Heritable Variation, Genetic and Phenotypic Correlations for Tuber Traits and Host Plant Resistance to Late Blight for Potato Breeding in Scandinavian Testing Sites

Potato breeding aims to improve crop productivity, quality and resilience based on heritable characteristics. Estimating the trait heritability and correlations—both genetic and phenotypic—among characteristics in a target population of environments allows us to define the best breeding method that leads to selection gains. Breeding clones (47) and released cultivars (209) were grown using simple lattice designs at three testing sites in northern and southern Sweden to estimate the best linear unbiased predictors (BLUPs) derived from mixed linear models for characteristics such as tuber weight (total and according to sizes), host plant resistance to late blight (caused by the oomycete Phytophthora infestans) and tuber quality (starch percentage based on specific gravity measurements and reducing sugars). There was significant heritable variation for all the characteristics investigated. Tuber starch percentage and total tuber weight were the traits with the highest broad-sense heritability (H2), while the weight for the smallest size (<40 mm) had the highest H2 among the different tuber categories. These results show the potential for further improving these traits for Scandinavia through recombination and selection in segregating offspring. The genetic and phenotypic correlations among the tuber weight characteristics were significant (p ≤ 0.05) irrespective of their sizes, but none were significant (p > 0.05) with tuber starch percentage. Host plant resistance to late blight was negatively and significantly associated with tuber weight and starch percentage, thereby showing the strong effects of this disease on the productivity and quality of the potatoes.

Development of domestic potato breeding and seed production on the principles of public-private partnership

В последние годы, по данным ФГБУ «Россельхозцентр», доля сертифицированного семенного картофеля сортов зарубежной селекции продолжает возрастать с 77,4% в 2017 году до 86,7% в 2021 году, в то время как доля отечественных сортов снижается с 22,6% в 2017 году до 13,3% в 2021 году. При этом зарубежные селекционно-семеноводческие компании стремятся не только удовлетворить потребности современного рынка, но и способствуют его активному развитию за счет постоянного сортообновления и сортосмены. В отличие от зарубежных, отечественные сорта медленно продвигаются на поля товаропроизводителей и не составляют им конкуренцию. Для повышения конкурентоспособности российских сортов требуется максимальное соответствие отечественных селекционных достижений лучшим зарубежным сортам-аналогам, востребованным на рынке семенного и товарного картофеля. В сложившихся обстоятельствах повышение эффективности селекции с переводом ее на качественно новый уровень возможно реализовать только на основе государственного-частного партнерства. Основа развития отечественной селекции картофеля – организация двух-трех федеральных селекционно-генетических центров с обеспечением их необходимым бюджетным финансированием для выполнения этапа пребридинга или предселекции, включающей скрининг и постоянное обновление генофонда, поиск эффективных доноров хозяйственно полезных признаков, гибридизацию по различным направлениям селекции, освоение биоинженерных технологий и маркер-вспомогательной селекции. Региональных научных учреждений и агропредприятий, позиционируемых в качестве базовых селекционно-семеноводческих центров в количестве 7-8 в России достаточно для создания современных отечественных разработок, соответствующих требованиям рынка и конкурентоспособных с лучшими зарубежными селекционными достижениями. Кооперация федеральных и региональных научно-производственных структур по селекции и семеноводству картофеля представляется таким образом, что основным звеном создания и продвижения новых перспективных сортов становится региональный селекционно-семеноводческий центр, заинтересованный в успешной реализации сорта на рынке семенного и товарного картофеля и способный собирать роялти за его использование. При этом появляется возможность финансовой поддержки науки в лице селекционно-генетических центров на договорных условиях с селекционно-семеноводческими центрами. In recent years, according to the FSBI Rosselkhoznadzor, the share of certified seed potatoes of varieties of foreign selection continues to increase from 77.4% in 2017 to 86.7% in 2021, while the share of domestic varieties decreases from 22.6% in 2017 to 13.3% in 2021. At the same time, foreign seed breeding companies strive not only to meet the needs of the modern market, but also contribute to its active development through constant variety renewal and variety exchange. Unlike foreign varieties, domestic varieties are slowly moving into the fields of commodity producers and do not compete with them. To increase the competitiveness of Russian varieties, maximum compliance of domestic breeding achievements with the best foreign varieties-analogues in demand on the market of seed and commodity potatoes is required. Under the circumstances, it is possible to increase the efficiency of breeding with its transfer to a qualitatively new level only on the basis of public and private partnership. The basis for the development of domestic potato breeding is the organization of two or three federal breeding and genetic centers, providing them with the necessary budget funding to complete the stage of prebreeding or preselection, including screening and constant updating of the gene pool, the search for effective donors of economically useful traits, hybridization in various areas of breeding, the development of bioengineering technologies and marker-assisted selection.Regional scientific institutions and agro-enterprises positioned as basic seed breeding centers in the number of 7-8 in Russia are enough to create modern domestic developments that meet the requirements of the market and are competitive with the best foreign breeding achievements. The cooperation of federal and regional scientific and production structures for potato breeding and seed production is presented in such a way that the main link in the creation and promotion of new promising varieties becomes a regional seed breeding center interested in the successful sale of varieties on the market of seed and commodity potatoes and able to collect royalties for its use. At the same time, there is an opportunity for financial support of science in the face of breeding and genetic centers on contractual terms with breeding and seed centers. Key words: potatoes, breeding, varieties, competitiveness, public-private partnership.

Diversity And Population Structure of Nordic Potato Cultivars and Breeding Clones Grown Under Long Daylength in Europe

The genetic diversity and population structure of breeding germplasm is central knowledge for crop improvement. To gain insight into the genetic potential of the germplasm used for potato breeding in a Nordic breeding program as well as the collections from the Nordic genebank (NordGen), 133 potato genotypes were genotyped using the Infinium Illumina 20K SNP array. After SNP filtering, 11 610 polymorphic SNPs were included in the analysis. In addition, data from three important breeding traits – percent dry matter and uniformity of tuber shape and eye – were scored to measure the variation be-tween groups. The genetic diversity among the genotypes was estimated using principal coordinate analysis based on the genetic distance between individuals, as well as by using the software STRUC-TURE. Both methods suggest that the collected breeding material and the germplasm from the gene-bank are closely related, with a low degree of population structure between the groups. The phenotypic distribution among the genotypes revealed significant differences, especially between farmer’s cultivars and released cultivars and breeding clones. The percent heterozygosity was similar between the groups, with a mean average of 58–60%. Overall, the breeding germplasm and the collection of genotypes from the Nordic gene bank seems to be closely related with similar genetic background. This gains insight that the genetic potential of available Nordic potato breeding germplasm is low, and for genetic hybridi-zation purposes, genotypes from outside the Nordic region should be employed.

Optimal Plot Dimensions for Performance Testing of Hybrid Potato in the Field

Field trials to evaluate the performance of new varieties are an essential component of potato breeding. Besides the genetic differences, environmental factors can lead to variation in a trial. In variety trials, the observed differences amongst varieties should reflect genetic differences, without a large impact of the random or systematic variation in the field. One way to reduce within-field variation is to adjust the plot size and its shape in a trial. Two years of field trials in which individual plants in 90-plant plots of both diploid hybrid and tetraploid varieties were measured provided data to derive relationships between LSD% and plot size and shape. We provide a method to estimate the equations to calculate the expected variation when using different plot dimensions in a relatively homogeneous trial field for tuber yield, tuber volume, tuber count, tuber shape and the standard deviations of tuber volume and shape. Compared with the yield traits, the variation for tuber shape was relatively small. The effect of plot shape was minor. With these equations, breeders can determine what plot dimensions are needed to reach the desired precision for each trait.

NLR Genes Related Transcript Sets in Potato Cultivars Bearing Genetic Material of Wild Mexican Solanum Species

The long history of potato breeding includes the numerous introgressions of resistance genes from many wild species of South and Central America as well as from cultivated species into the breeding genepool. Most R genes belong to the NLR family with nucleotide-binding site–leucine-rich repeat. The aim of this research concerns an evaluation of NLR genes expression in transcriptomes of three potato cultivars (Evraziya, Siverskij, Sudarynya), which combine genetic material from wild and cultivated potato species, and each bears intragenic markers of RB/Rpi-blb1/Rpi-sto1 genes conferring broad-range resistance to late blight. The transcriptomes of the cultivars were compared before and 24 h after the Phytophthora infestans inoculation. The induction of RB/Rpi-blb1/Rpi-sto1 transcript after 24 h of inoculation was detected in the resistant cultivars Siverskij and Sudarynya but not in susceptible cv. Evraziya. This demonstrates the importance of transcriptomic assay for understanding the results of marker-assisted selection and phenotyping. Interestingly, assembling the transcriptomes de novo and analysis with NLR-parser tool revealed significant fractions of novel NLR genes with no homology to the reference genome (from 103 (cv. Siverskij) to 160 (S. stoloniferum, 30514/15). Comparison of novel NLRs demonstrated a relatively small intersection between the genotypes that coincided with their complex pedigrees with several interspecific hybridization events. These novel NLRs may facilitate the discovery of new efficient R genes.

Little heterosis found in Diploid Hybrid Potato

Hybrid potato breeding has become a novel alternative to conventional potato breeding allowing breeders to overcome intractable barriers (e.g. tetrasomic inheritance, masked deleterious alleles, obligate clonal propagation) with the benefit of seed-based propagule, flexible population design, and the potential of hybrid vigour. Until now, however, no formal inquiry has adequately examined the relevant genetic components for complex traits in hybrid potato populations. In this present study, we use a two-step modelling approach to estimate the relevant variance components to assess the magnitude of the general and specific combining abilities (GCA and SCA, respectively) in diploid hybrid potato (DHP). SCA effects were identified for all yield components studied here warranting evidence of non-additive genetic effects in hybrid potato yield. However, the estimated GCA effects were on average two times larger than their respective SCA quantile across all yield phenotypes. Tuber number GCAs and SCAs were found to be highly correlated with total yield's genetic components. Tuber volume appearing under-selected in this population. The prominence of additive effects found for all traits presents evidence that breeders can perform hybrid potato evaluation using the mid-parent value alone. Heterotic vigour stands be useful in bolstering simpler traits but this will be very dependent on the target market of a population. This study represents the first diallel analysis of its kind in diploid potato using material derived from a commercial hybrid breeding programme.

Breeding Late Blight Resistant Potatoes for Organic Farming—a Collaborative Model of Participatory Plant Breeding: the Bioimpuls Project

In organic potato production, the need for varieties with durable late blight resistance developed through classical breeding programmes is urgent. Besides late blight resistance, other variety characteristics needed in organic potato production are early canopy closure for weed suppression and good tuber dormancy to eliminate the need for (chemical) sprouting inhibition during storage, amongst others. This paper is a unique example of collaboration between researchers, farmers and professional breeders of both large, medium and small breeding companies. The aim of the resulting breeding project, Bioimpuls, was to provide a substantial impulse to both the organic and conventional potato breeding sector by enlarging the access to various sources of late blight resistance. The Bioimpuls activities include providing true seed populations for variety selection with five available sources of R-genes against Phytophthora infestans, early and advanced introgression breeding with six new R-genes, and education and communication. The results achieved over the 11-year period (2009–2019) are analysed. Many true seed populations containing multiple resistance genes are produced and selected, and a constant flow of breeding clones is entering the evaluation and positioning trials of companies. However, it will still take a considerable amount of time before varieties with stacked resistance genes will replace the new resistant single gene varieties entering the market in the next few years. Five out of six new sources of R-genes need more years of backcrossing before they are ready for commercial use. Bioimpuls successfully introduced a training course for farmer breeders, and published a manual for potato breeding.