Developing tomato breeding lines resistant to tomato yellow leaf curl virus

Abstract Using controlled whitefly‐mediated inoculation techniques, seven Lycopersicon chilense accessions, highly resistant to isolates of tomato yellow leaf curl virus(TYLCV) from Southern Europe, TYLCV‐Sr, were selected. All exhibited similar levels of partial resistance, being symptomless and with low levels of viral DNA accumulation. However, a differential response to infection was found in interspecific hybrids with tomato and inbred lines derived from different L. chilense accessions, allowing a precise discrimination among them. This selection procedure which considers the expression of the resistance genes in the tomato genetic background led to the selection of two highly resistant F 1 hybrids derived from L. chilense LA 1932 and LA 1938. A backcrossing programme was initiated, selecting for horticultural characteristics and TYLCV resistance, in field and controlled inoculation conditions. As a result of this programme, six advanced breeding lines (UPV Ty 1, 3, 6, 9, 17 and 53), exhibiting a high level of resistance to TYLCV‐Sr, were obtained. Under high inoculum pressure conditions these lines suffered only 30‐40% yield loss relative to non‐infected control plants, and compared with 90‐95% yield loss in susceptible controls. These lines also have horticultural characteristics appropriate for the fresh market tomato cultivation system in this area, and are a good base material for obtaining commercial hybrids highly resistant to different isolates of TYLCV.