BACKGROUND and OBJECTIVES Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) are two begomoviruses (Geminiviridae) which cause Tomato yellow leaf curl disease (Tylc) in the Mediterranean countries. The disease has been successfully managed from the end of the 90s with the use of cultivars bearing the tolerance gene Ty-1. In 2010, a new TYLCV/TYLCSV recombinant virus (IS76) was detected on tolerant plants exhibiting the typical Tylc symptoms in Souss, the region with the most intensive tomato production in southern Morocco. The prevalence of IS76 was determined with an intensive survey and its origin was inferred with Bayesian analysis. MATERIAL & METHODS As IS76 was not detectable with the tools previously reported to detect TYLCV/TYLCSV recombinants, a multiplex PCR test was designed to determine the infection status of each individual plant. A total of 800 tomato plant samples collected between 1998 and 2014 in the Souss and other tomato producing areas of Morocco were tested for the presence of the Mediterranean Tylc-associated viruses (TYLCV-IL, TYLCV-Mld, TYLCSVES) and potentially all TYLCV/TYLCSV recombinants. The date of IS76 recombination event was inferred with BEAST using Genbank sequences of TYLCV and sequences of TYLCV and IS76 generated in this study. RESULTS With a 76 nt TYLCSV inherited fragment, IS76 was identified to be different from the canonical TYLCV/TYLCSV recombinant previously reported (1 & 2). It has virtually replaced its parental viruses, (TYLCVIL, TYLCSV-ES) in the Souss between 2003 and 2012 and has spread northwards up to the Mediterranean coast of Morocco where it was detected in co-infection with parental viruses and canonical recombinants(3). Its detection was not necessarily associated with Tylc symptoms, which was consistent with the fact that Ty-1 tolerant tomato plants remained symptomless following their infection with an infectious clone of IS76. According to phylogeny and Beast inference,