Reaction of seventy-two cultivars of durum wheat to Wheat spindle streak mosaic virus in Central Italy.

In Italy, Wheat spindle streak mosaic (WSSMV) was first detected in a field near Rome in 1985. Subsequently it has been identified - either alone or in mixed infection with Soil-borne cereal mosaic virus (SBCMV) - at about 20 other sites throughout the northern and central and regions of the country. Field trials were carried out in 1998/99, 2003/04 and 2006/07 at the Experimental Farm of the Cereals Research Institute near Rome in a field with with natural inoculum sources of both WSSMV and SBCMV to evaluate the reaction to WSSMV of 72 cultivars of durum wheat marketed in Italy using DAS-ELISA. Nine of these cvs. were grown over three seasons, 17 cvs. over two seasons, and 46 cvs. in one season only. The cultivars were grown in 10 sq. m. solid-seeded plots distributed in the field according to a randomized block design with either two (1999) or three replicates (2004 and 2007). Virus concentration was determined on extracts from a bulk of the apical half of the second and third youngest leaves of ten randomly chosen plants / plot collected March 18 (1999), March 16 (2003) and February 27 (2007). Simple correlation coefficients between ELISA values in different seasons were relatively low (r = 0.482* for 22 cvs. tested both in 1999 and 2004; r = 0.710* for 10 cvs. tested both in 1999 and 2007; and r = 0.482 n.s. for 12 cvs. tested both in 2004 and 2007). DAS-ELISA readings obtained in different years are presented as such and as percentage of the highest reading obtained in each season (ELISA index). Among the nine cvs. assayed three seasons, the lowest mean ELISA index was observed for cv. Claudio (0.5%), which therefore seems – at present - the best choice for soils with WSSMV in Italy. Among the seventeen cvs. tested two seasons the lowest mean ELISA index were observed for cvs. Colorado (11.2%), Rusticano (11.4%) and Provenzal (11.9%). Cultivars Tiziana (0.1%), Italo (1.3%), Ofanto (4.4%) and Dupri (5.4%), assayed one season only, also furnished relatively low ELISA values. Cultivars Colorado, Provenzal, Tiziana and Dupri appear of particuar interest in that they have shown a high degree of resistance towards SBCMV in Italy.