Almond witches’-broom phytoplasma (Candidatus <i>Phytoplasma phoenicium</i>): a real threat to almond, peach and nectarine.

Abstract

Within less than a decade, Almond witches’-broom (AlmWB) phytoplasma killed over a hundred thousand almond trees in Lebanon (Abou-Jawdah et al., 2002). AlmWB belongs to the pigeon pea witches’ broom group (16SrIX), and the scientific name (Candidatus Phytoplasma phoenicium) was suggested (Verdin et al., 2003). Grafting experiments revealed that AlmWB may also affect peaches and nectarines (Abou-Jawdah et al, 2003). Later on, a similar disease was reported in Iran (Verdin et al., 2003; Salehi et al., 2006). This disease is still spreading on almond trees to new areas in North Lebanon, but more recently shoot proliferation with succulent small light green leaves were observed on peach and nectarine in South Lebanon, where the disease seemed to be spreading relatively fast. DNA sequencing showed over 99% sequence homology with AlmWB (Abou-Jawdah et al. 2008). This report shows that epidemics of AlmWB may occur also on peach and nectarine under field conditions, and strongly suggests the presence of an efficient vector.