Occurrence and incidence of phytoplasmas of the 16SrII-D subgroup on solanaceous and cucurbit crops in Egypt

Symptoms reminiscent of phytoplasma infection were observed in four provinces (governorates) of Egypt in fields of eggplants, tomato plants and squash. Diseased plants exhibited stunting, leaf yellows and flower development abnormalities. PCR amplification of 16SrDNA with phytoplasma-specific primer pairs confirmed the phytoplasma presence. Sequencing and phylogenetic analysis indicated that all phytoplasmas had the same partial 16SrDNA sequence, assigning them to the 16SrII-D phytoplasma subgroup. Disease incidence was about 1% among the 20 squash fields surveyed and equally varied from 4% to 15% in the 20 eggplant fields and in the 40 tomato fields inspected. The widespread distribution of this phytoplasma in annual solanaceous and cucurbit crops suggests a wider plant host range including wild plants that could act as reservoir and insist on the need for a insect vector survey. A finer genetic differentiation of Egyptian 16SrII-D phytoplasma strains from different geographical origins and different host plants should help to better trace such epidemics.