Sugar Beet Breeding Research Articles

A standard area diagram for Fusarium yellows rating in sugar beet (Beta vulgaris)

AbstractMembers of the Fusarium oxysporum species complex are pathogens of sugar beet causing Fusarium yellows. Fusarium yellows can reduce plant stand, yield and extractable sugar. Improving host plant resistance against Fusarium‐induced diseases, like Fusarium yellows, represents an important long‐term breeding target in sugar beet breeding programmes. Current methods for rating Fusarium yellows disease severity rely on an ordinal scale, which limits precision for intermediate phenotypes. In this study, we aimed to improve the accuracy and precision of rating Fusarium yellows by developing a standard area diagram (SAD). Two SAD versions were created using images of sugar beets infected with Fusarium oxysporum strain F19. Each version was tested using inexperienced raters. Version 1 and the improved version 2 SAD showed no statistical differences in Lin's concordance correlation coefficient (LCC) values, which was used to assess accuracy and precision between the two versions (Cb = 0.99 for both versions, c = 0.97 and 0.96 for version 1 and 2, respectively). In addition, five naïve Bayesian machine‐learning models that used pixel classification to determine disease score were tested for congruency to human estimates in SAD version 2. Root mean square error was lowest compared to the ‘true’ values for the unweighted model and a model where necrotic tissue was given a 2× weight (12.4 and 12.6, respectively). The creation of this SAD enables breeding programmes to make consistent, accurate disease ratings regardless of personnel's previous experience with Fusarium yellows. Additionally, more iterations of pixel quantification equations may overcome accuracy issues for rating Fusarium yellows.

Genome-Wide Identification of GRAS Transcription Factors and Their Functional Analysis in Salt Stress Response in Sugar Beet.

GAI-RGA-and-SCR (GRAS) transcription factors can regulate many biological processes such as plant growth and development and stress defense, but there are few related studies in sugar beet. Salt stress can seriously affect the yield and quality of sugar beet (Beta vulgaris). Therefore, this study used bioinformatics methods to identify GRAS transcription factors in sugar beet and analyzed their structural characteristics, evolutionary relationships, regulatory networks and salt stress response patterns. A total of 28 BvGRAS genes were identified in the whole genome of sugar beet, and the sequence composition was relatively conservative. According to the topology of the phylogenetic tree, BvGRAS can be divided into nine subfamilies: LISCL, SHR, PAT1, SCR, SCL3, LAS, SCL4/7, HAM and DELLA. Synteny analysis showed that there were two pairs of fragment replication genes in the BvGRAS gene, indicating that gene replication was not the main source of BvGRAS family members. Regulatory network analysis showed that BvGRAS could participate in the regulation of protein interaction, material transport, redox balance, ion homeostasis, osmotic substance accumulation and plant morphological structure to affect the tolerance of sugar beet to salt stress. Under salt stress, BvGRAS and its target genes showed an up-regulated expression trend. Among them, BvGRAS-15, BvGRAS-19, BvGRAS-20, BvGRAS-21, LOC104892636 and LOC104893770 may be the key genes for sugar beet's salt stress response. In this study, the structural characteristics and biological functions of BvGRAS transcription factors were analyzed, which provided data for the further study of the molecular mechanisms of salt stress and molecular breeding of sugar beet.

Sugar beet PMT5a and STP13 carriers suitable for proton-driven plasma membrane sucrose and glucose import in taproots.

Sugar beet (Beta vulgaris) is the major sugar-producing crop in Europe and Northern America, as the taproot stores sucrose at a concentration of around 20%. Genome sequence analysis together with biochemical and electrophysiological approaches led to the identification and characterization of the TST sucrose transporter driving vacuolar sugar accumulation in the taproot. However, the sugar transporters mediating sucrose uptake across the plasma membrane of taproot parenchyma cells remained unknown. As with glucose, sucrose stimulation of taproot parenchyma cells caused inward proton fluxes and plasma membrane depolarization, indicating a sugar/proton symport mechanism. To decipher the nature of the corresponding proton-driven sugar transporters, we performed taproot transcriptomic profiling and identified the cold-induced PMT5a and STP13 transporters. When expressed in Xenopus laevis oocytes, BvPMT5a was characterized as a voltage- and H+-driven low-affinity glucose transporter, which does not transport sucrose. In contrast, BvSTP13 operated as a high-affinity H+/sugar symporter, transporting glucose better than sucrose, and being more cold-tolerant than BvPMT5a. Modeling of the BvSTP13 structure with bound mono- and disaccharides suggests plasticity of the binding cleft to accommodate the different saccharides. The identification of BvPMT5a and BvSTP13 as taproot sugar transporters could improve breeding of sugar beet to provide a sustainable energy crop.

AMMI and GGE biplot analysis for genotype × environment interactions affecting the yield and quality characteristics of sugar beet.

Sugar beet, an important sugar crop, contributes significantly to the world's sugar production. However, genotype-environment interactions (GEI) often affect the quality characteristics of sugar beet. Hence, understanding the effects of GEI on sugar beet quality can aid in identifying high-quality genotypes that can adapt to different environments. Traditional variance analysis can only be used to examine the yield of a variety and not its specific adaptability to specific conditions. Therefore, more comprehensive analytical methods are required to evaluate the characteristics of the variety under specific environments. Additive main effects and multiplicative interaction (AMMI) and genotype main effect and genotype × environment interaction (GGE) biplot models can be employed to comprehensively evaluate different varieties and address the drawbacks associated with a single evaluation method. Moreover, these models also allow us to explore new varieties more objectively and comprehensively. In this study, the adaptability and stability of 16 sugar beet varieties, in terms of yield and sugar content, were evaluated using AMMI and GGE biplot analysis in seven pilot projects undertaken in 2022. In the assessment of a small but significant proportion of the total GEI variance for the two qualitative traits (yield and sugar content), 80.58% of the variance was explained by the cumulative contribution of IPC1, IPC2, and IPC3. AMMI and GGE biplots clearly highlighted that KWS4207 (G3) exhibited high and stable quality. They also demonstrated that the experiments in Jalaid Banner (Inner Mongolia) (E7) were the most representative. Together, the results suggested that the comprehensive application of AMMI and GGE biplot analysis allowed for a more comprehensive, scientific, and effective evaluation of sugar beet varieties across different regions. The findings offer a theoretical basis for sugar beet breeding and could guide the rational design of experiments for testing new varieties of sugar beet.

Genome-Wide Analysis of Q-Type C2H2 ZFP Genes in Response to Biotic and Abiotic Stresses in Sugar Beet.

A plant's Q-type C2H2-type ZFP plays key roles in plant growth and development and responses to biotic and abiotic stresses. Sugar beet (Beta vulgaris L.) is an important crop for sugar production. Salt stress and viral infection significantly reduce the root yield and sugar content of sugar beet. However, there is a lack of comprehensive genome-wide analyses of Q-type C2H2 ZFPs and their expression patterns in sugar beet under stress. In this study, 35 sugar beet Q-type C2H2 ZFPs (BvZFPs) containing at least one conserved "QALGGH" motif were identified via bioinformatics techniques using TBtools software. According to their evolutionary relationship, the BvZFPs were classified into five subclasses. Within each subclass, the physicochemical properties and motif compositions showed strong similarities. A Ka/Ks analysis indicated that the BvZFPs were conserved during evolution. Promoter cis-element analysis revealed that most BvZFPs are associated with elements related to phytohormone, biotic or abiotic stress, and plant development. The expression data showed that the BvZFPs in sugar beet are predominantly expressed in the root. In addition, BvZFPs are involved in the response to abiotic and biotic stresses, including salt stress and viral infection. Overall, these results will extend our understanding of the Q-type C2H2 gene family and provide valuable information for the biological breeding of sugar beet against abiotic and biotic stresses in the future.

Assessment of genetic diversity, yield and quality performance of O-Type Sugar Beet (Beta vulgaris L.) breeding lines

Assessment of genetic diversity, yield and quality performance of O-Type Sugar Beet (Beta vulgaris L.) breeding lines

High Precision Leaf Instance Segmentation for Phenotyping in Point Clouds Obtained Under Real Field Conditions

Measuring plant traits with high throughput allows breeders to monitor and select the best cultivars for subsequent breeding generations. This can enable farmers to improve yield to produce more food, feed, and fiber. Current breeding practices involve extracting leaf parameters on a small subset of the leaves present in the breeding plots, while still requiring substantial manual labor. To automate this process, an important step is the precise distinction between separate leaves, which is the problem we address in this paper. We exploit recent advancements in 3D deep learning to build a convolutional neural network that learns to segment individual leaves. As done in current breeding practices, we select a subset of leaves to be used for phenotypic trait evaluation as this allows us to alleviate the influence of segmentation errors on the phenotypic trait estimation. To this extent we propose to use an additional neural network to predict the quality of each segmented leaf and discard inaccurate leaf instances. The experiments show that our network yields higher segmentation accuracy on sugar beet breeding plots planted under the supervision of the German Federal Office for Plant Varieties. Furthermore, we show that our neural network helps in filtering out leaves with lower segmentation accuracy.

A study on the adaptive potential of new sterile cytoplasm of Beta patula and Beta maritima L. from wild beets of the genus Beta L.: cold resistance and traits of early sugar accumulation in introduced alloplasmic lines

Purpose. Assessment of new sugar beet breeding genotypes by a set of economically valuable traits to determine their suitability for the efficiency of the process of managing the production of bioethanol with the study of the activity of photosynthesis according to the content of chlorophylls a and b, early accumulation of carbohydrates, tolerance to low temperatures, germination of apozygous seeds and using new plasma of the substituted lines of sugar beet with introduced sterile cytoplasms from wild species Beta patula and B. maritima L. and apozygous lines A9 with S vulgaris Owen's cytoplasm. Methods. Field methods were used (pollen-free regime for the reproduction of apozygotic seeds in conditions of isolation and seed monogermity of the seed plants), laboratory methods (selection of the best experimental genotypes for cold resistance, analysis of productivity and dynamics of carbohydrate accumulation). Results. Self-fertile pollen-sterile lines A9 Beta vulgaris Sxxzz rr with an apomictic method of seed reproduction of seeds (Yaltushkiv EBS) and commercial hybrids with early carbohydrate accumulation were selected for the recessive colour of the hypocotyl r-r- and gametophytic reduced parthenogenesis for hybridization according to the scheme: A9 Beta vulgaris Sxxzz rr × Beta vulgaris Mm Rr. The influence of cytoplasmic inheritance of B. maritima and B. patula on cold resistance indicators was studied and seed samples of the experimental genotypes No. 17225, 17221, 17222, 17220, 17226, 17223 were selected among substituted lines with seed germination rates at +4°C varying from 14.3 to 40.3%. Experimental genotypes of the substituted lines, grown in the conditions of pots were selected and examined by the indicators of early accumulation of sugars, which had values from 16.2 to 17.6% during four months of vegetation; photosynthetic activity with indicators of the content of chlorophyll varying from 2.06 to 1.32%, and chlorophyll b from 1.02 to 0.65%. Conclusions. Sugar beet hybrids, created with the use of cold-resistant substituted pollen-sterile lines of sugar beet, thanks to the natural evolution of the introduced cytoplasmic genome, ensure the extension of the growing season, high productivity, early accumulation of sugars and enrichment of the crop adaptation potential. The article contains the results of the study of the early carbohydrate accumulation, photosynthetic activity of selected experimental genotypes of the substituted sugar beet lines with high seed quality and 100% monogermity. Root crops of apomictic lines were selected based on R+r hypocotyl colour, generative reduced parthenogenesis, and studied for their specifics of seed set under the pollen-free regime.

Перспективная стратегия применения молекулярных маркеров в селекции Beta vulgaris L. (обзор)

Abstract. Aim of the investigations is to study, summarize and analyze domestic and foreign literature concerning interaction of molecular genetics and classical sugar beet breeding for improvement of resistance to biotic and abiotic stresses. The problems are: 1) to analyze a current state of molecular-genetic investigations in domestic and foreign literature; 2) to study problems of marker-oriented breeding; 3) to estimate development prospects of sugar beet molecular research in Russian Federation. Methods. Analytical methods to inspect and handle information from international databases (PubMed, NCBI, and Academy Google) have been used to study modern strategy of molecular-genetic marking. Results. Use of DNA-technologies is an important part of modern breeding of agricultural crops. There have been discussed the research data permitting to get a more comprehensive idea of current state of sugar beet molecular genetics and breeding that is necessary to work out programs of their further development. There have been presented the results of foreign authors’ experiments and our own investigations on determining DNA-markers to study genetical polymorphism of sugar beet breeding material, select parent pairs for hybridization, identify genes of resistance to bolting, select breeding material with genes of resistance to biotic (Fusarium spp., nematodes, rhizomania) and abiotic stressors (salinization, drought, heavy metals). Now, wide-scale studies on using molecular-genetic markers in sugar beet breeding process have been carried out by Federal State Budgetary Scientific Institution “The A.L. Mazlumov All-Russian Research Institute of Sugar Beet and Sugar”. Use of molecular markers is one of the basic methods in plant breeding because of their general allocation throughout a genome and practical universality of application. In the article, advisability to use actual methods of sugar beet genome analysis employing DNA-markers in breeding process is considered. Scientific novelty involves estimation of the current state of Beta vulgaris L. molecular-genetic investigations in Russian Federation and abroad and their use in the crop breeding process.

Resistance genes of salinization in sugar beet

Aim of the investigations was to study genes of resistance to salinization in sugar beet breeding materials. The experiment was conducted using the sugar beet hybrids (Beta vulgaris L.): F119170 (VNIISS), Karioka, Mitika and Hamber (Lion Seeds), Lgovka (Lgovskaya OSS). Expression of genes coding ascorbate peroxidase and NHX-antiporter were studied. In the work, specific primers were used: APX, NHX1, NHX4.1, NHХ5.1 and NHX5. Studying of NHX1, NHX4 and NHX5 genes resulted in selection of the sugar beet genotypes: MS17070, Op18094, F119170 and Humber, the hybrid of Lgovskaya OSS. From the results of gene expression analysis, a main role of NHX5 gene in formation of resistance to salinization was determined. As for ascorbate peroxidase activity, the highest indices were also revealed in the domestic genotypes of MS17070 (115.01 U/mg when treated with 70 mM NaCl), Op18094 (42.3 U/mg when treated with 70 mM NaCl) and Humber (68.6 U/mg when treated with 70 mM NaCl). The sufficiently high level of APO activity was shown both in F119170 (18.8 U/mg when treated with 150 mМ NaCl) and the hybrid of Lgovskaya OSS (13.2 U/mg when treated with 150 mM NaCl). It was determined that BvNHX1 and BvNHX5 genes made a special contribution to formation of resistance to salinization, i.e. they could work as independent units. On the contrary, BvNHX4 was supposed to work only together with them and could not provide stable resistance when BvNHX1 and BvNHX5 were inhibited.

Genotype by Environment Interaction Effects on the Crop of Sugar Beet (Beta vulgaris L.) Using Multivariate Analysis

Evaluation of genotypes under Egyptian desert conditions comes in the first order for the Plant Breeding and Conservation Program of the Desert Research Center (DRC). The objective of this study was to analyze the effect of the genotype by environment interaction of sugar beet across various locations using multivariate models. Data for studied traits of sugar beet were obtained from experiments at three regions: Saint Catherine, South Sinai Governorate (E1); Baloza station, North Sinai Governorate (E2); and East El- Qantra station, El-Ismailia Governorate (E3) in Egypt. All examined traits were significantly impacted (p <0.05 or 0.01) by environment (E), genotypes (G), and their interaction (GEI) using the AMMI model, with the exception of root length/plant by the environments as well as leaves weight/plant and total soluble solids percentage % traits by the genotypes. GEI was partitioned into two principal components (PCs), which were significant for all studied traits (P < 0.05 and P < 0.01). The highest variability from the total variance was recorded by environmental influences for leaves weight/plant and total soluble solids percentage % traits, as well as by genotype effects for the other studied traits. The environmental index showed that some environments were favorable and some environments were unfavorable for the two traits. The highest root weight/plant and most studied traits were noticed in the E2 environment. Based on the GGE model for root weight/plant, the test environments E1 and E2 are more representative and have the greatest ability to discriminate genotypes, thus favoring the selection of superior genotypes. The genotypes G2, G5, and G6 perform best in the E1 and E2 environments as well as are the most productive and stable compared with the other genotypes. According to PCA and cluster analysis, the genotypes G5 and G6 showed the best performance in response to environments and positive association with root weight/plant and most studied traits. Based on the results of statistical methods used in this study, G5 and G6 genotypes should be used in future sugar beet breeding in an effort to improve productivity and sustainable production of sugar beet in Egypt.

Evaluation of resistance and determination of stability of different sugar beet (Beta vulgaris L.) genotypes in rhizomania-infected conditions.

Plant diseases are considered one of the main factors reducing yield and quality of crops, which are constantly developing and creating more virulent races and cause the resistance of more genes to break. Identifying resistance sources and including them in breeding programs will improve resistant genotypes. Rhizomania is the most common, widespread, and devastating disease of sugar beet in Iran and worldwide. Breeding genotypes with disease resistance genes is one of the most important ways to deal with this destructive disease. Twenty sugar beet genotypes along with five controls were evaluated in a randomized complete block design with four replications in rhizomania-infected conditions in four regions of Mashhad, Shiraz, Miandoab, and Hamedan for 2 years. The results of genotypic reaction to rhizomania showed that the genotypes with resistance reaction were much more frequent than those with susceptibility reaction. The analysis of multiplicative effects of the AMMI model showed that the first six components were significant and explained 98.80% of the interaction variations. The biplot obtained from the mean white sugar yield and the first interaction principal component confirmed the superiority of the RM5 genotype due to its high white sugar yield and stability in infected conditions. The results obtained from the first three principal components biplot showed that the RM9 genotype with a mean white sugar yield of 11.91 t. ha-1 was a genotype with vast general stability in all disease-infected environments. Based on the results of the MTSI index, RM3, RM17, RM9, RM13, and RM15 are introduced as stable genotypes under rhizomania-infected conditions. In conclusion, it seems that the studied genotypes have valuable and useful genes inherited from their parents to deal with rhizomania disease. Applying these genotypes in sugar beet breeding programs can effectively prevent the threat of rhizomania.

Breeding value of multi-sprout pollinator lines of different inbreeding generations as parental components of sugar beet hybrids on а CMS basis

Aim. Creation of combination-capable lines of multi-sprout pollinators of sugar beets of different levels of homozygosity, establishment of criteria for their selection based on basic productivity, reproductive capacity and hybridization potential at various stages of the selection process for the formation of parental components of hybrids on the cytoplasmic male-sterile (CMS) basis. Methods. Field (experiments, phenological observations), laboratory (to determine sugar content), measuring and weighing (to determine the crop structure), statistical (mathematical processing of research results). The research was carried out at the Tobacco Research Station of the National Scientific Center "Institute of Agriculture of the National Academy of Agrarian Sciences" in the laboratory of sugar beet breeding during the 2015–2021. The starting material was three hybrid multi-sprout populations of sugar beet Um. 17/02-1705, Um. 21/01-33 and Um. 14/05-752. Linear materials were obtained by the inbreeding method. Results. It was established that the lines of multi-sprout pollinators of sugar beets of the second-third generations of inbreeding (I2-I3) are characterized by the highest productivity. The yield of root crops exceeded the standard by 8.1–9.3%, sugar content by 8.6–8.8% and sugar collection by 16.5–17.9%. As the depth of inbreeding increases, the quality of pollen deteriorates sharply. If in the lines of the first generation of inbreeding (I1), the fertility of pollen in plants of of multi-sprout pollinators was 95.1%, then in the lines of the fifth generation (I5) it decreased to 31.0%. The number of non-viable pollen grains in them was 72.2%, seed germination was 29%. Experimental hybrids with the best performance were obtained by using as pollinators lines of the second to third generations of inbreeding. According to the complex characteristic "sugar collection", they exceeded the group standard by 19.7–21.3%. Conclusions. It has been established that for the formation of line materials of sugar beet multi-sprout pollinators, as parent components of hybrids on а CMS basis, the main criterias for the selection of valuable plant genotypes, in addition to the hybridization potential, are high level of their basic productivity and reproductive capacity. The best experimental sugar beet hybrids were obtained by using lines of multi-sprout pollinators of the second to third inbreeding generations.

Current Approaches to Genome Sequencing in Sugar Beet (Beta Vulgaris) and Its Wild Relatives

Şeker pancarı (Beta vulgaris L. ssp. vulgaris), hem gıda hem de şeker üretimi için yetiştirilen, ekonomik olarak önemli kültür bitkilerinden biridir. Yetiştiriciler, istekleri doğrultusunda bitki özelliklerini geliştirmek için ıslah çalışmaları sürdürmektedirler. Şeker pancarı ıslahı ile birlikte; verimli, şeker içeriği yüksek, dayanıklı üstün çeşitler geliştirilmektedir. Bununla birlikte, kültür pancarlarındaki düşük genetik çeşitlilik, hastalık ve zararlılara hassasiyet gibi özellikleri iyileştirmek amacıyla yabani akrabalarından yararlanılmaktadır. Yabani akrabalar belirli habitatlara adapte olduklarından, pancar yetiştirme havuzu için önemli bir genetik kaynak oluştururlar. Genom dizileme yoluyla pancarda bulunan genlerin ve alellerin sayısı, kimliği ve çeşitliliği hakkında bilgi edinmek, pancarlarda yeni özellikleri tanıtmak ve geliştirmek için önemlidir. Bitkinin yabani akrabalarında bulunan özellikler olan tolerans ve direnç özelliklerini kültür çeşitlerine aktarmak için bu özelliklerin belirlenmesi gerekir. Bu amaçla şeker pancarının genetik tabanının genişletilmesi, ekolojik açıdan önemli özelliklerin korunması açısından önemlidir. Bunun için kültür pancarı ve yabani akrabalarının genetik bilgilerinin belirlenmesi ve birbirlerine göre filogenetik sınıflandırılmaları çok önemlidir.

Genomic and transcriptomic-based analysis of agronomic traits in sugar beet (Beta vulgaris L.) pure line IMA1.

Sugar beet (Beta vulgaris L.) is an important sugar-producing and energy crop worldwide. The sugar beet pure line IMA1 independently bred by Chinese scientists is a standard diploid parent material that is widely used in hybrid-breeding programs. In this study, a high-quality, chromosome-level genome assembly for IMA1was conducted, and 99.1% of genome sequences were assigned to nine chromosomes. A total of 35,003 protein-coding genes were annotated, with 91.56% functionally annotated by public databases. Compared with previously released sugar beet assemblies, the new genome was larger with at least 1.6 times larger N50 size, thereby substantially improving the completeness and continuity of the sugar beet genome. A Genome-Wide Association Studies analysis identified 10 disease-resistance genes associated with three important beet diseases and five genes associated with sugar yield per hectare, which could be key targets to improve sugar productivity. Nine highly expressed genes associated with pollen fertility of sugar beet were also identified. The results of this study provide valuable information to identify and dissect functional genes affecting sugar beet agronomic traits, which can increase sugar beet production and help screen for excellent sugar beet breeding materials. In addition, information is provided that can precisely incorporate biotechnology tools into breeding efforts.

Genome-Wide Identification and Salt Stress Response Analysis of the bZIP Transcription Factor Family in Sugar Beet.

As one of the largest transcription factor families in plants, bZIP transcription factors play important regulatory roles in different biological processes, especially in the process of stress response. Salt stress inhibits the growth and yield of sugar beet. However, bZIP-related studies in sugar beet (Beta vulgaris L.) have not been reported. This study aimed to identify the bZIP transcription factors in sugar beet and analyze their biological functions and response patterns to salt stress. Using bioinformatics, 48 BvbZIP genes were identified in the genome of sugar beet, encoding 77 proteins with large structural differences. Collinearity analysis showed that three pairs of BvbZIP genes were fragment replication genes. The BvbZIP genes were grouped according to the phylogenetic tree topology and conserved structures, and the results are consistent with those reported in Arabidopsis. Under salt stress, the expression levels of most BvbZIP genes were decreased, and only eight genes were up-regulated. GO analysis showed that the BvbZIP genes were mainly negatively regulated in stress response. Protein interaction prediction showed that the BvbZIP genes were mainly involved in light signaling and ABA signal transduction, and also played a certain role in stress responses. In this study, the structures and biological functions of the BvbZIP genes were analyzed to provide foundational data for further mechanistic studies and for facilitating the efforts toward the molecular breeding of stress-resilient sugar beet.

Bacterial endophytes as indicators of susceptibility to Cercospora Leaf Spot (CLS) disease in Beta vulgaris L.

The fungus Cercospora beticola causes Cercospora Leaf Spot (CLS) of sugar beet (Beta vulgaris L.). Despite the global importance of this disease, durable resistance to CLS has still not been obtained. Therefore, the breeding of tolerant hybrids is a major goal for the sugar beet sector. Although recent studies have suggested that the leaf microbiome composition can offer useful predictors to assist plant breeders, this is an untapped resource in sugar beet breeding efforts. Using Ion GeneStudio S5 technology to sequence amplicons from seven 16S rRNA hypervariable regions, the most recurring endophytes discriminating CLS-symptomatic and symptomless sea beets (Beta vulgaris L.ssp. maritima) were identified. This allowed the design of taxon-specific primer pairs to quantify the abundance of the most representative endophytic species in large naturally occurring populations of sea beet and subsequently in sugar beet breeding genotypes under either CLS symptomless or infection stages using qPCR. Among the screened bacterial genera, Methylobacterium and Mucilaginibacter were found to be significantly (p < 0.05) more abundant in symptomatic sea beets with respect to symptomless. In cultivated sugar beet material under CLS infection, the comparison between resistant and susceptible genotypes confirmed that the susceptible genotypes hosted higher contents of the above-mentioned bacterial genera. These results suggest that the abundance of these species can be correlated with increased sensitivity to CLS disease. This evidence can further prompt novel protocols to assist plant breeding of sugar beet in the pursuit of improved pathogen resistance.

Efficiency of different cycles of multiple individual-family selection in the breeding of multi-sprout sugar beet pollinators

Purpose. To create multi-sprout sugar beet pollinators with a narrowed genetic basis, to assess their productivity and combining ability over time at different stages of multiple individual-family selection.&#x0D; Materials and methods. The studies were conducted at the Tobacco Experimental Station of the National Research Center «Institute of Agriculture of NAAS» in the Laboratory of Sugar Beet Breeding in 2009–2020. Seven diploid multi-sprout sugar beet populations bred in Ukraine were taken as starting material. New multi-sprout pollinators were obtained by multiple individual-family selection. Breeding accessions were tested by the method developed by scientists of the Institute of Bioenergy Crops and Sugar Beet of NAAS. The GCA was evaluated using unidirectional cyclic crosses on the basis of three CMS-testers.&#x0D; Results and discussion. The results demonstrated a high efficiency of two and three cycles of individual-family selection for increasing the root yields of the multi-sprout sugar beet pollinators. The root yields increased by 11.7% and 13.5% after two and three selection cycles, respectively, related to the original populations. Subsequent selection cycles (four and five) were less effective due to inbreeding depression. The yields of the multi-sprout pollinators was 106.3% and 98.2% after four and five selection cycles, respectively, related to the original populations. The multi-sprout pollinators from selection cycles four and five had the highest sugar content in roots: 121.6% and 119.5%, respectively, related to the original populations.&#x0D; As to the compound trait of «sugar collection», the highest productivity in the multi-sprout pollinators was observed after three selection cycles (119.5%). In subsequent cycles of selection, this parameter decreased.&#x0D; The yield and sugar content in roots of the best diploid multi-sprout sugar beet pollinators varied between 108.2–116.3% and 98.6–105.5%, respectively, related to the group reference. As to the sugar collection and output, they exceeded the group reference by 9.2–19.2% and 9.5–21.8%, respectively.&#x0D; Conclusions. In the 2009–2020 studies, the changes in the performance characteristics of the multi-sprout sugar beet pollinators from different cycles of multiple individual-family selection were investigated over time. The highest basic productivity was seen in the multi-sprout pollinators from selection cycle 3, which should be used both as sources of valuable genotypes – ancestors of lines and directly as parents of hybrids. Ten highly productive multi-sprout sugar beet pollinators with the optimal combinations of the most significant breeding-genetic traits have been created.

Development of an SNP Assay for Marker-Assisted Selection of Soil-Borne Rhizoctonia solani AG-2-2-IIIB Resistance in Sugar Beet.

Rhizoctonia solani, causing Rhizoctonia crown and root rot, is a major risk to sugar beet (Beta vulgaris L.) cultivation. The development of resistant varieties accelerated by marker-assisted selection is a priority of breeding programs. We report the identification of a single-nucleotide polymorphism (SNP) marker linked to Rhizoctonia resistance using restriction site-associated DNA (RAD) sequencing of two geographically discrete sets of plant materials with different degrees of resistance/susceptibility to enable a wider selection of superior genotypes. The variant calling pipeline utilized SAMtools for variant calling and the resulting raw SNPs from RAD sequencing (15,988 and 22,439 SNPs) were able to explain 13.40% and 25.45% of the phenotypic variation in the two sets of material from different sources of origin, respectively. An association analysis was carried out independently on both the datasets and mutually occurring significant SNPs were filtered depending on their contribution to the phenotype using principal component analysis (PCA) biplots. To provide a ready-to-use marker for the breeding community, a systematic molecular validation of significant SNPs distributed across the genome was undertaken to combine high-resolution melting, Sanger sequencing, and rhAmp SNP genotyping. We report that RsBv1 located on Chromosome 6 (9,000,093 bp) is significantly associated with Rhizoctonia resistance (p < 0.01) and able to explain 10% of the phenotypic disease variance. The related SNP assay is thus ready for marker-assisted selection in sugar beet breeding for Rhizoctonia resistance.

SNP Alleles Associated With Low Bolting Tendency in Sugar Beet.

The identification of efficient molecular markers related to low bolting tendency is a priority in sugar beet (Beta vulgaris L.) breeding. This study aimed to identify SNP markers associated with low bolting tendency by establishing a genome-wide association study. An elaborate 3-year field trial comprising 13 sugar beet lines identified L14 as the one exhibiting the lowest bolting tendency along with an increased survival rate after autumnal sowing. For SNP discovery following phenotyping, contrasting phenotypes of 24 non-bolting and 15 bolting plants of the L14 line were sequenced by restriction site-associated DNA sequencing (RAD-seq). An association model was established with a set of 10,924 RAD-based single nucleotide polymorphism (SNP) markers. The allelic status of the most significantly associated SNPs ranked based on their differential allelic status between contrasting phenotypes (p < 0.01) was confirmed on three different validation datasets comprising diverse sugar beet lines and varieties adopting a range of SNP detection technologies. This study has led to the identification of SNP_36780842 and SNP_48607347 linked to low bolting tendency and can be used for marker-assisted breeding and selection in sugar beet.