Monitoring the dynamics of emergence of a non-canonical recombinant of Tomato yellow leaf curl virus and displacement of its parental viruses in tomato

- A TYLCV recombinant with a non-canonical recombination profile (IS76) was detected.
- An original multiplex PCR test had to be developed to detect IS76 type recombinants.
- Parental viruses were replaced by the recombinants in the Souss (South of Morocco).
- Date and location of IS76 emergence were inferred from extensive samplings and BEAST.
- IS76 emergence coincides with the use of tolerant tomato cultivars in the 2000s.

Recombinant viruses are increasingly being reported but the dynamics of their emergence is rarely documented. A new recombinant Tomato yellow leaf curl virus (TYLCV-IS76) was detected for the first time in 2010 in Southern Morocco (Souss). An original diagnostic tool was needed to fit its unusual recombination profile. Although IS76 was detected following the appearance of Tylc symptoms on tolerant tomato plants, symptoms could not be associated to IS76 or to a synergy with criniviruses. According to infection profiles of Tylc-associated viruses determined on 879 plant samples collected between 1998 and 2014 and a Bayesian inference applied to genomic sequences of representatives of TYLCV, IS76 emerged in Southern Morocco at the end of the 1990s, replaced the parental viruses between 2004 and 2012 in Souss and is spreading towards the North of Morocco. The emergence of IS76 coincides with the increasing use of tolerant cultivars in the 2000s.