Genetic multiplex state study of some advanced potato clones conferring Potato virus Y NTN (PVYNTN) extreme resistance

Potato virus Y is known as the most important potato-infecting agent in many parts of the world. In this study, the genetic structure of 16 advanced potato clones that carry the alleles of Ry as an extreme resistance genewereinvestigated. Additionally, multiplex (duplex, triplex or quadruplex) state of genetic of selected clones, where the alleles originate from different species such as Solanum stoloniferum (4X), S. tuberosum subsp. andigena (4X), S. hougassi (6X), were evaluated using artificial mechanical and graft inoculations under greenhouse conditions. ELISA was used to confirm experimental materials infection. Results showed that potato clones designated as 96.353, 97.557, 97.559, 97.560, 98.433, 99.373, 99.384, 397097-2, 397082-10, 397074-9, 397081-1 and 396136-1 contain extreme resistance genes (ER) against PVYNTN.. These selected clones were crossed with a PVYNTN susceptible line, S440. At least 200 genotypes of each family were evaluated in three replications using mechanical infection with the PVYNTN. Chi square test was used to prove the fitness of observed segregation ratios in comparison to predicted ones. The results of X2 test showed that 99.373, 99.384 and 98.433 clones follow the duplex manner while 96.353, 97.560 and 97.559 were carrying the resistance gene in a simplex state. For 97.557, 397097-2, 397082-10, 397074-9, 397081-1 and 396136-1, there was a significant difference between the observed and expected ratios even for simplex, duplex or triplex stages. The identified duplex genotypes have the potential to provide a durable PVY genetic resistance and can decrease the virus titer in the harboring genotype.