First Report of Fusarium solani Causing Root Rot of Olive in Southeastern Argentina

In Argentina, olive (Olea europaea L.) is cultivated in the mountainous, warm, arid northwest (Andes range), where Fusarium solani (blue sporodochia) is frequently found to be causing death of nursery and young field plants (1). Recently, olive orchards were established more than 1,600 km to the southeast (Pampas) in a plain with a temperate and humid climate and in the arid Patagonia, both influenced by the Atlantic Ocean. This area includes part of Buenos Aires and Rio Negro provinces. In March 2008, 10-year-old ‘Barnea’ olive trees with high incidence of root rot, dried leaves, dead branches, and dead plants were observed in the Coronel Dorrego District of Buenos Aires Province, where oat, barley or other cereals are planted between rows of olive trees. Planting material originated from olive nurseries located in Mendoza Province, 1,200 km from Coronel Dorrego. Diseased roots were disinfected in 2% NaOCl and 70% ethanol, cut into small pieces, plated onto rose bengal-glycerin-urea medium, and incubated at 20°C with a 12-h photopheriod. A fungus was purified through successive transfers of hyphal tips from the margin of a sparsely growing colony onto 2% water agar (2). Colonies grown on Spezieller Nährstoffarmer agar (3) and carnation leaf-piece agar were used for morphological identification, and those on grown on potato dextrose agar were used for evaluation of pigmentation and colony growth rate. Sporodochium color, cream, was typical of F. solani (Mart.) Sacc. This isolate was deposited in the IMYZA Microbial Collection as INTA-IMC 73. Mycelium was cultured in liquid Czapek-Dox medium supplemented with sucrose, peptone, yeast extract, sodium nitrate, and vitamins for 4 days and fungal DNA was obtained with a DNA extraction kit. Primers ITS1 and ITS4 were used to amplify the internal transcribed spacer (ITS) region of ribosomal genes. The purified PCR product was sequenced and the DNA sequence compared with GenBank records. The sequence shared 100% identity with 27 entries for F. solani and 97% identity with F. solani obtained from olive in Nepal (4), corresponding to EU912432 and EU912433. The nucleotide sequence was registered in GenBank as JF299258. Pathogenicity was confirmed on ‘Manzanilla’ plants at the eight-leaf stage. Pieces of water agar with mycelium were applied to small wounds at the stem base and on roots of 10 plants and were covered with cotton soaked in sterile distilled water. Plants were incubated at 20°C and a 14-h photoperiod. On control plants, water agar pieces without mycelium were applied to the wounds. After 33 days, inoculated plants showed dark brown lesions (average length 1.4 cm) and leaf chlorosis. Two plants showed wilting with leaves remaining attached to branches. F. solani was reisolated from roots and stem bases of inoculated plants. Controls remained asymptomatic. To our knowledge, this is the first report of F. solani occurring on olive in the temperate part of the Pampas of Argentina where cereals, which are susceptible to Fusarium species, are grown with olive trees. Sporodochium color (cream) of these isolates differed from the blue color of previously reported isolates of F. solani on olive in northwestern Argentina (1). References: (1) S. Babbitt et al. Plant Dis. 86:326, 2002. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (3) H. I. Nirenberg. Releases Fed. Biol. Res. Center Agric. For. (Berlin-Dahlem) 169:1, 1976. (4) A. M. Vettraino et al. Plant Dis. 23:200, 2009.

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First Report of Fusarium Crown and Root Rot Caused by Fusarium solani on St. John's-Wort in Argentina

Plant Disease ◽

10.1094/pdis.2004.88.9.1050b ◽

2004 ◽

Vol 88 (9) ◽

pp. 1050-1050 ◽

Cited By ~ 1

Author(s):

S. Gaetán ◽

M. Madia ◽

R. Cepeda

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Fusarium Species ◽

Buenos Aires Province ◽

Single Spore ◽

Susceptible Host ◽

First Report ◽

St John’S Wort ◽

St John's Wort ◽

Crown And Root Rot

Since 2001, 15 to18% of commercial plantings of the medicinal plant St. John's-wort (Hypericum perforatum L.) in Buenos Aires Province, Argentina were affected by a new disease. Disease symptoms of crown and root rot, wilting, chlorosis, and necrosis of the leaves appeared in circular-to-irregular shaped sectors of 12- to 14-month-old plants. Symptoms began with foliage turning yellow followed by an irregular, brown necrosis of the leaf margins. Lesions coalesced to form large necrotic areas causing a severe defoliation of the basal and upper leaves. A soft rot affected the crown and roots causing a complete maceration of these tissues. Infected plants broke off easily because the crown region and the roots were destroyed. As the disease developed, a dark brown discoloration girdled the stems that progressed above the soil line to the apex. The infected stems became dry and breakable. Finally, the affected plants died. Segments (1 cm long) were taken from roots and rotted crowns of diseased plants, dipped in 70% ethanol, surface sterilized with NaOCl (1%) for 1 min, and rinsed in sterile water. Each segment was blotted dry and placed on potato dextrose agar. Plates were incubated in the dark at 26°C for 4 to 7 days. The predominate fungus isolated from the diseased tissue was identified as Fusarium solani (Mart.) Sacc. (1). Koch's postulates were completed by dipping the roots of seedlings in a 2 × 106 conidia per ml suspension of a single spore isolate for 45 min. Plants were repotted (20 inoculated and 10 controls) in a sterilized soil mix (soil/sand 2:1) and held in the greenhouse at 23 to 26°C. Characteristic symptoms identical to the original developed on 90% of inoculated plants within 2 weeks after inoculation. Symptoms included wilt and collapse, crown and root rot, and death of the plants. The fungus was recovered from symptomatic tissues. Control plants dipped into distilled water remained healthy. The experiment was repeated, and the results were identical to the first inoculations. To our knowledge, this is the first report of St. John's-wort as a susceptible host of F. solani. Reference: (1) P. E. Nelson et al. Fusarium species. An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983.

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Phylogeny and Mycotoxin Profile of Pathogenic Fusarium Species Isolated from Sudden Decline Syndrome and Leaf Wilt Symptoms on Date Palms (Phoenix dactylifera) in Tunisia

Toxins ◽

10.3390/toxins13070463 ◽

2021 ◽

Vol 13 (7) ◽

pp. 463

Author(s):

Amal Rabaaoui ◽

Chiara Dall’Asta ◽

Laura Righetti ◽

Antonia Susca ◽

Antonio Logrieco ◽

...

Keyword(s):

Rna Polymerase Ii ◽

Fusarium Solani ◽

Fusarium Species ◽

Elongation Factor ◽

Phoenix Dactylifera ◽

Fusarium Proliferatum ◽

Fruit Rot ◽

Morphological Identification ◽

Single Strain ◽

Date Palms

In 2017–2018, extensive symptoms of sudden decline and fruit rot were observed on date palms in southern Tunisia. Samples of diseased plants were randomly collected in six localities. Based on morphological identification, Fusarium was the most frequent fungal genus detected. A sequencing of translation elongation factor, calmodulin, and second largest subunit of RNA polymerase II genes was used to identify 63 representative Fusarium strains at species level and investigate their phylogenetic relationships. The main species detected was Fusarium proliferatum, and at a much lesser extent, Fusarium brachygibbosum, Fusarium caatingaense, Fusarium clavum, Fusarium incarnatum, and Fusarium solani. Pathogenicity on the Deglet Nour variety plantlets and the capability to produce mycotoxins were also assessed. All Fusarium species were pathogenic complying Koch’s postulates. Fusarium proliferatum strains produced mainly fumonisins (FBs), beauvericin (BEA), and, to a lesser extent, enniatins (ENNs) and moniliformin (MON). All F. brachygibbosum strains produced low levels of BEA, diacetoxyscirpenol, and neosolaniol; two strains produced also T-2 toxin, and a single strain produced HT-2 toxin. Fusarium caatingaense, F. clavum, F. incarnatum produced only BEA. Fusarium solani strains produced MON, BEA, and ENNs. This work reports for the first time a comprehensive multidisciplinary study of Fusarium species on date palms, concerning both phytopathological and food safety issues.

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New host and distribution expansion for Pterygodermatites (Multipectines) affinis

Helminthologia ◽

10.1515/helmin-2015-0076 ◽

2016 ◽

Vol 53 (1) ◽

pp. 81-86 ◽

Cited By ~ 1

Author(s):

N. P. Scioscia ◽

P. M. Beldomenico ◽

G. M. Denegri

Keyword(s):

Buenos Aires ◽

Buenos Aires Province ◽

New Host ◽

Fecal Samples ◽

First Report ◽

First Case ◽

Small Intestines

SummaryThe present study reports the first case of infection by Pterygodermatites affinis in Lycalopex gymnocercus, and the first report of this nematode in Argentina. Examining 80 foxes from Buenos Aires province, specimens of this species were recovered from 21.25 % of the small intestines and eggs were found in 7.5 % of the fecal samples.

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First Report of Dactylonectria torresensis Causing Foot and Root Rot of Olive Trees

Plant Disease ◽

10.1094/pdis-09-17-1381-pdn ◽

2019 ◽

Vol 103 (4) ◽

pp. 768-768 ◽

Cited By ~ 2

Author(s):

F. Nigro ◽

I. Antelmi ◽

V. Sion ◽

P. Parente ◽

A. Pacifico

Keyword(s):

Root Rot ◽

First Report ◽

Dactylonectria Torresensis ◽

Olive Trees

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First Report of a New Lineage in the Fusarium solani Species Complex Causing Root Rot on Sunn Hemp in Brazil

Plant Disease ◽

10.1094/pdis-08-15-0947-pdn ◽

2016 ◽

Vol 100 (8) ◽

pp. 1784 ◽

Cited By ~ 1

Author(s):

M. P. Melo ◽

J. E. A. Beserra ◽

K. S. Matos ◽

C. S. Lima ◽

O. L. Pereira

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Species Complex ◽

First Report ◽

Fusarium Solani Species Complex ◽

Sunn Hemp

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First Report of Fusarium solani Causing Root Rot on Coptis chinensis in Southwestern China

Plant Disease ◽

10.1094/pdis-02-14-0164-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1273-1273 ◽

Cited By ~ 2

Author(s):

X.-M. Luo ◽

J.-L. Li ◽

J.-Y. Dong ◽

A.-P. Sui ◽

M.-L. Sheng ◽

...

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Southwestern China ◽

Molecular Characteristics ◽

Distilled Water ◽

Conidial Suspension ◽

Storage Roots ◽

Coptis Chinensis ◽

Causal Organism ◽

First Report

China is the world's largest producer country of coptis (Coptis chinensis), the rhizomes of which are used in traditional Chinese medicine. Since 2008, however, root rot symptoms, including severe necrosis and wilting, have been observed on coptis plants in Chongqing, southwestern China. Of the plants examined from March 2011 to May 2013 in 27 fields, 15 to 30% were covered with black necrotic lesions. The leaves of infected plants showed wilt, necrotic lesions, drying, and death. The fibrous roots, storage roots, and rhizomes exhibited brown discoloration and progressive necrosis that caused mortality of the infected plants. Infected plants were analyzed to identify the causal organism. Discoloration of the internal vascular and cortical tissues of the rhizomes and taproots was also evident. Symptomatic taproots of the diseased coptis were surface sterilized in 1% sodium hypochlorite for 2 min, rinsed in sterile distilled water for 2 min, and then air-dried in sterilized atmosphere/laminar flow. Small pieces of disinfested tissue (0.3 cm in length) were transferred to petri dishes containing potato dextrose agar (PDA) supplemented with 125 μg ml–1 streptomycin sulfate and 100 μg ml–1 ampicillin, and incubated for 5 days at 25°C with a 12-h photoperiod. Four distinct species of fungal isolates (HL1 to 4) derived from single spores were isolated from 30 plants with root rot symptoms collected from the study sites. To verify the pathogenicity of individual isolates, healthy coptis plants were inoculated by dipping roots into a conidial suspension (106 conidia/ml) for 30 min (15 plants per isolate), as described previously (1). Inoculated plants were potted in a mixture of sterilized quartz sand-vermiculite-perlite (4:2:1, v/v) and incubated at 25/18°C and 85 to 90% relative humidity (day/night) in a growth chamber with a daily 16-h photoperiod of fluorescent light. Plants dipped in sterile distilled water were used as controls. After 15 days, symptoms similar to those observed in the field were observed on all plants (n = 15) that were inoculated with HL1, but symptoms were not observed on plants inoculated with HL2, HL3, and HL4, nor on control plants. HL1 was re-isolated from symptomatic plants but not from any other plants. Morphological characterization of HL1 was performed by microscopic examination. The septate hyphae, blunt microconidia (2 to 3 septa) in the foot cell and slightly curved microconidia in the apical cell, and chlamydospores were consistent with descriptions of Fusarium solani (2). The pathogen was confirmed to be F. solani by amplification and sequencing of the ribosomal DNA internal transcribed spacer (rDNA-ITS) using the universal primer pair ITS4 and ITS5. Sequencing of the PCR product revealed a 99 to 100% similarity with the ITS sequences of F. solani in GenBank (JQ724444.1 and EU273504.1). Phylogenetic analysis (MEGA 5.1) using the neighbor-joining algorithm placed the HL1 isolate in a well-supported cluster (97% bootstrap value based on 1,000 replicates) with JQ724444.1 and EU273504.1. The pathogen was thus identified as F. solani based on its morphological and molecular characteristics. To our knowledge, this is the first report of root rot of coptis caused by F. solani in the world. References: (1) K. Dobinson et al. Can. J. Plant Pathol. 18:55, 1996. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, 2006.

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First Report of Medical Tree Peony Root Rot Caused by Fusarium solani in Tongling, China

Plant Disease ◽

10.1094/pdis-02-12-0142-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 909-909 ◽

Cited By ~ 10

Author(s):

M. Guo ◽

Y. M. Pan ◽

Z. M. Gao

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Tap Water ◽

Blood Stasis ◽

The United States ◽

Effective Control ◽

Conidial Suspension ◽

Tree Peony ◽

First Report ◽

Peony Root

Tree peony bark, a main component of Chinese traditional medicine used for alleviating fever and dissipating blood stasis, is mainly produced in Tongling, China. Recently, tree peony cultivation in this area was seriously affected by root rot, with approximately 20 to 30% disease incidence each year. The disease severely affects yield and quality of tree peony bark. During the past 2 years, we collected 56 diseased tree peony plants from Mudan and Fenghuang townships in Tongling. We found reddish brown to dark brown root rot in mature roots, especially on those with injuries. Plant samples collected were disinfected with 2% sodium hypochlorite and isolations were conducted on potato sucrose agar (PSA). Eleven isolates were obtained and all had white fluffy aerial hypha on PSA. Two types of conidia were produced; the larger, reaphook-shaped ones had three to five septa and the smaller, ellipse-shaped ones had one or no septum. The reaphook-shaped conidia were 20.15 to 37.21 × 3.98 to 5.27 μm and the ellipse-shaped conidia were 6.02 to 15.52 × 2.21 to 5.33 μm in size. Chlamydospores were produced, with two to five arranged together. Biological characteristics of the fungi indicated that the optimum temperature for the mycelial growth on PSA was 25 to 30°C and the optimum pH range was 5.5 to 7.0. The above morphological characteristics point the fungal isolates to be Fusarium solani. To confirm pathogenicity, 30 healthy 1-year-old tree peony seedling plants were grown in pots (25 cm in diameter) with sterilized soil and a conidial suspension from one isolate (FH-1, 5 × 105 conidia/ml) was used for soil inoculation. Inoculated seedlings were maintained at 28°C in a greenhouse with a 12-h photoperiod of fluorescent light. Seedlings inoculated with distilled water were used as controls. After 3 weeks, the roots were collected and rinsed with tap water. Dark brown lesions were observed in the inoculated mature roots but not in the control roots. To confirm the identity of the pathogen, F. solani strains were reisolated from the lesions and total genomic DNA was extracted with the cetyltriethylammnonium bromide method from the mycelia of the reisolated strains (1). PCR was performed using the fungal universal primers ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) and ITS5 (5′-GGAAGTAAAAGTCGTAACAAGG-3′) to amplify a DNA fragment of approximately 590 bp. The purified PCR products were sequenced (Invitrogen Co., Shanghai, China) and shared 100% sequence identity with each other. A comparison of the sequence (JQ658429.1) by the Clustal_W program (2) with those uploaded in GenBank confirmed with the fungus F. solani (100% sequence similarity to isolate S-0900 from the Great Plains of the United States; EU029589.1). To our knowledge, this is the first report of F. solani causing medical tree peony root rot in China. The existence of this pathogen in China may need to be considered for developing effective control strategies. References: (1). C. N. Stewart et al. Biotechniques 14:748, 1993. (2). J. D. Thompson et al. Nucleic Acids Res. 22:4673, 1994.

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First Report of Fusarium root rot in Asian Pear Caused by Fusarium solani in China

Plant Disease ◽

10.1094/pdis-07-16-0998-pdn ◽

2017 ◽

Vol 101 (1) ◽

pp. 252-252

Author(s):

L. W. Zhu ◽

X. M. Tang ◽

T. Y. Lin ◽

S. S. Zhou ◽

P. Liu ◽

...

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Fusarium Root Rot ◽

First Report ◽

Asian Pear

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First Report of Phytophthora syringae on Cedrus libani in Turkey

Plant Disease ◽

10.1094/pdis-09-13-0962-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 846-846 ◽

Cited By ~ 1

Author(s):

T. Doğmuş-Lehtijärvi ◽

A. G. Aday Kaya ◽

A. Lehtijärvi ◽

T. Jung

Keyword(s):

Average Length ◽

Morphological Characteristics ◽

Soil Samples ◽

Morphological Identification ◽

First Report ◽

Cedrus Libani ◽

Initial Symptoms ◽

Lebanon Cedar ◽

Forest Nurseries ◽

Β Tubulin

Cedrus libani, commonly known as Lebanon cedar, is one of the most important coniferous tree species in Turkey. Its main distribution is in the Taurus Mountains in the Mediterranean Region. The total area of pure Taurus cedar forest covers 109,440 ha in Turkey, all located in the southwestern regions of the country. Due to its drought resistance, Taurus cedar has been commonly used for afforestations in these semi-arid areas (1). In September 2011, during surveys for Phytophthora spp. in forest nurseries in Adapazari and İzmir in eastern Turkey, initial symptoms such as death of fine roots, yellowing, and wilting of Taurus cedar seedlings were observed. Soil samples were collected from 10 symptomatic C. libani seedlings and isolation tests for Phytophthora species were carried out using leaflets from young Quercus suber, Azalea sp., and Rhodendron sp. saplings as baits floated over flooded soil. Necrotic baits were blotted dry, cut into small pieces, and placed on selective PARPNH carrot agar. Out growing colonies were subcultured on carrot agar and kept at 12°C for morphological and molecular identifications (2). In total, six Pythiaceous isolates were obtained from the C. libani soil samples. The isolates were investigated using a light microscope and grouped according to their morphological characteristics (3). DNA was extracted from two representative isolates using Qiagen DNeasy Plant Mini Kit following the manufacturer's instructions. PCR amplifications and sequencing of the internal transcribed spacer (ITS) region of rDNA and the β-tubulin gene were performed using ITS1 and ITS4 and Tub1 and Tub2 primer sets (4). Sequencing of the PCR products in both directions was conducted by IonTek Inc. (Istanbul, Turkey) in an ABI PRISM automated sequencer. The obtained sequences were compared with those in the GenBank and Phytophthora database using BLAST search. On the basis of morphological features and molecular analyses, the two isolates were identified as Phytophthora syringae. Morphological characteristics on carrot agar were identical with the description of P. syringae (2). At 20°C, colonies reached 7 cm in diameter after 1 week. Sporangia were semipapillate to non-papillate, ovoid, with average length of 59 μm (SD ± 2.8) (range 58 to 70 μm). Oogonia were 38 μm (SD ± 5.4) in diameter (range 30 to 47 μm) with paragynous antheridia. The morphological identification was confirmed by sequence comparison at GenBank with 99% homology for both ITS and β-tubulin. The ITS sequences of the two isolates were deposited in GenBank with the accession nos. KF430614 and KF944377. Under-bark inoculation tests with mycelia plugs were conducted with both isolates of P. syringae at 18°C in a growth chamber on a total of six 1-year-old shoots cut from two C. libani trees. Lesions with an average length of 19 mm (SD ± 6) developed after 10 days. P. syringae was consistently re-isolated from the margins of necrotic tissues. Control shoots remained symptomless. To our knowledge, this is the first report of damage caused by P. syringae on C. libani seedlings in forest nursery in Turkey. References: (1) T. Çalışkan. Pages 109-130 in: Proceedings of Workshop “Hızlı gelişen türlerle ilgili rapor,” Ankara, Turkey, 1998. (2) T. Jung et al. Eur. J. For. Pathol. 26:253, 1996. (3) T. Jung et al. Mycol. Res. 107:772, 2003. (4) L. P. N. M. Kroon et al. Fung. Genet. Biol. 41:766, 2004.

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First Report of Ilyonectria macrodidyma Causing Root Rot of Olive Trees (Olea europaea) in California

Plant Disease ◽

10.1094/pdis-04-12-0330-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1378-1378 ◽

Cited By ~ 8

Author(s):

J. R. Úrbez-Torres ◽

F. Peduto ◽

W. D. Gubler

Keyword(s):

Root Rot ◽

Small Subunit ◽

Internal Transcribed Spacer Region ◽

Olive Cultivar ◽

Field Station ◽

First Report ◽

Light Yellow ◽

Significant Difference ◽

Root Necrosis ◽

Olive Trees

The California olive industry produces 99% of the U.S. olive crop, which represented a value of over $113 million in 2010. During the 2008 and 2009 growing seasons, decline of young super-high-density olive cvs. Arbequina, Arbosana, and Koroneiki trees (<4 years old) was observed in orchards throughout Glenn, Yolo, and San Joaquin Counties. Symptomatic trees showed stunted growth and chlorotic leaves with roots having black, sunken, necrotic lesions, which frequently prolonged into the base and crown of the tree. Twenty-five trees were collected from different orchards and necrotic roots as well as infected trunk tissue were plated onto potato dextrose agar amended with 0.01% tetracycline hydrochloride. Cultures were incubated at room temperature (23 ± 2°C) until fungal colonies were observed. In 17 out of 25 trees collected (68%), light yellow fungal colonies were observed from the symptomatic tissue after 7 to 10 days. Colonies turned dark yellow to orange with age and showed an orange-dark brown reverse. Both microconidia (hyaline, ellipsoidal to ovoidal and aseptate (n = 60) (6.5) 11.5 to 13.5 (17.1) × (3) 3.4 to 4.5 (5.6) μm) and macroconidia (hyaline, cylindrical, straight and/or slightly curved with one, two or three septa (n = 60) (12.5) 26.5 to 38.5 (44.1) × (4) 5.5 to 7.5 (8.5) μm) were observed. Culture and conidial morphology were in concordance with previous published description of Ilyonectria macrodidyma (Halleen, Schroers & Crous) P. Chaverri & C. Salgado (1,3,4). Identification to species level was confirmed by sequence comparison of four Californian isolates (UCCE958, UCCE959, UCCE960, and UCCE961) with sequences available in GenBank using the internal transcribed spacer region (ITS1-5.8S-ITS2) of the rDNA (primers ITS1/ITS4), a portion of the β-tubulin gene (BT1a/BT1b), and a partial sequence of the mitochondrial small subunit rDNA (NMS1/NMS2) (4). Fungal sequences of isolates from olive from California (GenBank JQ868543 to JQ868554) showed 99 to 100% homology with previously identified and deposited I. macrodidyma isolates in Genbank for all three genes. Pathogenicity of I. macrodidyma in olive cvs. Arbequina, Arbosan, and Koroneiki was investigated using two fungal isolates (UCCE958 and UCCE960) as reported by Petit and Gubler (4). The roots of 10 1-year-old trees per fungal isolate for each olive cultivar were individually inoculated with 25 ml of a 106 conidia/ml spore suspension and placed in a lath house at the UC Davis field station. Additionally, 10 trees per cultivar were inoculated with sterile water as controls. Six months after inoculation, most of the inoculated olive plants showed chlorotic leaves similar to those observed in commercial orchards. Root necrosis for each cv. was expressed as the percentage of root length having lesions (2). No significant difference was observed between isolates and average root necrosis was 29.4, 35.6, and 38.3% in Koroniki, Arbosana, and Arbequina, respectiveley. I. macrodidyma was recovered from symptomatic roots in each of the cvs. and identified based on morphology. No root rot symptoms were observed in the controls. To our knowledge, this is the first report of I. macrodidyma causing root rot of olive trees not only in California but anywhere in the world. References: (1) P. Chaverri et al. Stud. Mycol. 68:57, 2011. (2) M. Giovanetti and B. Mosse. New Phytol. 84:489, 1980. (3) F. Halleen et al. Stud. Mycol. 50:421, 2004. (4) E. Petit and W. D. Gubler. Plant Dis. 89:1051, 2005.

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