Abstract

Tomato yellow leaf curl virus (TYLCV) is one of the most economically important plant viruses globally and due to its continuing quick spread, now it afflicts many tomato growing countries in the Mediterranean basin, Africa, southern Asia, as well as South, Central and North America. Infection of tomato plants with TYLCV can reach 100% causing a severe reduction in tomato production, especially when plants are infected in the early stage of growth. Therefore, this study was conducted, during the growing season 2018-19 at the college of Agriculture, Kerbala University, Iraq, to isolate and diagnose three different isolates of TYLCV, infecting tomato, using the polymerase chain reaction technology (PCR) and determining the nucleotide sequences of PCR- amplified products and the effect of TYLCV infection on the plant contents of some hormones (gibberellin, cytokinin, and Indole acetic acid). Results of PCR amplification showed the possibility of amplifying a 789bp PCR product from each virus isolate (1, 2, 3, and 4). Analysis of the nucleotide sequences of PCR products using BLAST showed that all the diagnosed isolates belong to TYLCV. By comparing the sequences of nucleotide sequences, there was a genetic similarity of 100% among these isolates. However, all tomato genotypes tested in this study were found to be susceptible to TYLCV with different degrees of infection. TYLCV infection also had a significant effect in reducing the level of the hormone gibberellin in the infected genotypes. Increased levels of the cytokinin and indole acetic acid hormones were also observed in the TYLCV-infected genotypes.