Identification of the Molecular Make-Up of the Potato virus Y Strain PVY^Z: Genetic Typing of PVY^Z-NTN

Abstract

Potato virus Y (PVY) strains were originally defined by interactions with different resistance genes in standard potato cultivars. Five distinct strain groups are defined that cause local or systemic hypersensitive responses (HRs) in genetic background with a corresponding N gene: PVY(O), PVY(N), PVY(C), PVY(Z), and PVY(E). The nucleotide sequences of multiple isolates of PVY(O) and PVY(N) differ from each other by ≈8% along their genomes. Additionally, complete genome sequences of multiple recombinant isolates are composed of segments of parental PVY(O) and PVY(N) sequences. Here, we report that recombinant isolate PVY-L26 induces an HR in potato 'Maris Bard' carrying the putative Nz gene, and is not recognized by two other resistance genes, Nc and Ny(tbr). These genetic responses in potato, combined with the inability of PVY-L26 to induce vein necrosis in tobacco, clearly define it as an isolate from the PVY(Z) strain group and provide the first information on genome structure and sequence of PVY(Z). The genome of PVY-L26 displays typical features of European NTN-type isolates with three recombinant junctions (PVY(EU-NTN)), and the PVY-L26 is named PVY(Z)-NTN. Three typical PVY(NTN) isolates and two PVY(N) isolates, all inducing vein necrosis in tobacco, were compared with PVY-L26. One PVY(NTN) isolate elicited HR reactions in Maris Bard, similar to PVY-L26, while two induced a severe systemic HR-like reaction quite different from the quasi-symptomless reaction induced by two PVY(N) isolates. 'Yukon Gold' potato from North America produced HR against several PVY(NTN) isolates, including PVY-L26, but only late and limited systemic necrosis against one PVY(N) isolate. Consequently, according to symptoms in potato indicators, both PVY(Z) and PVY(NTN) isolates appeared biologically very close and clearly distinct from PVY(O) and PVY(N) strain groups.

Potato cv. Romano reaction to primary and secondary infection with potato necrotic strain Y virus (PVYNTN)

“…Subsequent biological characterization of PVY NTN isolates on cvs. Desiree and King Edward showed induced systemic tuber necrosis (Kerlan et al, 2011). Baldauf et al (2006) found PVY NTN to cause ringspot necrosis of potato tubers, while PVY O , PVY C , PVY N and PVY N:O did not.…”

Comparison of three methods for the detection of Potato virus Y in seed potato certification

“…However, due to a single nucleotide change at nucleotide 1627 (A to G), resulting in a single amino acid change (D to G) in the HC-Pro, this isolate does not cause vein necrosis in tobacco. Therefore, it was later assigned to PVY Z by Kerlan et al (2011).…”

The amino acid 419 in HC-Pro is involved in the ability of PVY isolate N605 to induce necrotic symptoms on potato tubers

“…However, some of these tuber necrotic symptoms were reported to be atypical as they were roughly circular, sunken necrotic lesions on the surface of the potato tuber instead of the typical external ring pattern of PTNRD symptoms (Piche et al, 2004). The ability to induce tuber necrosis on Yukon Gold was also reported for NE-11, PVY-L26 and PVY-MON isolates, the only representatives for PVY-NE11, PVY Z and PVY E groups, respectively (Piche et al, 2004;Lorenzen et al, 2008;Kerlan et al, 2011;Galvino-Costa et al, 2012). Actually, it has been proposed that all PVY N isolates are able, under appropriate growing conditions, to induce necrosis on potato tubers (Kerlan and Tribodet, 1996).…”