Genus-specific biochemical markers for Phytomonas spp.

Phytomonas spp. are digenetic (two host) flagellated protozoa isolated from plants, with a wide geographical distribution [1,2]. They have been found in 17 different families of plant and are believed to be transmitted by phytophagous hemipteran insects of the families Coreidae, Lygaeidae, Pyrrhocoridae and Pentatomidae [1–5]. Phytomonas spp. have been isolated from latex tubes of laticiferous plants, from the phloem of trees, from mature fruits of many plant families and from seeds such as maize [1–3,6,7]. The intraphloemic isolates, all from South America, are specifically associated with pathological syndromes in plants, while a latex-associated P. françai causes ‘chochamento das raizes’ (empty roots) in manioc [1,2,8]. Classically, Phytomonas spp. have been described as plant trypanosomatids with a typical promastigote appearance [9], but this definition is at least ambiguous, because promastigote stages also occur in Leptomonas and Herpetomonas, flagellates that can be found together with Crithidia and Blastocrithidia, in Phytomonas vectors [1,4], and which have sometimes been detected in plant tissues, probably as transient infections [10]. Therefore, there exist no well defined criteria for attributing different plant-isolated trypanosomes to the genus Phytomonas. A simple and unambiguous marker is thus urgently needed. Agglutination [6,11], isoenzyme profiles [12–14] and immunological methods [15,16], genomic or kinetoplastic DNA fingerprinting [14,17,18], seAbbre6iations: aHADH, a-hydroxyacid dehydrogenase; iPDH, iso-propanol dehydrogenase; MDH, malate dehydrogenase. * Corresponding author. Tel.: +32 2 7647439; fax: +32 2 7626853; e-mail: [email protected]