First Report of Soft Rot of Potatoes Caused by Dickeya dadantii in Zimbabwe

A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in April 2009 to assess the prevalence of bacterial soft rot. A total of 125 tubers with soft rot symptoms were collected. The disease caused severe economic losses ranging from 20 to 60% on tubers in the field and in storage. Affected tubers had symptoms that ranged from light vascular discoloration to complete seed piece decay. Infected tuber tissue was often cream colored and soft to the touch. In the field, plants showed severe wilting, often accompanied by a slimy, brown necrosis of the lower stems. Seventy-five of 125 isolations from diseased tubers yielded pectolytic bacteria on crystal violet pectate (CVP) medium and colonies were characterized after purification on King's B medium. All 75 isolates were gram-negative rods, oxidase negative, facultatively anaerobic, able to degrade pectate, and rot potato slices. They grew at 37°C, were sensitive to erythromycin, positive for phosphatase, indole production, cis-aconitate, lactose, d-arabinose, meso-tartrate, casein, d-melibiose, myo-inositol, and malonate utilization, while negative for acid production from trehalose, inuline, and α-methyl glucose. Dickeya dadantii (Erwinia chrysanthemi 3937 from the Scottish Research Institute) was included in all biochemical and pathogenicity tests. These characteristics are typical for two species, D. zeae and D. dadantii (2). Thus, the 75 isolates were further identified by PCR amplification with BOX and REP primers (3) and five isolates by gyrB sequence analysis (1). These analyses give support for the isolates being D. dadantii. Partial gyrB sequence analysis showed that the analyzed isolates had 96% sequence identity with the D. dadantii type strain Ech 586T (GenBank Accession No. CP001836.1). One-microliter suspensions (108 CFU per ml) of 20 samples were injected into the stolon end of potato tubers (S. tuberosum L.) cv. BP1. Each isolate was inoculated into three tubers, which were maintained at 25°C. Three control tubers were inoculated with sterile distilled water. Soft rot symptoms identical to those observed in the field and in storage appeared on all inoculated tubers 1 to 2 days after inoculation but not on the control tubers. A bacterium with identical characteristics to those described above was consistently reisolated from the rotted tissue of inoculated tubers. To our knowledge, this is the first report of soft rot on potato in Zimbabwe caused by D. dadantii, formerly referred to as E. chrysanthemi. This finding has implications for import and export of potato material into and out of Zimbabwe. Zimbabwe imports seed from various countries because of the current seed shortage and exports table potatoes to other African states. References: (1) C. Brady et al. Int. J. Syst. Evol. Micobiol. 59:2339, 2009. (2) R. Samson et al. Int. J. Syst. Evol. Microbiol. 55:1415, 2005. (3) J. Versalovic et al. 1991. Nucleic Acids Res. 19:6823, 1991.

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First Report of a Fruit Rot of Pumpkin Caused by Acidivorax avenae subsp. citrulli in Georgia

Plant Disease ◽

10.1094/pdis.1999.83.2.199b ◽

1999 ◽

Vol 83 (2) ◽

pp. 199-199 ◽

Cited By ~ 31

Author(s):

D. B. Langston ◽

R. D. Walcott ◽

R. D. Gitaitis ◽

F. H. Sanders

Keyword(s):

Polyclonal Antibodies ◽

Pcr Amplification ◽

Tween 80 ◽

Soft Rot ◽

Fruit Rot ◽

Identification System ◽

Banding Patterns ◽

First Report ◽

Microbial Identification ◽

Necrotic Spots

In September 1998, a fruit rot was reported affecting pumpkin (Cucurbita pepo) in a commercial field in Terrell Co., Georgia. Symptoms on the surface of fruit occurred as round, necrotic spots or cracks a few millimeters in diameter. With age, the tissue surrounding these lesions became soft and wrinkled. A soft rot expanded into the flesh of the pumpkin, originating from the lesions observed on the surface. In time, infected pumpkins totally collapsed. V-shaped, necrotic lesions occurred at the margin of the leaf and extended inward toward the mid-rib. Samples were collected from the field and bacteria were isolated from fruit and leaf lesions onto King's medium B (1). The bacterium isolated was rod shaped, gram negative, nonflourescent, oxidase positive, Tween 80 positive, carboxymethyl cellulose positive, β-OH butyrate positive, and malonate negative. The bacterium reacted positively with polyclonal antibodies specific for the watermelon fruit blotch pathogen Acidivorax avenae subsp. citrulli and was identified as A. avenae subsp. citrulli by MIDI (Microbial Identification System, Newark, DE) according to statistical analysis of fatty acid data. Results from polymerase chain reaction (PCR) amplification of the bacterium isolated from pumpkin yielded 360-bp fragments that, when digested with the restriction enzyme HaeIII, had DNA banding patterns identical to those of stock A. avenae subsp. citrulli DNA. Koch's postulates were completed successfully with 2-week-old watermelon seedlings. This is the first report of A. avenae subsp. citrulli causing fruit rot of pumpkin in Georgia. Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

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First Report of Black Soft Rot of Indian Gooseberry Caused by Syncephalastrum racemosum

Plant Disease ◽

10.1094/pdis.2004.88.5.575c ◽

2004 ◽

Vol 88 (5) ◽

pp. 575-575 ◽

Cited By ~ 2

Author(s):

Neelima Garg ◽

Om Prakash ◽

B. K. Pandey ◽

B. P. Singh ◽

G. Pandey

Keyword(s):

Cellulase Activity ◽

Basal Medium ◽

Petri Dish ◽

Soft Rot ◽

Cellulolytic Activity ◽

Academic Press ◽

First Report ◽

Syncephalastrum Racemosum ◽

Indian Gooseberry ◽

Pathogenicity Tests

Indian gooseberry (Emblica officinalis Gaertn.) is a medicinal plant with high nutraceutical value. During November and December 2003, soft rot was noticed on harvested and stored (20 ± 5°C and 65 ± 5% relative humidity) fruits at the experimental farm in Rehmanhera, Lucknow, India (26°50′N, 80°54′E). These fruits had numerous, minute brown necrotic lesions showing white mycelial growth. A pronounced halo of water-soaked, faded tissue surrounded the lesion between the fringe of mycelium and healthy tissues. The rotted surface was covered with a black, powdery layer of spores. On Czapek yeast extract agar, fungal colonies were blackish grey, moderately dense, and covered the entire petri dish. The fungus produced aseptate mycelium. The sporangial heads were 30 to 50 μm in diameter with sporangiospores found linearly within cylindrical sacs (merosporangia) borne on spicules around the columella. Sporangiospores, spherical to cylindrical in shape and borne in chains, measured 3.0 to 5.0 μm long. The fungus was morphologically and physiologically identified as Syncephalastrum racemosum Schr. (2). For pathogenicity tests, healthy fruits (10 replicates) were surface sterilized and punctured inoculated aseptically with 1.0 × 106 conidia and incubated at 20 ± 5°C Typical symptoms of the disease appeared after 4 days. The fungus exhibited a strong level of cellulolytic activity as indicated by prolific growth on Indian gooseberry fiber waste under solid-state fermentation conditions. The level of cellulase activity (1) was 21 filter paper activity unit per ml at 72 hr in culture supernatant of basal medium having carboxymethyl cellulose as the carbon source. The fungus showed resistance to tannins (as much as 2%), since it could grow well in liquid growth medium (Czapek Dox broth) with 2% tannins and aonla juice with 1.8% tannins. Since Indian gooseberry is rich in fiber (2.5 to 3.4%) and tannins (1.5 to 2.0%), this may be an important pathogen. To our knowledge, this is the first report of the occurrence of Syncephalastrum racemosum on Indian gooseberry fruits. References: (1) T. K. Ghose. Pure Appl. Chem. 59(2):257, 1987. (2) J. I. Pitt and A. D. Hocking. Fungi and Food Spoilage. Academic Press. North Ryde, Australia, 1985.

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Emergence of Bacterial Soft Rot in Cucumber Caused by Pectobacterium carotovorum subsp. brasiliense in China

Plant Disease ◽

10.1094/pdis-05-16-0763-re ◽

2017 ◽

Vol 101 (2) ◽

pp. 279-287 ◽

Cited By ~ 14

Author(s):

Xianglong Meng ◽

Ali Chai ◽

Yanxia Shi ◽

Xuewen Xie ◽

Zhanhong Ma ◽

...

Keyword(s):

Sequence Analysis ◽

Soft Rot ◽

Economic Losses ◽

Pectobacterium Carotovorum ◽

Bacterial Soft Rot ◽

Bacterial Strains ◽

Phenotypic Properties ◽

Gene Sequence Analysis ◽

Wide Range ◽

Carotovorum Subsp

During 2014 to 2015, a devastating bacterial soft rot on cucumber stems and leaves occurred in Shandong, Shanxi, Hebei, Henan, and Liaoning provinces of China, resulting in serious economic losses for cucumber production. The gummosis emerged on the surface of leaves, stems, petioles, and fruit of cucumber. The basal stem color was dark brown and the stem base turned to wet rot. Yellow spots and wet rot emerged at the edge of the infected cucumber leaves and gradually infected the leaf centers. In total, 45 bacterial strains were isolated from the infected tissues. On the basis of phenotypic properties of morphology, physiology, biochemistry, and 16S ribosomal RNA gene sequence analysis, the pathogen was identified as Pectobacterium carotovorum. Multilocus sequence analysis confirmed that the isolates were P. carotovorum subsp. brasiliense, and the pathogens fell in clade II. The pathogenicity of isolated bacteria strains was confirmed. The strains reisolated were the same as the original. The host range test confirmed that strains had a wide range of hosts. As far as we know, this is the first report of cucumber stem soft rot caused by P. carotovorum subsp. brasiliense in China as well as in the world, which has a significant economic impact on cucumber production.

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Pectobacterium carotovorum subsp. brasiliense Causes Soft Rot and Death of Neobuxbaumia tetetzo in Zapotitlan Salinas Valley, Puebla, Mexico

Plant Disease ◽

10.1094/pdis-02-18-0370-re ◽

2019 ◽

Vol 103 (3) ◽

pp. 398-403 ◽

Cited By ~ 3

Author(s):

Dimas Mejía-Sánchez ◽

Sergio Aranda-Ocampo ◽

Cristian Nava-Díaz ◽

Daniel Teliz-Ortiz ◽

Manuel Livera-Muñoz ◽

...

Keyword(s):

Soft Rot ◽

Genetic Identification ◽

Pectobacterium Carotovorum ◽

Bacterial Isolates ◽

First Report ◽

Whole Plant ◽

Salinas Valley ◽

Pathogenicity Tests ◽

Carotovorum Subsp ◽

Rdna Igs

Neobuxbaumia tetetzo (Coulter) Backeberg (tetecho) is a columnar cactus endemic to Mexico. Tetecho plants, flowers, fruits, and seeds play an important role in the semiarid ecosystem, as they serve as a refuge and food for insects, bats, and birds, and are widely used by ethnic groups since pre-Hispanic times. Tetecho is affected by a soft rot that damages the whole plant and causes its fall and disintegration. Eight bacterial colonies of similar morphology were isolated from plants showing soft rot and inoculated in healthy tetecho plants, reproducing typical symptoms of soft rot 9 days after inoculation. Ten representative isolates were selected for phenotypic and genetic identification using 16s rDNA, IGS 16S-23S rDNA, and rpoS genes and for pathogenicity tests on several members of the cactus family and other plants. Based on the results, these bacterial isolates were identified as Pectobacterium carotovorum subsp. brasiliense. Inoculation of this bacteria caused soft rot in different cacti, fruits, leaves, and roots of other plants. This is the first report of the subspecies brasiliense of P. carotovorum causing soft rot and death in cacti in the world and the first report of this subspecies in Mexico.

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Identification of Dickeya zeae as a Causal Agent of Bacterial Soft Rot in Banana in China

Plant Disease ◽

10.1094/pdis-07-13-0711-re ◽

2014 ◽

Vol 98 (4) ◽

pp. 436-442 ◽

Cited By ~ 12

Author(s):

Jingxin Zhang ◽

Huifang Shen ◽

Xiaoming Pu ◽

Birun Lin ◽

John Hu

Keyword(s):

Sequence Analysis ◽

16S Rdna ◽

Reference Strain ◽

Guangdong Province ◽

Soft Rot ◽

Bacterial Soft Rot ◽

Dickeya Dadantii ◽

Guangzhou City ◽

Rice Pathogens ◽

Biochemical Testing

Bacterial soft rot of banana was first noticed in 2009 in Guangzhou city, China. The disease also was observed on various banana cultivars of different genotypes in several other cities. Symptoms of the disease included leaf wilting, collapse of pseudostems, and unusual odor. Five isolated strains that fulfilled Koch's postulates were used for biochemical testing. The five strains were most similar to Dickeya dadantii or D. zeae, but were much less similar to D. paradisiaca when using several phenotype characteristics. Sequence analysis of 16S rDNA, dnaX, gryB, and recA of a reference strain revealed a similarity of 99% with the sequences of D. zeae, rather than D. paradisiaca. Phylogenic analysis of concatenated sequences of dnaX, gryB, and recA indicated that the banana strain constituted a distinguishable clade with several D. zeae strains involving rice pathogens D. zeae EC1 and ZJU1202 from Guangdong province, but the banana pathogen had several characteristics that distinguished it from the rice pathogens. Therefore, the banana pathogen was determined to be D. zeae. This is the first report of banana soft rot caused by D. zeae in China; however, the pathogen can infect other important crops.

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First report of soft rot of cabbage caused by Pectobacterium wasabiae in Japan

Plant Disease ◽

10.1094/pdis-02-21-0238-pdn ◽

2021 ◽

Author(s):

Taketo Fujimoto ◽

Takato Nakayama ◽

Takehiro Ohki ◽

Tetsuo MAOKA

Keyword(s):

Sequence Analysis ◽

Dna Sequences ◽

Acid Production ◽

Field Experiments ◽

Soft Rot ◽

Likelihood Method ◽

Bacterial Suspension ◽

Aconitate Hydratase ◽

First Report ◽

Pectolytic Activity

Cabbage (Brassica oleracea var. capitata) is one of the important vegetables in Japan. In the summer of 2019, some cabbages with soft rot were found in commercial fields in Hokkaido, the northern island in Japan. All diseased plants showed grey to brown discoloration and expanding water-soaked lesions on leaves. We obtained two independent strains (NACAB191 and NACAB192) from diseased leaves. DNA from these strains yielded an expected single size amplicon with the primer set of PhF/PhR for P. wasabiae (De Boer et al. 2012) by PCR, but did not yield the expected amplicon with the primer set of BR1f/L1r for P. carotovorum subsp. brasiliense (Duarte et al. 2004) and Eca1f/Eca2r for P. atrosepticum (De Boer et al., 1995) by PCR. These two strains grew at 37°C, and their ability to utilize raffinose and lactose. These bacterial strains were gram-negative and rod-shaped. The bacterium was positive for O-nitrophenyl-beta-D-galactopyranoside, N-acetylglucosaminyl transferase, gelatin liquefaction, and acid production from D-galactose, lactose, melibiose, raffinose, citrate, and trehalose. The bacterium was negative for indole production and acid production from maltose, α-methyl-D-glucoside, sorbitol, D-arabitol, inositol, inulin, and melezitose. All strains exhibited pectolytic activity on potato slices. The sequence analysis of 16S rDNA (LC597897 and LC597898) showed more than 98% identities to P. wasabiae strain (e.g. HAFL01 in Switzerland) by BLAST analysis. In addition, Multi-locus sequence analysis (Ma et al. 2007) was performed by MEGA10 (Kumer et al. 2018) using concatenated DNA sequences of seven housekeeping genes (aconitate hydratase(acnA, LC597923 and LC597924), glyceraldehyde-3-phosphate dehydrogenase A(gapA, LC597970 and LC597971), isocitrate dehydrogenase (icdA, LC597996 and LC597997), malate dehydrogenase(mdh, LC598022 and LC598023), mannitol-1-phosphate dehydrogenase (mtlD, LC598048 and LC598049), glucose-6-phosphate isomerase (pgi, LC598074 and LC598075) and gamma-glutamyl phospate reductase (proA, LC598079 and LC598080)), and all clustered NACAB191 and NACAB192 into a clade containing other confirmed strains of P. wasabiae. As a result, these two strains shared high identity with each other (>98%, E-Values showed 0). The clade containing these two strains was consistently placed in a larger clade with the other P. wasabiae and 100% bootstrap support for its separation from other Pectobacterium species available in GenBank when the consensus tree constructed using Maximum Likelihood method. Pathogenicity of these strains against cabbage (cv. ‘Rakuen’) was confirmed by the field experiments with five weeks growth plants sprayed with bacterial suspension (1×107cfu/ml). Thirty cabbages per strain were used in this study, 12 plants treated the suspension of NACAB191 and 16 plants treated the suspension of NACAB192 which died with the same soft rot symptoms about four weeks after inoculation. Whereas water-inoculated plants remained symptomless. Strains re-isolated from the artificially diseased stems were confirmed as P. wasabiae using the methods as biochemical characterization and multiple genetic analyses. Based on the disease symptoms, the cultural, molecular, and pathological features of the strains, we conclude that the soft rot symptoms of cabbage in Hokkaido in 2019 were caused by P. wasabiae. To our knowledge, this is the first report of P. wasabiae as the soft rot disease agent of cabbage in Japan.

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First Report of Anthracnose of Sunflower Sprouts Caused by Colletotrichum acutatum in New Mexico

Plant Disease ◽

10.1094/pdis-08-12-0805-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 838-838

Author(s):

J. M. French ◽

J. J. Randall ◽

R. A. Stamler ◽

A. C. Segura ◽

N. P. Goldberg

Keyword(s):

New Mexico ◽

Sequence Analysis ◽

The United States ◽

Disease Diagnosis ◽

Colletotrichum Acutatum ◽

Economic Losses ◽

Distilled Water ◽

Koch’S Postulates ◽

First Report ◽

Koch's Postulates

In December 2011, edible sunflower sprouts (Helianthus annus) of two different commercially grown cultivars (Sungrown and Tiensvold) exhibiting stem and cotyledon lesions were submitted to the New Mexico State University Plant Clinic for disease diagnosis. The sample originated from an organic farm in Santa Fe County where the grower utilizes a small indoor growing facility. Stem lesions were elongate, reddish brown, and often constricted, resulting in stem girdling. Lesions on the cotyledons were dark brown with tan centers and round to irregular in shape. In some cases, the entire cotyledon was blighted. Fungal hyphae were observed on some lesions using a dissecting microscope. Colletotrichum acutatum was isolated from stem and cotyledon lesions when symptomatic tissue was plated on water agar. Conidia were fusiform ranging from 6.4 to 18.4 μm long and 2.1 to 5.1 μm wide and averaged 11.9 μm × 3.4 μm. Spores were measured from cream-colored colonies produced on acidified potato dextrose agar. PCR amplification and sequence analysis of 5.8S ribosomal DNA and internal transcribed spacers I and II was performed using primers ITS4 and ITS6 (2). An amplification product of approximately 600 base pairs in size was directly sequenced (GenBank Accession No. JX444690). A BLAST search of the NCBI total nucleotide collection revealed a 99% identity to multiple C. acutatum (syn: C. simmondsii) isolates. Four isolates were identified as C. acutatum based on morphological characteristics and DNA analysis. Koch's postulates were performed using four isolates of the pathogen and the two commercial sunflower cultivars (Sungrown and Tiensvold) originally submitted for disease analysis. Sunflower seeds were imbibed in distilled water for 24 h then sewn into peat plugs. Prior to seed germination, 5 ml of a C. acutatum spore solution (1 × 106/ml) from each isolate was applied to five peat plugs using an atomizer. Control plants were inoculated with distilled water and otherwise treated identically. Both sunflower cultivars were inoculated with each isolate of the pathogen and the test was replicated twice. The sewn peat plugs were incubated for 5 days at 21°C and 50% relative humidity. Symptoms similar to the original samples were present on 100% of the sprouts after 5 days. PCR and sequence analysis performed on cultures obtained from lesions showed a 100% match to the original New Mexico isolates fulfilling Koch's postulates. In an indoor organic facility, such as the one in NM, this disease has the potential to be very difficult to manage and the potential to infect a high percentage of the crop resulting in significant economic losses. To our knowledge, this is the second report of C. acutatum on sunflower sprouts in the United States (1) and the first report in New Mexico. References: (1) S. T. Koike et al. Plant Dis. 93:1351, 2009. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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First Report of a New Leaf Spot Caused by Plectosphaerella cucumerina on Field Grown Endive (Cichorium endivia) in Italy

Plant Disease ◽

10.1094/pdis-12-12-1168-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 848-848 ◽

Cited By ~ 11

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

G. Ortu ◽

M. L. Gullino

Keyword(s):

Leaf Spot ◽

Economic Losses ◽

Leaf Spot Disease ◽

Fluorescent Light ◽

Conidial Suspension ◽

Fresh Market ◽

First Report ◽

Cichorium Endivia ◽

Pathogenicity Tests ◽

Plectosphaerella Cucumerina

During summer 2012, symptoms of a new leaf spot disease were observed in several commercial fields in Treviglio (Bergamo, northern Italy) on plants of curly (Cichorium endivia var. crispum) and Bavarian (C. endivia var. latifolium) endive (Asteraceae). This crop is widely grown in the region for fresh market. The first symptoms on leaves of affected plants consisted of small (1 mm) black-brown spots of irregular shape, later coalescing into larger spots, up to 10 to 15 mm diameter. Eventually, spots were surrounded by a yellow halo. Particularly, affected tissues rotted quickly under high moisture. Disease severity was greatest at 75 to 90% RH and air temperature between 23 and 30°C, where affected tissues rotted quickly. This disease resulted in severe production losses. On one farm in particular, three different fields totaling 2 ha, 5 to 13% of the plants were affected. Diseased tissue was excised, immersed in a solution containing 1% sodium hypochlorite for 60 s, rinsed in water, then placed on potato dextrose agar (PDA) medium, containing 25 mg/liter of streptomycin sulphate. After 5 days, a fungus developed producing a whitish-orange mycelium when incubated under 12 h/day of fluorescent light at 23°C. The isolates obtained were purified on PDA. On this medium, they produced hyaline elliptical and ovoid conidia, rarely septate, measuring 5.0 to 9.0 × 1.7 to 3.9 (average 6.0 × 2.9) μm. Conidia were born on phialides, single, clavate, and 2.8 × 1.4 μm. Such characteristics are typical of Plectosphaerella sp. (1,2). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (3) and sequenced. BLAST analysis of the 530-bp segment obtained from C. endivia var. crispum isolate PLC28 and of the 527-bp from C. endivia var. latifolium isolate PLC 30, respectively, showed 99% similarity with the sequence of Plectosphaerella cucumerina (anamorph Plectosporium tabacinum), GenBank EU5945566. The nucleotide sequences of isolates PLC 28 and PLC 30 have been assigned the GenBank accession numbers KC293994 and KC293993, respectively. To confirm pathogenicity, tests were conducted on 30-day-old C. endivia plants. C. endivia var. crispum cv Myrna and C. endivia var. latifolium cv. Sardana plants, grown in 2-liter pots (1 plant per pot, 10 plants per treatment) were inoculated by spraying a 106 CFU/ml conidial suspension of the two isolates of P. cucumerina, prepared from 10-day-old cultures, grown on PDA. Inoculated plants were maintained in a growth chamber at 25 ± 1°C and 90% RH for 5 days. Non-inoculated plants, only sprayed with water, served as controls. All plants inoculated with the two isolates, showed typical leaf spots 7 days after the artificial inoculation, similar to those observed in the field. Later, spots enlarged and leaves rotted. Non-inoculated plants remained healthy. P. cucumerina was reisolated from inoculated plants. The pathogenicity tests were conducted twice with identical results. This is, to our knowledge, the first report of P. cucumerina on endive n Italy, as well as worldwide. Due to the importance of the crop in Italy, this disease can cause serious economic losses. References: (1) A. Carlucci et al. Persoonia 28:34, 2012. (2) M. E. Palm et al. Mycologia 87:397, 1995. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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First Report of Bacterial Soft Rot on Anubias barteri var. nana Caused by Dickeya dadantii in China

Plant Disease ◽

10.1094/pdis-03-15-0291-pdn ◽

2016 ◽

Vol 100 (2) ◽

pp. 518

Author(s):

J. Wang ◽

L. Wang ◽

F. Wang ◽

G. Cao ◽

G. P. RAO ◽

...

Keyword(s):

Soft Rot ◽

Bacterial Soft Rot ◽

Dickeya Dadantii ◽

First Report

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First Report of Fusarium solani Fruit Rot of Pumpkin (Cucurbita pepo) in Trinidad

Plant Disease ◽

10.1094/pdis-93-5-0547b ◽

2009 ◽

Vol 93 (5) ◽

pp. 547-547

Author(s):

S. N. Rampersad

Keyword(s):

Fusarium Solani ◽

Cucurbita Pepo ◽

Morphological Characteristics ◽

Soft Rot ◽

The United States ◽

Fruit Rot ◽

Laboratory Manual ◽

First Report ◽

Pathogenicity Tests ◽

Negative Controls

Trinidad is a major exporter of pumpkins (Cucurbita pepo L.) to other Caribbean countries, Canada, and the United States. Producers and exporters have reported 50 to 80% yield losses because of soft rot and overnight collapse of fruit at the pre- and postharvest stages. Severe fruit rot occurred in fields in Victoria County in South Trinidad between April and May 2006 (mid-to-late dry season) with an increase in the severity and number of affected fruit in the rainy season (July to December). Symptoms began as water-soaked lesions on the fruit of any age at the point of contact with the soil. The disease progressed to a soft rot with leakage and whole fruit collapse. A dark brown, soft decay also developed at the base of the main vines. Fusarium solani was isolated on selective fusarium agar and potato dextrose agar (PDA) (1) after 7 to 10 days of incubation at 25°C. The pathogen was identified by morphological characteristics and pathogenicity tests. Colonies were fast growing with white aerial mycelia and a cream color on the reverse side; hyphae were septate and hyaline, conidiophores were unbranched, and microconidia were abundant, thin walled, hyaline, fusiform to ovoid, generally one to two celled, and 8 to 10 × 2 to 4 μm. Macroconidia were hyaline, two to three celled, moderately curved, thick walled, and 25 to 30 × 4 to 6 μm. Pathogenicity tests for 10 isolates were conducted on 2-week-old pumpkin seedlings (cv. Jamaican squash; seven plants per isolate) and mature pumpkin fruit (2). Briefly, seedlings were inoculated by dipping their roots in a spore suspension (1 × 104 spores per ml) for 20 min. The plants were repotted in sterile potting soil. For negative controls, plant roots were dipped in sterile water. After the rind of fruit was swabbed with 70% ethanol followed by three rinses with sterile distilled water, 0.4-cm-diameter agar plugs of the isolates were inserted into wounds made with a sterile 1-cm-diameter borer. Sterile PDA plugs served as negative controls. Fruit were placed in sealed, clear, plastic bags. Inoculated plants and fruit were placed on greenhouse benches (30 to 32°C day and 25 to 27°C night temperatures) and monitored over a 30-day period. Tests were repeated once. Inoculated fruit developed a brown, spongy lesion that expanded from the initial wound site over a period of approximately 17 days after inoculation. White mycelia grew diffusely over the lesion. Inoculated plants developed yellow and finally necrotic leaves and lesions developed on stems at the soil line approximately 21 days after inoculation. No symptoms developed on the control plants. The fungus was reisolated from symptomatic tissue, fulfilling Koch's postulates. To my knowledge, this is the first report of Fusarium fruit rot of pumpkin in Trinidad. References: (1) J. Leslie and B. Summerell. Page 1 in: The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, 2006. (2) W. H. Elmer. Plant Dis. 80:131, 1996.

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