First record of Barley yellow dwarf and Cereal yellow dwarf viruses in Tunisia

A survey for Barley yellow dwarf (BYDV) and Cereal yellow dwarf viruses (CYDV) was carried out during April 2001 covering seven major cereal-growing regions (Beja, Bizerte, Cap-Bon, Jendouba, Le Kef, Siliana and Zaghouan) of Tunisia. A total of 1650 samples (466 barley, 765 durum wheat and 419 bread wheat) with yellowing, stunting or striping were collected from 12 barley, 23 durum wheat and 13 bread wheat fields. These samples were tested at the Virology Laboratory, ICARDA, Aleppo, Syria, for the presence of five viruses by the tissue-blot immunoassay (Makkouk and Comeau, 1994), using a battery of polyclonal and monoclonal antibodies. Specific rabbit polyclonal antisera were used for BYDV-PAV (genus Luteovirus, family Luteoviridae), BYDV-SGV and BYDV-RMV (family Luteoviridae); all provided by R. Lister, Purdue University, USA (Webby and Lister, 1992; Webby et al., 1993). In addition, two specific monoclonal antibodies for the detection of CYDV-RPV (genus Polerovirus, family Luteoviridae) (ATCC PVAS-669) and BYDV-MAV (genus Luteovirus, family Luteoviridae) (ATCC PVAS-673) were used.

Serological tests showed that all five viruses were identified in Tunisia from all seven regions surveyed. Among the viruses detected, BYDV-PAV was the most common, being detected in 377 cereal samples out of 1650 tested (22.8%), followed by BYDV-SGV (17.2%), BYDV-RMV (5.5%), BYDV-MAV (1.1%) and CYDV-RPV (0.7%). The occurrence of the five viruses was higher (75.3%) in barley than in wheat (36%). Mixed infections of two or more viruses were found in all the regions surveyed. Even though BYDV-PAV has been identified earlier (Najar et al., 2000), this is the first report on identification and relative occurrence of all Barley yellow dwarf and Cereal yellow dwarf viruses in Tunisia.