strawberry cultivars including ‘Taoyuan No. 1’ and ‘Xiang-Shui’. Early symptoms were angular, water-soaked lesions on the abaxial leaf surface, and later, reddish-brown irregular spots and coalesced lesions developed on the adaxial surface. In the humid conditions, sticky bacterial ooze exuding from lesions was observed. To isolate the causal agent, leaves showing water-soaked lesions were surface sterilized, cut into small pieces and soaked in 5 ml sterile water for at least 15 min. The supernatant from the cut-up pieces was serially diluted followed by spreading on sucrose peptone agar (SPA) (Hayward 1960). After incubating at 20°C for 4-5 days, single colonies grown on SPA were transferred to a new SPA plate and cultured at 20°C until colonies appeared. The yellow, glossy and mucoid colonies, which resembled the colony morphology of Xanthomonas fragariae, were selected as candidates for further confirmation. First, bacterial DNA of four candidate isolates, B001, B003 and B005 from Miaoli County and B004 from Taoyuan City, was PCR amplified with X. fragariae-specific primers: XF9/XF12 (Roberts et al. 1996) and 245A/B and 295A/B (Pooler et al. 1996). All four isolates could be detected by XF9/XF12 primer. Furthermore, isolates B003 and B004 could be detected by both 245A/B and 295A/B primers, while B001 and B005 could be detected by 295A/B only. Next, DNA gyrase subunit B (gyrB) was PCR amplified with the primers XgyrB1F/XgyrB1R (Young et al. 2008). The gyrB sequences of these four isolates were deposited in GenBank with accession numbers MT754942 to MT754945. The gyrB phylogenetic tree was constructed based on Bayesian inference analysis and maximum likelihood analysis. The gyrB sequences of the four isolates from Taiwan clustered in the clade containing the type strain of X. fragariae ICMP5715, indicating that they belong to X. fragariae. B001 and B005 formed a sub-group separated from B003 and B004, suggesting genetic differences between these isolates. To fulfill Koch’s postulates, the abaxial surface of strawberry leaves were syringe infiltrated (KJP Silva et al., 2017) or wounded inoculated (Wang et al., 2017) with bacterial suspensions (final OD600 = 1.0-2.0) prepared from colonies of B001 and B003 washed from SPA plates. Inoculated plants were enclosed in a plastic bag (> 90% RH) at 25/20°C (day/night) under a 12-h/12-h photoperiod. After 7-14 days, water-soaked lesions similar to those observed in the field were developed on all inoculated leaves. The bacteria were successfully re-isolated from lesions of inoculated leaves and confirmed by specific primers XF9/XF12, 245A/B and 295A/B. We also found that the disease commonly occurs in the strawberry fields/nurseries with sprinkler irrigation during winter or early spring, and was particularly serious in the windward side or near riverside. To our knowledge, this is the first report of X. fragariae causing angular leaf spot on strawberry in Taiwan. Currently, the disease only occurs severely in certain regions, but establishment of effective management strategies will be needed to prevent spreading of this disease and potential economic loss in the future.

scholarly journals The Use of Aerated Steam as a Heat Treatment for Managing Angular Leaf Spot in Strawberry Nursery Production and Its Effect on Plant Yield

2020 ◽  
pp. PHYTOFR-08-20-0
Author(s):  
William W. Turechek ◽  
Ole Myhrene ◽  
Janet Slovin ◽  
Natalia A. Peres
Keyword(s):  
Heat Treatment ◽  
Thermal Treatment ◽  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Commercial Application ◽  
Small Scale ◽  
Nursery Stock ◽  
Wide Range ◽  
Small Plot ◽  
The Impact

Xanthomonas fragariae, the bacterium causing angular leaf spot (ALS) of strawberry, is found routinely on strawberry nursery stock. Although ALS can be a serious disease in production fields, it can be particularly problematic in the sale and trade of commercial nursery stock because of international trade regulations. Heat treatment has been shown to be an effective treatment for managing ALS on nursery stock in small-scale experimental trials. The objective of this research was to design, build, and trial precision thermotherapy units for managing ALS for both research and commercial applications and to test a new thermotherapeutic protocol on strawberry nursery stock that combines a conditioning thermal treatment with an eradicative thermal treatment. Small-plot trials were conducted to evaluate the efficacy of precision thermotherapy on control of ALS using known sources of infected nursery stock. Additionally, trials were conducted in cooperation with commercial nurseries to determine the impact of thermotherapy on plant health and yield and on the natural development of ALS. In the small-plot trials, ALS incidence was significantly lower in plots treated with precision thermotherapy. In the commercial trials, precision thermotherapy had a variable, but negligible, effect on plant growth and yield. ALS, when it occurred, was always lower in thermotherapy-treated plots. Heat is a near-universal biocide. Thus, in addition to managing ALS, the commercial application of precision thermal therapy to strawberry nursery stock may be effective for managing a wide range of pest and disease threats to strawberry while simultaneously reducing pesticide usage. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CCO “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.

scholarly journals Finished Genome Sequences of Xanthomonas fragariae , the Cause of Bacterial Angular Leaf Spot of Strawberry

2016 ◽  
Vol 4 (6) ◽  
Author(s):  
Peter M. Henry ◽  
Johan H. J. Leveau
Keyword(s):  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Northern California ◽  
Strawberry Fruit ◽  
Genome Sequences ◽  
Xanthomonas Fragariae ◽  
Foliar Pathogen ◽  
Nursery Production ◽  
Long Read ◽  
Field Production

Xanthomonas fragariae is a foliar pathogen of strawberry that is of significant concern to nursery production of strawberry transplants and field production of strawberry fruit. Long-read sequencing was employed to generate finished genomes for two isolates (each with one chromosome and two plasmids) from symptomatic plants in northern California.

scholarly journals First Report of Angular Leaf Spot on Strawberry Caused by Xanthomonas fragariae in Iran

Plant Disease ◽  
2017 ◽  
Vol 101 (6) ◽  
pp. 1031 ◽  
Author(s):  
S. B. Kamangar ◽  
J. Van Vaerenbergh ◽  
S. Kamangar ◽  
M. Maes
Keyword(s):  
Leaf Spot ◽  
Angular Leaf Spot ◽  
First Report ◽  
Xanthomonas Fragariae

Outbreak of angular leaf spot, caused by Xanthomonas fragariae, in a Queensland strawberry germplasm collection

2011 ◽  
Vol 40 (3) ◽  
pp. 286-292 ◽  
Author(s):  
Anthony J. Young ◽  
Thomas S. Marney ◽  
Mark Herrington ◽  
Don Hutton ◽  
Apollo O. Gomez ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Germplasm Collection ◽  
Angular Leaf Spot ◽  
Xanthomonas Fragariae

scholarly journals Inhibition of Xanthomonas fragariae, Causative Agent of Angular Leaf Spot of Strawberry, through Iron Deprivation

2016 ◽  
Vol 7 ◽  
Author(s):  
Peter M. Henry ◽  
Samantha J. Gebben ◽  
Jan J. Tech ◽  
Jennifer L. Yip ◽  
Johan H. J. Leveau
Keyword(s):  
Causative Agent ◽  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Iron Deprivation ◽  
Xanthomonas Fragariae

scholarly journals Angular Leaf Spot: A Bacterial Disease in Strawberries in Florida

EDIS ◽  
1969 ◽  
Vol 2005 (1) ◽  
Author(s):  
Natalia A. Peres ◽  
Silvia I. Rondon ◽  
James F. Price ◽  
Daniel J. Cantliffe
Keyword(s):  
Leaf Spot ◽  
Gray Mold ◽  
Angular Leaf Spot ◽  
Publication Date ◽  
Bacterial Disease ◽  
University Of Florida ◽  
Pythium Root Rot ◽  
Xanthomonas Fragariae ◽  
Rapid Spread ◽  
Sphaerotheca Macularis

Angular Leaf Spot (ALS) is a bacterial disease caused by Xanthomonas fragariae Kennedy & King, a pathogen highly specific to wild and cultivated strawberry, Fragaria x ananassa Duchesne (Legard et al. 2003). ALS is an important disease on winter strawberry production worldwide. In the U.S., it ranks 6th in economic importance after gray mold (Botrytis cinerea L.), verticillium wilt (Verticillium alboatrum Reinke & Berth), powdery mildew (Sphaerotheca macularis L.), anthracnose (Colletotrichum spp.), and pythium root rot (Pythium spp.) (Sorensen et al. 1997). The rapid spread of ALS is influenced by the increasing rate of interchange of plant material. This is document PP-199, a publication of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: June 2004. PP-199/PP120: Angular Leaf Spot of Strawberries (ufl.edu)

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