Figure 1. Culture of Phytophthora andina grown on V-8 juice agar. (Courtesy Jean B. Ristaino)

 

Figure 2. Semipapillate sporangium of Phytophthora andina. Bar = 10 µm. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Figure 3. Oogonium, elongated amphigynous antheridia, and oospore of Phytophthora andina produced in pear melon fruits. Bar = 10 µm. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Figure 4. Blight symptoms caused by Phytophthora andina on Solanum species belonging to the Anarrhichomenum complex. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Figure 5. Blight symptoms caused by Phytophthora andina on Solanum species belonging to the Anarrhichomenum complex. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Figure 6. Blight symptoms caused by Phytophthora andina on Solanum betaceum. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Figure 7. Blight symptoms caused by Phytophthora andina on Solanum betaceum. (Courtesy Ricardo Oliva and Gregory Forbes; Reproduced, by permission, from Oliva et al., 2010)

 

Introduction

Phytophthora andina  Adler & Flier (2010)

 

Phytophthora andina was first isolated from Solanum brevifolium by N. Adler (Alder et al., 2004). Three clonal lineages (US-1, EC-1, and EC-3) and one heterogeneous group (originally designated as EC-2) were found in association with different Solanum species in the Andean highlands of Ecuador (Oliva et al., 2002; Ordoñez et al., 2000). Due to taxonomic uncertainties of the EC-2 and EC-3 groups, the population of P. infestans in Ecuador was referred to as P. infestans sensu lato (Adler et al., 2004). EC-2 lineages have an unusual mitochondrial DNA haplotype (type 1c) (Adler et al., 2004). Kroon et al. (2004) used multigene phylogenies and included P. andina in their analysis of many Phytophthora species. The full description of the species has recently been described (Gomez-Alpizar et al., 2008; Oliva et al., 2010). P. andina is a group IV Phytophthora species (Stamps et al., 1990). P. andina is a member of clade 1c and is closely related to P. mirabilis and P. infestans (Cline et al., 2008; Cooke et al., 2000; Kroon et al., 2004).

Cultural Characteristics

Cultures of P. andina grow on rye V-8 or V-8 media. The mycelium is white and fluffy (Fig. 1). The minimum temperature for growth is 5°C, the optimum temperature for growth is 24°C, and the maximum temperature for growth is 30°C.

Reproductive Structures

Asexual Structures
Sporangiophores:

Sporangiophores form aerially on rye A media with erect, compound sympodial branching, with a small characteristic swelling at the base of each branch.

 

Sporangia:

Sporangia are semipapillate and caducous with short pedicels (up to 3 µm long). Sporangia are abundant on host as well as on solid media. Sporangia are ellipsoid or ovoid. They range in length from 39.5 to 62.5 µm, with a length–breadth ratio of 2.4:2.7 (Fig. 2).

 

Chlamydospores and Hyphal Swellings:

Chlamydospores and hyphal swellings do not occur. 

 

Sexual Structures

 

P. andina is heterothallic.

 

Antheridia:

Antheridia are amphigynous. They are elongated, cylindrical, and 22 µm.

 

Oogonia:

Oogonia are smooth walled and 34–41 µm in diameter, with a tapered base.

 

Oospores:

Oospores are smooth walled, 26–37 µm in diameter (average 30 µm), and tinted yellow-brown and almost fill the oogonial cavity (Fig. 3).

Host Range and Distribution

Host

Common Name

Disease

Geographical Distribution

Anarrhichomenum complex

 

Leaf blight

South America, Ecuador

Solanum betaceum

Tree tomato

 Leaf blight South America, Ecuador

Solanum brevifolium

 

Leaf blight

South America, Ecuador

Solanum muricatum

Pear melon

Leaf blight

South America, Ecuador

Solanum tetrapetalum

 

Leaf blight

South America, Ecuador

 

P. andina, previously referred to as P. infestans sensu lato, infects several wild non-tuber-bearing species in the family Solanaceae. Solanum muricatum (pear melon) is host to both the US-1 genotype of P. infestans (A1 mating type) and the A2 mating type of P. andina. P. andina does not infect cultivated potato or tomato and is believed to be indigenous to the Andean highlands of South America.

Symptoms

Lesions are formed on leaves and stems. The leaf foliage can show symptoms at any time during the infection. Infections usually occur at the tip of the leaf margin and leaves develop purple-black or brownish black lesions (Fig. 4). Infected foliage first becomes yellow and then water-soaked and eventually turns black (Figs. 5 and 6). Masses of sporangia appear on the underside of the leaf (Fig. 7). Sporangia can be spread by wind and rain.

References

Adler, N. E., Erselius, L. J., Chacón, M. G., Flier, W. G., Ordoñez, M. E., Kroon, L. P. N. M., and Forbes, G. A. 2004. Genetic diversity of Phytophthora infestans sensu lato in Ecuador provides new insight into the origin of this important plant pathogen. Phytopathology 94:154-162.

 

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.

 

Cooke, D. E. L., Drenth, A., Duncan, J. M., Wagels, G., and Brasier, C. M. 2000. A molecular phylogeny of Phytophthora and related oomycetes. Fungal Genet. Biol. 30:17-32.

 

Gomez-Alpizar, L., Hu, C.-H., Oliva, R., Forbes, G., and Ristaino, J. B. 2008. Phylogenetic relationships of a new species, Phytophthora andina, from the highlands of Ecuador that is closely related to the Irish potato famine pathogen Phytophthora infestans. Mycologia 100:590-602.

 

Kroon, L. P. N. M., Bakker, F. T., van den Bosch, G. B. M., Bonants, P. J. M., and Flier, W. G. 2004. Phylogenetic analysis of Phytophthora species based on mitochondrial and nuclear DNA sequences. Fungal Genet. Biol. 41:766-782.

 

Oliva, R. F., Erselius, L. J., Adler, N. E., and Forbes, G. A. 2002. Potential of sexual reproduction among host-adapted populations of Phytophthora infestans sensu lato in Ecuador. Plant Pathol. 51:710-719.

 

Oliva, R. F., Kroon, L. P. N. M., Chacón, G., Flier, W. G., Ristaino, J. B., and Forbes, G. A. 2010. Phytophthora andina sp. nov., a newly identified heterothallic pathogen of solanaceous hosts in the Andean highlands. Plant Pathol. 59:613-625.

 

Ordoñez, M. E., Hohl, H. R., Velasco, J. A., Ramon, M. P., Oyarzun, P. J., Smart, C. D., Fry, W. E., Forbes, G. A., and Erselius, L. J. 2000. A novel population of Phytophthora, similar to P. infestans, attacks wild Solanum species in Ecuador. Phytopathology 90:197-202.

 

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.