First Report of Peach latent mosaic viroid Infecting Peach in Egypt

Peach latent mosaic viroid (PLMVd) is a widespread pathogen of stone fruit trees in some European and Mediterranean countries and also in North America. To access the presence of the viroid in Egypt, a survey was conducted that covered five commercial peach orchards in the El Khatatba Region in Al Minufiya Governorate. During 2003 and 2004, 73 peach trees (cv. Florida grafted on Nemagard rootstock) were visually inspected and sampled. No symptoms characteristic of PLMVd infection, such as mosaic, delayed growth, or fruit suture cracking, were observed. All samples were tested for the presence of PLMVd using dot-blot hybridization and reverse transcription (RT)-PCR. Aliquots (5 μl) of total nucleic acids extracted from approximately 2 mg of leaf tissue were spotted onto positively charged nylon membranes and hybridized under stringent conditions with a digoxigenin-labeled riboprobe (2). The extracts (1 μl) also were used in RT-PCR as described (1). Only 1 of the 73 peach trees was positive for PLMVd using these detection techniques. The RT-PCR product was of the size expected for PLVMd and was cloned and sequenced. The 339 nucleotide sequence was deposited in GenBank as Accession No. DQ839564. The sequence of this Egyptian PLMVd isolate was 94% identical to the reference PLMVd variant (GenBank Accession No. M83545) and most closely (95%) related to Canadian isolate variant 16 (GenBank Accession No. AJ550911). Such a low incidence compared with other countries may be because the survey was restricted to a limited number of samples, conducted on newly reclaimed lands where no sources of infection existed before, and material with relatively low PLMVd incidence might have been used for planting. Although the incidence of PLMVd was low in this survey, the occurrence represents a threat to the stone fruit tree industry in this country and regular screening of PLMVd in certification programs is suggested. To our knowledge, this is the first report of PLMVd on peach in Egypt. References: (1) S. Loreti et al. EPPO Bull. 29:433, 1999. (2) A. M. Shamloul et al. Acta Hortic. 386:522, 1995.