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) causesdevastation worldwide and in Italy is associated withTomato yellow leaf curl virus (TYLCV) and Tomato yellowleaf curl Sardinia virus (TYLCSV). Starting from thevaluable traditional tomato cv. Eraldo, which is susceptibleto TYLCD, crosses were made with accessions carryingTy-1 and Ty-2 resistance loci. The F2 progenieswere selected using both known and newly developedTy-associated markers. F3 families derived from markerselectedF2 plants were challenged with isolates ofTYLCV and TYLCSV present in Italy, under controlledgreenhouse conditions. Genotypes carrying marker allelesassociated with the Ty-1 gene showed mild symptomsin all cases (tolerance), but the number of plants infectedby TYLCV was much higher than those infected byTYLCSV. The majority of plants carrying the marker allelesassociated to Ty-2 did not allow any TYLCV replicationbut, when challenged with TYLCSV, most ofthem were infected and showed severe yellow leaf curlsymptoms. To our knowledge this is the first report ofTy-1 and Ty-2-carrying tomato plants challenged withthe type-strain of TYLCSV.