scholarly journals First Report of Phytophthora nicotianae and P. citricola Associated with English Walnut Decline in Europe

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 315-315 ◽  
Author(s):  
A. Belisario ◽  
M. Maccaroni ◽  
A. M. Vettraino ◽  
A. Vannini
Keyword(s):  
Lateral Roots ◽  
Juglans Regia ◽  
The United States ◽  
Phytophthora Nicotianae ◽  
Malt Extract ◽  
Veneto Region ◽  
Internal Transcribed Spacer Region ◽  
Campania Region ◽  
First Report ◽  
English Walnut

English (Persian) walnut (Juglans regia), among the most widely cultivated species of Juglans worldwide, is cultivated primarily for fruit production but also for timber. In the last 10 years, walnut decline causing leaf yellowing, sparse foliage, overall decline, and plant death has increased in Italian commercial orchards. In Italy, Phytophthora cactorum, P. cambivora, P. cinnamomi, and P. cryptogea are associated with this disease (1,4). Over the last 5 years, P. cinnamomi was the most widely isolated and destructive species (1). Recently, a different species of Phytophthora was isolated from diseased roots and soil from around lateral roots of 10 declining trees in two orchards in the Veneto Region of northern Italy. Another species of Phytophthora was isolated consistently from rotted roots of declining walnut trees in two orchards in the Campania Region of southern Italy. Phytophthora spp. were isolated directly from plant material or Rhododendron spp. leaf baiting on soil samples with PARBhy selective medium (10 mg of pimaricin, 250 mg of ampicillin [sodium salt], 10 mg of rifampicin, 50 mg of hymexazol, 15 mg of benomyl, 15 g of malt extract, 20 g of agar in 1,000 ml of H2O). Two species of Phytophthora were identified based on morphological and cultural characteristics (2). The species from trees in the Veneto Region was identified as P. nicotianae. All isolates produced papillate, spherical to obturbinate, occasionally caducous sporangia with short pedicels, terminal and intercalary chlamydospores, and were mating type A2. The species isolated from trees in the Campania Region was identified as P.citricola. Isolates were homothallic, produced semipapillate, persistent, obclavate to obpyriform sporangia, occasionally with two apices, and antheridia paragynous. Identifications were confirmed by comparing restriction fragment length polymorphism patterns of the internal transcribed spacer region of rDNA with those obtained from previously identified species of Phytophthora. Pathogenicity of two isolates each of P. citricola and P. nicotianae was tested on 2-year-old potted walnut seedlings. Inocula were prepared by inoculating sterilized millet seeds moistened with V8 broth with plugs of mycelium and incubated for 4 weeks at 20°C in the dark. Infested seeds were added to potting soil at a rate of 3% (wt/vol). One day later, pots were flooded for 48 h to promote sporulation. Ten noninoculated seedlings were used as the control. Symptoms were assessed 2 months after inoculation. Seedlings inoculated with P. nicotianae developed necrosis of feeder and lateral roots, but only limited infection of taproots. Seedlings inoculated with P. citricola developed necroses at the insertion points of lateral roots. All four isolates produced visible damage to lateral roots on inoculated plants. P. nicotianae and P. citricola were reisolated from respectively infected roots. Results from these inoculations confirmed P. nicotianae and P. citricola as root pathogens of English walnut. Both species were associated with walnut decline as reported in the United States (3). To our knowledge, this is the first report of P. nicotianae and P. citricola on J. regia in Europe. References: (1) A. Belisario et al. Petria 11:149. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) M. E. Matheron and S. M. Mircetich. Phytopathology 75:977, 1985. (4) A. M. Vettraino et al. Plant Dis. 86:328, 2002.

scholarly journals First Report of Phytophthora cryptogea in Walnut Stands in Italy

Plant Disease ◽  
2002 ◽  
Vol 86 (3) ◽  
pp. 328-328 ◽  
Author(s):  
A. M. Vettraino ◽  
A. Belisario ◽  
M. Maccaroni ◽  
N. Anselmi ◽  
A. Vannini
Keyword(s):  
Lateral Root ◽  
Root Zone ◽  
Lateral Roots ◽  
Juglans Regia ◽  
Central Italy ◽  
The United States ◽  
Selective Medium ◽  
Northern Italy ◽  
Internal Transcribed Spacer Region ◽  
First Report

English (Persian) walnut (Juglans regia L.) is among the most widely cultivated species in pure and mixed plantations of broadleaved trees in Italy. A decline of walnut of increasing occurrence has been reported recently in new plantations in central and northern Italy. Symptoms of the decline were typically characterized by yellowing of the foliage, defoliation, and plant death. Dark, flame-shaped necroses were often present at the collar. Phytophthora cactorum, P. cambivora, and P. cinnamomi were among the species associated with necrotic tissues of the collar and main roots (1). Furthermore, a Phytophthora sp. was isolated from soil removed from the lateral root zone of 6 of 15 declining trees in 3 walnut plantations, 2 in northern Italy and 1 in central Italy. Isolations were made by baiting with Rhododendron leaves and plating on PARBhy selective medium (3). The species isolated was identified as P. cryptogea on the basis of morphological and cultural characteristics (2). All isolates produced oval to obpyriform, nonpapillate sporangia and were mating type A2. Identification of the isolates was confirmed by comparing the restriction fragment length polymorphism patterns of the internal transcribed spacer region of ribosomal DNA with those obtained from previously identified Phytophthora species. Pathogenicity tests on potted 2-year-old walnut seedlings were conducted using two isolates of P. cryptogea. Inoculum was prepared by growing isolates on sterilized millet seeds added to soil at 2.5% (wt/vol). Sporulation was induced by 24-h flooding of the soil. Symptoms were assessed 1 month after inoculation. Ten uninoculated seedlings were used as controls. Inoculated seedlings showed no symptoms on the tap root, but there were extensive necroses of lateral roots ranging from 14 to 75% (average 38.6 ± 6.7 SE) of total lateral root (dry weight) compared with values of 0 to 11% (average 3 ± 1.5 SE) for uninoculated seedlings. P. cryptogea was easily reisolated from infected lateral roots and from the soil of inoculated pots. The inoculation trials confirmed P. cryptogea as a feeder-root pathogen of walnut in Italy. To our knowledge, this is the first report of P. cryptogea on English walnut in Italy. This species often has been associated with walnut decline in the United States (2) and on other woody plants in Italy (3). References: (1) A. Belisario et al. Petria 11:127, 2001. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Association, St. Paul, MN, 1996. (3) A. M. Vettraino et al. Plant Pathol. 50:90, 2001.

scholarly journals First Report of Wilt and Dieback on Pokeweed (Phytolacca decandra) Caused by Phytophthora nicotianae

Plant Disease ◽  
2003 ◽  
Vol 87 (1) ◽  
pp. 101-101
Author(s):  
A. Belisario ◽  
M. Maccaroni ◽  
L. Corazza
Keyword(s):  
Tap Water ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Phytophthora Nicotianae ◽  
Malt Extract ◽  
Internal Transcribed Spacer Region ◽  
Invasive Weed ◽  
Disease Symptoms ◽  
First Report ◽  
Perennial Plant

Pokeweed (Phytolacca decandra, synonym Phytolacca americana) is a root perennial plant that produces a succulent annual stem. In late June 2001, a severe dieback occurred on a group of pokeweed plants being grown as ornamentals in a garden in Rome. Disease symptoms consisted of leaf wilting followed by collapse of the plant. Stem collars and roots had dark brown-to-black water-soaked lesions. A wet rot was observed on plants with advanced disease symptoms. Isolations, from sections of roots and stems previously washed in running tap water, were made on PARBhy selective medium (10 mg of pimaricin, 250 mg of ampicillin [sodium salt], 10 mg of rifampicin, 50 mg of hymexazol, 15 mg of benomyl, 15 g of malt extract, and 20 g of agar in 1,000 ml of H2O) (2), followed by incubation at 20°C. A species of Phytophthora identified based on morphological and cultural characteristics (1) was isolated consistently from rotted roots and collars of diseased plants. All isolates produced papillate, spherical, ovoid to obturbinate, noncaducous sporangia and terminal and intercalary chlamydospores. Hyphal swellings with hyphal outgrowths were present. Observed characteristics were similar to those described for P. nicotianae. Isolates were mating type A2 with amphigynous antheridia in paired cultures with the A1 tester isolate of P. nicotianae. Identification was confirmed by comparing restriction fragment length polymorphism patterns of the internal transcribed spacer region of ribosomal DNA with those obtained from previously identified Phytophthora species. Pathogenicity tests were conducted on 10 2-month-old potted pokeweed plants. Inoculum was prepared by inoculating sterilized millet seeds moistened with V8 broth with plugs of mycelium and growing for 4 weeks. The inoculum was added to potting soil at 3% (wt/vol), and sporulation was induced by flooding the soil for 48 h. Five uninoculated plants were used as controls. Plants were maintained outdoors and assessed for symptoms within 2 months after inoculation. Wilting, root rot, and dark brown lesions on the collar developed on inoculated plants. The pathogen was reisolated from the inoculated plants and morphologically identical to the original isolates, which confirmed P. nicotianae as the causal agent of the disease. Few diseases have been reported on Phytolacca decandra. This species is not only an invasive weed, but is also cultivated as an ornamental and medicinal plant. In addition, antiviral (PAP) and antifungal (Pa-AFP) proteins that are used as a remedy for several human and plant infections have been extracted from the plant. To our knowledge, this is the first report of P. nicotianae on pokeweed. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) A. M.Vettraino et al. Plant Pathol. 50:90, 2001.

scholarly journals First Report of Twig and Branch Dieback of English Walnut (Juglans regia) Caused by Neofusicoccum mediterraneum in California

Plant Disease ◽  
2010 ◽  
Vol 94 (10) ◽  
pp. 1267-1267 ◽  
Author(s):  
F. P. Trouillas ◽  
J. R. Úrbez-Torres ◽  
F. Peduto ◽  
W. D. Gubler
Keyword(s):  
Juglans Regia ◽  
Petroleum Jelly ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Fungal Isolates ◽  
Agar Plug ◽  
Vascular Discoloration ◽  
English Walnut ◽  
Branch Dieback ◽  
Olive Green

California produces 99% of the U.S. English walnut crop with more than 30 cultivars on ~89,000 ha. Production for 2008 was ~436,000 tons with a value of $527 million. In early summer of 2009 and 2010, branch and twig dieback of English walnut (Juglans regia L.) was detected in orchards in Yolo County and submitted to our diagnostic laboratory. Disease symptoms included death of twig tips, branch dieback, wood lesions, and canker formation. Pycnidia were embedded within the bark of dead twigs. Conidia from pycnidia were hyaline, fusoid-ellipsoidal, widest usually in the middle, and 21 to 24 (–27) × 5 to 7 μm (n = 30). Isolations from cankers yielded the fungus Neofusicoccum mediterraneum Crous, M.J. Wingf. & A.J.L. Phillips (1). Fungal colonies of N. mediterraneum grew light olive green to gray on potato dextrose agar, becoming dark olive green with age. Identification of fungal isolates was confirmed by sequence comparison of Californian isolates with ex-type (CBS 121558) sequences in GenBank (3) using the internal transcribed spacer region of the rDNA, a portion of the β-tubulin gene, and part of the translation elongation factor. Sequences of Californian isolates (GenBank HM443604–HM443609) were identical to the ex-type sequences for all three genes. Previous studies in California reported the occurrence and pathogenicity of N. mediterraneum into grapevine (Vitis vinifera L.) (3) and almond trees (Prunis dulcis L.) (2). Inderbitzin et al (2) investigated the host range of N. mediterraneum in California and reported the occurrence of pycnidia on English walnut trees. However, this study did not investigate the pathogenicity of N. mediterraneum on this host. In the current study, the pathogenicity of N. mediterraneum in J. regia cvs. Hartley and Chandler was investigated in an orchard at UC Davis using two fungal isolates. Pathogenicity tests were performed by inoculating eight 2- to 4-year-old branches of mature J. regia trees. Inoculations were made in June 2009 with a 5-mm cork borer to remove bark and placing an 8-day-old 5-mm-diameter agar plug bearing fresh mycelium of the fungal isolates directly into the fresh wound, mycelium side down. An additional eight branches of each cultivar were inoculated with noncolonized agar plugs to serve as controls. Inoculated wounds were covered with petroleum jelly and wrapped with Parafilm to retain moisture. Branches were harvested after 10 months of incubation and checked for canker development. The extent of vascular discoloration was measured in each branch and isolations were made from the edge of discolored tissue to confirm Koch's postulates. Statistical analyses were performed with analysis of variance and Dunnett's t-test to assess significant differences in the extent of vascular discoloration between inoculations with N. mediterraneum and the control. Necrosis length for the two isolates averaged 131.5 mm in Hartley branches and 110 mm in the Chandler branches. Average necrosis lengths in the control branches were 18.5 mm and 16.7 mm, respectively, significantly lower (P < 0.05) than the average necrosis length found in branches inoculated with N. mediterraneum. Fungal recovery was 75% in both varieties. To our knowledge, this study is the first report of N. mediterraneum as a pathogen of J. regia trees in California. References: (1) P. W. Crous et al. Fungal Planet 19, 2007. (2) P. Inderbitzin et al. Mycologia. Online publication. doi:10.3852/10-006, 2010. (3) J. R. Úrbez-Torres et al. Plant Dis. 94:785, 2010.

scholarly journals First Report of Stem Canker of English Walnut Caused by Fusarium solani in South Africa

Plant Disease ◽  
2000 ◽  
Vol 84 (5) ◽  
pp. 592-592 ◽  
Author(s):  
W. Chen ◽  
W. J. Swart
Keyword(s):  
South Africa ◽  
Fusarium Solani ◽  
Juglans Regia ◽  
Stem Canker ◽  
The United States ◽  
First Report ◽  
Surface Sterilization ◽  
Similar Disease ◽  
English Walnut ◽  
Artificial Inoculations

Cultivation of English walnut (Juglans regia L.) has considerable economic potential in South Africa. In February 1999, die-back of walnut trees was observed on ≈30% of trees in an orchard in Gauteng Province, South Africa. Die-back was associated with characteristic cankers and discoloration of the cambial tissue of twigs and young branches. Fifty pieces of discolored tissue from the margins of cankers of five trees were transferred to potato dextrose agar (PDA) after surface-sterilization with 0.5% NaOCl. Fungal colonies emerged from all 50 pieces of diseased tissue. Fungi recovered included Fusarium solani (74.5%), Alternaria tenuissima (17.3%), and a Phoma sp. (6.2%). Small pieces of sterile cheesecloth (10 × 5 mm) were cultured on PDA with an isolate of F. solani from infected walnut trees. Colonized pieces of cheesecloth were applied to stems (≈5-mm diameter) of nine potted J. regia plants in a glasshouse. Each stem was wounded by lightly scraping off a length of bark (5 × 5 mm). Colonized cheesecloth was wrapped around the wound and covered with Parafilm to prevent desiccation of mycelia in the cheesecloth. Nine walnut stems were similarly treated with sterile cheesecloth pieces to serve as control treatments. After 4 weeks, die-back of foliage was observed in all plants artificially inoculated with F. solani. Cheesecloth pieces and surrounding bark were removed, and the length and width of each cambial lesion was measured. The mean area of cambial lesions (length by width) resulting from artificial inoculations was 27.3 × 8.5 mm. None of the control plants developed any symptoms. Koch's postulates were confirmed by consistently reisolating F. solani from inoculated plants. A similar disease of black walnut (J. nigra) was reported by Carlson et al. (1) from five central states in the United States. Our findings represent the first report of F. solani as a causal agent of stem canker of English walnut in South Africa. Reference: (1) J. C. Carlson et al. N. J. Appl. For. 10:1, 1993.

scholarly journals First Report of Monosporascus cannonballus on Melon in Mexico

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 1068-1068 ◽  
Author(s):  
Y. I. Chew-Madinaveitia ◽  
A. Gaytán-Mascorro ◽  
T. Herrera-Pérez
Keyword(s):  
Citrullus Lanatus ◽  
The United States ◽  
Internal Transcribed Spacer Region ◽  
Oat Hulls ◽  
Monosporascus Cannonballus ◽  
First Report ◽  
The North ◽  
Root Necrosis ◽  
Vine Decline ◽  
Melon Seeds

In 2009, 2010, and 2011, melon plants (Cucumis melo L.) exhibited vine decline in commercial fields in the Municipality of Viesca, State of Coahuila, in the north-central region of Mexico known as La Comarca Lagunera. Symptoms included wilting, leaf yellowing, and vine collapse prior to harvest. Diseased plants showed necrotic root lesions and loss of secondary and tertiary roots. Numerous perithecia containing asci and ascospores typical of Monosporascus cannonballus Pollack & Uecker (3) were found in the root system. M. cannonballus is a typical fungus of hot semiarid climates such as La Comarca Lagunera in which daytime temperatures above 40°C are frequent during the melon growing season. Small root pieces were disinfected with 1.5% sodium hypochlorite for 1 min and plated onto potato dextrose agar (PDA) medium with 0.5 g l–1 streptomycin sulfate and incubated for 7 days at 25°C under dark conditions. The mycelium of the fungus colony was initially white, turning gray about 3 weeks later and yielding black perithecia with one ascospore per asci. The internal transcribed spacer region of ribosomal DNA of isolate 4 was sequenced and submitted to GenBank with Accession No. JQ51935. Pathogenicity of this isolate was confirmed on melon plants (cv. Cruiser) in the greenhouse at 25 to 32°C. Fungus inoculum was produced in a sand-oat hull medium (0.5 l of sand, 45 g of oat hulls, and 100 ml of distilled water), and incubated at 25°C for 50 days (1). Melon seeds were sown in sterile sand in 20-cm diameter and 12-cm depth polyurethane containers, and the inoculum was added to produce a concentration of 20 CFU g–1. Sowing was done in five inoculated containers and thinned to two plants per container, each container representing a replication. Plants were also grown in five noninoculated containers that were used as controls. After 50 days under greenhouse conditions, plants were evaluated for disease symptoms. Melon plants inoculated with M. cannonballus exhibited root necrosis as opposed to healthy roots observed in noninoculated plants. M. cannonballus was reisolated from symptomatic plants, confirming Koch's postulates. M. cannonballus causes root rot and vine decline on melon and has been reported in Brazil, Guatemala, Honduras, India, Iran, Israel, Italy, Japan, Libya, the Netherlands (plants from Russia), Pakistan, Saudi Arabia, Spain, Taiwan, Tunisia, and the United States. M. cannonballus was reported in 1996 in southeastern Mexico in the State of Colima, where watermelon (Citrullus lanatus (Thunb.) Matsum.& Nakai) showed wilting and plant collapse prior to harvest (2). However, to our knowledge, this is the first report of M. cannonballus on melon in Mexico. This is relevant because La Comarca Lagunera region is one of the major melon producing areas in Mexico and M. cannonballus is a pathogen that may cause yield losses of up to 100%. References: (1) B. D. Bruton et al. Plant Dis. 84:907, 2000. (2) R. D. Martyn et al. Plant Dis. 80:1430, 1996. (3) F. G. Pollack and F. A. Uecker. Mycologia 66:346, 1974.

scholarly journals First Report of Phomopsis citri Associated with Dieback of Citrus lemon in India

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1281-1281 ◽  
Author(s):  
S. Mahadevakumar ◽  
Vandana Yadav ◽  
G. S. Tejaswini ◽  
S. N. Sandeep ◽  
G. R. Janardhana
Keyword(s):  
Fungal Pathogen ◽  
The United States ◽  
Apical Region ◽  
Post Inoculation ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Internal Transcribed Spacer Region ◽  
Productivity Level ◽  
First Report ◽  
Dieback Disease

Lemon (Citrus lemon (L.) Burm. f.) is an important fruit crop cultivated worldwide, and is grown practically in every state in India (3). During a survey conducted in 2013, a few small trees in a lemon orchard near Mysore city (Karnataka) (12°19.629′ N, 76°31.892′ E) were found affected by dieback disease. Approximately 10 to 20% of trees were affected as young shoots and branches showed progressive death from the apical region downward. Different samples were collected and diagnosed via morphological methods. The fungus was consistently isolated from the infected branches when they were surface sanitized with 1.5% NaOCl and plated on potato dextrose agar (PDA). Plates were incubated at 26 ± 2°C for 7 days at 12/12 h alternating light and dark period. Fungal colonies were whitish with pale brown stripes having an uneven margin and pycnidia were fully embedded in the culture plate. No sexual state was observed. Pycnidia were globose, dark, 158 to 320 μm in diameter, and scattered throughout the mycelial growth. Both alpha and beta conidia were present within pycnidia. Alpha conidia were single celled (5.3 to 8.7 × 2.28 to 3.96 μm) (n = 50), bigittulate, hyaline, with one end blunt and other truncated. Beta conidia (24.8 to 29.49 × 0.9 to 1.4 μm) (n = 50) were single celled, filiform, with one end rounded and the other acute and curved. Based on the morphological and cultural features, the fungal pathogen was identified as Phomopsis citri H.S. Fawc. Pathogenicity test was conducted on nine healthy 2-year-old lemon plants via foliar application of a conidial suspension (3 × 106); plants were covered with polythene bags for 6 days and maintained in the greenhouse. Sterile distilled water inoculated plants (in triplicate) served as controls and were symptomless. Development of dieback symptoms was observed after 25 days post inoculation and the fungal pathogen was re-isolated from the inoculated lemon trees. The internal transcribed spacer region (ITS) of the isolated fungal genomic DNA was amplified using universal-primer pair ITS1/ITS4 and sequenced to confirm the species-level diagnosis (4). The sequence data of the 558-bp amplicon was deposited in GenBank (Accession No. KJ477016.1) and nBLAST search showed 99% homology with Diaporthe citri (teleomorph) strain 199.39 (KC343051.1). P. citri is known for its association with melanose disease of citrus in India, the United States, and abroad. P. citri also causes stem end rot of citrus, which leads to yield loss and reduction in fruit quality (1,2). Dieback disease is of serious concern for lemon growers as it affects the overall productivity level of the tree. To the best of our knowledge, this is the first report of P. citri causing dieback of lemon in India. References: (1) I. H. Fischer et al. Sci. Agric. (Piracicaba). 66:210, 2009. (2) S. N. Mondal et al. Plant Dis. 91:387, 2007. (3) S. P. Raychaudhuri. Proc. Int. Soc. Citriculture 1:461, 1981. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

scholarly journals First Report of Cytospora punicae Causing Wood Canker and Branch Dieback of Pomegranate (Punica granatum) in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 853-853 ◽  
Author(s):  
F. Peduto Hand ◽  
R. A. Choudhury ◽  
W. D. Gubler
Keyword(s):  
United States ◽  
Elongation Factor ◽  
Punica Granatum ◽  
The United States ◽  
Internal Transcribed Spacer Region ◽  
Intermittent Light ◽  
First Report ◽  
Consensus Sequences ◽  
Vascular Discoloration ◽  
Branch Dieback

Pomegranates (Punica granatum L.) are an expanding industry in the United States with California growing approximately 32,000 acres with a crop value of over $155 million (1). During June and July of 2012, we observed severe limb and branch dieback in pomegranate orchards cv. Wonderful located in Contra Costa, Kings, and Kern counties of California. Disease symptoms included yellowing of leaves, branch and limb dieback, wood lesions, and canker formation. Dark brown Cytospora-like cultures were consistently isolated from active cankers on potato dextrose agar (PDA) amended with 100 mg l−1 tetracycline hydrochloride. Three isolates (UCCE1223, UCCE1233, and UCCE1234) representative of each orchard were sub-cultured onto PDA and incubated at 22°C under fluorescent intermittent light (12 h light, 12 h dark). Fungal colonies had whitish mycelia that turned olive green to dark brown with maturity and formed globose and dark brown pycnidia after 12 days. Conidia were hyaline, aseptate, allantoid, and (4) 4.5 to 5 (6) × (1) 1.5 (2) μm (n = 180). Pycnidia formed in culture measured (250) 350 to 475 (650) μm in diameter (n = 40). Identification of the isolates was confirmed by sequence comparison of the internal transcribed spacer region (ITS1-5.8S-ITS2) of the rDNA and part of the translation elongation factor 1-α gene (EF1-α) with sequences available in GenBank. Consensus sequences of both genes of all isolates showed 99% homology to the species Cytospora punicae Sacc. (2). All sequences were deposited in GenBank (Accession Nos. KJ621684 to 89). Pathogenicity of the isolates was determined by branch inoculation. In December 2012, 3-year-old branches of P. granatum cv. Wonderful were inoculated by placing 5-mm-diameter mycelium plugs from the growing margin of 14-day-old PDA cultures in fresh wounds made with a 5-mm-diameter cork-borer. Eight branches per isolate were inoculated on eight different trees. Eight control branches were inoculated with non-colonized PDA agar plugs. Inoculations were covered with Vaseline and wrapped with Parafilm to retain moisture. Branches were harvested in August 2013 and examined for canker development and the extent of vascular discoloration spreading downward and upward from the inoculation point. Isolations from the edge of discolored tissue were conducted to fulfill Koch's postulates. C. punicae was re-isolated from 100% of the inoculated branches. Total length of vascular discoloration averaged 30.2 mm in branches inoculated with the three C. punicae isolates and 9 mm in the control branches. No fungi were isolated from the slightly discolored tissue of the controls. To our knowledge, this is the first report of C. punicae as a fungal trunk pathogen of pomegranate trees in the United States. References: (1) California County Agricultural Commissioners' Data, 2010 Crop Year. USDA NASS California field office, retrieved from http://www.nass.usda.gov/Statistics_by_State/California/ Publications/AgComm/201010cactb00.pdf , 2011. (2) P. A. Saccardo. Sylloge Fungorum 3:256, 1884.

scholarly journals First Report of Leaf Spot of Lettuce (Lactuca sativa L.) Caused by Phoma tropica in Italy

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1380-1380 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
G. Ortu ◽  
M. L. Gullino
Keyword(s):  
Relative Humidity ◽  
Lactuca Sativa ◽  
Leaf Spot ◽  
Morphological Characteristics ◽  
The United States ◽  
Fluorescent Light ◽  
Malt Extract ◽  
Pathogenicity Test ◽  
First Report ◽  
Lactuca Sativa L

Lettuce (Lactuca sativa L.) is widely grown in Italy, with the production for the preparation of ready-to-eat salads becoming increasingly important. During the spring of 2011, a previously unknown leaf spot was observed on L. sativa plants, cv Rubia, grown in several plastic tunnels in Lumbardy (northern Italy), 20 to 25 days after sowing. Thirty to forty per cent of leaves of the plants growing in the part of the tunnel with the highest relative humidity were affected. Leaves of infected plants showed extensive, irregular, dark brown, necrotic lesions with a chlorotic halo. Lesions initially ranged from 0.5 to 3 mm, then eventually coalesced, reaching 2 to 3 cm, showing a well-defined, dark brown border. Affected leaves senesced and withered. The crown was not affected by the disease. Diseased tissue was excised, immersed in a solution containing 1% sodium hypochlorite for 60 s, rinsed in water, then cultured on potato dextrose agar (PDA), amended with 25 mg/l of streptomycin sulphate. After 5 days, a fungus developed, producing a greenish grey mycelium with a white border when incubated under 12 h/day of fluorescent light at 21 to 23°C. In order to favor the production of conidia, the fungus was transferred on malt extract agar (MA) and maintained under 12 h/day of fluorescent light at 22°C. After 15 days, black pycnidia, 175 to 225 μm, developed, with hyaline, elliptical, unicellular conidia, measuring 3.21 to 6.7 × 1.08 to 3.2 (average 5.5 × 1.9) μm. On the basis of these morphological characteristics, the fungal causal agent of the disease could be related to the genus Phoma (2). The internal transcribed spacer (ITS) region of rDNA of the isolate PHT30 was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 466-bp segment showed a 99% similarity with the sequence of Phoma tropica (GenBank Accession No. JF923820.1). The nucleotide sequence has been assigned the GenBank Accession No. JQ954396. Pathogenicity tests were performed by spraying healthy 20-day-old lettuce plants, cv Rubia, with a spore suspension (1 × 105 conidia/ml) prepared from 14-day-old colonies of the strain PHT30 grown on MA cultures. Plants inoculated with water alone served as controls. Ten plants per isolate were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a growth chamber at 20°C and 80% relative humidity. The first foliar lesions, similar to those occurring on the naturally infected plants, developed on leaves 12 days after inoculation. Control plants remained healthy. The pathogen was consistently reisolated from leaf lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of P. tropica on lettuce in Italy as well as worldwide. In the United States, the presence of P. exigua was reported in 2006 (3). The economic importance of the disease at present is limited, probably also because symptoms can be confused with those caused by Botrytis cinerea. However, P. tropica could become a more significant problem because of the importance of the crop. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema. Trans. Br. Mycol. Soc. 67:289, 1976. (3) S. Y. Koike. Plant Dis. 90:1268, 2006.

scholarly journals Shoot Blight of Forsythia × intermedia in Virginia Nurseries Caused by Phytophthora nicotianae

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 430-430 ◽  
Author(s):  
C. X. Hong ◽  
P. A. Richardson ◽  
P. Kong
Keyword(s):  
Single Strand Conformation Polymorphism ◽  
The United States ◽  
Morphological Characters ◽  
Selective Medium ◽  
Shoot Tips ◽  
Phytophthora Nicotianae ◽  
First Report ◽  
Plastic Bags ◽  
Shoot Blight ◽  
Polymorphism Pattern

A severe blighting of shoots on Forsythia × intermedia cv. Lynwood Gold plants was observed at several commercial nurseries in Virginia from 2001 to 2004. Crop losses ranged from 10 to 35%. Symptoms first occurred at the tips of shoots, including those that were trimmed and not trimmed, and then progressed downward. Diseased shoots wilted quickly and usually turned black, and foliage on these shoots withered and became necrotic. With PARP-V8 selective medium (2), a species of Phytophthora was isolated consistently from symptomatic shoots (including tissues from shoot tips, leaves, and stems) as well as from apparently healthy roots. These isolates produced arachnoid mycelia and numerous noncaducous, papillate sporangia but did not produce sexual structures on isolation plates; these morphological characters are consistent with those of Phytophthora nicotianae. All isolates produced a single-strand conformation polymorphism pattern typical of P. nicotianae (3). To test pathogenicity, 1-year-old, healthy-appearing cv. Lynwood Gold forsythia plants (canopy size = 100 cm × 60 cm) in four 12-liter containers were sheared. Two plants were inoculated by spraying each plant with 200 ml of a zoospore suspension (1.6 × 104 spores per ml, prepared from one isolate), and the other two plants were not treated and served as controls. Plants were covered with plastic bags overnight to encourage infection and then were grown in a field (temperature range = 20 to 33°C). Severe blight developed on trimmed shoots and new shoot tips of inoculated plants within 1 week after inoculation. The same pathogen was isolated from all blighted leaf and stem pieces assayed. Blight symptoms were not observed on control plants during a 1-month observation period. Phytophthora nicotianae has been reported to attack F. viridissima in Italy (1) causing root and collar rot but not shoot blight. To our knowledge, this is the first report of shoot blight on Forsythia spp. caused by P. nicotianae and the first report of P. nicotianae on Forsythia spp. in the United States. References: (1) S. O. Cacciola et al. Plant Dis. 78:525, 1994. (2) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (3) P. Kong et al. Fun. Gen. Biol. 39:238, 2003.

First Report of Alternaria alternata and Fusarium spp. Causing Brown Apical Necrosis in Walnut Fruit in Southern Chile

2021 ◽  
Author(s):  
Ernesto Antonio Moya-Elizondo ◽  
María Jose Lagos ◽  
Juan G. San Martín ◽  
Braulio E. Ruiz
Keyword(s):  
Alternaria Alternata ◽  
Fungal Pathogens ◽  
Juglans Regia ◽  
Bacterial Pathogen ◽  
Southern Chile ◽  
Fusarium Spp ◽  
First Report ◽  
Fruit Drop ◽  
English Walnut ◽  
Apical Necrosis

This is the first report of Alternaria alternata and Fusarium spp. causing brown apical necrosis (BAN) in walnut fruit in southern Chile. English walnut (Juglans regia L.) is the second most widely grown fruit in Chile. The bacterial pathogen Xanthomonas arboricola pv. juglandis affects walnut production in Chile and has been associated with apical necrosis symptom and premature fruit drop; this research focused on determining if fungal pathogens were associated with this damage. The presence of BAN in commercial walnut orchards in southern Chile reveals the need for improved phytosanitary programs to control this disease.

Sign in / Sign up

Export Citation Format

Share Document