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First Report of a Group 16SrII Phytoplasma Infecting Chickpea in Oman

Chickpea (Cicer arietinum), locally known as “Dungo”, is grown for legume and animal feed mainly in the interior region of Oman. During February 2006, survey samples of chickpea leaves from plants showing yellows disease symptoms that included phyllody and little leaf were collected from the Nizwa Region (175 km south of Muscat). Total nucleic acid was extracted from asymptomatic and symptomatic chickpea leaves using a cetyltrimethylammoniumbromide method with modifications (3). All leaf samples from eight symptomatic plants consistently tested positive using a polymerase chain reaction assay (PCR) with phytoplasma universal primers (P1/P7) that amplify a 1.8-kb phytoplasma rDNA product and followed by nested PCR with R16F2n/R16R2 primers yielding a product of 1.2 kb (2). No PCR products were evident when DNA extracted from healthy plants was used as template. Restriction fragment length polymorphism analysis of nested PCR products by separate digestion with Tru9I, HaeIII, HpaII, AluI, TaqI, HhaI, and RsaI restriction enzymes revealed that a phytoplasma belonging to group 16SrII peanut witches'-broom group (2) was associated with chickpea phyllody and little leaf disease in Oman. Restriction profiles of chickpea phytoplasma were identical with those of alfalfa witches'-broom phytoplasma, a known subgroup 16SrII-B strain (3). To our knowledge, this is the first report of phytoplasma infecting chickpea crops in Oman.

References: (1) A. J. Khan et al. Phytopathology, 92:1038, 2002. (2). I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998 (3) M. A. Saghai-Maroof et al. Proc. Natl. Acad. Sci. USA. 81:8014, 1984.