Diagnostic PCR-based markers for biotic stress resistance breeding in potatoes ( Solanum tuberosum L.)

Potato is the third most important crop. Its production and quality is greatly affected by various biotic stresses. In this study, 216 Solanum tuberosum subsp. tuberosum accessions were screened for late blight, viruses (PVY and PVX) and potato cyst nematodes (PCNs) resistance using robust molecular markers. Solitary or combined late blight resistant genes ( R1 , Rpi-abpt , R3a , R3b ) presence was observed in 51 accessions. For PVY resistance, markers STM0003, RYSC3, and YES3-3 A were found in 38, 3, and 1 accession, respectively, and PVX resistance gene markers 1Rx1 and 106Rx2 were found in 19 and 10 accessions, respectively. The STM0003 marker was present in 38 accessions, of which 12 were resistant to PVY and 10 were susceptible. The genotype data on six markers for both the species of PCN showed 45 resistant accessions. A combined analysis of all markers for late blight identified six accessions with all the three resistance genes. Similarly, four accessions, i.e., CP 4226, CP 2049, CP 3696, and CP 3651 had both Rx1 and Rx2 genes for PVX resistance, while only one accession, viz., CP 2049 showed the presence of both H1 and HC genes along with the Gpa2 marker for PCN resistance. There were also seven resistance genes found in CP 2049 for late blight (2), PCN (4), and PVX (2), but none of the accession had genes for all four traits. The results revealed that developing potato varieties with combined resistance to late blight, viruses, and PCN requires concerted hybridization between different parental lines.