Figure 1. Morphology of Phytophthora iranica. A, Mycelium; B, papillate sporangia; C, chlamydospores; D, oogonia; and E, oospores. (Reproduced, by permission, from Ershad, 1971) Click image to see larger view.

 

Figure 2. Culture of Phytophthora iranica grown on V-8 juice agar. (Courtesy Jean B. Ristaino)

 

Figure 3. Oogonia of Phytophthora iranica with amphigynous antheridia and an aplerotic oospore. (Courtesy Jean B. Ristaino)

 
 
 
 
 
 
 
 
 
 
 

Introduction

Phytophthora iranica  Ershad (1971)

 

Phytophthora iranica was isolated from the roots of eggplant in Iran in 1971 (Ershad, 1971). Isolates that infect myrtle have been reclassified to P. italica (Belisario et al., 1993; Cacciola et al., 1996; Cline et al., 2008). It is considered a group I species (Stamps et al., 1990) (Fig. 1).

Cultural Characteristics

The minimum temperature for growth is 10°C, the optimum temperature for growth is 27.5°C, and the maximum temperature for growth is 35°C (Fig. 2).

Reproductive Structures

Asexual Structures

 

Sporangiophores:

Sporangiophores are short and sympodially branched.

 

Sporangia:

Sporangia are papillate; may have multiple papillae; are ovoid, obpyriform, ellipsoid to spherical, or irregular in shape; and are 22–51 × 30–72 µm (average 36.8 × 47.9 µm). The length–breadth ratios are 1.3:1. Sporangia are noncaducous (Fig. 1B).

 

Chlamydospores:

Development of chlamydospores is rare, but when formed they are 17–41 µm in diameter (average 28.7 µm). Chlamydospores are normally intercalary and rarely terminal (Fig. 1C).

 

Hyphae:

No hyphal swellings occur. 

 

Sexual Structures

 

P. iranica is homothallic.

 

Antheridia:

Antheridia are paragynous and occasionally amphigynous.

 

Oogonia:

Oogonia are relatively large and subspherical and are 21–45 µm in diameter (average 34 µm) (Fig. 1D).

 

Oospores:

Oospores are aplerotic and 15–37 µm in diameter (average 29.3 µm) (Fig. 3). Oospore walls are 1–5 µm thick (average 3 µm) (Fig. 1E).

Host Range and Distribution

P. iranica was first isolated in Iran from infected roots of Solanum melongena (eggplant). Inoculated fruit of Lycopersicon esculentum (tomato), tubers of Solanum tuberosum (potato), and roots of Beta vulgaris (sugar beet) are infected, but fruits of eggplant, cucumber, sweet orange, and apple are not (Erwin and Ribeiro, 1996). A previous stem rot on myrtle (Myrtus spp.) is now attributed to P. italica (Erwin and Ribeiro, 1996).

Symptoms

The pathogen infects the roots of eggplant but not the fruit. It can cause a soft rot of potato tubers, and infected tubers can turn pink, similar to the infection caused by P. erythroseptica. The pathogen is weakly pathogenic on the other hosts listed above (Cline et al., 2008).

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.