Evaluation of Resistance to Potato Virus Y of Cultivars in Pre-registration (Statutory) Trials

The paper describes testing potato cultivars for resistance to potato viruses in field and greenhouse condi-tions according to the scheme of the statutory trials. Seed tubers of tested cultivar are planted in the field in two replications with 30 tubers each. On both sides of each cultivar, 15 PVY-infected tubers, i.e. the source for PVY inoculation, are planted. The evaluation includes standard cultivars of known resistance levels to PVY. The progeny tubers are collected in autumn and growing-on testing is carried out in greenhouse condi-tions to estimate the number of plants infected with PVY. The other method is to evaluate the resistance of potato cultivars in greenhouse conditions. At present, the resistance of cultivars is evaluated only with respect to PVY, the most important potato virus. Two strains are used in the evaluation, i.e. PVYN-Wi and PVYNTN. For each testing cultivar, 10 plants are mechanically inoculated with each PVY strain. The analysis of the results makes it possible to classify the cultivars into four resistance groups on a 1-9 scale: highly resistant (with the resistance score of 8), resistant (with a value of 7), mid-resistant (with a value 5-6), and susceptible (with a value of 3-4). The ”9” rating is specified after the registration of the cultivars based on molecular tests, that validate the presence of a marker linked to extreme resistance (ER) gene Rysto

Resistance to PVM in potato parental lines bred in Młochów Research Center, IHAR.

During last 22 years in the Potato Genetics and Parental Lines Department at Młochów Research Center more than 210 parental lines resistant to Potato virus M (PVM) have been bred. Genes controlling resistance to PVM originated from two sources Solanum megistacrolobum (the gene Rm) or/and S. gourlayi (the gene Gm) were introduced into tetraploid breeding material. From these resistant lines 59 progenitors were chosen and offered to the potato breeders. The first resistant to PVM cultivar Triada and second one cv. Korona were registered in Poland in 1996 and 2002, respectively. At present 13 advanced breeding clones from different breeding stations derived from progenitors offered to breeders in 1986-1990 are evaluated in Preliminary Trials. One candidate cultivar tested in Registration Trials appeared to be resistant to PVM. Moreover 15 advanced breeding clones derived from progenitors offered during 1991-1995 were tested in Preliminary Trials. The mechanical and graft inoculations were used to identify the type of resistance to PVM in potatoes. The parental lines, which resistance to PVM is controlled by the gene Rm or/and Gm, express field resistance even under the high natural infection pressure. Increasing number of resistant to PVM new potato cultivars is expected

The reaction to virus infection of potato cultivars from the Polish National List in 2010

Scharakteryzowano 134 odmiany ziemniaka znajdujące się w 2010 roku w Krajowym Rejestrze, pod kątem odporności i reakcji roślin na zakażenie wirusami ziemniaka: Y (PVY), liściozwoju (PLRV), M (PVM), X (PVX) i S (PVS). Odmiany pochodzenia zagranicznego: Kuras, Roko, Sante i Zuzanna oraz 23 polskie odmiany krańcowo odporne na PVY nie uległy porażeniu żadnym z czterech szczepów tego wirusa użytych do zakażeń. W tych odmianach, z wyjątkiem odmian Rudawa, Rumpel i Sante, stwierdzono obecność genu Ry. Polskie odmiany ziemniaka są stosunkowo odporne na stare szczepy PVYo i PVYN Ny, natomiast większość podlega „nowym” szczepom PVYN W i PVYNTN. Nekrozy na bulwach roślin zakażonych PVYNTN znaleziono w 25 odmianach wprowadzonych do Krajowego Rejestru i trzech dopuszczonych do uprawy na przetwórstwo: Erntestolz, Hermes i Saturna. Wśród odmian polowo odpornych na PLRV inokulowanych przez szczepienie, 12 reagowało nietolerancyjnie. Oceniono nasilenie objawów chorobowych wywoływanych w odmianach ziemniaka po inokulacji roślin PLRV przy użyciu mszyc jako wektorów. Ocenę reakcji na PVM przeprowadzono po inokulacji mechanicznej roślin silnym szczepem PVM. Cztery odmiany z genem Rm: Ametyst, Eugenia, Finezja i Korona okazały się odporne na PVM, z pozostałych badanych odmian większość wykazała podatność na infekcję połączoną ze słabymi objawami chorobowymi, 32 odmiany wykazały silne objawy, a kilkanaście odmian średnią odporność na zakażenie. Odporność krańcową na PVX warunkowaną obecnością genu RX, lub wysoką odporność różnego pochodzenia wykazały 24 polskie i 13 zagranicznych odmian. Odmiana Neptun, jako jedyna wśród badanych posiada gen NS i odznacza się odpornością na wirus S ziemniaka.The resistance level and characteristics of disease symptoms caused by PVY, PLRV, PVM, PVX and PVS were described for 134 potato cultivars registered in Poland. The cultivars of foreign origin: Kuras, Roko, Sante and Zuzanna and 23 Polish potato cultivars extremely resistant to PVY were not infected with four PVY strains used to the plant inoculation. In these cultivars except Rudawa, Rumpel and Sante the gene Ry was identified. Polish potato cultivars are relatively resistant to old PVY strains (PVYo and PVYN Ny) but majority of cultivars could be infected with PVYNW and PVYNTN. Necrotic rings (PTNRD disease) on tubers infected with PVYNTN appeared in 25 cultivars being on the Polish National List and also in three cultivars growing for processing: Erntestolz, Hermes and Saturna. Among cultivars field resistant to PLRV 12 reacted intolerantly to the graft infection. The disease symptoms caused by PLRV after inoculation with aphids used as the virus vector were evaluated. The reaction to PVM was evaluated after mechanical inoculation of plants with severe PVM strain. Four cultivars: Ametyst, Eugenia, Finezja and Korona possessing the gene Rm are resistant to PVM, while majority of cultivars are susceptible to the infection and reacted with mild symptoms, several are midresistant and reacted with severe symptoms. Extreme resistance to PVX connected with the Rx gene or high resistance of various origin appeared in 37 cultivars (24 of Polish and 13 of foreign origin). Out of 134 cultivars only one cv Neptun possess the gene Ns and is resistant to PVS infection

Recombinants of PVY Strains Predominate Among Isolates from Potato Crop in Poland

plex Reverse Transcription-Polymeraze Chain Reaction (RT-PCR). Recombinants of PVY strains predominate among the isolates tested. Using one-step triplex RT-PCR most PVYN-Wi isolates were classified as subgroup PVYNWi-P and most PVYN and/or PVYNTN isolates as the recombinant PVYNTN strain. A recombinant PVYNTN isolate (12/94) and two additional PVYN and/or PVYNTN isolates were not detect-ed by one-step triplex RT-PCR. Twelve isolates were identified as the PVYO strain but PVYN, non-recombinant PVYNTN and PVYC strains were not found. Serological and biological assays of 144 isolates of PVYN-Wi strain showed that 100 isolates were the expected PVYO serotype with vein necrosis (VN) symptoms on tobacco. However, 10 isolates of the PVYNWi-P subgroup exhibited vein clearing (VCl) on tobacco and 2 isolates of the PVYNN242 subgroup unexpectedly exhibited as the PVYN serotype. All the isolates of PVYN-Wi strain induced severe local lesions (LL) on Chenopodium amaranticolor. Out of 126 isolates of PVYNTN strain tested, 76 were typical PVYN serotype with VN on tobacco, but their reactions on C. amaranticolor were different: 13 isolates did not show symptoms, 23 isolates induced weak, and 40 isolates induced severe LL. The remaining isolates of PVYN-Wi, PVYN and/or PVYNTN or PVYO were serologically PVYN and PVYO positive or exhibited unpredictable serological and biological reactions