The two most important bacterial diseases of cultivated potato, blackleg of stems and tuber soft rot, are caused by Erwinia species. Genetic resistance currently present in cultivars is insufficient to protect the crop. New sources of polygenic resistance to Erwinia carotovora ssp. atroseptica (van Hall) Dye (Eca) have been selected in diploid hybrids originating from intercrossing Solanum tuberosum L with the wild species S. chacoense Bitter and S. yungasense Hawk. One F1 hybrid population derived from these materials was used to locate, on the molecular map of potato, quantitative trait loci (QTL) for resistance of tubers and leaves to Eca. A linkage map was constructed based on AFLP and RFLP markers including three resistance‐gene‐like (RGL) markers. Clustering of AFLP markers in putative centromeric regions was observed. QTL analysis revealed complex inheritance of resistance to Eca. Genetic factors affecting resistance to Eca were located on all 12 potato chromosomes. Putative QTL for tuber resistance were identified on 10 chromosomes. The QTL with the largest and most reproducible effect on tuber resistance mapped to chromosome I. Effects on leaf resistance were less reproducible than effects on tuber resistance. Putative QTL for leaf resistance were identified on 10 chromosomes. Inheritance of tuber and leaf resistance to Eca was largely independent. Several QTL for resistance to Eca were linked to RGL loci. Four of those QTL mapped to genomic segments that have been shown to contain factors for qualitative and quantitative resistance to different pathogens in potato, tomato (Lycopersicon esculentum Mill.), or tobacco (Nicotiana tabacum L.).

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Despite the long history of breeding potatoes resistant to Phytophthora infestans, this oomycete is still economically the most important pathogen of potato worldwide. The correlation of high levels of resistance to late blight with a long vegetation period is one of the bottlenecks for progress in breeding resistant cultivars of various maturity types. Solanum phureja was identiWed as a source of eVective late blight resistance, which was transferred to the cultivated gene pool by interspeciWc crosses with dihaploids of Solanum tuberosum. A novel major resistance locus, Rpiphu1, derived most likely from S. phureja and conferring broad-spectrum resistance to late blight, was mapped to potato chromosome IX, 6.4 cM proximal to the marker GP94. Rpi-phu1 was highly eVective in detached leaXet, tuber slice and whole tuber tests during 5 years of quantitative phenotypic assessment. The resistance did not show signiWcant correlation with vegetation period length. Our Wndings provide a well-characterized new source of resistance for breeding early and resistant-to-P. infestans potatoes.

Phytophthora infestans causes an economically important disease of potato called late blight. The epidemic is controlled chemically but resistant potatoes can become an environment-friendly and Wnancially justiWed alternative solution. The use of diploid Solanum tuberosum derived from European tetraploid cultivars enabled the introgression of novel genes encoding foliage resistance and tuber resistance from other species into the modern cultivated potato gene pool. This study evaluated the resistance of the obtained hybrids, its quality, expression in leaXets and tubers and its relation to the length of vegetation period. We also identiWed genetic loci involved in late blight resistance and the length of vegetation period. A family of 156 individuals segregating for resistance to late blight was assessed by three laboratory methods: detached leaXet, tuber slice and whole tuber test, repeatedly over 5 years. Length of vegetation period was estimated by a Weld test over 2 years. The phenotypic distributions of all traits were close to normal. Using sequence-speciWc PCR markers of known chromosomal position on the potato genetic map, six quantitative trait loci (QTLs) for resistance and length of vegetation period were identiWed. The most signiWcant and robust QTL were located on chromosomes III (explaining 17.3% of variance observed in whole tuber tests), IV (15.5% of variance observed in slice tests), X (15.6% of variance observed in leaXet tests) and V (19.9% of variance observed in length of vegetation period). Genetic characterization of these novel resistance sources can be valuable for potato breeders and the knowledge that the most prominent QTLs for resistance and vegetation period length do not overlap in this material is promising with respect to breeding early potatoes resistant to P. infestans.

This study demonstrates the new sources of resistance available in potato cv. Etola, which represent multiple strain-specific resistance genes against three strains of Potato virus Y (PVY). Etola is the first documented cultivar of this sort in Europe that exhibits hypersensitive resistance (HR) to PVY NTN isolate PVY-3202, and different levels of partial resistance to PVY N-Wi isolate PVY-3411 and PVY Z -NTN isolate PVY-3303. The isolate PVY-3411 induced severe symptoms and faster systemic viral coat protein and RNA accumulation in the noninoculated upper leaves, whereas PVY-3303 caused mild symptoms and delayed viral spreading. This study provides the first example of strain-specific alteration of a set of host microRNAs (miRNAs) and their targets in the potato-PVY interaction. The tested miRNAs and targets are altered only in plants of cv. Etola infected with PVY-3411 but not those infected with PVY-3303 nor PVY-3202. The up-regulation of stu-miR162, stu-miR168a and miR172e, together with their target transcripts, DCL1, AGO1-2 and TOE3, respectively, in PVY-3411-infected plants correlates with high abundance of HC-Pro RNA encoding an RNA-silencing suppressor and might be linked with the severe symptoms in leaves. Moreover, PVY-3411 causes parallel increases in two members of stu-miR482 and their mRNA targets Gpa2 and CC-NBS-LRR that are involved in the defence response.

In breeding for resistance to late blight, ( Phytophthora infestans Mont. de Bary), an economically important disease affecting potatoes, the search for new sources of durable resistance includes the non-host wild Solanum species. The aim of this work was to evaluate the resistance to P. infestans in the somatic hybrids between S. nigrum L. and diploid potato clone ZEL-1136. Sixteen somatic hybrids, their fusion parents, and three standard potato cultivars were screened for resistance to P. infestans in two types of tests-on whole plants and detached leaves-with two highly aggressive and virulent isolates of P. infestans, US8 and MP322. In the whole plant assay, the foliage of the somatic hybrids showed no symptoms of infection, while the foliage of the potato fusion parent and the standard cultivars was infected with P. infestans. In the detached leaflet assay, the breaking-down of resistance of the S. nigrum L. parent and the variable response of individual hybrid clones were noted. Nine S. nigrum L. (+) ZEL-1136 hybrids showed a resistance that was significantly higher than that of S. nigrum, while six clones expressed a resistance to P. infestans similar to that of S. nigrum. The results confirm the effective transfer of late blight resistance of S. nigrum into its somatic hybrids with potato.

Potato and tomato are the two major hosts for Phytophthora infestans causing late blight. The susceptibility of leaves and whole plants of Solanum nigrum, S. villosum, and S. scabrum to infection by P. infestans was tested under laboratory conditions. Out of 39 plants representing 38 different S. nigrum accessions, 16 were highly resistant (seven accessions did not show any symptoms of infection, nine were highly resistant showing necrotic lesions in the place of infection), and 23 plants of S. nigrum were colonized by, at least, 1 of the 2 isolates of P. infestans (17 accessions were infected with two P. infestans isolates, and 6 accessions showed different reactions depending on the isolate used for inoculation). Three accessions of S. villosum, and one accession of S. scabrum were tested and did not show any symptoms of infection. The majority of S. nigrum accessions infected by P. infestans in a detached leaf assay were also infected in the whole plant assay. The reaction of field-and greenhousegrown plants to inoculation with P. infestans in detached leaf assays was similar, but in some cases leaves from field-grown plants reacted as resistant in comparison with the leaves from greenhouse-grown plants, which were susceptible.

Aims This study aims the detection of proteins associated with increased resistance of tubers to necrotrophic bacteria Dickeya solani in tetraploid and diploid potato plants. Methods Comparative analysis of differently expressed proteins in tuber tissue of potato cultivars and diploid interspecific hybrids of Solanum, differing in resistance to Dickeya solani, was performed using nano-liquid chromatography coupled with tandem mass spectrometry (LC-MS-MS/MS). Two highly resistant (Bea and Humalda) and three susceptible (Irys, Katahdin, Ulster Supreme) potato cultivars, and the highly resistant (DG 00-270) and the susceptible (DG 08-305) diploid clones, were studied. Proteins were extracted from wounded potato tubers inoculated with bacteria at an early symptomatic phase of infection and from controls, i.e., intact tubers and wounded mock-inoculated tubers. Data are available via ProteomeXchange with identifier PXD013009. Results Eight constitutive differentially expressed proteins with fold changes ≥1.9 and q-value ≤0.1 between the resistant and susceptible cultivar groups after D. solani infection were selected. Probable inactive patatin-03-Kuras 1 and the proteinase inhibitor PTI exhibited significantly increased protein abundances after bacterial inoculation in both resistant cultivars compared to the susceptible cultivars. In the diploid clones, o n l y m e t a l l o c a r b o x y p e p t i d a s e a n d metallocarboxypeptidase-like inhibitors exhibited much higher fold changes following pathogenic invasion (274.4-and 368.6-fold, respectively) than after mock inoculation (165.5-and 130.7-fold, respectively). Conclusions These results show that different proteins indicating significant fold changes between the resistant and susceptible potato cultivars and diploid clones are induced at an early phase of symptomatic D. solani infection.