First Report of Fragaria chiloensis cryptic virus, Fragaria chiloensis latent virus, Strawberry mild yellow edge virus, Strawberry necrotic shock virus, and Strawberry pallidosis associated virus in Single and Mixed Infections in Strawberry in Central Mexico.

Abstract

For phytosanitary purposes, the prevalence and incidence of viruses found in strawberry production within a centralized breeding program was investigated in Abasolo and Irapuato Counties, Guanajuato State, Mexico. Single and mixed infections of Strawberry mottle virus (SMoV) and Strawberry crinkle virus (SCV) were originally reported in the area (3), and subsequently, Strawberry latent ringspot virus (SLRSV) was also found (4). Samples of strawberry plants showing viral symptoms: stunting, mild chlorosis and reddening, occasional wrinkled, curled, and deformed leaves that may exhibit mottling, and chlorotic spots, forming a putative virus complex were collected in April and December 2007 and July and December 2008. The detection and identification of viruses reported in the United States, the country of origin of most of the imported plantlets, was carried out with sets of primers for 11 viruses, through reverse transcription (RT)-PCR (developed by Robert Martin and Ioannis Tzanetakis in Corvallis, OR). The endogenous NADH 2 subunit was employed to test the quality of the RNA extracted. Amplification conditions were: 40 cycles of 1 min at each temperature, denaturation at 95°C, annealing at 50°C for Strawberry necrotic shock virus (SNSV); 52°C for Strawberry mild yellow edge virus (SMYEV); 55°C for Fragaria chiloensis latent virus (FClLV), Strawberry pallidosis associated virus (SPaV), Fragaria chiloensis cryptic virus (FClCV), and SMoV; and 58°C for SCV and NADH dehydrogenase, followed by a final extension at 72°C of 5 min after completion of the 40 cycles. The cloning and nucleotide sequencing of amplified fragments revealed the presence of seven viral species in 40 samples collected. These were FClLV, SCV, SMoV, SNSV, SPaV, and SMYEV, which were allocated GenBank accession numbers of JQ629412, JQ629413, JQ629414, JQ629415, JQ629416, and JQ629417, respectively. Strawberry UC-4 and UC-10 (1,2) were planted as indicators of viral infections on an experimental plot. All seven viruses were detected in single or mixed infections. SMoV was the most commonly found in combination with other viruses. Out of 40 samples, 35 were positive for the presence of viruses and six had single infections, of which five had SMoV and one had SPaV. The remaining 29 samples had mixed infections with two or more viruses in a total of 22 combinations. The combination of FCICV + SMoV was present in five samples, whereas the combination of SMoV + SMYEV was in two samples. All other samples had two and up to six different viruses per plant. SMoV was detected in 26 out of the 40 samples tested. SNSV and FClCV were detected in 14 samples. SMYEV was present in 13 samples. SCV was present in nine samples, whereas SPaV and FClLV were found in eight samples each. To the best of our knowledge, this is the first report of FClLV, FClCV, SNSV, SMYEV, and SPaV in Mexico.