In a 1998-2000 survey, witches' broom disease of sugar beet (Beat vulgaris) was found in several fields in Chahgeer region in Abarque (Yazd Province). The associated agent was transmitted from sugar beet to sugar beet, periwinkle and eggplant and from periwinkle to sugar beet via dodder inoculation and from periwinkle to periwinkle and from eggplant to eggplant, ornamental eggplant and tomato by grafting. Polymerase chain reaction (PCR) using universal phytoplasma primer pairs P1/P7 and R16F2 / R16R2 consistently amplified segments of expected size (1.8 and 1.2kb, respectively) when DNA extracts of midrib samples of affected sugar beet plants were used as template. Phylogenetic and putative restriction site analyses and percent similarity values showed that sugar beet witches' broom phytoplasma is closest to yet distinct from members of peanut witches' broom phytoplasma group (16Srll). It is related only distantly to two phytoplasmas reported from sugar beet, i. e., the phytoplasma associated with low sugar disease in France (stolbur group, 16SrXII) and another phytoplasma associated with a similar but distinct disease in Hungary (aster yellows group,16SrI). This is the first report of a 16Srll related phytoplasma group in sugar beet.