The symptoms consisted of light-brown skin discolorations with spongy to firm flesh texture and a darker pericarp than the infected area.
Pathologists from the Faculty of Agricultural Sciences at Talca University (Chile) analysed infected apples and isolated the causal agent. After 7 days of incubation at 20°C, a Phytophthora species was isolated.
Sporangia were persistent, semipapillate, ovoid to pyriform and with an average dimension of 25 to 39 x 19 to 25 µm and a length:width ratio between 1.3:1 and 1.6:1. Oospores were plerotic, round and with a diameter between 25 and 30 µm.
Based on the characteristics described, the isolates have been identified as Phytophthora syringae, though the genome was also sequenced. The DNA sequences were deposited in GenBank (Accession nos. KU170701 to KU170703). Analyses showed a 100% homology with P. syringae (AF266803).
The pathogenicity test was conducted with two isolates (MZ-PHY-1 and MZ-PHY-3) on ripe Pink Lady and Granny Smith apples, which were inoculated and stored in crates at 0°C and 95%UR for 45 days. All inoculated apples developed necrotic lesions similar to the original symptoms, measuring 24.5 to 29.4 mm in diameter for Granny Smith and 11.2 to 15.2 mm for Pink Lady.
"Phytophthora syringae was reported to cause apple fruit rot in the USA and in the UK. To the best of our knowledge, this is the first report of fruit rot caused by P. syringae in cold stored apples in Chile. Further studies are needed to know the extent of the risk of Phytophthora fruit rot in the Maule region."
Source: M. Lolas, J. M. Contreras, R. Méndez, M. Cáceres, and G. A. Díaz, 'First Report of Phytophthora Fruit Rot in Apple Caused by Phytophthora syringae During Cold Storage in Maule Region, Chile', Plant Disease, July 2016, Volume 100, Number 7, Page 1507. dx.doi.org/10.1094/PDIS-12-15-1462-PDN