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Comparative Infection Progress Analysis of Lettuce big-vein virus and Mirafiori lettuce virus in Lettuce Crops by Developed Molecular Diagnosis Techniques

First and sixth authors: Instituto de Biología Molecular y Celular de Plantas (IBMCP), UPV-CSIC, Avda. dels Tarongers, s/n, 46022 Valencia, Spain; second author: Departamento de Biología Aplicada, Universidad Miguel Hernández, Avda. Ferrocarril, s/n, 03202 Elx, Spain; third and fourth authors: PRIMAFLOR S.A.T., La Estacion 2, Pulpi, 04640 Almeria, Spain; and fifth author: Centro de Edafología y Biología Aplicada del Segura (CEBAS), CSIC, Campus Universitario de Espinardo, P.O. Box 164, 30100 Murcia, Spain

Nonisotopic molecular dot blot hybridization technique and multiplex reverse transcription-polymerase chain reaction assay for the specific detection of Lettuce big-vein virus (LBVV) and Mirafiori lettuce virus (MiLV) in lettuce tissue were developed. Both procedures were suitable for the specific detection of both viruses in a range of naturally infected lettuce plants from various Spanish production areas and seven different cultivars. The study of the distribution of both viruses in the plant revealed that the highest concentration of LBVV and MiLV occurred in roots and old leaves, respectively. LBVV infection progress in a lettuce production area was faster than that observed for MiLV. In spite of different rates of virus infection progress, most lettuce plants became infected with both viruses about 100 days posttransplant. The appearance of both viruses in lettuce crops was preceded by a peak in the concentration of resting spores and zoosporangia of the fungus vector Olpidium brassicae in lettuce roots.