scholarly journals First Report of Fusarium avenaceum Causing Postharvest Decay of ‘Gala’ Apple Fruit in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 690-690
Author(s):  
L. P. Kou ◽  
V. L. Gaskins ◽  
Y. G. Luo ◽  
W. M. Jurick
Keyword(s):  
United States ◽  
Cold Storage ◽  
The United States ◽  
Apple Fruit ◽  
Fusarium Avenaceum ◽  
Primary Concern ◽  
Processing Industry ◽  
First Report ◽  
Postharvest Decay ◽  
Fusarium Rot

Apples are kept in controlled atmosphere cold storage for 9 to 12 months and are highly susceptible to postharvest decay caused by various fungi. Fusarium avenaceum is a wound pathogen that has been shown to account for the majority of Fusarium rot on apple fruit in Croatia (1). F. avenaceum produces an array of mycotoxins including moniliformin, acuminatopyrone, and chrysogine, which are of primary concern for the apple processing industry (2). In February 2013, ‘Gala’ apple fruits with soft, circular, brown, watery lesions with characteristic abundant whitish mycelium covering the surface of the colonized fruit were obtained from bins from a commercial storage facility located in Pennsylvania. Several samples were collected and prepared for pathogen isolation. Apples were rinsed with sterile water, and the lesions were sprayed with 70% ethanol until runoff. The apple skin was aseptically removed with a scalpel, and asymptomatic tissue was placed onto full strength potato dextrose agar (PDA) petri plates without antibiotics and incubated at 25°C under natural light. Two single-spore isolates were propagated on PDA and permanent cultures were maintained as slants and stored in a cold room at 4°C in the dark. Fungal colonies initially formed abundant fluffy white mycelium and produced a golden orange pigment on PDA at 25°C. Isolates were identified as Fusarium based on cultural and conidial morphology as macroconidia were slightly falcate, thin-walled, usually 3 to 5 septate, with a tapering apical cell that was on average 23.6 μm long × 5.0 μm wide (n = 50). Microconidia were produced on PDA plates while chlamydospores were not evident. Identity of the isolates was confirmed through DNA extraction followed by amplification and sequencing of the translation elongation factor (EF-1α, 350 bp) gene region. The amplicons were sequenced using the forward and reverse primers and assembled into a consensus representing 2X coverage. MegaBLAST analysis revealed that both isolates were 100% identical with many other culture collection F. avenaceum sequences in Genbank (Accessions JQ949291.1, JQ949305.1, and JQ949283.1), which confirms their identification in conjunction with the morphological observations. Koch's postulates were conducted to determine pathogenicity using organic ‘Gala’ apple fruit that were surface sanitized with soap and water, sprayed with 70% ethanol, and wiped dry. The fruit were wounded with a finishing nail to 3 mm depth, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml) using a hemocytometer, and stored at 25°C in 80-count boxes on paper trays for 21 days. Water-only controls were symptomless. Ten fruit composed a replicate for each isolate, and the experiment was repeated. Symptoms observed on artificially inoculated ‘Gala’ apple fruit were identical to the decay observed on ‘Gala’ apples that were obtained from cold storage. Decay caused by F. avenaceum may represent an emerging problem for the apple storage and processing industry. Therefore, it is important to monitor for this pathogen to prevent future losses and mycotoxin contamination of processed fruit products caused by this fungus. To the best of our knowledge, this is the first report of Fusarium rot caused by F. avenaceum on apple fruit from cold storage in the United States. References: (1) Z. Sever et al. Arch. Ind. Hygiene Toxicol. 63:463, 2012. (2) J. L. Sorenson. J. Agric. Food Chem. 57:1632, 2009.

scholarly journals First Report of Colletotrichum fioriniae Causing Postharvest Decay on ‘Nittany’ Apple Fruit in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 993-993 ◽  
Author(s):  
L. P. Kou ◽  
V. Gaskins ◽  
Y. G. Luo ◽  
W. M. Jurick
Keyword(s):  
United States ◽  
Cold Storage ◽  
Management Practices ◽  
The United States ◽  
Apple Fruit ◽  
Morphological Identification ◽  
Conidial Suspension ◽  
First Report ◽  
Postharvest Decay ◽  
Bitter Rot

Bitter rot of apple is caused by Colletotrichum acutatum and C. gleosporioides and is an economically important disease in the mid-Atlantic and southern regions of the United States (1). However, other Colletotrichum spp. have been found to infect apple and pear fruit in Croatia that include C. fioriniae and C. clavatum (3). The disease is favorable under wet, humid conditions and can occur in the field or during storage causing postharvest decay (2). In February 2013, ‘Nittany’ apples with round, brown, dry, firm lesions having acervuli in concentric rings were observed at a commercial cold storage facility in Pennsylvania. Samples were placed on a paper tray in an 80-count apple box and immediately transported to the lab. Fruit were rinsed with sterile water, and lesions were sprayed with 70% ethanol until runoff. The skin was aseptically removed with a scalpel, and tissue under the lesion was placed onto potato dextrose agar (PDA) petri dishes. Dishes were incubated at 25°C with constant light, and a single-spore isolate was propagated on PDA. Permanent cultures were maintained as PDA slants stored at 4°C in darkness. The isolate was identified as a Colletotrichum sp. based on culture morphology, having light gray mycelium with a pinkish reverse and abundant pin-shaped melanized acervuli oozing pink conidia on PDA. Conidia were fusiform, pointed at one or both ends, one-celled, thin-walled, aseptate, hyaline, and averaged 10.5 μm (7.5 to 20 μm) long and 5.1 μm (5 to 10 μm) wide (n = 50). Genomic DNA was extracted from mycelia and amplified using conventional PCR and gene specific primers for 313 bp of the Histone 3 gene and with ITS4/5 primers for the internal transcribed spacer (ITS) rDNA region. MegaBLAST analysis of both gene sequences showed that our isolate was identical to other Colletotrichum fioriniae sequences in GenBank and was 100% identical to culture-collection C. fioriniae isolate CBS:128517, thus confirming the morphological identification. To prove pathogenicity, Koch's postulates were conducted using organic ‘Gala’ apple fruit that were washed with soap and water, sprayed with 70% ethanol, and wiped dry. The fruit were wounded with a sterile nail to a 3-mm depth, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml), and stored at 25°C in 80-count boxes on paper trays for 14 days. Lesion diameter was measured from 10 replicate fruit with a digital micrometer and averaged 31.2 mm (±2.5 mm) over two experiments (n = 20). Water-only controls were symptomless. Artificially inoculated ‘Gala’ apples had identical external and internal symptoms (v-shaped decay pattern when the fruit were cut in half) to those observed on ‘Nittany’ apples that were originally obtained from cold storage. Bitter rot caused by C. fioriniae may become an emerging problem for the pome fruit growing industry in the near future, and may require investigation of new disease management practices to control this fungus. This is the first report of postharvest decay caused by C. fioriniae on apple fruit from cold storage in the United States. References: (1) H. W. Anderson. Diseases of Fruit Crops. McGraw-Hill, New York, 1956. (2) A. R. Biggs et al. Plant Dis. 85:657, 2001. (3) D. Ivic et al. J. Phytopathol. 161:284, 2013.

scholarly journals First Report of Alternaria tenuissima Causing Postharvest Decay on Apple Fruit from Cold Storage in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 690-690 ◽  
Author(s):  
L. P. Kou ◽  
V. L. Gaskins ◽  
Y. G. Luo ◽  
W. M. Jurick
Keyword(s):  
United States ◽  
South Africa ◽  
Cold Storage ◽  
Fungal Pathogens ◽  
The United States ◽  
Apple Fruit ◽  
Conidial Suspension ◽  
Single Spore ◽  
Alternaria Tenuissima ◽  
First Report

Apples are grown and stored for 9 to 12 months under controlled atmosphere conditions in the United States. During storage, apples are susceptible to various fungal pathogens, including several Alternaria species (2). Alternaria tenuissima (Nees) Wiltshire causes dry core rot (DCR) on apples during storage and has recently occurred in South Africa (1). Losses range widely, but typically occur at 6 to 8% annually due to this disease (2). In February 2013, ‘Nittany’ apples with round, dark-colored, dry, spongy lesions were obtained from wooden bins in a commercial cold storage facility located in Pennsylvania. Symptomatic fruits were transported to the lab, rinsed with sterile water, and the lesions were sprayed with 70% ethanol until runoff and wiped dry. The skin was aseptically removed with a scalpel, and asymptomatic tissue was placed onto potato dextrose agar (PDA) and incubated at 25°C. Two single-spore isolates were propagated on PDA and permanent cultures were maintained as slants and stored at 4°C. The fungus produced a cottony white mycelium that turned olive-green to brown with abundant aerial hyphae and had a dark brown to black reverse on PDA. Isolates were identified as Alternaria based on conidial morphology as the spores were slightly melanized and obclavate to obpyriform catentulate with longitudinal and transverse septa attached in unbranched chains on simple short conidiophores. Conidia ranged from 10 to 70 μm long (mean 27.7 μm) and 5 to 15 μm wide (mean 5.25 μm) (n = 50) with 1 to 6 transverse and 0 to 2 longitudinal septa. Conidial beaks, when present, were short (5 μm or less) and tapered. Mycelial genomic DNA was extracted, and a portion of the histone gene (357 bp) was amplified via gene specific primers (Alt-His3-F/R) using conventional PCR (Jurick II, unpublished). The forward and reverse sequences were assembled into a consensus representing 2× coverage and MegaBLAST analysis showed that both isolates were 100% identical to Alternaria tenuissima isolates including CR27 (GenBank Accession No. AF404622.1) that caused DCR on apple fruit during storage in South Africa. Koch's postulates were conducted using 10 organic ‘Gala’ apple fruit that were surface sterilized with soap and water, sprayed with 70% ethanol, and wiped dry. The fruit were aseptically wounded with a nail to a 3 mm depth, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml), and stored at 25°C in 80 count boxes on paper trays for 21 days. Mean lesion diameters on inoculated ‘Gala’ apple fruit were 19.1 mm (±7.4), water only controls (n = 10 fruit) were symptomless, and the experiment was repeated. Symptoms observed on artificially inoculated ‘Gala’ apple fruit were similar to the decay observed on ‘Nittany’ apples from cold storage. Based on our findings, it is possible that A. tenuissima can cause decay that originates from wounded tissue in addition to dry core rot, which has been reported (1). Since A. tenuissima produces potent mycotoxins, even low levels of the pathogen could pose a health problem for contaminated fruit destined for processing and may impact export to other countries. To the best of our knowledge, this is the first report of alternaria rot caused by A. tenuissima on apple fruit from cold storage in the United States. References: (1) J. C. Combrink et al. Decid. Fruit Grow. 34:88, 1984. (2) M. Serdani et al. Mycol. Res. 106:562, 2002. (3) E. E. Stinson et al. J. Agric. Food Chem. 28:960, 1980.

scholarly journals First Report of Phytophthora syringae Causing Rot on Apples in Cold Storage in the United States

Plant Disease ◽  
2002 ◽  
Vol 86 (6) ◽  
pp. 693-693 ◽  
Author(s):  
R. A. Spotts ◽  
G. G. Grove
Keyword(s):  
United States ◽  
Cold Storage ◽  
The United States ◽  
River Valley ◽  
Fruit Rot ◽  
Commonwealth Mycological Institute ◽  
Postharvest Diseases ◽  
First Report ◽  
Postharvest Decay ◽  
Wide Range

A decay of ‘Granny Smith’ apples (Malus domestica Borkh.) was observed in 1988, 1990, and 1991 on fruit grown in the lower Hood River Valley of Oregon and stored at 0°C. Harvested fruit were drenched with thiabendazole and stored in October in all years. In mid-November, fruit were sized, drenched with sodium hypochlorite, and returned to cold storage. Decay was observed in January when fruit were removed from cold storage, sorted, and packed. Decayed areas were light brown and firm with a slightly indefinite margin. Losses were less than 1% of fruit packed. Diseased fruit were surface-disinfested with 95% ethanol, and tissue pieces were transferred aseptically to potato dextrose agar acidified with lactic acid and incubated at approximately 22°C. The fungus consistently isolated was identified as Phytophthora syringae (Kleb.) Kleb. based on morphological characters (3). Sporangia were persistent and averaged 60 μm long (range 59 to 69) × 40 μm wide (range 37 to 43). Antheridia were paragynous, and oospores averaged 37 μm (range 31 to 46). ‘Golden Delicious’, ‘Granny Smith’, and ‘Gala’ apples were inoculated with mycelial plugs from a 7-day-old culture of P. syringae and incubated 12 days at 5°C and 7 to 12 days at 22°C. Twenty fruit of each cultivar were used—ten were inoculated, and ten uninoculated fruit served as controls. Lesions developed on all inoculated fruit but not on uninoculated controls. Lesions were spherical, chocolate brown, and firm with no evidence of external mycelia. Lesion morphology was similar on all cultivars. P. syringae was reisolated from lesion margins of all infected fruit. This postharvest decay of apples has not been observed in the Hood River Valley since 1991. Fruit rot of apples caused by P. syringae is known in Canada (1) and is common in the United Kingdom (2), but has not been reported previously in the United States. To our knowledge, this is the first report of postharvest decay of apples by P. syringae in the United States. References: (1) R. G. Ross and C. O. Gourley. Can. Plant Dis. Surv. 49:33, 1969. (2) A. L. Snowdon. A Color Atlas of Postharvest Diseases. CRC Press, Inc., Boca Raton, FL, 1990. (3) G. M. Waterhouse. The Genus Phytophthora. Misc. Publ. 12. The Commonwealth Mycological Institute, Kew, Surrey, England, 1956.

scholarly journals First Report of Alternaria alternata Causing Postharvest Decay on Apple Fruit During Cold Storage in Pennsylvania

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 690-690 ◽  
Author(s):  
W. M. Jurick ◽  
L. P. Kou ◽  
V. L. Gaskins ◽  
Y. G. Luo
Keyword(s):  
Cold Storage ◽  
Alternaria Alternata ◽  
The United States ◽  
Apple Fruit ◽  
Conidial Suspension ◽  
Single Spore ◽  
Koch’S Postulates ◽  
First Report ◽  
Postharvest Decay ◽  
Koch's Postulates

Alternaria rot, caused by Alternaria alternata (Fr.) Keissl., occurs on apple fruit (Malus × domestica Borkh) worldwide and is not controlled with postharvest fungicides currently registered for apple in the United States (1). Initial infections can occur in the orchard prior to harvest, or during cold storage, and appear as small red dots located around lenticels (1). The symptoms appear on fruits within a 2 month period after placement into cold storage (3). In February 2013, ‘Nittany’ apple fruit with round, dark, dry, spongy lesions were collected from bins at commercial storage facility located in Pennsylvania. Symptomatic apples (n = 2 fruits) were placed on paper trays in an 80 count apple box and immediately transported to the laboratory. Fruit were rinsed with sterile water, and the lesions were superficially disinfected with 70% ethanol. The skin was removed with a sterile scalpel, and tissues underneath the lesion were cultured on potato dextrose agar (PDA) and incubated at 25°C with constant light. Two single-spore isolates were propagated on PDA, and permanent cultures were maintained on PDA slants and stored at 4°C in darkness. Colonies varied from light gray to olive green in color, produced abundant aerial hyphae, and had fluffy mycelial growth on PDA after 14 days. Both isolates were tentatively identified as Alternaria based on multicelled conidial morphology resembling “fragmentation grenades” that were medium brown in color, and obclavate to obpyriform catentulate with longitudinal and transverse septa attached in chains on simple conidiophores (2). Conidia ranged from 15 to 60 μm (mean 25.5 μm) long and 10 to 25 μm (mean 13.6 μm) wide (n = 50) with 1 to 6 transverse and 0 to 1 longitudinal septa per spore. To identify both isolates to the species level, genomic DNA was extracted from mycelial plugs and gene specific primers (ALT-HIS3F/R) were used via conventional PCR to amplify a portion of the histone gene (357 bp) (Jurick II, unpublished). Amplicons were sequenced using the Sanger method, and the forward and reverse sequences of each amplicon were assembled into a consensus representing 2× coverage. A megaBLAST analysis revealed that the isolates were 99% identical to Alternaria alternata sequences in GenBank (Accession No. AF404617), which was previously identified to cause decay on stored apple fruit in South Africa. To prove pathogenicity, Koch's postulates were conducted using organic ‘Gala’ apples. The fruit were surface disinfested with soap and water and sprayed with 70% ethanol to runoff. Wounds, 3 mm deep, were done using a sterile nail and 50 μl of a conidial suspension (1 × 104 conidia/ml) was introduced into each wound per fruit. Fruit were then stored at 25°C in 80 count boxes on paper trays for 21 days. Water only was used as a control. Ten fruit were inoculated with each isolate or water only (control) and the experiment was repeated once. Symptoms of decay observed on inoculated were ‘Gala’ apple fruit were identical to the symptoms initially observed on ‘Nittany’ apples obtained from cold storage after 21 days. No symptoms developed on fruit in the controls. A. alternata was re-isolated 100% from apple inoculated with the fungus, completing Koch's postulates. A. alternata has been documented as a pre- and postharvest pathogen on Malus spp. (3). To our knowledge, this is the first report of postharvest decay caused by A. alternata on apple fruit during cold storage in Pennsylvania. References: (1) A. L. Biggs et al. Plant Dis. 77:976, 1993. (2) E. G. Simmons. Alternaria: An Identification Manual. CBS Fungal Biodiversity Center, Utrecht, the Netherlands, 2007. (3) R. S. Spotts. Pages 56-57 in: Compendium of Apple and Pear Diseases, A. L. Jones and H. S. Aldwinkle, eds. American Phytopathological Society, St. Paul, MN, 1990.

scholarly journals First Report of Five Sooty Blotch and Flyspeck Fungi on Prunus americana in the United States

Plant Disease ◽  
2007 ◽  
Vol 91 (12) ◽  
pp. 1685-1685 ◽  
Author(s):  
J. Latinović ◽  
J. C. Batzer ◽  
K. B. Duttweiler ◽  
M. L. Gleason ◽  
G. Sun
Keyword(s):  
United States ◽  
The United States ◽  
Apple Fruit ◽  
Economic Losses ◽  
Research Station ◽  
First Report ◽  
Sooty Blotch ◽  
Sooty Blotch And Flyspeck ◽  
Pcr Products ◽  
Pure Cultures

The sooty blotch and flyspeck (SBFS) complex includes more than 30 fungi that blemish the cuticle of apple fruit, causing economic losses in humid regions worldwide (1). In August 2005, we sampled SBFS-infested wild plum (Prunus americana) fruit growing in hedgerows in Iowa. Colonies were categorized according to mycelial type (1), and isolates were made from representative colonies onto acidified water agar (AWA). Plum skins with SBFS signs were excised, pressed, and photographed. DNA was obtained from purified isolates and also from mycelium and fruiting bodies scraped directly from plum fruit skins. Extracted DNA was amplified using primer pair ITS1-F/Myc1-R (ACTCGTCGAAGGAGCTACG) and PCR products were sequenced using primer pair ITS-1F/ITS4. Six sequences were obtained from pure cultures and seven from colonies on plum fruit skin. BLAST analysis of the 470-bp sequences showed 100% homology to five known species in the SBFS complex: Zygophiala cryptogama, Zygophiala wisconsinensis, Pseudocercosporella sp. RH1, and Stomiopeltis spp. RS1 and RS2 (GenBank Accession Nos. AY598854, AY598853, AY5988645, AY598882, and AY598883, respectively). Observations of colony and fruiting structure morphology from cultures on potato dextrose agar (PDA) and colonies on plums confirmed species identity. A modified version of Koch's postulates was conducted to verify that these fungi caused the signs observed on plum and could also infest apple fruit. In June 2006, 1-month-old cultures on PDA were pulverized in a blender with sterile distilled water, passed through four layers of sterile cheesecloth, and transferred to sterile jars. Each isolate was inoculated onto 20 fruit on plum trees (P. americana) on the Iowa State University (ISU) campus and 20 fruit on cv. Golden Delicious apple trees at the ISU Research Station, Gilbert, IA. Each fruit was disinfested with 70% ethanol, air dried, swabbed with inoculum, and covered with a Fuji bag. At harvest, fungal colonies on fruit were reisolated onto AWA. DNA was extracted from pure cultures; when isolations on agar were unsuccessful, DNA was extracted directly from colonies on fruit. PCR was conducted using ITS1-F/Myc1-R, and PCR products were sequenced using ITS1-F/ITS4. All five species were reisolated and sequenced from apple. Pseudocercosporella sp. RH1 and Stomiopeltis sp. RS1 were sequenced from inoculated plums. Although flyspeck, presumably caused by Schizothyrium pomi, was reported on Japanese plum (P. salicina) in Japan (2) and black cherry (P. serotina) in the United States (3), to our knowledge this is the first report of SBFS fungi on plum in the United States and the first confirmation that fungi from plum can produce SBFS signs on apple fruit. Wild plum may therefore act as a reservoir host, providing inoculum for SBFS infestations on apple. References: (1) J. Batzer et al. Mycologia 97:1268, 2005. (2) H. Nasu and H. Kunoh. Plant Dis. 71:361, 1987. (3) T. B. Sutton. Plant Dis. 72:801, 1988.

scholarly journals First Report of Neofusicoccum ribis Causing Postharvest Decay of Apple Fruit from Cold Storage in Pennsylvania

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 999-999
Author(s):  
W. M. Jurick ◽  
I. Vico ◽  
V. L. Gaskins ◽  
W. J. Janisiewicz ◽  
K. A. Peter
Keyword(s):  
Cold Storage ◽  
Microscopic Investigation ◽  
Apple Fruit ◽  
Storage Facility ◽  
First Report ◽  
Postharvest Decay ◽  
Application Rates ◽  
White Mycelium ◽  
Stem Cankers ◽  
Mycelial Suspension

Neofusicoccum ribis (Slippers, Crous & M.J. Wingf.), previously known as Botryosphaeria ribis (Grossenb. & Duggar), is an aggressive fungal plant pathogen that is part of the N. ribis/N. parvum species complex that causes stem cankers on a variety of woody plant species (2). An isolate of N. ribis was obtained from decayed ‘Honeycrisp’ apple fruit from a commercial cold storage facility located in Pennsylvania in October of 2011. The decayed apple fruit sample had a brownish lesion that was soft, dry, and leathery on the surface while sporulation was not evident. To conduct Koch's postulates, three ‘Golden Delicious’ apple fruits were wound-inoculated with a 50-μl mycelial suspension, obtained from aseptically scraping a 7-day-old potato dextrose agar (PDA) culture of the fungus, and was repeated using ‘Fuji’ apple fruit. The inoculated fruit developed lesions, while water-inoculated fruit were symptomless after 5 days at 20°C. N. ribis was reisolated from infected tissue and was morphologically identical to the original isolate. Genomic DNA was isolated, a portion of the β-tubulin gene was amplified with the gene specific primers, and the amplicon was sequenced and analyzed using BLAST (1). The nucleotide sequence (GenBank Accession No. KC47853) had 99% identity with N. ribis SEGA8 isolate (JN607146.1). The N. ribis isolate produced a grayish-white mycelium with abundant aerial hyphae on PDA and had an olive-colored reverse. Microscopic investigation revealed septate mycelia with right angle branching and conidiomata were not evident on PDA, V8, oatmeal agar (OMA), or water agar (WA). Growth on WA was sparse and transparent, and aerial mycelial growth was not produced. Growth rate analyses were conducted on PDA, V8, and OMA and were 10.1 (±1.39), 20.4 (±1.15), and 17.6 (±0.70) mm/day at 20°C and the experiment was repeated. The minimum inhibitory concentrations (MIC) for the N. ribis isolate was carried out for three postharvest fungicides as described by Pianzzola et al. (3). Briefly, 96 well plates were filled with PDA alone (0 ppm) and PDA amended with 10 fungicide concentrations ranging from 1 to 1,200 ppm for thiabendazole (Mertect), and 1 to 1,000 ppm for fludioxonil (Scholar) and pyrimethanil (Penbotec). A mycelial suspension of the fungus was obtained from pure culture, 50 μl of the mycelial suspension was pipetted into each well, and allowed to grow for 72 h at 25°C. The experiment was conducted twice. The N. ribis isolate displayed MIC values of >1 ppm thiabendazole (Mertect), >1 ppm fludioxonil (Scholar), and 50 ppm pyrimethanil (Penbotec), which are all well below the labeled application rates for these postharvest fungicides. To our knowledge, this is the first report of N. ribis causing postharvest decay on apple fruit obtained from a commercial storage facility in Pennsylvania. References: (1) S. F. Altschul et al. J. Mol. Biol. 215:403, 1990. (2) D. Pavlic et al. Mycologia 101:636, 2009. (3) M. J. Pianzzola et al. Plant Dis. 88:23, 2004.

scholarly journals First Report of Penicillium expansum Isolates Resistant to Pyrimethanil from Stored Apple Fruit in Pennsylvania

Plant Disease ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 1004-1004 ◽  
Author(s):  
H. J. Yan ◽  
V. L. Gaskins ◽  
I. Vico ◽  
Y. G. Luo ◽  
W. M. Jurick
Keyword(s):  
United States ◽  
The United States ◽  
Apple Fruit ◽  
Washington State ◽  
Penicillium Expansum ◽  
Economic Losses ◽  
Conidial Suspension ◽  
Blue Mold ◽  
First Report ◽  
Penicillium Spp

Apples in the United States are stored in low-temperature controlled atmospheres for 9 to 12 months and are highly susceptible to blue mold decay. Penicillium spp. cause significant economic losses worldwide and produce mycotoxins that contaminate processed apple products. Blue mold is managed by a combination of cultural practices and the application of fungicides. In 2004, a new postharvest fungicide, pyrimethanil (Penbotec 400 SC, Janseen PMP, Beerse, Belgium) was registered for use in the United States to control blue mold on pome fruits (1). In this study, 10 blue mold symptomatic ‘Red Delicious’ apples were collected in May 2011 from wooden bins at a commercial facility located in Pennsylvania. These fruit had been treated with Penbotec prior to controlled atmosphere storage. Ten single-spore Penicillium spp. isolates were analyzed for growth using 96-well microtiter plates containing Richards minimal medium amended with a range of technical grade pyrimethanil from 0 to 500 μg/ml. Conidial suspensions adjusted to 1 × 105 conidia/ml were added to three 96-well plates for each experiment; all experiments were repeated three times. Nine resistant isolates had prolific mycelial growth at 500 μg/ml, which is 1,000 times the discriminatory dose that inhibited baseline sensitive P. expansum isolates from Washington State (1). However, one isolate (R13) had limited conidial germination and no mycelial proliferation at 0.5 μg/ml and was categorized as sensitive. One resistant (R22) and one sensitive (R13) isolate were selected on the basis of their different sensitivities to pyrimethanil. Both isolates were identified as P. expansum via conventional PCR using β-tubulin gene-specific primers according to Sholberg et al. (2). Analysis of the 2X consensus amplicon sequences from R13 and R22 matched perfectly (100% identity and 0.0 E value) with other P. expansum accessions in GenBank including JN872743.1, which was isolated from decayed apple fruit from Washington State. To determine if pyrimethanil applied at the labeled rate of 500 μg/ml would control R13 or R22 in vivo, organic ‘Gala’ apple fruit were wounded, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml) of either isolate, dipped in Penbotec fungicide or sterile water, and stored at 25°C for 7 days. Twenty fruit composed a replicate within a treatment and the experiment was performed twice. Non-inoculated water-only controls were symptomless, while water-dipped inoculated fruit had 100% decay with mean lesion diameters of 36.8 ± 2.68 mm for R22 and 38.5 ± 2.61 mm for R13. The R22 isolate caused 30% decay with 21.6 ± 5.44 mm lesions when inoculated onto Penbotec-treated apples, while the R13 isolate had 7.5% decay incidence with mean lesion diameters of 23.1 ± 3.41 mm. The results from this study demonstrate that P. expansum pyrimethanil-resistant strains are virulent on Penbotec-treated apple fruit and have the potential to manifest in decay during storage. To the best of our knowledge, this is the first report of pyrimethanil resistance in P. expansum from Pennsylvania, a major apple growing region for the United States. Moreover, these results illuminate the need to develop additional chemical, cultural, and biological methods to control this fungus. References: (1) H. X. Li and C. L. Xiao. Phytopathology 98:427, 2008. (2) P. L. Sholberg et al. Postharvest Biol. Technol. 36:41, 2005.

scholarly journals First Report of Mucor Rot on Stored ‘Gala’ Apple Fruit Caused by Mucor piriformis in Pennsylvania

Plant Disease ◽  
2014 ◽  
Vol 98 (8) ◽  
pp. 1157-1157 ◽  
Author(s):  
J. Li ◽  
V. L. Gaskins ◽  
H. J. Yan ◽  
Y. G. Luo ◽  
W. M. Jurick II
Keyword(s):  
United States ◽  
Cultural Practices ◽  
The United States ◽  
Apple Fruit ◽  
Morphological Identification ◽  
Natural Light ◽  
First Report ◽  
Consensus Sequences ◽  
Mucor Piriformis ◽  
Atmosphere Storage

Mucor piriformis E. Fischer causes Mucor rot of pome and stone fruits during storage and has been reported in Australia, Canada, Germany, Northern Ireland, South Africa, and portions of the United States (1,2). Currently, there is no fungicide in the United States labeled to control this wound pathogen on apple. Cultural practices of orchard sanitation, placing dry fruit in storage, and chlorine treatment of dump tanks and flumes are critical for decay management (3,4). Cultivars like ‘Gala’ that are prone to cracking are particularly vulnerable as the openings provide ingress for the fungus. Mucor rot was observed in February 2013 at a commercial packing facility in Pennsylvania. Decay incidence was ~15% on ‘Gala’ apples from bins removed directly from controlled atmosphere storage. Rot was evident mainly at the stem end and was light brown, watery, soft, and covered with fuzzy mycelia. Salt-and-pepper colored sporangiophores bearing terminal sporangiospores protruded through the skin. Five infected apple fruit were collected, placed in an 80-count apple box on trays, and temporarily stored at 4°C. Isolates were obtained aseptically from decayed tissue, placed on potato dextrose agar (PDA) petri plates, and incubated at 25°C with natural light. Five single sporangiospore isolates were identified as Mucor piriformis based on cultural characteristics according to Michailides and Spotts (1). The isolates produced columellate sporangia attached terminally on short and tall, branched and unbranched sporangiophores. Sporangiospores were ellipsoidal, subspherical, and smooth. Chlamydospore-like resting structures (gemmae), isogametangia, and zygospores were not evident in culture. Mycelial growth was examined on PDA, apple agar (AA), and V8 agar (V8) at 25°C with natural light. Isolates grew best on PDA at rates that ranged from 38.4 ± 5.3 to 34.5 ± 2.41 mm/day, followed by AA from 30.5 ± 1.22 to 28.5 ± 2.51 mm/day, and V8 from 29.2 ± 3.0 to 26.7 ± 2.17 mm/day. Species-level identification was conducted by isolating genomic DNA, amplifying a portion of the 28S rDNA gene, and directly sequencing the products. MegaBLAST analysis of the 2X consensus sequences revealed that all five isolates were 99% identical to M. piriformis (GenBank Accession No. JN2064761) with E values of 0.0, which confirms the morphological identification. Koch's postulates were conducted using organic ‘Gala’ apples that were surface sanitized with soap and water, then sprayed with 70% ethanol and allowed to air dry. Wounds 3 mm deep were created using the point of a finishing nail and then inoculated with 50 μl of a sporangiospore suspension (1 × 105 sporangiospores/ml) for each isolate. Ten fruit were inoculated with each isolate, and the experiment was repeated. The fruit were stored at 25°C in 80-count boxes on paper trays for 14 days. Decay observed on inoculated ‘Gala’ fruit was similar to symptoms originally observed on ‘Gala’ apples from storage and the pathogen was re-isolated from inoculated fruit. This is the first report of M. piriformis causing postharvest decay on stored apples in Pennsylvania and reinforces the need for the development of additional tools to manage this economically important pathogen. References: (1) T. J. Michailides, and R. A. Spotts. Plant Dis. 74:537, 1990. (2) P. L. Sholberg and T. J. Michailides. Plant Dis. 81:550, 1997. (3) W. L. Smith et al. Phytopathology 69:865, 1979. (4) R. A. Spotts. Compendium of Apple and Pear Diseases and Pests: Second Edition. APS Press, St. Paul, MN, 2014.

First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

2010 ◽  
Vol 11 (1) ◽  
pp. 42 ◽  
Author(s):  
F. Mathew ◽  
B. Kirkeide ◽  
T. Gulya ◽  
S. Markell
Keyword(s):  
United States ◽  
Helianthus Annuus ◽  
The United States ◽  
Fusarium Sporotrichioides ◽  
Charcoal Rot ◽  
Koch’S Postulates ◽  
First Report ◽  
Fusarium Acuminatum ◽  
Helianthus Annuus L ◽  
Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

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