Introgression of resistance to two mediterranean virus species causing Tomato Yellow Leaf Curl into a valuable traditional tomato variety

Tomato yellow leaf curl disease (TYLCD) causes devastation worldwide and in Italy is associated with Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV). Starting from the valuable traditional tomato cv. Eraldo, which is susceptible to TYLCD, crosses were made with accessions carrying Ty-1 and Ty-2 resistance loci. The F2 progenies were selected using both known and newly developed Ty-associated markers. F3 families derived from marker-selected F2 plants were challenged with isolates of TYLCV and TYLCSV present in Italy, under controlled greenhouse conditions. Genotypes carrying marker alleles associated with the Ty-1 gene showed mild symptoms in all cases (tolerance), but the number of plants infected by TYLCV was much higher than those infected by TYLCSV. The majority of plants carrying the marker alleles associated to Ty-2 did not allow any TYLCV replication but, when challenged with TYLCSV, most of them were infected and showed severe yellow leaf curlsymptoms. To our knowledge this is the first report of Ty-1 and Ty-2-carrying tomato plants challenged with the type-strain of TYLCSV.