Genetic Diversity of Tomato Yellow Leaf Curl Virus (TYLCV) in Mauritius

Background and Objective: Tomato yellow leaf curl disease (TYLCD), caused by tomato yellow leaf curl virus (TYLCV), was first reported in Mauritius in 2009. This study reports on the status regarding the genetic identity of TYLCV isolates in Mauritius, based on data collected in 2015-2018. Materials and Methods: The TYLCV-infected plants showing clear symptoms were collected from 21 localities around the island. The presence of TYLCV was confirmed using standard TAS-ELISA tests and triplicates of each leaf sample were subject to DNA extraction followed by PCR amplification of part of the C1 replication-associated gene and the PCR products were sequenced and edited and subjected to a similarity search using the BLASTN tool. The sequences were then aligned using MEGA11 software and phylogenetic trees were generated using the UPGMA method with 1000 bootstrap values. Results: This study revealed 12 genetically distinct isolates of TYLCV, with 4 of them seemingly representing the ancestral TYLCV-IL lineage, 6 of them representing variants or recombinants of the ancestral lineage and 2 isolates which could potentially represent new strains. This study shows that, over a period of 9 years, with the continued cultivation of susceptible tomato varieties and the presence of alternate hosts, the original 2009 TYLCV isolate underwent multiple mutation events that eventually resulted in the appearance of two possibly novel strains. Conclusion: The TYLCV has shown a very rapid rate of mutation on Mauritius Island, possibly evolving into new strains and now constitutes an important economic threat to local tomato production.