Late Blight Resistance Research Articles

Identification and mapping of QTLs for late blight resistance in the wild tomato (Solanum pimpinellifolium) accession PI 270442 via selective genotyping

Late blight (LB), caused by the oomycete Phytophthora infestans, is one of the most devastating diseases of the cultivated tomato (Solanum lycopersicum) worldwide. Attempts to control the disease through fungicide applications are becoming less effective, as new and aggressive genotypes of the pathogen emerge. Further, some new P. infestans genotypes overcome the currently available resistance in tomato, necessitating the identification, characterization, and utilization of new sources of host resistance. In the present study, to detect QTLs underlying LB resistance in a recently-identified LB-resistant S. pimpinellifolium accession (PI 270442), an F2 population (n = 1,175) of a cross between PI 270442 and LB-susceptible tomato breeding line Fla. 8059 was screened for LB resistance and subjected to selective genotyping. A total of 19,839 single-nucleotide polymorphisms (SNPs) were identified from reduced representation libraries (RRLs) constructed from the parents, of which 212 were used to build a genetic linkage map and locate QTLs. Ten LB-resistance QTLs were identified in PI 270442 on chromosomes 1, 2, 5, 6, 10, 11 and 12, of which those on chromosomes 6, 10 and 11 were the strongest and co-localized with previously-reported LB-resistance QTLs. Genomic locations of the QTLs were compared with the tomato physical map, which resulted in the identification of several candidate genes that might be underpinning the LB resistance in PI 270442. The identified QTL-linked markers can be used in breeding programs to transfer resistance from PI 270442 into the cultivated tomato via marker-assisted breeding and to develop near-isogenic lines for fine mapping of the QTLs.

Potato NPH3/RPT2-like (NRL) member StNRL-9 interacts with Stphots and negatively regulates late blight resistance.

Blue light enhances the susceptibility of Nicotiana benthamiana to Phytophthora infestans, a causative agent of late blight disease. Investigating how blue light affects potato late blight resistance is an interesting aspect of exploring new ways to control late blight disease. Blue light photoreceptor phototropins (phot1, phot2) and their downstream interact protein StNRL1 have been shown to negatively regulate late blight resistance. In order to investigate whether other potato NPH3/RPT2-Like (NRL) family members are involved in regulating late blight resistance, this study focused on the potato NRL proteins containing RxSxS motif at the C-terminus. Another potato NRL protein StNRL-9, containing RxSxS motifs, was found to negatively regulate P. infestans resistance in potato and N. benthamiana. Overexpression of StNRL-9 in potato and N. benthamiana suppresses the accumulation of reactive oxygen species (ROS) and expression of the PTI marker genes NbWRKY7 and NbWRKY8. Similar to StNRL1, StNRL-9 interacts with the blue light receptors Stphot1 and Stphot2 on the cell membrane and could promote the degradation of a positive immune regulator StSWAP70. However StNRL-9 does not inhibit INF1-mediated cell death (ICD), whichis different from the StNRL1 that inhibits ICD, indicating that both StNRL1 and StNRL-9 inhibit plant immunity in diverse ways. This study provides valuable information for further exploration of how plant phototropins and NRL family proteins regulate plant immunity.

Transcriptional Modulation of Plant Defense Genes by a Bipartite Begomovirus Promotes the Performance of Its Whitefly Vector

The majority of plant viruses rely on insect vectors for inter-plant transmission. Amid virus transmission, vector-borne viruses such as begomoviruses may significantly modulate host plants in various ways and, in turn, plant palatability to insect vectors. While many case studies on monopartite begomoviruses are available, bipartite begomoviruses are understudied. More importantly, detailed elucidation of the molecular mechanisms involved is limited. Here, we report the mechanisms by which an emerging bipartite begomovirus, the Sri Lankan cassava mosaic virus (SLCMV), modulates plant defenses against whitefly. SLCMV infection of tobacco (Nicotiana tabacum) plants significantly downregulated defenses against whitefly, as whitefly survival and fecundity increased significantly on virus-infected plants when compared to the controls. We then profiled SLCMV-induced transcriptomic changes in plants and identified a repertoire of differentially expressed genes (DEGs). GO enrichment analysis of DEGs demonstrated that the term defense response was significantly enriched. Functional analysis of DEGs associated with defense response revealed that four downregulated DEGs, including putative late blight resistance protein homolog R1B-17 (R1B-17), polygalacturonase inhibitor-like (PGI), serine/threonine protein kinase CDL1-like (CDL1), and Systemin B, directly contributed to plant defenses against whitefly. Taken together, our findings elucidate the role of novel plant factors involved in the modulation of plant defenses against whitefly by a bipartite begomovirus and shed new light on insect vector–virus–host plant tripartite interactions.

Potato β-aminobutyric acid receptor IBI1 manipulates VOZ1 and VOZ2 transcription factor activity to promote disease resistance.

Upon infection with non-pathogenic microorganisms or treatment with natural or synthetic compounds, plants exhibit a more rapid and potent response to both biotic and abiotic stresses. However, the molecular mechanisms behind this phenomenon, known as defense priming, are poorly understood. β-aminobutyric acid (BABA) is an endogenous stress metabolite that enhances plant tolerance to various abiotic stresses and primes plant defense responses, providing the ability to resist a variety of pathogens (broad-spectrum resistance). In this study, we identified an aspartyl-tRNA synthetase (AspRS), StIBI1 (named after Arabidopsis IMPAIRED IN BABA-INDUCED IMMUNITY 1; IBI1), as a BABA receptor in Solanum tuberosum. We elucidated the regulatory mechanisms by which StIBI1 interacts with two NAC (NAM, ATAF1, 2, and CUC2) transcription factors (TFs), StVOZ1 and StVOZ2 (VASCULAR PLANT ONE ZINC FINGER, VOZ), to activate BABA-induced resistance (BABA-IR). StVOZ1 represses, whereas StVOZ2 promotes, immunity to the late blight pathogen Phytophthora infestans. Interestingly, BABA and StIBI1 influence StVOZ1- and StVOZ2-mediated immunity. StIBI1 interacts with StVOZ1 and StVOZ2 in the cytoplasm, reducing the nuclear accumulation of StVOZ1 and promoting the nuclear accumulation of StVOZ2. Our findings indicate that StVOZ1 and StVOZ2 finely regulate potato resistance to late blight through distinct signaling pathways. In summary, our study provides insights into the interaction between the potato BABA receptor StIBI1 and the TFs StVOZ1 and StVOZ2, which affects StVOZ1 and StVOZ2stability and nuclear accumulation to regulate late blight resistance during BABA-IR. This research advances our understanding of the primary mechanisms of BABA-IR in potato and contributes to a theoretical basis for the prevention and control of potato late blight using BABA-IR.

Genetic analysis of late blight (Phytophthora infestans (mont.) de Bary) resistance in tomato

ABSTRACT Diallel analysis provides basic genetic information that is critically important to identify parents involved in hybridization breeding programs. This study was initiated to estimate combining ability effects and determine the type of gene action involved in inheritance of late blight resistance. Five tomato lines and 10F1 progenies produced by crossing of parents in a 5 × 5 half-diallel fashion were assessed for late blight resistance in field conditions. The combining ability ratio was greater than unity for all traits considered in this stud. At the same time, the degree of dominance was less than unity for all the traits, indicating a greater importance of additive gene effects for the inheritance of late blight resistance. The parents ’Eshete’ and ’Roma VF’ were general combiners, exhibiting significantadverse general combining ability effects for all studied traits. Specific combining ability effects of ’Roma VF × Eshete’ and ’Melkashola × Eshete’ were significantly negative for disease incidence, with all the lines exhibiting significant negative general combining ability effects for the trait, indicating transgressive segregants that are late blight resistant could be produced from crossing of these parental lines. These results, accordingly, indicated that the parents could be utilized in the crossing programme to develop late blight resistant transgressive segregant varieties.

Evaluation of tuber quality, yield and yield related traits of potato (Solanum tuberosum L.) genotypes at Holetta, Central Ethiopia

In Ethiopia, potato is a food security and income generating crop for millions of smallholder farmers. Previous research efforts related to variety development was focusing on tube yield and late blight resistance with wide adaptability. So far, the potato research program in the country however, devoted less on tuber quality traits and processing parameters except few recently released varieties that considered tuber quality traits for processing. These few potato varieties with processing qualities not yet satisfied the ever-emerging processing industries for chips and French fries in the country. Hence, this study aimed to seek evaluating more potato genotypes that have merits for tuber quality traits used for processing and yield attributes. The experiment was laid out in a randomized completed block design with three replications using 24 potato genotypes to evaluate the processing quality traits of advanced potato genotypes at Holetta Agricultural Research Centre in 2017 main cropping season. The results of the analysis of variance revealed that all the traits showed significant differences among the genotypes indicating there is wide genetic variation. The highest and significantly different tuber physical quality traits of geometric mean diameter and surface area was recorded from CIP395017.229, sphericity of the tuber from CIP396027.205, and length to width ratio from CIP399075.7. The specific gravity of tubers, dry matter content and total starch content also ranged from 1.070 to 1.103 gcm−3, 18.67 to 25.75%, and 12.64% to 18.95%, respectively. The five advanced genotypes CIP398098.65, CIP392617.54, CIP398190.404, CIP394611.112, and C398190.89 were selected for their high total tuber yields over 36.80 t/ha, with more than 31.47 t/ha marketable tuber yield, greeter than 69.92 g/tuber average tuber weight, higher than 58.41 mm3 geometric mean diameter, more than 21.25% dry matter content, excellent tuber characteristics and processing quality traits for chips and French fries making. From this study, selection of potato genotypes that consider both external and internal tuber quality traits would expedite the process of advancing ample potato varieties with processing qualities in the country considering comprehensive study by including more potato genotypes across wider growing environments.

Evaluating tomato lines resistance to Late Blight and molecular genetic screening with the use of molecular markers

Relevance. Tomato late blight caused by Phytophthora infestans can cause almost 100% yield loss in open ground in cool and humid conditions. At the same time, the genetic characteristics of P. infestans allow it to overcome the genetic resistance of host plants over time, which requires breeders to look for new genes for resistance to late blight and to obtain new varieties that have several resistance genes at once.Material and methods. 12 tomato lines, or a total of 335 plants, were obtained from the N.N. Timofeev breeding station collection and planted in an artificially infected background. For molecular genetic screening, 12 plants from the Kr6 line were used. The markers linked to the late blight resistance genes Ph-3, R1, and R3a were utilized.Results. On an artificial infectious background, phenotypic evaluation of tomato resistance to late blight showed 1 line of plants free of pathogen damage, 5 lines of plants fully afflicted by late blight, and 6 lines with only partial plant damage. According to molecular genetic investigation the resistant plants were heterozygotes for the Ph-3 gene. Furthermore, the R1 gene was present in most of the plants under study; but, without the Ph-3 gene, this gene did not provide plant resistance against late blight.Conclusions. The results of this research led to the selection of tomato plants for further breeding that were resistant to late blight. It was shown that markers linked to the Ph-3 and R1 genes might be used for marker-mediated selection. Furthermore, it has been established that tomato plants are more effectively protected against P. infestans when several resistance genes are present.

A search for tomato disease resistance genes using molecular markers to create new genotypes

Background. The creation of tomato cultivars and hybrids with a complex of resistance genes is the main task of a breeder. This process can be accelerated through the use of molecular markers at the stages of initial forms selection and the offspring analysis. There is a large amount of information in the literature about DNA markers of resistance genes. Their significant part was recommended for the use in marker-assisted breeding. The purpose of our work was to screen a collection of tomato varieties and hybrids using molecular markers of genes for resistance to the most common diseases of open-ground tomato (late blight, root nematodes, tomato bronzing virus (TSWV)) and to identify gene sources for breeding work. The following markers were selected for research: Sw-5-2 (Sw-5b gene of resistance to TSWV), Mi23 (Mi1.2 gene of resistance to the root-knot nematode), 2 markers NC-LB-9-78 and NC-LB-9-79 (late blight resistance gene Ph-3). During the work, a collection of 46 accessions of tomato cultivars and hybrids was analyzed. Results. The molecular genetic analysis has yielded clear, reproducible fragments that corresponded to the expected ones. All the used markers were codominant. Analysis of the studied collection accessions found the analyzed genes to be polymorphic. The cultivars and hybrids F1 of tomato identified as promising for the use in breeding have resistance to root nematodes (F1 hybrids: A-01, ‘Imitator’, ‘Manon’, cultivars ‘Elegiya’ and ‘Buoy-Tur’), to tomato spotted wilt virus (TSWV) (F1 hybrids: A-01, ‘Manon’ and cultivar ‘Buoy-Tur’), and also to late blight (hybrids F1: А-01, ‘Azhur’, ‘Barin’, ‘Vlastelin stepej’, ‘Zhirdyaj’, Luchshij SeDeK, ‘Manon’ and cultivars: ‘Buoy-Tur’, ‘Zefir v shokolade’, ‘Zolotaya kaplya’, ‘Krasavec’, ‘Lodochka’, ‘Metelitsa’, ‘Alice's Dream’, ‘Sibirskij tigr’, ‘Slavyanskij shedevr’, ‘Elegiya’). It is advisable to use these accessions as sources of resistance genes. Based on the obtained data, five initial forms were selected for breeding and assessed for the intracultivar polymorphism of the studied genes. Cultivars ‘Krasavec’ and ‘Sibirskij tigr’ were used as parent forms. Their hybridization was carried out and hybrid forms homozygous for the dominant allele of the Ph-3 gene were obtained. Conclusions. The use of molecular markers in the conducted study allowed screening the collection of tomato varieties and hybrids for the presence of resistance genes to the most common diseases. Based on the obtained data, parental pairs were selected, hybridization carried out, and hybrid forms with the late blight resistance gene obtained.

Sustainable Potato Production through MAS and Late Blight Resistance

Sustainable Potato Production through MAS and Late Blight Resistance

Transcriptome, hormonal, and secondary metabolite changes in leaves of DEFENSE NO DEATH 1 (DND1) silenced potato plants

DEFENSE NO DEATH 1 (DND1) is a cyclic nucleotide-gated ion channel protein. Earlier, it was shown that the silencing of DND1 in the potato (Solanum tuberosum L.) leads to resistance to late blight, powdery mildew, and gray mold diseases. At the same time, however, it can reduce plant growth and cause leaf necrosis. To obtain knowledge of the molecular events behind the pleiotropic effect of DND1 downregulation in the potato, metabolite and transcriptome analyses were performed on three DND1 silenced lines of the cultivar ‘Désirée.’ A massive increase in the salicylic acid content of leaves was detected. Concentrations of jasmonic acid and chlorogenic acid and their derivatives were also elevated. Expression of 1866 genes was altered in the same way in all three DND1 silenced lines, including those related to the synthesis of secondary metabolites. The activation of several alleles of leaf rust, late blight, and other disease resistance genes, as well as the induction of pathogenesis-related genes, was detected. WRKY and NAC transcription factor families were upregulated, whereas bHLHs were downregulated, indicating their central role in transcriptome changes. These results suggest that the maintenance of the constitutive defense state leads to the reduced growth of DND1 silenced potato plants.

Accumulation of dually targeted StGPT1 in chloroplasts mediated by StRFP1, an E3 ubiquitin ligase, enhances plant immunity.

Chloroplasts play a crucial role in essential processes, such as photosynthesis and the synthesis of primary and diverse secondary metabolites. Recent studies have also highlighted their significance linked to phytohormone production in plant immunity, especially SA and JA. Ubiquitination, a key posttranslational modification, usually leads to target protein degradation, which acts as a signal for remodeling the proteome via the induction of protein endocytosis or targeting to other membrane associated systems. Previously, the potato E3 ligase StRFP1 was shown to enhance resistance against Phytophthora infestans, but its mechanism remained unclear. Here, we demonstrate that StRFP1 interacted with the dually localized plastid glucose 6-phosphate transporter StGPT1 on the endoplasmic reticulum (ER). Transiently expressed StGPT1-GFP located on the chloroplast and ER in plant cells. Overexpression of StGPT1 enhances late blight resistance in potato and Nicotiana benthamiana, activates immune responses, including ROS bursts and up-regulation of PTI marker genes. The resistance function of StGPT1 seems to be related to its dual localization. Remarkably, StRFP1 ubiquitinates StGPT1 at the ER, possibly due to its merely transient function in peroxisomes, leading to apparent accumulation in chloroplasts. Our findings point to a novel mechanism by which a plant E3 ligase contributes to immunity via interacting with dually targeted GPT1 at the ER of plant cells.

Potato Breeding for Late Blight Resistance in Central and East Africa

Potato late blight is a disease of great loss, which can go beyond 75% in Central and Eastern Africa. With this in mind, in order to limit the excessive use of synthetic fungicides, the use of resistant varieties is a better alternative. This study focuses on the synthesis of works already carried out in the improvement of potato resistance to late blight in Central and East Africa in order to have a general overview. For this purpose, 76 documents were consulted, including 67 scientific articles, eight books, and a web page. The literature has shown that the improvement of potato resistance to late blight in these areas is mainly based on conventional methods throughout the breeding scheme. These studies are mainly led by the International Potato Center. This review covers yield losses due to late blight, the biology of Phytophthora infestans, late blight management methods, the genetics of late blight resistance, genetic resources for late blight resistance in Central and East Africa, screening methods and breeding approaches for potato late blight resistance.

Transcriptome analysis reveals genes associated with late blight resistance in potato

Late blight is a serious disease of potato worldwide. Our study aimed to unveil genes involved in late blight resistance in potato by RNA-seq analysis after artificial inoculation under controlled conditions. In this study, two potato somatic hybrids (P7 and Crd6) and three varieties such as Kufri Girdhari, Kufri Jyoti and Kufri Bahar (control) were used. Transcriptiome analysis revealed statistically significant (p < 0.05) differentially expressed genes (DEGs), which were analysed into up-regulated and down-regulated genes. Further, DEGs were functionally characterized by the Gene Ontology annotations and the Kyoto Encyclopedia of Genes and Genomes pathways. Overall, some of the up-regulated genes in resistant genotypes were disease resistance proteins such as CC-NBS-LRR resistance protein, ankyrin repeat family protein, cytochrome P450, leucine-rich repeat family protein/protein kinase family, and MYB transcription factor. Sequence diversity analysis based on 38 peptide sequences representing 18 genes showed distinct variation and the presence of three motifs in 15 amino acid sequences. Selected genes were also validated by real-time quantitative polymerase chain reaction analysis. Interestingly, gene expression markers were developed for late blight resistant genotypes. Our study elucidates genes involved in imparting late blight resistance in potato, which will be beneficial for its management strategies in the future.

A Complex Approach to Control Black Dot Disease in Potato

In recent years, skin blemish diseases of potato (including black dot (BD) caused by Colletotricum coccodes) have begun to be important for global potato marketing, since consumers often reject tubers with an imperfect appearance, which results in financial losses caused by the disposal of unwanted potatoes. Like for many non-fatal plant diseases, BD severity may depend on the immune status of plants influenced by other infectious agents. Using a set of 98 potato cultivars differing in their late blight (LB) resistance, we examined the correlation between the intensity of their infection with LB determined by their LB resistance and the occurrence of the BD disease under field conditions with a high background level of both diseases. Using LB-susceptible (Arizona) and moderately susceptible (Sante) cultivars, we also evaluated the effect of a crop protection against LB on BD development under the same field conditions. A strong negative correlation (r = −0.81, p &lt; 0.05) between the LB resistance and the BD occurrence has been revealed. An experiment using the two cultivars, chemically protected against LB, showed a significant reduction in BD occurrence of 30% (cv. Arizona) and 20% (cv. Sante) compared to the untreated controls; the total yield and marketability of potatoes increased by 103.6 and 62.5% for cv. Arizona and by 65.9 and 43.8% for cv. Sante. The reduction in the LB affection of potato is one of the key factors improving the immune status of potato cultivars in relation to BD infection, so methods of LB protection should be included in a complex approach to BD control.

Multiplex PCR for Early Generation Identification of Tomato Segregants Carrying Ty-2, Ty-3 and Ph-3 Resistance Alleles Against Leaf Curl and Late Blight Diseases.

Deployment of different natural disease resistance alleles is the most sustainable and eco-friendly way for multiple disease management in tomato. Diagnostic molecular markers are indispensible in this effort as they offer early generation identification of resistance alleles in an environment-independent manner. Moreover, optimized multiplex polymerase chain reaction (PCR) for detecting different disease resistance alleles in a single reaction can speed-up the selection process with cost and labour-effectiveness. Here we report the optimized multiplex detection and stacking of leaf curl disease resistance alleles Ty-2 and Ty-3 along with late blight disease resistance allele Ph-3 in tomato genotypes and F2 segregants. The triplex assay could be replaced by a duplex assay (for Ty-2 and Ty-3 resistance alleles) followed by analysis at Ph-3 locus to achieve further cost-effectiveness. We identified two plants in F2 populations derived from the Arka Samrat (F1) x Kashi Chayan combination to carry the Ty-2, Ty-3 and Ph-3 resistance alleles in homozygous condition. Early generation genotyping also allowed us to identify a few morphologically better segregants, where further marker assisted selection (MAS) should identify superior multiple disease resistant lines. Thus we advocate the utility of multiplex PCR in MAS to address multiple disease resistance breeding in tomato.

Modern Breeding Strategies and Tools for Durable Late Blight Resistance in Potato.

Cultivated potato (Solanum tuberosum) is a major crop worldwide. It occupies the second place after cereals (corn, rice, and wheat). This important crop is threatened by the Oomycete Phytophthora infestans, the agent of late blight disease. This pathogen was first encountered during the Irish famine during the 1840s and is a reemerging threat to potatoes. It is mainly controlled chemically by using fungicides, but due to health and environmental concerns, the best alternative is resistance. When there is no disease, no treatment is required. In this study, we present a summary of the ongoing efforts concerning resistance breeding of potato against this devastating pathogen, P. infestans. This work begins with the search for and selection of resistance genes, whether they are from within or from outside the species. The genetic methods developed to date for gene mining, such as effectoromics and GWAS, provide researchers with the ability to identify genes of interest more efficiently. Once identified, these genes are cloned using molecular markers (MAS or QRL) and can then be introduced into different cultivars using somatic hybridization or recombinant DNA technology. More innovative technologies have been developed lately, such as gene editing using the CRISPR system or gene silencing, by exploiting iRNA strategies that have emerged as promising tools for managing Phytophthora infestans, which can be employed. Also, gene pyramiding or gene stacking, which involves the accumulation of two or more R genes on the same individual plant, is an innovative method that has yielded many promising results. All these advances related to the development of molecular techniques for obtaining new potato cultivars resistant to P. infestans can contribute not only to reducing losses in agriculture but especially to ensuring food security and safety.

Potato E3 ubiquitin ligase StRFP1 positively regulates late blight resistance by degrading sugar transporters StSWEET10c and StSWEET11.

Potato (Solanum tuberosum) is the fourth largest food crop in the world. Late blight, caused by oomycete Phytophthora infestans, is the most devastating disease threatening potato production. Previous research has shown that StRFP1, a potato Arabidopsis Tóxicos en Levadura (ATL) family protein, positively regulates late blight resistance via its E3 ligase activity. However, the underlying mechanism is unknown. Here, we reveal that StRFP1 is associated with the plasma membrane (PM) and undergoes constitutive endocytic trafficking. Its PM localization is essential for inhibiting P. infestans colonization. Through in vivo and in vitro assays, we investigated that StRFP1 interacts with two sugar transporters StSWEET10c and StSWEET11 at the PM. Overexpression (OE) of StSWEET10c or StSWEET11 enhances P. infestans colonization. Both StSWEET10c and StSWEET11 exhibit sucrose transport ability in yeast, and OE of StSWEET10c leads to an increased sucrose content in the apoplastic fluid of potato leaves. StRFP1 ubiquitinates StSWEET10c and StSWEET11 to promote their degradation. We illustrate a novel mechanism by which a potato ATL protein enhances disease resistance by degrading susceptibility (S) factors, such as Sugars Will Eventually be Exported Transporters (SWEETs). This offers a potential strategy for improving disease resistance by utilizing host positive immune regulators to neutralize S factors.

The use of &lt;i&gt;in vitro&lt;/i&gt; androgenesis for the involvement of interspecific hybrids between &lt;i&gt;Solanum tuberosum&lt;/i&gt; L. and wild allotetraploid potato species &lt;i&gt;Solanum stoloniferum&lt;/i&gt; Schltdl. et Bouché into breeding

Wild allotetraploid potato species Solanum stoloniferum Schltdl. &amp; Bouché from Mexico is regarded as a valuable source of resistance genes for use in breeding. However, introgression of its resistance genes into breeding material is hampered by a set of reproductive barriers. The genomic difference between S. stoloniferum (genome ААВВ) and S. tuberosum L. (AAAA) is one of them. This makes questionable the possibility of transferring a variety of valuable genes of the wild species localized on the chromosomes of its genome B into the genome of cultivated potatoes. It is proposed to produce tetraploid (4x, AAAB) interspecific hybrids of S. stoloniferum, which are regarded as more promising for homoeological recombination than pentaploid (5x, ААААВ) hybrids commonly used in the introgression schemes. However, the effective ploidy of tetraploid hybrids (3EBN) hinders their backcrossing to cultivated potatoes (4 EBN). For instance, our attempts to involve the tetraploid hybrid of S. stoloniferum IGC16/36.1 obtained by us into hybridization with potato varieties were unsuccessful for a number of years. To solve this problem, we suggested a technique based on the production of 4x plants obtained in anther culture of this hybrid. The present research was aimed at assessing the efficiency of this approach.Thirty-one plants were obtained in anther culture (androgenic clones, androclones) of the hybrid IGC16/36.1 in 2018. Most of them exceeded the initial hybrid in habitus strength and flowering intensity. As a result of crosses made in 2019, 1039 hybrid seeds were obtained from crossing 21 androclones with the ‘Lemhi Russet’ variety (8.7 seeds/pollination), 1017 seeds (7.5 seeds/pollination) from crosses of 23 androclones with the ‘Quarta’ variety, and 716 seeds (12.3 seeds/pollination) from crosses of 11 androclones and a diploid potato line IGC 17n8 capable of producing fertile unreduced (2n) pollen. The hybrid seeds had good germination rate of 70-90%. Among the androclones that gave progeny in crosses with potato varieties, we identified genotypes carrying DNA markers of late blight (LB) resistance genes Rpi-sto1, R2 and R3b, PVY resistance genes Ryadg, Rysto and Rychc, and potato wart disease resistance gene Sen2 (these markers were found in the initial accession of S. stoloniferum PI 205522 and in the IGC 16/36.1 hybrid). Despite the complex nature of inheritance of the analyzed markers in progenies of backcrosses of androclones, a number of isolated hybrids carried several markers, including those of the Rpi-sto1, a broad-spectrum gene for high resistance to late blight. Hybrids with relatively high tuber productivity, features of cultivated potatoes such as regularly shaped tubers with small eyes, and high field resistance to late blight were selected.The prospects for using androclones of the tetraploid interspecific hybrid IGC 16/36.1 for increasing the frequency of homoeologous A/B recombination of chromosomes are discussed.

De novo assembly-based transcriptome analysis of resistant and susceptible potato varieties to Phytophthora infestans

AbstractAn effective tool for discovering differentially expressed genes (DEGs) related to late blight (LB) resistance is the transcriptome sequencing of potatoes. The aim of this study was to compare transcriptome expression analysis in incompatible and compatible interactions via high-throughput sequencing. Furthermore, we performed a bioinformatics analysis to screen a large number of specific transcription factors (TFs) and DEGs linked to Phytophthora infestans infection. Two locally cultivated potato varieties were chosen from evaluation assays conducted in two consecutive seasons and based on the disease severity (DS) values. These varieties were the highly resistant Jelly (HR) to P. infestans and the moderately susceptible Annabelle (MS). Ribonucleic acid-sequencing (RNA-seq) was achieved for the two varieties with their controls through the BGISEQ-500 sequencing platform. The RNA-seq analysis identified P. infestans-responsive genes and their expression in potatoes. The mechanism of the response of these cultivars to the P. infestans pathogen by TFs and DEG genes, which play an important role in defense response, was investigated. The Gene Ontology (GO) analysis classified 46,248 unigenes in the HR and 26,921 unigenes in MS into the following three categories: biological process, cellular component, and molecular functions. More genes were responsible for the cellular component category, biological process, and molecular functions in HR compared to MS. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the significantly enriched DEGs were included in the plant–pathogen interaction, biosynthesis of secondary metabolites, and ribosome. In addition, 1874 transcription factor genes belonging to 85 families were indicated in the DEGs, of which MYB and AP2-EREBP genes were the most abundant. Besides, multiple genes related to LB resistance showed differential expression during infection. It also sheds light on the molecular mechanisms behind potato resistance to P. infestans infection.

Tomato families possessing resistance to late blight also display high-quality fruit

In recent years, several efforts have been made to develop tomato cultivars displaying both late blight resistance and good organoleptic fruit quality. Selection indexes are considered the best option to perform genotype selection when many different traits are being considered to select genotypes as close to the desired ideotype as possible. Therefore, this study aimed at selecting late blight-resistant tomato families based on their fruit quality attributes using factor analysis and ideotype-design / best linear unbiased predictor (FAI-BLUP) index. For this purpose, we assessed the fruit quality parameters of 81 F3:5 tomato families previously selected as late blight resistant. The tomato cultivars Thaise, Argos, and Liberty were included in the trial as checks. The experimental arrangement consisted of complete randomized blocks with three replicates. Each plot was formed by five plants, three of which were used in the fruit quality assessment. The quality parameters assessed were fruit diameter, fruit length, fruit color (L, a*, C, and H), fruit firmness, titratable acidity, soluble solids content, hydrogen potential, and SS:TA ratio. Fruit quality data were analyzed using the mixed model methodology via REML/BLUP (restricted residual maximum likelihood / best linear unbiased prediction) to obtain BLUPs that were further subjected to the FAI-BLUP selection index. The FAI-BLUP was efficient in selecting late blight-resistant tomato genotypes based on their fruit quality attributes. Fourteen tomato families were classified as closest to the desirable ideotype for fruit quality. These genotypes should move on to the following stages of the tomato breeding program.