Collar and Root Rot of Olive Trees Caused by Phytophthora megasperma in Sicily

Olive (Olea europea L.) is grown on about 154,000 ha in Sicily (southern Italy). In the summer of 1999, a few 3-year-old olive trees with decline symptoms were observed in a recently planted commercial orchard in the Enna province (Sicily). The trees were propagated on wild olive (O. europea L. var. sylvestris Brot.) rootstock. Aerial symptoms, consisting of leaf chlorosis, wilting, defoliation, and twig dieback followed in most cases by plant death, were associated with root rot and basal stem cankers. A Phytophthora sp. was consistently isolated from rotted rootlets and trunk cankers using the BNPRAH (benomyl, nystatin, pentachloronitrobenzene, rifampicin, ampicillin, and hymexazol) selective medium. Pure cultures were obtained by single-hypha transfers. The species isolated from symptomatic olive trees was identified as P. megasperma Drechsler on the basis of morphological and cultural characteristics. All isolates were homothallic, with paragynous antheridia. The diameter of oospores varied from 28 to 42 μm (mean ± SE = 36.3 ± 0.4) when they were produced on potato-dextrose agar (PDA) and from 30 to 43 μm (mean ± SE = 37.8 ± 0.4) when they were produced in saline solution. Sporangia were non-papillate. Optimum and maximum temperatures for radial growth of the colonies on PDA were 25 and 30°C, respectively. At 25°C, radial growth rate was about 6 mm per day. The identification was confirmed by the electrophoresis of mycelial proteins on a polyacrylamide slab gel. The electrophoretic banding patterns of total soluble proteins and three isozymes (esterase, fumarase, and malate dehydrogenase) of the isolate from olive were identical to those of two isolates of P. megasperma obtained from cherry and from carrot in Italy and characterized previously (1). Conversely, they were clearly distinct from the electrophoretic patterns of four isolates of P. megasperma var. sojae Hildebr. from soybean (= P. sojae Kauf. & Ger.), from those of three isolates from asparagus tentatively identified as P. megasperma sensu lato (1) and from those of reference isolates of various species producing non-papillate sporangia, including P. cambivora (Petri) Buisman, P. cinnamomi Rands, P. cryptogea Pethybr. & Laff., P. drechsleri Tucker, and P. erythroseptica Pethybr. Pathogenicity of the isolate from olive was tested in the greenhouse at 18 to 25°C using 18-month-old rooted cuttings of olive cv. Biancolilla. Cuttings were inoculated on the lower stem by inserting a 3-mm plug taken from actively growing colonies on PDA into an incision made with a sterile scalpel. The wound was sealed with waterproof tape. Agar plugs with no mycelium were placed into the stem of cuttings used as a control. The bark was stripped and lesion areas were traced and measured 60 days after inoculation. The isolate from olive produced a brown necrotic lesion (mean size = 500 mm2) around the inoculation wound and was reisolated from the lesion. Conversely, the wound healed up on control plants. P. megasperma has previously been recognized as a pathogen of olive in Greece and Spain (3). However, this is the first report of P. megasperma causing root and collar rot of olive in Italy. References: (1) S. O. Cacciola et al. Inf. Fitopatol. 46:33, 1996. (2) D. C. Erwin and O. K. Ribeiro, 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. (3) M. E. Sánchez-Hernádez et al. Plant Dis. 81:1216, 1997.

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Wilt and Collapse of Cuphea ignea Caused by Phytophthora tropicalis in Italy

Plant Disease ◽

10.1094/pd-90-0680a ◽

2006 ◽

Vol 90 (5) ◽

pp. 680-680 ◽

Cited By ~ 7

Author(s):

S. O. Cacciola ◽

D. Spica ◽

D. E. L. Cooke ◽

F. Raudino ◽

G. Magnano di San Lio

Keyword(s):

Selective Medium ◽

Phytophthora Species ◽

Width Ratio ◽

Broad Host Range ◽

Rdna Sequences ◽

Electrophoretic Patterns ◽

Pure Cultures ◽

Length Width ◽

Single Hypha ◽

Cardinal Temperatures

The genus Cuphea (Lythraceae) includes approximately 250 species of annual, evergreen perennials and short shrubs native to Central and South America. During the springs of 2003 and 2004, 10% of the nursery stock of approximately 12,000 potted cigar-flowers (C. ignea A. DC) grown in a screenhouse at a commercial ornamental nursery near Piedimonte Etneo, Sicily, had symptoms of wilt, defoliation, and rapid collapse of the entire plant. These foliar symptoms were associated with a reduced root system, browning of the collar, and dark brown discolored roots. A Phytophthora species was consistently recovered by plating small pieces of rotted roots of symptomatic plants onto selective medium (3); pure cultures were obtained by single-hypha transfers. On potato dextrose-agar (PDA), cardinal temperatures for growth were 10 to 35°C and the optimum was 28 to 30°C. Sporangiophores were umbellate or in a close monoclasial sympodium and mean dimensions of sporangia were 52 × 26 mm, with a mean length/width ratio of 2:1. Sporangia produced on V8 juice agar (VJA) were ellipsoid, fusiform, or limoniform with a tapered base. They were papillate, occasionally bipapillate, caducous, with a long pedicel (as much as 150 μm). All isolates were mating type A1 determined by pairing with A2 reference isolates of P. palmivora (Butl.) Butl. and P. nicotianae Breda de Haan. Oogonia with amphigynous antheridia were formed on VJA after 10 to 15 days at 24°C in the dark. Occasionally, 10 of 15 isolates formed small chlamydospores on VJA. Electrophoretic patterns of total mycelial proteins and four isozymes (acid and alkaline phosphatase, esterase, and malate dehydrogenase) on polyacrylamide slab gels (3) of all Cuphea isolates were very similar to those of reference isolates of P. tropicalis M. Aragaki & J. Y. Uchida from Convolvulus cneorum L. (IMI 391714) and Rhamnus alaternus L., respectively. In addition, the Cuphea isolates were clearly distinct from reference isolates of other species including P. capsici Leon., P. citricola Sawada, P. citrophthora (R. E. Smith & E. H. Smith) Leon., P. nicotianae, and P. palmivora. On the basis of morphological cultural characters and the electrophoretic phenotype, the isolates were identified as P. tropicalis. Internal transcribed spacer (ITS) regions of rDNA sequences (2) confirmed the identification. Koch's postulates were fulfilled by testing three cigar-flower isolates, including isolate IMI 391709, on 10 6-month-old potted cuttings of Cuphea inoculated by applying a 10-ml zoospore suspension (2 × 104 zoospores/ml) to the crowns, incubated for 24 h at 100% relative humidity, and maintained in the greenhouse at 20 to 24°C. After 10 days, crowns and stems were brown and all plants wilted within 20 days. Ten control plants treated with water remained healthy. P. tropicalis was reisolated from infected tissues. The test was repeated with similar results. In Europe, P. tropicalis has been reported on Cyclamen persicum Mill. in Germany (4) and C. cneorum and R. alaternus in Italy (1), indicating a broad host range and spreading in ornamental nurseries. References: (1) S. O. Cacciola et al. Boll. Acc. Gioenia Sci. Nat. 31:57, 1999. (2) S. O. Cacciola et al. For. Snow Landsc. Res. 76:387, 2001. (3) D. C. Erwin and O. K. Ribeiro. Pages 39–41, 138–139 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul MN. 1996. (4) W. W. P. Gerlach and A. Schubert. Plant Dis. 85:334, 2001.

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First Report of a Decline and Wilt of Young Olive Trees Caused by Simultaneous Infections of Verticillium dahliae and Phytophthora palmivora in Sicily

Plant Disease ◽

10.1094/pdis-07-10-0480 ◽

2010 ◽

Vol 94 (11) ◽

pp. 1372-1372 ◽

Cited By ~ 3

Author(s):

V. Lo Giudice ◽

F. Raudino ◽

R. Magnano di San Lio ◽

S. O. Cacciola ◽

R. Faedda ◽

...

Keyword(s):

Verticillium Dahliae ◽

Dry Weight ◽

Selective Medium ◽

Phytophthora Palmivora ◽

Conidial Suspension ◽

Reference Isolate ◽

Leaf Chlorosis ◽

Pure Cultures ◽

Olive Trees ◽

Single Hypha

In summer 2008, leaf chlorosis, defoliation, exceptional fruit set, twig dieback, and wilt were observed on 4-year-old olive (Olea europea L.) trees cv. Tonda Iblea in a drip-irrigated orchard in eastern Sicily. Rot of fine roots was associated with these symptoms and on ~15% of symptomatic trees rot extended to the crown and basal stem. Trees declined slowly or collapsed suddenly with withered leaves still attached. Incidence of affected trees was ~10%. A fungus identified as Verticillium dahliae Kleb. was isolated from the xylem of main roots and basal stem. An oomycete identified as Phytophthora palmivora (Butler) Butler was isolated from roots and basal trunk bark. Both pathogens were recovered from symptomatic trees with mean frequency of positive isolations per tree of 80 and 30% for V. dahliae and P. palmivora, respectively. To isolate V. dahliae, wood chips were surface disinfested in 0.5% NaOCl for 1 min and plated onto potato dextrose agar (PDA). The fungus was identified on the basis of microsclerotia, verticillate arrangement of phialides on conidiophores, and hyaline single-celled conidia. Ten monoconidial isolates were characterized by PCR using primer pairs INTND2f/INTND2r and DB19/espdef01 (3). Only 824-bp amplicons, diagnostic of the virulent, nondefoliating V. dahliae pathotype, were obtained. P. palmivora was isolated on selective medium (2) and pure cultures were obtained by single-hypha transfers. Colonies grew on PDA between 10 and 35°C (optimum at 27°C). Chlamydospores and elliptical to ovoid, papillate, caducous (mean pedicel length = 5 μm) sporangia (length/breadth ratio of 1.8) were produced on V8 juice agar. All isolates were paired with reference isolates of P. nicotianae and produced gametangia only with isolates of the A2 mating type. PCR amplicons of a representative isolate generated using primers ITS 6 and ITS 4 (1) were sequenced and found to be identical to those of a reference isolate of P. palmivora (GenBank No. AY208126). Pathogenicity of V. dahliae (IMI 397476) and P. palmivora (IMI 397475) was tested on 6-month-old rooted cuttings of olive cv. Tonda Iblea. Ten cuttings were transplanted into pots with steam-sterilized soil and inoculum of P. palmivora (4% vol/vol) produced on wheat kernels. Ten olive cuttings were inoculated with V. dahliae by injecting the stem with 150 μl of a conidial suspension (107 conidia ml–1) and 10 cuttings were stem inoculated with V. dahliae and transplanted into soil infested with P. palmivora. Controls were 10 noninoculated cuttings transplanted into steam-sterilized soil. Pots were kept in a greenhouse (25 ± 3°C) for 4 months. No aerial symptoms were observed on cuttings transplanted into soil infested with P. palmivora. However, root dry weight was reduced by 40% in comparison with the controls. Cuttings inoculated solely with V. dahliae had a 15% reduction in height compared with the controls but only four cuttings wilted. All cuttings inoculated with P. palmivora and V. dahliae wilted, indicating a synergism between the two pathogens. Controls remained healthy. Each pathogen was reisolated solely from inoculated cuttings and both pathogens were reisolated from cuttings with double inoculations. A similar syndrome ‘seca’ (drying) was reported in Spain (4). References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) H. Masago et al. Phytopathology 67:425, 1977. (3) J. Mercado-Blanco et al. Plant Dis. 87:1487, 2003. (4) M. E. Sánchez-Hernández et al. Eur. J. Plant Pathol. 104:34, 1998.

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First Report of Phytophthora megasperma and Pythium irregulare As Olive Tree Root Pathogens

Plant Disease ◽

10.1094/pdis.1997.81.10.1216b ◽

1997 ◽

Vol 81 (10) ◽

pp. 1216-1216 ◽

Cited By ~ 4

Author(s):

M. E. Sánchez-Hernández ◽

A. Ruiz-Dávila ◽

A. Trapero-Casas

Keyword(s):

Root Rot ◽

Olive Tree ◽

The United States ◽

Damping Off ◽

Phytophthora Megasperma ◽

Root Rots ◽

Foliar Symptoms ◽

Root Pathogens ◽

Root Necrosis ◽

Olive Trees

Several species of the genus Phytophthora are associated with root rot and trunk cankers in olive trees (Olea europaea L.). Among them, Phytophthora megasperma has been cited as being associated with olive root rots in Greece (1). Unidentified species of Pythium and Phytophthora have also been associated with olive tree root rots in the United States. However, the status of P. megasperma and Pythium spp. as olive tree root pathogens has remained unclear. Following a 5-year period of severe drought in southern Spain, autumn-winter rainfall rates in 1996 to 1997 steadily increased in both quantity and frequency. Under these unusually wet conditions, olive trees remained waterlogged for several months. During this period, we observed foliar wilting, dieback, and death of young trees, and later found extensive root necrosis. In 46 of 49 affected plantations surveyed, P. megasperma was consistently isolated from the rotted rootlets, particularly in young (<1- to 10-year-old trees) plantations. This fungus was not detected on plant material affected by damping-off from several Spanish olive tree nurseries. The opposite situation occurred with P. irregulare. This species was not associated with rotted rootlets in the field. In contrast, it was consistently isolated from necrotic rootlets from young olive plants affected by damping-off. These plants were grown in a sand-lime-peat soil mixture under greenhouse conditions and showed foliar wilting and extensive necrosis of the root systems. Pathogenicity tests were conducted with several isolates of P. megasperma and P. irregulare on 6-month-old rooted cuttings of olive, under both weekly watering and waterlogged conditions. Under waterlogged conditions, both fungal species produced extensive root necrosis 2 weeks after inoculation that resulted in wilting of the aerial parts and rapid plant death. Waterlogged control plants remained without foliar symptoms but a low degree of root necrosis was recorded. In addition, under weekly watering conditions, plants inoculated with either species showed some degree of root rot but foliar symptoms were not evident. No differences in pathogenicity were observed within the Phytophthora or Pythium isolates. Reference: (1) H. Kouyeas and A. Chitzanidis. Ann. Inst. Phytopathol. Benaki 8:175, 1968.

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Root and Foot Rot of Lantana Caused by Phytophthora cryptogea

Plant Disease ◽

10.1094/pd-89-0909b ◽

2005 ◽

Vol 89 (8) ◽

pp. 909-909 ◽

Cited By ~ 2

Author(s):

S. O. Cacciola ◽

A. Chimento ◽

A. Pane ◽

D. E. L. Cooke ◽

G. Magnano di San Lio

Keyword(s):

Sandy Loam ◽

Heavy Rain ◽

Early Spring ◽

Selective Medium ◽

Plant Diseases ◽

Infested Soil ◽

Foot Rot ◽

American Phytopathological Society ◽

Electrophoretic Patterns ◽

Pure Cultures

Lantana (Lantana camara L.) is an evergreen shrub in the Verbenaceae. In some countries, this plant has been declared a noxious weed. However, a number of sterile or near-sterile forms are cultivated as attractive flowered potted and garden plants. In early spring 2004, ≈4,000 potted, small trees of lantana grown in a screenhouse in a commercial nursery of ornamentals near Giarre, Sicily, showed symptoms of chlorosis, defoliation, and sudden collapse of the entire plant. These aboveground symptoms were associated with a reduced root system, rot of feeder roots, and brown discoloration of the base of the stem. A Phytophthora sp. was isolated consistently from roots and basal stems of symptomatic plants using the selective medium of Masago et al. (3). Cardinal temperatures for radial growth of pure cultures obtained by single hypha transfer were 2°C minimum, 25°C optimum, and 30 to 35°C maximum. Sporangia produced in the saline solution of Chen and Zentmyer (3) were obpyriform, persistent, and nonpapillate. All isolates were A1 mating type and differentiated oospores with amphigynous antheridia in dual cultures with A2 reference isolates of P. cryptogea Pethybr. & Laff. and P. drechsleri Tucker (3). Electrophoretic patterns of total mycelial proteins (3) of the isolates from lantana were very similar to those of reference isolates of P. cryptogea from different hosts, but clearly distinct from those of reference isolates of other species included in Waterhouse's taxonomic group VI (3). Indeed, isolates from lantana were identified as P. cryptogea on the basis of morphological and cultural characters as well as the electrophoretic phenotype. Sequences of internal transcribed spacer (ITS) regions of rDNA (1) confirmed the identification as P. cryptogea. Pathogenicity of a representative isolate from lantana (IMI 392045) was tested in a screenhouse by transplanting 20 6-month-old rooted cuttings of lantana in pots (12 cm in diameter) filled with infested soil; the soil was prepared by mixing steam-sterilized sandy loam soil at a concentration of 4% (vol/vol) with inoculum produced on a mixture of vermiculite and autoclaved oat seeds. Twenty control plants were transplanted in pots containing noninfested soil. The soil was saturated with water by plugging the pots' drainage holes for 48 h and watering. After 40 days, all plants except the controls showed symptoms of root and foot rot, and P. cryptogea was reisolated from infected tissues. To our knowledge, this is the first report of P. cryptogea on lantana. On this host and other species in the verbena family, only P. nicotianae van Breda de Haan (= P. parasitica Dastur) has been previously reported (2,3,4). A possible cause of the high incidence of this disease in the nursery was waterlogging due to heavy rain and excessive irrigation. References: (1) S. O. Cacciola et al. For. Snow Landsc. Res. 76:387, 2001. (2) M. L. Daughtrey et al. Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society, St. Paul, MN, 1995. (3) D. C Erwin and O. K. Ribeiro. Pages 39–41, 84–95, 138–139 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) K. H. Lamour et al. Plant Dis. 87:854, 2003.

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First Report of Phytophthora palmivora on Grevillea spp. in Italy

Plant Disease ◽

10.1094/pdis.2003.87.8.1006a ◽

2003 ◽

Vol 87 (8) ◽

pp. 1006-1006

Author(s):

S. O. Cacciola ◽

A. M. Pennisi ◽

G. E. Agosteo ◽

G. Magnano di San Lio

Keyword(s):

Mating Type ◽

Glucose Dehydrogenase ◽

Field Capacity ◽

Selective Medium ◽

Phytophthora Palmivora ◽

Width Ratio ◽

Submerged Cultures ◽

Reference Isolate ◽

Electrophoretic Patterns ◽

Pure Cultures

The genus Grevillea (family Proteaceae) comprises over 300 species and is a popular and widely cultivated group of Australian plants. In the last 3 years, numerous potted grevilleas with symptoms of decline associated with a rot of feeder roots were found in ornamental nurseries in Sicily. Aboveground symptoms were reduced growth, yellowing of foliage, wilt, dieback, and death of the entire plant. The disease was observed on many commercial cultivars and was especially severe on G. alpina (mountain grevillea), G. juniperina (juniper-leaf grevillea), G. lavandulacea (lavender grevillea), and G. rosmarinifolia (rosemary grevillea) as well as the hybrid cultivars Clearview David (G. lavandulacea × rosmarinifolia) and Poorinda Rondeau (G. baueri × lavandulacea), while G. lanigera (woolly grevillea) cv. Mount Tamboritha and G. thelemanniana subsp. obtusifolia appeared resistant. A species of Phytophthora was consistently isolated from rotted roots of symptomatic plants using a selective medium (4), and pure cultures were obtained by single-hypha transfers. The species was identified as P. palmivora (E.I. Butler) E.I. Butler on the basis of morphological and cultural characters. On solid media, all isolates produced elliptical to ovoid, papillate sporangia with a mean length/width ratio of 1.8. Sporangia were caducous with a short pedicel (5 μm) and a conspicuous basal plug. All isolates were heterothallic (mating type A1) and produced oogonia and oospores only when paired with A2 mating type reference isolates of P. nicotianae and P. palmivora. Antheridia were amphyginous. Identification was confirmed by electrophoresis of mycelial proteins in polyacrylamide slab gels (1). The electrophoretic patterns of total soluble proteins and six isozymes (alkaline phosphatase, esterase, fumarase, NAD-glucose dehydrogenase, malate dehydrogenase, and superoxide dismutase) of isolates from grevillea were identical to those of a reference isolate of P. palmivora from Coronilla valentina subsp. glauca (2) but distinct from those of reference strains of eight other papillate species of Phytophthora included in Waterhouse's taxonomic group VI. Koch's postulates were fulfilled using 6-month-old rosemary grevillea plants that were transplanted into pots filled with soil that was artificially infested with chlamydospores (50 per gram of soil) produced in submerged cultures (3) by grevillea isolate IMI 390579. Plants were maintained in a glasshouse at 20 to 28°C and watered to field capacity once a week. One month after transplanting, infected plants showed decline symptoms similar to those of naturally infected plants. Control plants grown in pots containing noninfested soil remained healthy. P. palmivora was reisolated from roots of symptomatic plants. It appears that P. palmivora has become a widespread root pathogen in commercial ornamental nurseries in Italy (2). References: (1) S. O. Cacciola et al. EPPO Bull. 20:47, 1990.D. (2) S. O. Cacciola et al. Plant Dis. 86:327, 2002. (3) J. Y. Kadooka and W. H. Ko. Phytopathology 63:559, 1973. (4) H. Masago et al. Phytopathology 67:425, 1977.

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First Report of Brown Rot and Wilt of Fennel Caused by Phytophthora megasperma in Italy

Plant Disease ◽

10.1094/pd-90-0110a ◽

2006 ◽

Vol 90 (1) ◽

pp. 110-110 ◽

Cited By ~ 2

Author(s):

S. O. Cacciola ◽

A. Pane ◽

D. E. L. Cooke ◽

F. Raudino ◽

G. Magnano di San Lio

Keyword(s):

Radial Growth ◽

Brown Rot ◽

Soft Rot ◽

Soil Extract ◽

Selective Medium ◽

Late Winter ◽

Broad Host Range ◽

Foeniculum Vulgare ◽

Phytophthora Megasperma ◽

First Report

Fennel (Foeniculum vulgare Mill. var. azoricum (Mill.) Thell.) in the Apiaceae family is native to southern Europe and southwestern Asia. It is an economically important crop in Italy that produces approximately 85% of all fennel worldwide. The main producing regions are Apulia, Campania, Latium, and Calabria. During the late winter of 2004 in the Crotone Province of the Calabria Region, following heavy rains, patches of fennel plants with symptoms of brown, soft rot of the bulb-like structure formed by the thickened leaf bases, development of yellow leaves, stunting, and wilting of the entire plant were observed in fields. A homothallic Phytophthora sp. was isolated consistently from the brownish tissues of the stout stems and leaf bases of symptomatic plants using a selective medium (3). Pure cultures were obtained by single hyphal tip transfers. On potato dextrose agar (PDA), the diameter of oospores varied from 28 to 42 μm (mean = 36.3 ± 0.4). Antheridia were primarily paragynous. Sporangia were not produced on solid media but were formed in sterile soil extract solution. They were nonpapillate, noncaducous, ovoid and obpyriform (25 to 45 × 35 to 60 μm), and internally proliferating. Optimum and maximum temperatures for radial growth of the colonies on PDA were 25 and 30°C, respectively. At 25°C, radial growth rate was approximately 6 mm per day. On the basis of morphological and cultural characteristics, the isolates were identified as Phytophthora megasperma Drechsler. Electrophoretic patterns of mycelial proteins and four isozymes (acid and alkaline phosphatase, esterase, and malate dehydrogenase) on polyacrylamide gels of the fennel isolates were identical to those of reference isolates of P. megasperma of the BHR (broad host range) group included in P. gonapodyides-P. megasperma Clade 6 (1,3), but distinct from those of the isolates of other nonpapillate species included in Waterhouse's taxonomic group VI. Internal transcribed spacer (ITS) regions of rDNA sequences (2) confirmed that fennel isolates belonged to P. megasperma BHR group. Pathogenicity of a fennel isolate from Calabria (IMI 391711) was confirmed by pouring a zoospore suspension at 2 × 104 zoospores per ml on the soil of 10 3-month-old potted fennel plants. The soil of the inoculated and 10 control seedlings was flooded for 24 h. After 10 days, stems and leaf bases of the seedlings showed a brown rot. Chlorosis and wilting of all seedlings developed after 20 days. Controls inoculated with water did not develop any symptoms. The pathogen was reisolated from typical brown rot and tests were repeated with similar results. To our knowledge, this is the first report of P. megasperma causing disease on fennel. References: (1) S. O. Cacciola et al. For. Snow. Landsc. Res. 76:387, 2001. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) H. Masago et al. Phytopathology, 67:425, 1977.

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Root and Basal Stem Rot of Scotch Broom Caused by Phytophthora citricola and P. drechsleri in Italy

Plant Disease ◽

10.1094/pd-89-1131a ◽

2005 ◽

Vol 89 (10) ◽

pp. 1131-1131

Author(s):

A. Pane ◽

S. O. Cacciola ◽

M. Adornetto ◽

G. Proietto Russo ◽

F. Badalà ◽

...

Keyword(s):

Root Rot ◽

Central Italy ◽

Field Capacity ◽

Selective Medium ◽

Width Ratio ◽

Potted Plants ◽

Scotch Broom ◽

Oat Seeds ◽

Pure Cultures ◽

Electrophoretic Phenotype

Scotch broom (Cytisus scoparius (L.) Link, Fabaceae), an evergreen shrub native to Europe, is cultivated as a garden plant. In 2003 and 2004, potted plants with symptoms of leaf chlorosis, defoliation, and eventual wilt and associated with root and collar rot were observed in ornamental nurseries in Sicily. As much as 10% of plants were affected in a single nursery. Two species of Phytophthora were consistently isolated alone or together from the same pot with the selective medium of Masago et al. (2). Pure cultures were obtained by single-hypha transfers and the species were identified as P. citricola Sawada (approximately 40% of isolations) and P. drechsleri Tucker (60% of isolations) on the basis of morphological, cultural characters, and electrophoretic phenotype. The isolates of P. drechsleri grew between 10 and 37°C (optimum 27°C) on potato dextrose agar (PDA). The sporangia produced on V8 juice agar (V8A) were ellipsoid to obpyriform, nonpapillate, persistent with internal proliferation, and often forming in a sympodium. Sizes varied, 30 to 60 × 20 to 40 μm (length/width ratio between 1.4 and 2.2). The hyphal swellings were produced in aqueous culture. All isolates were A1 mating type and formed plerotic oospores (mean diameter (ф) 25 μm) with amphigynous antheridia when paired with the A2 reference isolates of P. cryptogea on V8A plus β-sitosterol. The aryl-esterase and malate dehydrogenase isozymes of scotch broom isolates on polyacrylamide slab gels (1) were identical to those of the authentic isolate CBS 292.35 of P. drechsleri and differed from reference cultures of other nonpapillate species. The cardinal temperatures of P. citricola isolates on PDA ranged from 2 to 30°C (optimum 25°C). In liquid culture, the isolates produced irregular-shaped, obovoid to obpyriform sporangia 20 to 70 × 21 to 44 μm that were noncaducous, semipapillate or with inconspicuous papilla, often with two apices. The isolates were homothallic and produced oospores (mean ф 22 μm) with paragynous antheridia. The electrophoretic phenotype of these isolates was identical to the phenotype of P. citricola reference isolates and very different from that of the reference isolates of other semipapillate species. The pathogenicity tests of the representative isolates of P. drechsleri (IMI 391710) and P. citricola (IMI 391715) were carried out in a screenhouse. Twenty 3-month-old scotch broom seedlings were transplanted into pots (12 cm ф) filled with soil infested with the inoculum produced on a mixture of vermiculite and autoclaved oat seeds. The plants were maintained at 20 to 28°C and watered to field capacity once a week. After 30 to 40 days, all inoculated plants showed symptoms of wilting and root rot. The 20 control plants transplanted into pots containing noninfested soil remained healthy. P. citricola and P. drechsleri were reisolated from infected tissues. To our knowledge, this is the first report of P. citricola and P. drechsleri on scotch broom. A root rot of scotch broom caused by P. megasperma has been reported in central Italy (3). References: (1) S. O. Cacciola et al. Plant Dis. 86:327, 2002. (2) D. C Erwin and O. K. Ribeiro. Pages 39–41 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) A. M. Vettraino and A. Vannini. Plant Pathol. 53:417, 2003.

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Lavender Cotton Root Rot: A New Host of Phytophthora tentaculata Found in Spain

Plant Disease ◽

10.1094/pd-90-0523a ◽

2006 ◽

Vol 90 (4) ◽

pp. 523-523 ◽

Cited By ~ 2

Author(s):

L. A. Álvarez ◽

A. Pérez-Sierra ◽

M. León ◽

J. Armengol ◽

J. García-Jiménez

Keyword(s):

Root Rot ◽

Soil Extract ◽

Selective Medium ◽

Distilled Water ◽

Internal Transcribed Spacer Region ◽

New Host ◽

Stalk Rot ◽

Pure Cultures ◽

Pathogenicity Tests ◽

Short Pedicel

Lavender cotton, Santolina chamaecyparissus, is an evergreen shrub growing primarily in dry, calcareous habitats and is grown in rock gardens and mixed borders mainly for its ornamental and aromatic foliage. During 2004, several commercial nurseries in Valencia Province (eastern Spain) reported high mortality of lavender cotton. The foliage of the diseased plants turned brown, wilted, and died. A Phytophthora sp. was isolated consistently from the soil and roots of infected plants using apple baits and the selective medium PARBH (1), respectively. Four pure cultures (PS-31, PS-32, PS-33, and PS-34) were established from hyphal tips and characterized. Colony morphology on potato dextrose agar (PDA) at 24°C was stoloniferous (short stubby branches) with a growth rate of 2.2 mm per day. Sporangia, chlamydospores, and oospores were produced on V8 agar. The sporangia were ovoid to obpyriform, 27.5 to 64.8 (48.3) × 25 to 52.5 (37.5) μm, length/breadth ratio of 1.3:1, and papillate, from which 20% were caducous with a short pedicel (<5 μm). Hyphal swellings and chlamydospores (22 to 38 μm in diameter) were present. Isolates were homothallic, oogonia were globose, mostly terminal 27.5 to 40 (36.2) μm in diameter, 88% of the antheridia were paragynous, monoclinous, or diclinous, and occasionally with two paragynous antheridia per oogonium. Amphigynous antheridia (12%) were also observed. Oospores were aplerotic, 25 to 35 (32.3) μm in diameter, and thin walled. These characteristics and measurements conformed to the description of P. tentaculata described by Kröber and Marwitz (2). Sequencing the internal transcribed spacer region of Santolina isolates PS-32 and PS-34 and comparison of these sequences with other sequences available in GenBank revealed that they were identical to P. tentaculata (AF266775). Pathogenicity tests used 10 4-to-5-month-old potted lavender cotton and two methods. In the first method, inoculum was prepared on a media of 200 g of oats and 120 ml of V8 juice to 1 liter of distilled water. The medium was inoculated with P. tentaculata grown on PDA and incubated in the dark at 20°C for 4 weeks. Inoculum was buried into the compost mixture around the roots at a rate of 3% (w/v). The second method applied a zoospore drench of 50 ml per plant (1 × 104 zoospores per ml) obtained by inducing zoospores in sterile soil extract from cultures of V8 juice agar. The control plants were inoculated with sterile media and sterile distilled water. The following day, the pots were flooded for 2 days, plants were maintained in a glasshouse at 24 ± 5°C, and watered twice a week. All plants inoculated with the first method had wilted foliage and died within 2 months after inoculation, while plants inoculated with zoospores died after 3 months. P. tentaculata was reisolated and the test was repeated twice. The control plants did not show any symptoms of the disease. P. tentaculata was first reported causing root and stalk rot on Chrysanthemum frutescens hybrids, C. leucanthemum, Delphinium ajacis, and Verbena hybrids in Germany (2). It has also been reported on Verbena hybrids in Spain (3). To our knowledge, this is the first report of P. tentaculata causing root rot on lavender cotton. References: (1) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986. (2) H. Kröber and R. Marwitz. Z. Pflanzenkr. Pflanzenschutz 100:250, 1993. (3) E. Moralejo et al. Plant Pathol. 53:806, 2004.

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First Report of Root Rot Caused by Phytophthora cinnamomi on Avocado in Italy

Plant Disease ◽

10.1094/pdis.1998.82.11.1281c ◽

1998 ◽

Vol 82 (11) ◽

pp. 1281-1281 ◽

Cited By ~ 1

Author(s):

S. O. Cacciola ◽

A. Pane ◽

M. Davino ◽

G. Magnano di San Lio

Keyword(s):

Mating Type ◽

Root Rot ◽

Phytophthora Cinnamomi ◽

Glucose Dehydrogenase ◽

Selective Medium ◽

Field Resistance ◽

Persea Americana ◽

Tropical Fruit ◽

Experimental Field ◽

Electrophoretic Patterns

Root rot caused by Phytophthora cinnamomi Rands is generally recognized to be the most important disease of avocado (Persea americana Miller) wherever this tropical fruit tree is grown (3). The disease was first found in Italy in the spring of 1998. Eight-year-old trees, with symptoms ranging from initial to severe, were observed in an experimental field near Rocca di Caprileone, in Sicily. Few trees showed symptoms of both root rot and collar rot. Infected trees were of 13 commercial cultivars. Trees were grafted on two different rootstocks: Hass seedlings and G6 seedlings. G6 is a selection reported to have some field resistance to P. cinnamomi infections (2). However, no correlation was observed between symptom severity and rootstock. P. cinnamomi was isolated on BNPRAH selective medium (4) from trunk bark, feeder roots, and rhizosphere soil of diseased trees, and from roots of symptomless trees. The isolates, identified primarily on the basis of morphological and cultural characteristics, formed rosaceous colonies on potato dextrose agar (PDA) and on corn meal agar (CMA) coralloid-type mycelium, with abundant hyphal swellings, which were typically spherical and in clusters. Chlamydospores were either terminal or intercalary, and often occurred in characteristic grapelike clusters. Sporangia, which were produced in saline solution (1), were broadly ellipsoidal or ovoid, persistent, non-papillate and proliferous. The identification was confirmed by the electrophoresis of mycelial proteins on polyacrylamide slab gel. The electrophoretic patterns of total soluble proteins and eight isozymes (AKP [alkaline phosphatase], EST [esterase], FUM [fumarase], GLC [NAD-glucose dehydrogenase], G6PD [glucose-6-phosphate dehydrogenase], LDH [lactate dehydrogenase], MDH [malate dehydrogenase], and SOD [superoxide dismutase]) of the isolates from avocado were identical to those of two strains of P. cinnamomi, used as reference (isolate 70473 from International Mycological Institute, U.K., and an isolate from myrtle from the Institute of Plant Pathology, University of Catania, Italy). Conversely, the electrophoretic phenotype of the P. cinnamomi isolates from avocado was clearly distinct from those of reference strains of eight other species included in Waterhouse's taxonomic group VI. Pairings with isolates of a known mating type of P. cinnamomi, P. cryptogea, and P. drechsleri revealed that all the isolates from avocado were A2 mating type. It is possible that P. cinnamomi had been introduced into the experimental field on infected symptomless nursery trees. In Italy, root rot caused by P. cinnamomi could have a significant impact on commercial avocado plantings extending over about 20 ha. Moreover, this polyphagous pathogen may be a threat to other crops as well as to forest trees. References: (1) D. W. Chen and G. A. Zentmyer. Mycologia 62:397, 1970. (2) M. D. Coffey. Plant Dis. 71:1046, 1987. (3) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN. (4) H. Masago et al. Phytopathology 67:425, 1977.

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Phytophthora mediterranea sp. nov., a New Species Closely Related to Phytophthora cinnamomi from Nursery Plants of Myrtus communis in Italy

Forests ◽

10.3390/f12060682 ◽

2021 ◽

Vol 12 (6) ◽

pp. 682

Author(s):

Carlo Bregant ◽

Antonio A. Mulas ◽

Giovanni Rossetto ◽

Antonio Deidda ◽

Lucia Maddau ◽

...

Keyword(s):

New Species ◽

Root Rot ◽

Phytophthora Cinnamomi ◽

Colony Growth ◽

Phytophthora Species ◽

Maximum Temperature ◽

Pathogenicity Test ◽

Forest Nurseries ◽

Collar And Root Rot ◽

A New Species

Monitoring surveys of Phytophthora related diseases in four forest nurseries in Italy revealed the occurrence of fourteen Phytophthora species to be associated with collar and root rot on fourteen plants typical of Mediterranean and alpine regions. In addition, a multilocus phylogeny analysis based on nuclear ITS and ß-tubulin and mitochondrial cox1 sequences, as well as micromorphological features, supported the description of a new species belonging to the phylogenetic clade 7c, Phytophthora mediterranea sp. nov. Phytophthora mediterranea was shown to be associated with collar and root rot symptoms on myrtle seedlings. Phylogenetically, P. mediterranea is closely related to P. cinnamomi but the two species differ in 87 nucleotides in the three studied DNA regions. Morphologically P. mediterranea can be easily distinguished from P. cinnamomi on the basis of its smaller sporangia, colony growth pattern and higher optimum and maximum temperature values. Data from the pathogenicity test showed that P. mediterranea has the potential to threaten the native Mediterranean maquis vegetation. Finally, the discovery of P. cinnamomi in alpine nurseries, confirms the progressive expansion of this species towards cold environments, probably driven by climate change.

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