Huckleberry Gold: A Specialty Market Potato Cultivar with Purple-Skin,Yellow-Flesh,High Tuber Antioxidants,and Resistance to Potato Cyst Nematode (H1) and Potato virus X (Nb and Rx1)

Huckleberry Gold is a purple-skin, yellow-flesh fresh market cultivar with similar culinary qualities to the market standard Yukon Gold. It has lower specific gravity, sucrose and vitamin C content, but a significantly higher level of tuber antioxidants than Yukon Gold. Notable disease resistant characteristics are Potato virus X resistance based on the presence of molecular markers for the PVX resistance genes, Nb and Rx1. In addition it also has the H1 gene present which confers resistance to the potato cyst nematode, Globodera rostochiensis, which has been confirmed by bioassay to pathotype Ro1. The size profile of Huckleberry Gold is smaller than Yukon Gold, allowing a better fit into specialty markets that are geared to smaller size for fresh use. Huckleberry Gold represents the first purple-skin, yellow-flesh cultivar to come from the Northwest (Tri-State) Potato Variety Development program.     

Detection of PVY extreme resistance genes in potato germplasm from the uruguayan breeding program

Breeding goals in potato programs encompass several important commercial traits such as market aspects (skin color, eye depth, shape), category use (fresh or processed), yield, crop duration, and pest and disease resistance. In light of medium- and long-term changes in trait requirements, breeders rely on a range of wild and commercial germplasm in their efforts to reach the multiple objectives that determine the success of a new variety. Readily selectable markers for the recognition of multiple introgressed traits in breeding populations would therefore be practical high-value tools. In subtropical countries, warm climate and the continuous cropping of potato promote high vector pressure and the spread of viruses, rendering seed certification schemes difficult.Potato virus Y (PVY) constitutes a constant problem in several developing countries and it was recently reported as a challenge for seed production in the U.S.A. and Spain, resulting in rejection of seed lots in certification programs. Here we report the simultaneous use of two molecular markers to identify genes for extreme resistance to PVY in the Uruguayan potatobreeding program germplasm. Simplicity and compatibility of the marker system (allele specificity) were emphasized in implementing a reliable and efficient procedure. Forty-four percent of the genotypes tested were shown to carry extreme resistance to PVY, in the majority of cases fromSolanum tuberosum ssp.andigena (Ry_adg). Furthermore, a single marker originating fromSolanum stoloniferum (M45) could be used to recognize both Ry_sto and Ry_adg. The molecular phenotype data corresponding to M45-Ry genotypes was in accordance with virus field exposure observations of resistance.     

The germplasm release of F87084, a fertile, adapted clone with multiple disease resistances

F87084 is a germplasm release that has been developed by conventional breeding methods and can be traced back to very diverse germplasm sources. This clone has excellent female fertility, round-oval tubers and is well adapted to Eastern Canada. The vine maturity is slightly later than that of Kennebec, and the mean marketable yield is 78% of Kennebec. The specific gravity, boil, bake and chip scores are somewhat lower than Kennebec. F87084 is resistant to late blight,Verticillium dahliae, early blight, and the pathotypes of wart occurring in Newfoundland. F87084 has extreme resistance to PVY^o and PVX. It is also resistant to the potato cyst nematode pathotype Ro1. Progeny analyses indicate that F87084 is duplex for the genes controlling extreme resistance to PVX as well as resistance to the potato cyst nematode (Ro1).     

Fine screeningSolanum (potato) germplasm accessions for resistance to Colorado potato beetle

This study was conducted to investigate the utility of systematic screening at the genotype level withinSolanum accessions highly resistant to the Colorado potato beetle. Evaluations of clonally replicated genotypes showed that most accessions reported to be uniform when screened as populations contained small but significant variation among genotypes for resistance to oviposition, larvae, and defoliation, differences for numbers of larvae being most common. Adult counts and percentage defoliation were not as useful in evaluating among-genotype variability in beetle resistance. Genotypes ofS. pinnatisectum WRF 343 andS. tarijense PI 473227 were the most uniformly and highly resistant to Colorado potato beetle. Genotypes of S.berthaultii PI 473331,S. chacoense PI 473405, andS. tarijense PI 473336 were moderately to highly resistant, and genotypes ofS. bukasovii PI 473494 andS. canasense PI 230511 were uniformly susceptible to Colorado potato beetle. Nonparametric correlation analyses indicated that number of egg masses, small larvae, large larvae, and defoliation scores were positively correlated, negatively correlated, or not correlated, depending on the species. One generation of selection attempting to segregate resistance and susceptibility in nearly uniform and highly resistantS. pinnatisectum WRF 343 resulted in “divergent” populations that could not be distinguished from each other or the base population. Thus, through genotype (“fine”) screening and selection, we showed that some existing populations are virtually pure for extreme resistance. Use of individuals from such families would make screening breeding populations more efficient, and reduce the risk of losing resistance genes that have non-dominant effects. Fine screening, recurrent selection, and maintenance of such elite populations is recommended as an extension of population-based evaluation usually done by genebanks.     

Development of STS markers and establishment of multiplex PCR for Glu-A3 alleles in common wheat (Triticum aestivum L.)

Low-molecular-weight glutenin subunits (LMW-GS) play a key role in determining the processing quality of the end-use products of common wheat. The objectives of this study were to identify genes at Glu-A3 locus, develop the STS markers, and establish multiplex PCR with the STS markers for Glu-A3 alleles. Gene-specific PCR primers were designed to amplify six near-isogenic lines (NILs) and Glenlea with different Glu-A3 alleles (a, b, c, d, e, f and g) defined by the protein electrophoretic mobility. Three Glu-A3 genes with complete coding sequence were cloned, designated as GluA3-1, GluA3-2 and GluA3-3, respectively. Seven dominant allele-specific STS (sequence tagged sites) markers were designed based on the SNPs (single nucleotide polymorphisms) among different allelic variants for the discrimination of the Glu-A3 protein alleles a, b, c, d, e, f and g. Four multiplex PCRs were established including Glu-A3b + Glu-A3f, Glu-A3d + Glu-A3f, Glu-A3d + Glu-A3g, and Glu-A3b + Glu-A3e. These markers and multiplex-PCR systems were validated on 141 CIMMYT wheat varieties and advanced lines with different Glu-A3 alleles, confirming that they can be efficiently used in marker-assisted breeding.     

马铃薯Y病毒外壳蛋白基因的克隆及全序列测定

自田间采集的马铃薯病叶中提取马铃薯Y病毒 (PVY)总RNA ,人工合成引物P1、P2 ,通过RT PCR扩增合成PVY cp的cDNA ,并将其克隆到 pGEM TEasy载体上。经限制酶谱分析后进行全序列测定 ,结果表明 :该基因由 80 1个核苷酸组成 ,编码 2 67个氨基酸 ,与文献报道的 3个PVY cp基因相比同源性均在 90 %以上 ,且其编码的氨基酸同源性均在 94 4 %以上。说明PVY cp基因具有较高的保守性     

Co-current introgression of economically important traits in a potato-breeding program

Wild potato species contain many traits of economic importance. Late blight (LB) resistance and cold chipping are traits desired in potato cultivars. These traits could be co-currently introgressed if they occurred together in wild potato species. Our research objectives were (1) to determine if variation for cold chipping exists between potato species, accessions within species, and plants within accessions all having foliar LB resistance, and (2) to identify wild potato genotypes combining LB resistance and cold chipping. Materials include 665 genotypes from 43 LB-resistant accessions of 12 potato species having Endosperm Balance Numbers (EBN) of 1, 2, and 4, and 59 LB-resistant genotypes retained from these accessions for breeding. Potato chips were made from greenhouse-grown tubers following storage at 4 C for 6 months. Chip color was scored 1–10, ≤ 4 is acceptable by industry standards. Most of the variation for chip color was due to differences between species. Species ranged in the percentage of acceptably chipping genotypes (0% – 67%) with nine of 12 species having cold-chipping genotypes. Appreciable variation was present within accessions as well. The best chipping accessions wereS. verrucosum plant introduction (PI) 161173 – 4.33 / 0.67 (mean / proportion acceptable genotypes),S. stoloniferum PI 250510 -4.36 / 0.64,S. pinnatisectum PI 347766 -4.65 / 0.35 and 275233 -4.73 / 0.44, andS. megistacrolobum PI 195210 -5.14 / 0.29. Eleven 1EBN genotypes fromS. pinnatisectum andS. trifidum and five 2EBN genotypes fromS. verrucosum, S. fendleri,S. stoloniferum, andS. microdontum were identified that combined LB resistance and cold chipping. Co-current introgression would require fewer breeding cycles than other breeding methods to identify hybrid genotypes possessing both traits.     

Development and characterization of a Triticum aestivum-H. villosa T5VS•5DL translocation line with soft grain texture

The Hardness locus on the short arm of chromosome 5D is the main determinant of grain texture in bread wheat. The Pina and Pinb genes are tightly linked at this locus, and the soft kernel texture phenotype results when both genes are present and encode the wild-type puroindoline proteins PINA and PINB. In this study a compensating T5VS•5DL Triticum aestivum-Haynaldia villosa translocation line, NAU415, was characterized by chromosome C-banding, genomic in situ hybridization and molecular markers. Single Kernel Characterization System (SKCS) analysis and scanning electron microscopy indicated that NAU415 had soft endosperm although it lacked the wheat Pina-D1a and Pinb-D1a genes, suggesting the presence of functional Pin gene orthologs on chromosome 5VS. Using a PCR approach, Pina-related (designated Dina) and Pinb-related (Dinb) genes in H. villosa and NAU415 were identified and sequenced. The nucleotide and predicted amino acid sequences showed close similarities to the wild-type puroindolines of T. aestivum cv. Chinese Spring. The tryptophan-rich regions of both Dina and Dinb showed a sequence change from lysine-42 to arginine, a feature that may have an effect on grain texture. The potential of T5VS•5DL translocation line as a source of genes that may be used for modulation of endosperm texture and other valuable traits in wheat breeding is discussed.     

Resistance to <Emphasis Type="Italic">Potato virus Y</Emphasis> in a Multitrait Potato Breeding Scheme without Direct Selection in Each Generation

In an experimental breeding scheme to improve late blight (Phytophthora infestans) and white potato cyst nematode (Globodera pallida) resistance of tetraploid potato over three generations of crossing and selection, 15 clones survived the final selection, and these were derived from 15 great-grandparents. There was no direct selection for resistance to Potato virus Y (PVY), but 14 out of the 15 great-grandparents were resistant to PVY and three had extreme resistance. Thirteen of the 15 descendants had PVY resistance and one extreme resistance. This was within the range expected for a random (unselected) sample from the genotypes of the great-grandparents. Hence, we found no evidence for any positive or negative association between PVY resistance and the attributes selected. The conclusion is that laborious selection is not required in every generation when many parents have PVY resistance, including some with more than one copy of a PVY resistance gene or resistance at more than one locus. However, in the future, determining the major virus resistance genes present in potential parents in each generation using diagnostic molecular markers would prevent susceptible × susceptible crosses being made and maximise the number of resistant × resistant ones.     

Debate on the Exploitation of Natural Plant Diversity to Create Late Blight Resistance in Potato

This paper reports on a debate on intriguing propositions relating to the scientific, agronomic, societal and economic impact of the BIOEXPLOIT project, focusing on late blight resistance in potato. It discusses (i) whether identifying pathogen effectors will facilitate selecting durable R genes, (ii) whether breeding for durable late blight resistance requires deploying Rpi (for Resistance to P hytophthora i nfestans) genes, (iii) whether breeding strategies and cultural practices determine the durability of new resistance genes, (iv) whether marker-assisted breeding for Phytophthora infestans resistance is already in the stage of adoption, (v) to what extent genetically-modified organism technology can advance realizing late-blight resistant potato cultivars, and (vi) whether modifying R genes will result in novel broad spectrum resistance.     

Identification of late blight, Colorado potato beetle, and blackleg resistance in three Mexican and two South American wild 2x (1EBN)Solanum species

Wild potatoes are important sources of genes for resistance to disease and insect pests. A collection of wild Mexican and South AmericanSolarium species from the US potato Genebank was evaluated under laboratory and/or field conditions for their reaction to late blight (Phytophthora infestans), Colorado potato beetle (CPB,Leptinotarsa decemlineata Say), and blackleg (Erwinia carotovora subsp.atroseptica (van Hall) Dye) in order to identify individual genotypes with multiple resistance genes. Late blight inoculations using aggressive isolates (US-8/A2 and US-11/A1 mating types) of P.infestans revealed a wide range of variation for resistance between and within the accessions of the wild species tested. For late blight, susceptible as well as moderately to highly resistant genotypes were observed in all the species tested. However, at least one accession from the three Mexican and one South American wild diploid species tested showed a relatively uniform high level of resistance toP. infestans. These includedS. bulbocastanum, S. pinnatisectum, S. cardiophyllum, andS. circaeifolium. Two accessions from South American speciesS. commersonii were highly susceptible to late blight. For the Colorado potato beetle test, only one species,S. pinnatisectum appeared uniformly resistant to CPB under field conditions. Results of screening for blackleg resistance showed that there were major differences between genotypes in the wild species. Accessions ofS. circaeifolium PI 498119 andS. bulbocastanum PI 243504 were identified as having significantly higher blackleg resistance than cultivated potato and the other wild species tested. However, genotypes from these two accessions were more susceptible to late blight and CPB. Characterization of theP. infestans isolate P1801C.16 used for late blight evaluation and multi-locus isolate tests using US-8/A2 and US-11/A1 races revealed that the resistance inS. pinnatisectum genotypes tested corresponded to a race-non-specific genetic system, which was different from any existing R genes.Solanum pin-natisectum genotypes with both high levels of late blight and CPB resistance as well as blackleg resistance genotypes identified in the present study represent a diverse gene pool that may be useful for development of new potato cultivars with multiple disease and insect resistance. The potential utilization of these valuable sources for improvement of cultivated potato is discussed.     

Glycoalkaloids as pest resistance factors

Potato glycoalkaloids, a class of steroid glycosides, possess antimicrobial and pesticidal properties. These phytochemicals have been implicated as natural resistance factors inSolanum species against the Colorado potato beetle,Leptinotarsa decemlineata Say, and the potato leafhopper,Empoasca fabae (Harris). Adverse effects of these secondary metabolites on insect behavioral and developmental biology are described, as well as considerations in manipulation of foliar glycoalkaloids in breeding for varietal resistance to insects.     

Genetic variation in a population of tetraploid potatoes: Response to the potato leafhopper and the potato flea beetle

Progenies from a group of tetraploid parental clones from the USDA potato breeding program were used to investigate variation in resistance to the potato leafhopper,Empoasca fabae (Harris), and the potato flea beetle,Epitrix cucumeris (Harris). The study utilized two mating designs: i) selfing and testing both the parents and the S₁ progeny; and ii) nine clones, used as males, were each crossed to three different clones, and progenies from the resulting families were tested. Statistically significant differences between families were measured in each test for both insects. Non-additive genetic variance was larger than additive genetic variance in progeny reaction to leafhopper infestation and hopperburin, but was smaller in progeny reaction to flea beetles. Environmental variation contributed heavily to the total variation of plant reaction to both insect species. Selecting individuals was indicated to be slightly more effective than selecting males on half-sib progeny performance but not as effective as selecting clones on S₁ progeny performance. Because of the large environmental variance and small additive variance for both the leafhopper and flea beetle, slow progress in increasing the level of resistance to these two species in this sample population was predicted. Resistance to leafhopper infestation was genetically quite highly correlated (positive) with resistance to hopperburn, but phenotypically the correlation was considerably smaller. Negative genotypic, phenotypic, and environmental correlations between leafhopper infestation and flea beetle infestation suggest that selecting for resistance to one of these species, in the population sampled for these tests, would tend to increase susceptibility to the other.     

Assessment of PCR-based simple sequence repeats to fingerprint North American potato cultivars

Seven primer pairs flanking di- and tri-nucleotide repeat sequences, identified from previously sequenced regions of the potato genome, were examined for their potential use in DNA-fingerprinting of thirty-nineSolanum tuberosum subsp. tuberosum cultivars (released between 1861 and 1988) and one diploidS. phureja breeding line. Of the simple sequence repeats (SSRs), the primers for six SSRs amplified DNA sequences within the potato genome between cultivars for a total of 14 bands. The polymerase chain reaction (PCR)based amplification products generated from each primer pair consisted of 1 to 2 bands per cultivar but band variation among cultivars demonstrated up to 4 bands per SSR. A similarity matrix generated from five SSRs was able to distinguish 24 of the 40 cultivars. However, when the potato cultivars were grouped by tuber type (round white-skinned, long white-skinned, russetskinned, red-skinned, and yellow flesh) only five pairs of cultivars remained indistinguishable: Atlantic/Katahdin, Belchip/Wauseon, Red LaSoda/Bliss Triumph, Red Pontiac/Norland, and Burbank/Spunta. Although SSRs did not generate unique fingerprints for all of the North American genotypes examined, the potential to discriminate most cultivars should increase as additional SSRs are identified in potato.     

An Outlook on the Localisation and Structure-Function Relationships of R Proteins in <Emphasis Type="Italic">Solanum</Emphasis>

The co-evolution of plants and plant-pathogens shaped a multi-layered defence system in plants, in which Resistance proteins (R proteins) play a significant role. A fundamental understanding of the functioning of these R proteins and their position in the broader defence system of the plant is essential. Sub-project 3 of the BIOEXPLOIT programme studies how R proteins are activated upon effector recognition and how recognition is conveyed in resistance signalling pathways, using the solanaceous R proteins Rx1 (from S. tuberosum spp. andigena; conferring extreme resistance against Potato Virus X), I-2 (from S. lycopersicon; mediating resistance to Fusarium oxysporum) and Mi-1.2 (from S. lycopersicon; conferring resistance to Meloidogyne incognita) as model systems. The results obtained in this project will serve as a model for other R proteins and will be translated to potential applications or alternative strategies for disease resistance. These include the modification of the recognition specificity of R proteins with the aim to obtain broad spectrum resistance to major pathogens in potato.     

Susceptibility of potato varieties and advanced breeding lines (Solanum tuberosum L.) toPhytophthora infestans (Mont.) de Bary in greenhouse screenings

Late blight (Phytophthora infestons (Mont.) de Bary) has re-emerged as an important pathogen of the cultivated potato (Solanum tuberosum subsp.tubero-sum L.) in North America. The purpose of this study was to evaluate the relative susceptibility of potato germplasm in the greenhouse in order to initiate a breeding program for resistance to the US-8/A2 mating type which is the more aggressive and prevalent strain of late blight. Whole plants of 147 cultivars and breeding lines were evaluated. Percent plant area infection was visually assessed. Seven days after inoculation, infection ranged from 0 to 100% and the overall mean was greater than 50%. Two-thirds of the cultivars and breeding lines tested were very susceptible to the US-8 genotype. The highest resistance was identified in the somatic hybrids betweenS. tuberosum andS. bulbocastanum and their backcross derivatives. Pike and Snowden were less susceptible than the other North American cultivars. Zarevo was most resistant among the European cultivars. Seven of the advanced breeding lines were equivalent to Zarevo in infection levels. The host plant resistance identified among the material tested in this study can be used by breeding programs to develop improved cultivars with resistance to US-8 genotypes of late blight.     

Potato Breeding and Seed Production System Development in Russia

First, an extensive literature review was performed with respect to Potato virus Y (PVY) resistance sources and their further utilization in a breeding programme. On the basis of that review we present a scheme of backcrossing and new cultivar creation on the basis of five detected sources of PVY resistance and one source of Potato virus X resistance. Some cultivar pedigrees are presented reflecting the differences in the breeding strategies. Moreover, results of investigations on some polygenic traits such as field resistance against late blight and starch content are presented. For these purposes progenies were screened for suitable recombinant genotypes which were used in further crossings. Also the results of investigations on resistance to the potato golden nematode and on the selection of cultivars suitable for processing are briefly analysed. We also describe a programme of parallel evaluation of identical hybrid populations in different soils and climatic zones. The development of seed potato production systems facilitated the conditions to improve the quality of potato seed material, to increase potato production and to allow Russia to participate in the international potato market. Systems of virus detection, norms and methods of laboratory tests as well as requirements for quality and tolerance levels of different seed classes (generations) were unified and harmonized with European systems.     

Phylogenomic Relationships of Rice Oxalate Oxidases to the Cupin Superfamily and Their Association with Disease Resistance QTL

Rice oxalate oxidase genes (OXO) may play a role in resistance to Magnaporthe oryzae. Genome analyses showed four tandemly duplicated OXO genes, OsOXO1–OsOXO4, which mapped to a blast resistance QTL in chromosome 3. These genes have >90% nucleotide and amino acid identity, but they have unique gene structures, conserved motifs, and phylogeny compared to the 70 other members of the cupin superfamily in the Nipponbare genome, which were divided into several classes. In resistant and susceptible Vandana/Moroberekan advanced backcross lines, only OsOXO4 was expressed during rice–M. oryzae interactions, and its expression increased earlier in resistant than susceptible lines. The earlier expression of OsOXO4 in resistant lines correlated with a 26-bp promoter insertion containing an additional copy of the bacterial responsive nodulation cis-element. Our results showed that OsOXO1–4 are in a separate class of rice cupin genes and supports a role for the promoter variant of OsOXO4 in resistance to M. oryzae.