Figure 1. Distinctly papillate sporangia of Phytophthora italica stained with cotton blue in lactophenol. An inconspicuous basal plug is at the insertion of the sporangiophore in A. Bar = 10 μm. (Courtesy A. Belisario; Reproduced from Belisario et al., 1993) Click image to see larger view.

 

Figure 2. Sexual structures of Phytophthora italica from myrtle mounted in distilled water displaying the paragynous attachment of antheridia to the base of oogonia. (Courtesy A. Belisario; Reproduced from Belisario et al., 1993) Click image to see larger view.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Introduction

Phytophthora italica  Cacciola, Magnano & Belisario (1996)

 

Phytophthora italica was isolated from myrtle (Myrtus communis) in Italy in 1996 and identified as P. iranica (Belisario et al., 1993; Ershad, 1971). The isolate was compared with a type isolate of P. iranica and redescribed as P. italica by Cacciola et al. in 1996 (Cacciola et al., 1996; Cline et al., 2008; Erwin and Ribeiro, 1996). The name italica means “from Italy”. P. italica is a group I species (Stamps et al., 1990).

Cultural Characteristics

The minimum temperature for growth is 10°C, the optimum temperature for growth is 26°C, and the maximum temperature for growth is 35°C. Colonies grow slowly on potato dextrose agar, with a slight stellate pattern. Mycelium is uniform and white to yellowish brown with aerial mycelia.

Reproductive Structures

Asexual Structures

 

Sporangiophores:

Sporangiophores are simple and sympodial.

 

Sporangia:

Sporangia are mostly terminal and occasionally intercalary. Sporangia are papillate and ovoid to obpyriform or variable in shape. Sporangia are 11–38 × 14–56 µm (average 29 × 39 µm) (Fig. 1). The length–breadth ratios are 1.1:1–1.5:1.

 

Chlamydospores and Hyphal Swellings:

Chlamydospores are rare and no hyphal swellings occur.

 

Sexual Structures

 

P. italica is homothallic.

 

Antheridia:

Antheridia are single, unicellular, always paragynous, mostly subspherical (7.1 µm in diameter), and sometimes ovoid (4–10 × 6–12 µm). The antheridium diameter is smaller for P. italica than for P. iranica.

 

Oogonia:

Oogonia are subspherical and often slightly flattened or pyriform, with a short stalk and smooth walls. Oogonia are 15–29 µm in diameter (average 22 µm). Oogonia are smaller than those of P. iranica.

 

Oospores:

Oospores are aplerotic and 11–23 µm in diameter (average 16 µm) (Fig. 2).

Host Range and Distribution

Host

Common Name

Disease

Geographical Distribution

Myrtus communis

Myrtle

Root rot

Italy

Symptoms

P. italica causes a root rot of myrtle in Italy.

References

Belisario, A., Magnano di San Lio, G., and Cacciola, S. O. 1993. Phytophthora iranica, a new root pathogen of myrtle from Italy. Plant Dis. 77:1050-1055.

 

Cacciola, S. O., Magnano di san Lio, G., and Belisario, A. 1996. Phytophthora italica sp. nov. on myrtle. Phytopathol. Mediterr. 35:177-190.

 

Cline, E. T., Farr, D. F., and Rossman, A. Y. 2008. A synopsis of Phytophthora with accurate scientific names, host range, and geographic distribution. Plant Health Progress doi:10.1094/PHP-2008-0318-01-RS.

 

Ershad, D. 1971. Contribution to the knowledge of Phytophthora species in Iran and their phytopathogenic importance. Mitt. Biol. Bundesanst. Land- Forstwirtsch Berl.-Dahl. 140.

 

Erwin, D. C., and Ribeiro, O. K. 1996. Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN.

 

Stamps, D. J., Newhook, F. J., Waterhouse, G. M., and Hall, G. S. 1990. Revised tabular key to the species of Phytophthora de Bary. Mycol. Pap. 162. CAB International, Wallingford, United Kingdom; Commonwealth Mycological Institute, Kew, Surrey, England.