Combination Breeding and Marker-Assisted Selection to Develop Late Blight Resistant Potato Cultivars

(1) Background: Although resistance to pathogens and pests has been researched in many potato cultivars and breeding lines with DNA markers, there is scarce evidence as to the efficiency of the marker-assisted selection (MAS) for these traits when applied at the early stages of breeding. A goal of this study was to estimate the potential of affordable DNA markers to track resistance genes that are effective against the pathogen Phytophthora infestans (Rpi genes), as a practical breeding tool on a progeny of 68 clones derived from a cross between the cultivar Sudarynya and the hybrid 13/11-09. (2) Methods: this population was studied for four years to elucidate the distribution of late blight (LB) resistance and other agronomical desirable or simple to phenotype traits such as tuber and flower pigmentation, yield capacity and structure. LB resistance was phenotypically evaluated following natural and artificial infection and the presence/absence of nine Rpi genes was assessed with 11 sequence-characterized amplified region (SCAR) markers. To validate this analysis, the profile of Rpi genes in the 13/11-09 parent was established using diagnostic resistance gene enrichment sequencing (dRenSeq) as a gold standard. (3) Results: at the early stages of a breeding program, when screening the segregation of F1 offspring, MAS can halve the workload and selected SCAR markers for Rpi genes provide useful tools

Advanced liver disease in Russian children and adolescents with chronic hepatitis C.

Russia has one of the highest prevalences of paediatric chronic hepatitis C infection (CHC). Our aim was to provide a detailed characterization of children and adolescents with CHC including treatment outcomes. Thus, an observational study of children with CHC aged <18 years was conducted in three hepatology centres from November 2014 to May 2017. Of 301 children (52% male), 196 (65%) acquired HCV vertically, 70 (23%) had a history of blood transfusion or invasive procedures, 1 injecting drug use and 34 (11%) had no known risk factors. Median age at HCV diagnosis was 3.1 [interquartile range, IQR 1.1, 8.2] and 10.8 [7.4, 14.7] at last follow-up. The most common genotype was 1b (51%), followed by 3 (37%). Over a quarter of patients (84, 28%) had raised liver transaminases. Of 92 with liver biopsy, 38 (41%) had bridging fibrosis (median age 10.4 [7.1, 14.1]). Of 223 evaluated by transient elastography, 67 (30%) had liver stiffness ≥5.0 kPa. For each year, increase in age mean stiffness increased by 0.09 kPa (95% CI 0.05, 0.13, P < 0.001). There was significant correlation between liver stiffness and biopsy results (Tau-b = 0.29, P = 0.042). Of 205 treated with IFN-based regimens, 100 (49%) had SVR24. Most children (191, 93%) experienced adverse reactions, leading to treatment discontinuation in 6 (3%). In conclusion, a third of children acquired HCV via nonvertical routes and a substantial proportion of those with liver biopsy had advanced liver disease. Only half of children achieved SVR24 with IFN-based regimens highlighting the need for more effective and better-tolerated treatments with direct-acting antivirals. Further studies are warranted in Russia on causes and prevention of nonvertical transmission of HCV in children

Resistance of potato tubers to Phytophthora infestans evaluated in laboratory tests and field trials

Thirty potato genotypes of different maturity were evaluated for tuber blight resistance both under laboratory and field conditions. From 2000 to 2003 replicated experiments were conducted with three potato cultivars registered in Russia and 27 tetraploid interspecific hybrids that were generated at VIR. Each genotype was assessed twice using laboratory tests, and its resistance was evaluated every year in a field trial. The results showed that four hybrid clones: 88-2, 95-23-3, 97-152-6 and 97-162-5 exhibited a superior performance of tuber resistance to Phytophthora infestans both in laboratory tests and field trials. Two cultivars and 10 hybrid clones were found susceptible to infection in all tests. Significant differences between the remaining 14 genotypes in tuber slice resistance, whole tuber resistance and the expression of resistance to tuber blight in the field were observed

Evaluation of Responses of Potato Cultivars to Potato Spindle Tuber Viroid and to Mixed Viroid/Viral Infection

Potato spindle tuber viroid (PSTVd) is a harmful quarantine disease with wide geographic distribution. To date, experimentally proved resistance or tolerance of potato cultivars to PSTVd has not been reported. The aim of this study was to evaluate responses to four PSTVd strains of 39 modern potato cultivars of different origin. Four PSTVd strains of different origin, the intermediate VP35, VP87, and two sever strains FP10-13 and NicTr-3, deposited in GenBank, were used. Transcripts of these strains were used to inoculate tomato plants of the cv. Rutgers. Before PSTVd inoculation with tomato sap, all plants were tested for viral infection by ELISA. The presence of PSTVd in infected plants was verified by RT-PCR as well as by RT-qPCR at sixty days post-inoculation (dpi). The strain-specificity in the response of cultivars to viroid infection was revealed. Five cultivars were identified in which, after the first inoculation of plants with all PSTVd strains, normal in shape tubers were formed. All plants of the next generation derived from infected but normally shaped tubers showed strong symptoms of disease. PSTVd and mixed viroid/viral infection (PVY + PSTVd, PVM + PSTVd, and PVY + PVS + PSTVd) led to a significant decrease in the number and weight of tubers in most of the cultivars studied

Stacking Resistance Genes in Multiparental Interspecific Potato Hybrids to Anticipate Late Blight Outbreaks

Stacking (pyramiding) several resistance genes of diverse race specificity in one and the same plant by hybridization provides for high and durable resistance to major diseases, such as potato late blight (LB), especially when breeders combine highly efficient genes for broad-spectrum resistance that are novel to the intruding pathogens. Our collection of potato hybrids manifesting long-lasting LB resistance comprises, as a whole, the germplasm of 26 or 22 Solanum species (as treated by Bukasov and Hawkes, respectively), with up to 8&ndash;9 species listed in the pedigree of an individual hybrid. This collection was screened with the markers of ten genes for race-specific resistance to Phytophthora infestans (Rpi genes) initially identified in S. demissum (R1, R2, R3a, R3b, and R8), S. bulbocastanum/S. stoloniferum (Rpi-blb1/ Rpi-sto1, Rpi-blb2, Rpi-blb3) and S. venturii (Rpi-vnt1). The hybrids comprised the markers for up to four-six Rpi genes per plant, and the number of markers was significantly related to LB resistance. Nevertheless, a considerable portion of resistance apparently depended on presently insufficiently characterized resistance genes. Bred from these multiparental hybrids, the advanced lines with the stacks of broad-specificity Rpi genes will help anticipate LB outbreaks caused by rapid pathogen evolution and the arrival of new pathogen strains

Changes in the fatty acid composition of avocado fruit treated with preparations during storage

This article presents data on the fatty acid composition of avocado fruit and the dynamics of the free fatty acid content during storage of fruit treated with preparations “Agrohit”, “KHAN-8”, and “Extrasol-90”, which have antimicrobial properties. Avocado fruit treated with preparations by spraying and without treatment were placed in polymer containers and stored at a temperature of (4±1)°C and relative humidity of 90–95% for 45 days. During the storage of avocado fruit, the fat content was determined by the Soxhlet method and free fatty acids were determined on a Shimadzu 20-AD chromatograph. It has been established that palmitic, palmitoleic, oleic, and linolenic acids predominate in Fuerto avocado fruit. It has been shown that during storage of avocado fruit treated with preparations, the hydrolysis of fats (triacylglycerides) is slowed down, which reduces the accumulation of free fatty acids. It was determined that treatment of fruit with the preparation “KHAN-8” slows down the oxidation of arachidonic acid, which is a resistance inducer of the fruit to phytopathogens

Diversity of Late Blight Resistance Genes in the VIR Potato Collection

Late blight (LB) caused by the oomycete Phytophthora infestans (Mont.) de Bary is the greatest threat to potato production worldwide. Current potato breeding for LB resistance heavily depends on the introduction of new genes for resistance to P. infestans (Rpi genes). Such genes have been discovered in highly diverse wild, primitive, and cultivated species of tuber-bearing potatoes (Solanum L. section Petota Dumort.) and introgressed into the elite potato cultivars by hybridization and transgenic complementation. Unfortunately, even the most resistant potato varieties have been overcome by LB due to the arrival of new pathogen strains and their rapid evolution. Therefore, novel sources for germplasm enhancement comprising the broad-spectrum Rpi genes are in high demand with breeders who aim to provide durable LB resistance. The Genbank of the N.I. Vavilov Institute of Plant Genetic Resources (VIR) in St. Petersburg harbors one of the world’s largest collections of potato and potato relatives. In this study, LB resistance was evaluated in a core selection representing 20 species of seven Petota series according to the Hawkes (1990) classification: Bulbocastana (Rydb.) Hawkes, Demissa Buk., Longipedicellata Buk., Maglia Bitt., Pinnatisecta (Rydb.) Hawkes, Tuberosa (Rydb.) Hawkes (wild and cultivated species), and Yungasensa Corr. LB resistance was assessed in 96 accessions representing 18 species in the laboratory test with detached leaves using a highly virulent and aggressive isolate of P. infestans. The Petota species notably differed in their LB resistance: S. bulbocastanum Dun., S. demissum Lindl., S. cardiophyllum Lindl., and S. berthaultii Hawkes stood out at a high frequency of resistant accessions (7–9 points on a 9-point scale). Well-established specific SCAR markers of ten Rpi genes—Rpi-R1, Rpi-R2/Rpi-blb3, Rpi-R3a, Rpi-R3b, Rpi-R8, Rpi-blb1/Rpi-sto1, Rpi-blb2, and Rpi-vnt1—were used to mine 117 accessions representing 20 species from seven Petota series. In particular, our evidence confirmed the diverse Rpi gene location in two American continents. The structural homologs of the Rpi-R2, Rpi-R3a, Rpi-R3b, and Rpi-R8 genes were found in the North American species other than S. demissum, the species that was the original source of these genes for early potato breeding, and in some cases, in the South American Tuberosa species. The Rpi-blb1/Rpi-sto1 orthologs from S. bulbocastanum and S. stoloniferum Schlechtd et Bché were restricted to genome B in the Mesoamerican series Bulbocastana, Pinnatisecta, and Longipedicellata. The structural homologs of the Rpi-vnt1 gene that were initially identified in the South American species S. venturii Hawkes and Hjert. were reported, for the first time, in the North American series of Petota species

Quality Evaluation, Phytochemical Characteristics and Estimation of Beta-Carotene Hydroxylase 2 (Chy2) Alleles of Interspecific Potato Hybrids

Potatoes contain antioxidants such as flavonoids, carotenoids and ascorbic acid. High level consumption worldwide makes potato a valuable source of phytonutrients. Developing new potato varieties with high nutritional value in combination with resistance to pathogens is an important task. In this study, 25 interspecific potato hybrids with resistance to Synchytrium endobioticum, common scab, silver scab, rhizoctonia, nematodes and PVY were evaluated for total phenolics, total flavonoids, total carotenoids, ascorbic acid contents and antioxidant activity. The identification of the dominant allele related with yellow flesh color at the Chy locus was also performed by the specific CAPS marker. Total protein content was detected and ranged from 8.19 ± 0.59 to 30.17 ± 4.56 mg/g dry weight (DW). Total starch and total carbohydrate contents were in the range of 9.0–21.0% and 73.21 ± 20.94–676.36 ± 195.28, respectively. Total phenolic content of hybrids varied from 8.45 to 82.75 mg/100 g, and total flavonoids content—from 0.64 to 9.67 mg/100 g DW. It is possible to distinguish samples with high protein and carbohydrate contents, high level of substances with antioxidant activity and characterized by resistance to pathogens. Quality evaluation has shown that some of the samples have a high potential for processing and chip production in combination with high eating qualities. These samples can be used in breeding programs to develope varieties resistant to pathogens and with high nutritional value