Interspecific hybridization of potato: theoretical and applied aspects

The common potato Solanum tuberosum is the fourth most important crop in the world and like many other cultivated plants is characterized by low level of genetic diversity. The most effective approach to broaden genetic diversity of breeding varieties is based on the introgression of genetic material of wild and cultivated species belonging to section Petota Dumort. of the genus Solanum L. This section, according to estimates by different taxonomists, includes from 112 to 235 species. At the same time, because of the barriers of prezygotic and postzygotic incompatibility, only about 10 % of wild potato species have been actively involved into the breeding process and their genetic material has been introgressed into the gene pool of varieties. To date, molecular genetics, genomics, and biotechnology have accumulated a large amount of information, allowing the problems of extension of the genetic diversity of common potato to be addressed. The article presents a review of modern data about the genetic factors determining prezygotic and postzygotic incompatibility, about the features of involvement in the hybridization process of the self-compatible and self-incompatible species of section Petota and species with different values of the endosperm balance number (EBN), as well as possible mechanisms of interaction between the parental genomes during the formation of the endosperm of the hybrid seed. Data are provided on the value of the theory of EBN for the further development of applied research aimed at increasing the genetic diversity of the breeding gene pool. This review discusses the traditional and modern approaches and methods of overcoming interspecific incompatibility and gives examples of successful studies on introgressive hybridization of potato. The article is preceded by information about the genetic diversity of potato species belonging to section Petota of the genus Solanum

SvSv-lines is an effective tool for involvement of the valuable genepool of 1 EBN diploid potato species into breeding

There is a set of wild potato species valuable for breeding, in particular 1 EBN diploid species from Mexico, which is practically not crossable to cultivated potatoes, including Solanum tuberosum dihaploids (2х, 2 EBN), because of strict pre- and postzygotic interspecific reproductive barriers. It is proposed to involve that species germplasm into breeding by using the original SvSv-lines (F2 S. tuberosum dihaploids×S. verrucosum), in which St -alleles have been substituted for Sv from the self-compatible diploid species S. verrucosum not producing stylar S-RNase. It was anticipated that SvSv-lines have the same ability for elimination of prezygotic incompatibility in interspecific hybridization as S. verrucosum due to S-genes of that species in homozygous state. However, their use would help avoid undesirable effects associated with S. verrucosum application (male sterility and reduced tuber formation in hybrids). The aim of the research was estimation of the efficiency of using SvSv-lines, in comparison with S. verrucosum, as a bridge for involvement of the 1 EBN potato species S. bulbocastanum, S. pinnatisectum and S. polyadenium into breeding. It was revealed that SvSv-lines excels S. verrucosum in hybridization efficacy due to abundant and prolonged flowering in later term than S. verrucosum, when flowering of pollinator species occurs. There were significantly less sterile or low fertility genotypes among the hybrids between SvSv-lines and 1 EBN wild species. They had higher ability for tuber formation, and so they were suitable for long term field trials, contrast to hybrids with S. verrucosum. The interspecific hybrids produced were crossed as female parents to S. tuberosum dihaploids

Development of chromosome-specific markers for a study on introgressive hybridization of potato with the wild Mexican allotetraploid species Solanum stoloniferum Schltdl

In order to involve valuable germplasm of the wild Mexican allotetraploid potato species Solanum stoloniferum Schltdl. (genomic composition ААВВ) into breeding, pentaploid interspecific hybrids (ААAAВ) with cultivated potato S. tuberosum L. (АААА) and their backcross progenies are usually used. Homologous synapsis in meiosis of such hybrids is expected only between chromosomes of the A subgenome, therefore a question arose about a possibility of introgressing genetic material of the subgenome B into the A genome of cultivated potato. In this connection, development of various schemes for the B subgenome introgression into the genome of cultivated potato is considered as a topical issue. The previous research has yielded four schemes of S. stoloniferum involvement into breeding, which imply backcrossing with cultivated potato of the following interspecific hybrids: (1) hexaploids (genomic composition ААААВВ, the conventional introgression scheme), (2) tetraploids (putatively, АААВ), (3) self-pollination progeny of a 4x hybrid and (4) pentaploid hybrids with a putative genome composition of АААВВ. The present paper presents the first results of the development of chromosome-specific DNA markers for the identification of S. stoloniferum chromosomes in interspecific hybrids. An S. stoloniferum accession PI 205522 with a high degree of resistance to late blight and PVY had been found to possess several DNA-markers of the R-genes conferring resistance to these pathogens and was used in hybridization as a promising parent. A set of 23 SSR- and CAPS markers with the known chromosome location in S. tuberosum was generated. These markers detect polymorphism between parent genotypes, i.e., the diploid clone IGC 10/1.21 of cultivated potatoes S. tuberosum, and accession PI 205522 of S. stoloniferum. All the markers specific for the wild species were found in triploid (ААВ) and pentaploid (АААВВ) hybrids of S. stoloniferum × S. tuberosum. This set of markers will be used for efficiency assessment of different schemes for S. stoloniferum genetic material introgression into the obtained BC2-BC3 generations after crossing the interspecific hybrids with cultivated potato

Marker assisted selection of potato breeding lines with combination of PVY resistance genes from different wild species

Potato virus Y (PVY) is considered as one of the most harmful virus infections of this crop. Thus, it is a topical problem to breed potato varieties resistant against a wide range of PVY strains and to create initial breeding material that will have a combination of resistance genes from different species. The aim of the study was: (1) to genotype a collection of 376 breeding lines (BL), developed from complex interspecific hybrids, using DNA markers of PVY resistance genes, (2) to identify accessions with markers of resistance genes from different species for subsequent use in marker assisted selection (MAS), (3) to evaluate the suitability of DNA markers of PVY resistance genes for genotyping BL developed through interspecific hybridization. It was ascertained that the markers most widely represented in the collection were RYSC3 of the Ryadg gene (49.7%), Ry364 and RAPD38-530 of the Rychc gene (50.5% and 45.2%, respectively), and Yes3-3A of the Rysto gene (29.8%). The markers Ry186 of Rychc and GP122/EcoRV780 of  Ryf-sto  were found only in some accessions. The frequency of occurrence of BL that had markers of PVY resistance genes from two different species varied between 2.7% (Yes3-3a marker of Rysto and both two markers of Rychc) and 8.5-9.0% (RYSC3 marker of Ryadg and both two markers of Rychc, or only Ry364 marker of this gene). In total, the collection was found to contain 134 BL (47.6%) with markers of resistance genes from two different species. A combination of four markers for three genes of different origin (Ryadg, Rysto and Rychc) was found in 27 BL (7.2%). Extreme resistance to PVY of most BL (302 out of 357) was obviously determined by the presence in them of the currently used resistance genes detected by DNA markers applied in the study. Nevertheless, a significant part of accessions (55 of 61) that did not have any markers was resistant to PVY. At the same time, 13 BL (3.5%) with the markers were susceptible to the virus. Such a level of discrepancies is considered as acceptable for the initial MAS of breeding material. The obtained data on the presence of the markers of PVY resistance genes of different origin and their combination in BL ensures a more effective use of such BL in breeding in comparison with the BL resistant to the virus, though lacking corresponding markers

ДИПЛОИДНЫЕ ГИБРИДЫ МЕЖДУ ДИКИМ АЛЛОТЕТРАПЛОИДНЫМ ВИДОМ КАРТОФЕЛЯ SOLANUM STOLONIFERUM SCHLDTL. & BOUCHET И ДИПЛОИДНЫМИ КЛОНАМИ КУЛЬТУРНОГО КАРТОФЕЛЯ S. TUBEROSUM L., ИМЕЮЩИЕ ГЕНОМ В ДИКОГО ВИДА

We were the first who demonstrated the possibility to produce diploid hybrids (along with triploid ones) while pollinating some wild allotetraploid potato species with the pollen of S. tuberosum diploid clones. It was determined that these hybrids only retained one of the genomes of wild species (genome A). Here, we present the results of revealing diploid interspecific hybrids having genome B of wild species. There were selected four hybrids producing the viable pollen among 235 hybrids between valuable for breeding accessions of S. stoloniferum and fertile diploid clone of S. tuberosum. The analysis of meiosis in pollen mother cells showed that they had 24chromosomes. The DNA marker SolB of genome B of wild species was detected in diploid hybrids, as well as in parental clones of S. stoloniferum and triploid interspecific hybrids. The diploid hybrids inherited the typical for wild species markers RYSC 3 and Yes3-3A of Y-virus resistance genes, as well as the markers of late blight resistance genes R1 and R3b. Two of the diploid hybrids inherited markers of late blight resistance gene Rpi-sto1 presented in parental clones of the wild species lossless. The marker 517/1519 of this gene was not detected in one diploid hybrid and both markers (517/1519 and 1521/518) − in another one. Production of the hybrids with genome B makes the version on a possible mechanism of their formation through the selective elimination of one of the genomes of wild species in ontogenesis of initially triploid interspecific hybrids to be priority. Среди гибридов между дикими тетраплоидными видами картофеля и диплоидными клонами S. tuberosum наряду с ожидаемыми триплоидными гибридами встречаются диплоидные гибриды. Ранее нами было показано, что у них сохраняется только один из геномов дикого вида (геном А). В сообщении впервые представлены результаты выявления диплоидных межвидовых гибридов, несущих геном В дикого вида. Среди 235 сеянцев гибридов от скрещивания ценных для селекции образцов S. stoloniferum и фертильного диплоидного клона S. tuberosum отобраны четыре гибрида, формирующих жизнеспособную пыльцу. Анализ мейоза в материнских клетках пыльцы показал наличие у них 24 хромосом. У всех диплоидных гибридов, как и у родительских клонов S. stoloniferum и триплоидных гибридов выявлен ДНК маркер генома В SolB. Все диплоидные гибриды наследовали характерные для дикого вида маркеры генов устойчивости к Y-вирусу картофеля RYSC 3 и Yes3-3A, а также маркеры генов устойчивости к фитофторозу R1 и R3b. Два гибрида без потерь наследовали маркеры гена устойчивости к фитофторозу Rpi-sto1, представленные у родительских клонов дикого вида. У одного диплоидного гибрида не детектировался маркер 517/1519, а у одного гибрида произошла утрата обоих маркеров (517/1519 и 1521/518). Получение гибридов с геномом В делает приоритетной версию о возможном механизме их формирования за счет избирательной элиминации одного из геномов дикого вида в процессе развития изначально триплоидных межвидовых гибридов.

Мужская фертильность растений сортов картофеля с различным типом цитоплазм

The predominance of varieties and parental lines having low male fertility is a characteristic feature of potatoes as a culture with asexual reproduction. The growth of the share of male sterile varieties has been recently noticed as a result of use in breeding interspecific hybrids with sterile-type cytoplasm. It leads to narrowing the genetic basis of modern potato varieties since it limits the choice of pollinators for breeding. The objectives of this research were to assess male fertility characters of 130 potato varieties from the collection of the Institute of Genetics and Cytology of the National Academy of Sciences of Belarus and identify their cytoplasm type using the set of DNA markers. The obtained results are intended for selection of pollinators for conventional breeding of potato, as well as of varieties for production of dihaploids with fertile-type cytoplasm suitable for hybrid breeding at the diploid level. It was revealed that the accessions with T- and D-type cytoplasm prevailed in the collection (46.0 and 35.4 %, respectively), the share of the accessions with W-type cytoplasm was 18.5 %. Most of the effective pollinators were selected among the varieties having T/β-type cytoplasm (44.6 %). The varieties Aksamit, Briz, Dubrava, Uladar, Alwara, Ausonia, Carlita, Fresco, Labadia, Latona, Liu, Lyra, Quarta, Satina, Sissi with this cytoplasm type were selected as most promising for our purposes according to the combination of breeding characters. The potato varieties with D/α-type cytoplasm were present in the collection under study. Approximately one third (32.6 %) was able to produce functionally fertile pollen (PFF), however the level of its fertility was as a rule low. Nevertheless, the varieties Bashkirski, Delfin, Olga and Ponto formed pollen with PFF suitable to guarantee seed production in crosses. Most of the studied varieties with W/α-, W/β-, and W/γ-type cytoplasm were male sterile. The varieties Atlant and Vesna Belaya were revealed among them that were able to produce functionally fertile pollen.Для картофеля как вегетативно размножаемой культуры характерно преобладание сортов и родительских линий с пониженной мужской фертильностью. В последние годы отмечается рост доли мужски стерильных сортов, что связывают с широким использованием в селекции межвидовых гибридов, имеющих цитоплазмы стерильного типа. Это ведет к сужению генетической базы современных сортов картофеля, так как ограничивает выбор опылителей для комбинативной селекции. Целью работы являлась оценка показателей мужской фертильности 130 сортов картофеля из коллекции Института генетики и цитологии НАН Беларуси и определение типа их цитоплазм с помощью набора молекулярных маркеров. Результаты исследования предполагается использовать для выделения сортов-опылителей для традиционной селекции картофеля, а также отбора сортов для получения первичных дигаплоидов картофеля с фертильным типом цитоплазмы, пригодных для гетерозисной селекции на диплоидном уровне. Установлено, что в коллекции преобладают образцы с цитоплазмой T- и D-типа (46,0 и 35,4 % соответственно), доля образцов с типом цитоплазмы W составила 18,5 %. Наибольшее число эффективных опылителей выделено среди образцов с цитоплазматическим типом T/β (44,6 %). По комплексу селекционных признаков выбраны как наиболее перспективные для названных выше целей сорта с цитоплазмой этого типа Аксамит, Бриз, Дубрава, Уладар, Alwara, Ausonia, Carlita, Fresco, Labadia, Latona, Liu, Lyra, Quarta, Satina, Sissi. В изученной нами коллекции представлены сорта с цитоплазмой D/α. Около трети из них (32,6 %) были способны образовывать функционально фертильную пыльцу (ФФП), однако уровень ФФП был, как правило, невысоким. Тем не менее, сорта Башкирский, Дельфин, Olga, Ponto формировали пыльцу с фертильностью, достаточной для гарантированного получения семян. Большинство изученных сортов с типами цитоплазмы W/α, W/β и W/γ были мужски стерильны. Однако и среди них выявлены сорта Атлант и Весна Белая, способные образовывать функционально фертильную пыльцу

GISH Analysis of the Introgression of the B Subgenome Genetic Material of Wild Allotetraploid Species <i>Solanum stoloniferum</i> into Backcrossing Progenies with Potato

Wild relatives of cultivated potato are used in breeding to increase the genetic diversity of Solanum tuberosum (AAAA genome) varieties. Wild Mexican allotetraploid species Solanum stoloniferum (AABB genome) was used in breeding for extreme resistance to viruses and late blight. In this study, genomic in situ hybridization (GISH) was used for visualization of introgression of genetic material of the B subgenome of S. stoloniferum into the genome of backcross hybrids. The fertile hexaploid hybrid had 48 chromosomes of the A genome and 24 chromosomes of the B subgenome. Plants of the BC1 generation were pentaploid having the AAAAB genome constitution and three selected BC2 hybrids were aneuploid, containing one to six chromosomes of the B subgenome and 48 chromosomes of the A genome. The B subgenome of S. stoloniferum was inherited in the backcross generations as single chromosomes and in rare cases as recombinant chromosomes. GISH showed that chromosome pairing in the backcross hybrids was predominantly intragenomic. Most chromosomes of the B subgenome remained as univalents in backcross hybrids. Rare homeologous A/B chromosome pairing was detected in all analyzed hybrids. The obtained data indicate that the B subgenome of S. stoloniferum was able to recombine with the A genome