The expression of a gene, encoding a dehydrin protein designated as DHN24 was analyzed at the protein level in two groups of Solanum species differing in cold acclimation ability. The DHN24 protein displays consensus amino acid sequences of dehydrins, termed K- and S-segments. The S-segment precedes three K-segments, classifying the protein into SK3-type dehydrins. A group of Solanum species able to cold acclimation constituted by S. sogarandinum and S. tuberosum, cv. Aster, and a second one composed of a S. sogarandinum line, that lost ability to cold acclimation, and of S. tuberosum, cv. Irga, displaying low ability to cold acclimation were studied. Under control conditions, noticeable levels of the DHN24 protein was observed in stems, tubers, and roots of Solanum species. No protein was detected in leaves. During low temperature treatment the DHN24 protein level substantially increased in tubers, in transporting organs and in apical parts, and only a small increase was observed in leaves. The increase in protein abundance was only observed in the plants able to cold acclimate and was found to parallel the acclimation capacity. Upon drought stress, the DHN24 level decreased in stems and in leaves, but increased in apical parts. These results suggest that Dhn24 expression is regulated by organ specific factors in the absence of stress and by factors related to cold acclimation processes during low temperature treatment in collaboration with organ-specific factors. A putative function of the SK3-type dehydrin proteins during plant growth and in the tolerance to low temperature is discussed.

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Potato mop-top virus (PMTV

No abstract

Parthenocarpy (seedless fruits) is a desirable trait that has been achieved in many plant cultivars. We generated parthenocarpic cucumber fruits by introducing the chimeric DefH9-iaaM construct into the cucumber genome using an Agrobacterium tumefaciens-mediated protocol. The construct consists of the DefH9 promoter from Antirrhinum majus and the iaaM coding sequence from Pseudomonas syringae. Transgenic plants were obtained from nine independent transformation events: half of these were tetraploid and did not produce seeds following self-pollination, while the remaining half were capable of displaying parthenocarpy in the subsequent reproductive generation. Of the fruits produced by the transgenic lines, 70-90% were parthenocarpic. The segregation of the marker gene in the transgenic T 1 progeny indicated single gene inheritance. The seed set in the transgenic lines and their F 1 hybrids was lower than in the non-transgenic control plants. Some of the methodological details and the practical significance of the results are discussed.

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.

Main conclusion Using late blight resistance genes targeting conservative effectors of Phytophthora infestans and the constructing gene pyramids may lead to durable, broad-spectrum resistance, which could be accelerated through genetic engineering. Abstract Potato (Solanum tuberosum L.) is one of the most important food crops worldwide. In 2020, potato production was estimated to be more than 359 million tons according to the Food and Agriculture Organization (FAO). Potato is affected by many pathogens, among which Phytophthora infestans, causing late blight, is of the most economic importance. Crop protection against late blight requires intensive use of fungicides, which has an impact on the environment and humans. Therefore, new potato cultivars have been bred using resistance genes against P. infestans (Rpi genes) that originate from wild relatives of potato. Such programmes were initiated 100 years ago, but the process is complex and long. The development of genetic engineering techniques has enabled the direct transfer of resistance genes from potato wild species to cultivars and easier pyramiding of multiple Rpi genes, which potentially increases the durability and spectrum of potato resistance to rapidly evolving P. infestans strains. In this review, we summarize the current knowledge concerning Rpi genes. We also discuss the use of Rpi genes in breeding as well as their detection in existing potato cultivars. Last, we review new sources of Rpi genes and new methods used to identify them and discuss interactions between P. infestans and host.

Resistance to Potato virus Y (PVY) is one of the most important traits in seed and ware potato production. Currently the tobacco-necrosis inducing PVY N strain including PVY N-Wi and PVY NTN dominates in the PVY population in Poland. The PVY O strain which dominated in early 1980s is rarely detected. Since early 1950s, breeding for PVY resistance in IHAR was a part of the program developing parental lines, which resulted in selecting lines extremely resistant to PVY. The selection of these lines was improved by the application of developed molecular markers. Moreover, the group of genes conferring comprehensive hypersensitive resistance (HR) to all strains of PVY was identified and mapped. The cultivars obtained from parental lines have enhanced level of resistance to PVY. For registered cultivars, the level of resistance to PVY is monitored in field exposure tests, while the reaction to four different isolates of PVY is examined by artificial inoculations. The 36 cultivars with field resistance scores 7.5 and 9 expressed resistance to all tested isolates and 23 of them originated from IHAR parental lines. Several moderately resistant culti-vars varied in sensitivity to the PVY isolates and in majority they were more sensitive to isolates Wi (collect-ed in 1984) and 12/94 (collected in 1994), than to older isolates LW and Ny collected in 1970-ties. Resumen La resistencia al virus Y de la papa (PVY) es uno de los caracteres más importantes en la producción de papa para semilla y consumo. Actualmente, la variante que induce necro-sis en tabaco PVY N incluyendo PVY N-Wi y PVY NTN domina en la población de PVY en Polonia. Se detecta raramente la variante PVY O que dominó a principio de los 1980s. Desde el inicio de los 1950s el mejoramiento para resistencia a PVY en IHAR era parte del programa para el desarrollo de líneas parentales, lo que resultó en la selección de líneas extremada-mente resistentes al PVY. Se mejoró la selección de estas líneas mediante la aplicación de marcadores moleculares desarrolla-dos. Más aún, se identificó y mapeó el grupo de genes que confieren reacciones de hipersensibilidad (HR) que incluyen a todas las variantes de PVY. Las variedades que se obtuvieron de las líneas parentales han incrementado su nivel de resistencia al PVY. Para variedades registradas, se monitorea el nivel de resistencia al PVY en pruebas de exposición en el campo, mientras que se examina la reacción a cuatro variantes difer-entes de PVY mediante inoculaciones artificiales. Las 36 var-iedades con resistencia de campo alcanzan calificaciones de 7.5. Nueve expresaron resistencia a todos los aislamientos probados, y 23 de ellas se originaron de líneas parentales de IHAR. Diversas variedades moderadamente resistentes fluc-tuaron en sensibilidad a los aislamientos de PVY y en su mayoría fueron más sensibles a los aislamientos Wi (colectados en 1984) y 12/94 (colectados en 1994), que a aislamientos más viejos LW y Ny colectados en los 1970s.