Phenotypic and molecular screening of some tomato germplasm for resistance to tomato yellow leaf curl virus disease in Ghana

Tomato yellow leaf curl virus (TYLCV) is a major tomato virus in Ghana and Africa as a whole. In this study, 30 accessions of Solanum lycopersicum L. with reported TYLCV-resistance from AVRDC were assessed for resistance to TYLCV in Ghana. Plants were grown in a field, a hot spot of the disease and the reactions of plants were evaluated based on the disease symptoms when they were 30, 45 and 60 days after transplanting. Molecular screening was also done to re-confirm the phenotypic evaluation. All the tomato accessions demonstrated various degrees of disease symptoms. Phenotypic evaluation was confirmed by amplification of TYLCV DNA fragment in all tested accessions. Based on the phenotypic and molecular evaluations, no accession provided complete resistance to TYLCV in Ghana. However, accessions with milder symptoms of TYLCV in the field were considered as tolerant. The high level of susceptibility to viral infection noted in the field was not observed in the molecular screening. The viral DNA was detected using six different primers and the primers indicated polymorphism. TYLCV was detected in 23 accessions using primer pair GhF and GhR. The results suggested that accessions that indicated symptoms of the disease on the field but had no TYLCV DNA amplification could be due to other viruses or virus strain. Accessions with reported resistance in other countries but collapsed in Ghana could be attributed to genotype - environment interactions and or the emergence of new mutants of the TYLCV in Ghana. [PUBLICATION ABSTRACT]