Screening of pepino (Solanum muricatum) and wild relatives against four major tomato diseases threatening its expansion in the Mediterranean region

The pepino (Solanum muricatum) is an Andean vegetable crop closely related to tomato. In the last decades, it has been introduced in the Mediterranean region and other parts of the world as a potential new crop. However, several tomato major pathogens may threaten the expansion of pepino cultivation. We identified Fusarium oxysporum f. sp. lycopersici (FOL), Verticillium dahliae (VE), pepino mosaic virus (PepMV) and tomato mosaic virus (ToMV) as four of the most likely pathogens to cause damage to pepino crops in Mediterranean climates. In order to evaluate the response of the pepino genepool against these pathogens, as well as to identify sources of tolerance, we inoculated six accessions of cultivated pepino, nine accessions of seven pepino wild relatives, and one interspecific hybrid with FOL, VE, PepMV and ToMV and followed its symptomatology for 30 days (FOL and VE) or 60 days (PepMV and ToMV). ELISA tests were also performed for PepMV and ToMV. Susceptible tomato materials were used as controls. The pepino genepool displayed fewer symptoms than susceptible tomato controls after inoculation with FOL, with most accessions being tolerant or resistant. Regarding VE, a wide variation of values for the symptoms index (SI) was observed, with three cultivated pepino accessions displaying tolerance. For PepMV a wide variation for SI was also observed, with one accession of S. caripense being resistant, and several accessions of pepino and other wild relatives displaying different degrees of tolerance. PepMV absorbance values obtained by ELISA tests followed a pattern similar to that of SI. For ToMV no resistances were found, although two wild accessions and the interspecific hybrid displayed low values for the SI and were considered as moderately tolerant. ELISA tests against ToMV revealed that the virus replicated well in all materials. None of the accessions evaluated displayed resistance or high levels of tolerance to the four pathogens, but some of them were complementary for resistance or high levels of tolerance. Although the interspecific hybrid tested was not resistant to any of the pathogens, it was tolerant to FOL and PepMV and moderately tolerant to VE and ToMV. A multivariate hierarchical clustering revealed similar patterns among accessions in the response to the two fungal diseases (FOL and VE) on one side and to the two viral ones (PepMV and ToMV) on the other. The information generated in this study has allowed identifying materials within the pepino genepool for the development of multi-resistant pepino cultivars to major diseases threatening its expansion in the Mediterranean region.