Cultivated Potato Research Articles

Amino acid composition and nutritional value of four cultivated South American potato species

Protein content, amino acid composition, nutritional quality and patatin characteristics were determined in tubers of four South American cultivated potato species (Solanum andigenum, Solanum goniocalyx, Solanum phureja, Solanum stenotomum) and a cultivar of the commonly cultivated cultivar Desirée of Solanum tuberosum. Protein content (on dry matter basis) of S. andigenum and S. stenotomum was highest at 7.9% and 8.0%, respectively, and the relative quantities of patatin for both species were 41.7% and 34.0%, respectively. The nutritional value of patatin, in terms of essential amino acid index with respect to a reference protein of FAO/WHO (EAAIadult) ranged from 93.0% (S. phureja) to 112.5% (S. goniocalyx). In case S. goniocalyx, the patatin fraction was a nutritionally better protein fraction than a protein concentrate or tuber dry matter, which had EAAIadult values of 97.6% and 82.9%, respectively. This suggests that this species may have potential in potato breeding programmes and in human nutrition.

Tomato Tm-2 2 gene confers multiple resistances to TMV, ToMV, PVX, and PVY to cultivated potato

Viral infection seriously affects the yield and quality of potato tubers. Breeding of virus-resistant potato (Solanum tuberosum L.) varieties is essential. Introduction of resistance genes from other Solanaceae species into cultivated potato is likely to be a valuable method to achieve durable resistance to potato virus. Tm-22 resistance gene was cloned from tomato cv. KBV and introduced into the binary vector pBIN19 to yield Tm-22-constitutive expression vector under the control of the CaMV 35S promoter. The resultant vector was transferred into potato, and Tm-22 gene was successfully expressed in transgenic potato plants. After infection with TMV, ToMV, PVX, and PVY, transgenic potato plants showed the high level of resistance to these viruses, and potato tuber yield was significantly increased compared to wild type. qRT-PCR results showed that Tm-22 transgenic plants had much lower transcript levels of VIRUS-COAT genes than wild type, even no TMV- and ToMV-COAT RNAs were detected in upper non-inoculated systemic leaves of transgenic lines. These results indicate that Tm-22 confers different resistance responses against viruses depending on its expression level.

Diversity of potato genetic resources.

A considerable number of highly diverse species exist in genus Solanum. Because they can adapt to a broad range of habitats, potato wild relatives are promising sources of desirable agricultural traits. Potato taxonomy is quite complex because of introgression, interspecific hybridization, auto- and allopolyploidy, sexual compatibility among many species, a mixture of sexual and asexual reproduction, possible recent species divergence, phenotypic plasticity, and the consequent high morphological similarity among species. Recent researchers using molecular tools have contributed to the identification of genes controlling several types of resistance as well as to the revision of taxonomical relationships among potato species. Historically, primitive forms of cultivated potato and its wild relatives have been used in breeding programs and there is still an enormous and unimaginable potential for discovering desirable characteristics, particularly in wild species Different methods have been developed to incorporate useful alleles from these wild species into the improved cultivars. Potato germplasm comprising of useful alleles for different breeding objectives is preserved in various gene banks worldwide. These materials, with their invaluable information, are accessible for research and breeding purposes. Precise identification of species base on the new taxonomy is essential for effective use of the germplasm collection.

Fine Screening for Resistance to Cold-Induced Sweetening in Potato Hybrids ContainingSolanum raphanifoliumGermplasm

Potato is an indispensable part of human food. Many wild and cultivated potato relatives have been screened to find the best germplasm to improve productivity and quality, but only a small sample of the available biodiversity has been exploited. Most wild relatives are self-incompatible diploids. Genetic variability exists within and among populations, even within a species. Therefore, it is necessary to carry out fine screening to identify individuals carrying traits of interest. This study was carried out to quantify phenotypic variability for resistance to cold-induced sweetening, an important processing trait. Five families were evaluated for potato chip (crisp) color following cold storage of tubers harvested from four greenhouse trials and one field trial. The families were generated by crossing a single diploid clone to five plants from one accession of the wild potato relativeSolanum raphanifolium. Analysis of variance revealed that resistance against cold-induced sweetening was dependent on family and trial. This study underscores the importance of fine screening to select individuals in potato accessions for use in potato improvement.

TomatoTm-22Gene Confers Multiple Resistances to TMV, ToMV, PVX, and PVY to Cultivated Potato

Tomato<i>Tm-2²</i>Gene Confers Multiple Resistances to TMV, ToMV, PVX, and PVY to Cultivated Potato

Field Assessment of AtCBF1 Transgenic Potato Lines (Solanum tuberosum) for Drought Tolerance

Drought prone areas have been increasing around the world and it is expected that these areas will continue to expand and become more severe due to climate change. Increasing the drought stress tolerance of cultivated potato (Solanum tuberosum) could aid in feeding the growing global population. The Arabidopsis CBF1 gene (AtCBF1), which has been shown to increase drought tolerance in other plants, was transformed into a cultivated potato line under the control of the stress inducible promoter COR15a. The expression of the AtCBF1 transgene was verified by RT-PCR and the transformed lines were evaluated in field trials to assess agronomic performance under sub-optimal water management. Despite expression of the AtCBF1 gene, none of the transgenic lines out-performed the control cultivar under drought-stressed conditions. Abiotic stress responsive genes from cultivated potato and wild related species may yield more promising results thus CBF1 genes from S. tuberosum and S. commersonii will be transformed into the potato cultivar Desiree and will be field tested for drought tolerance.

Systematics, Diversity, Genetics, and Evolution of Wild and Cultivated Potatoes

The common potato, Solanum tuberosum L., is the third most important food crop and is grown and consumed worldwide. Indigenous cultivated (landrace) potatoes and wild potato species, all classified as Solanum section Petota, are widely used for potato improvement. Members of section Petota are broadly distributed in the Americas from the southwestern United States to the Southern Cone of South America. The latest comprehensive taxonomic treatment of section Petota was published by John (Jack) Hawkes in 1990; it recognized seven cultivated species and 228 wild species, divided into 21 taxonomic series. Since 1990, intensive field collections from throughout the range of the group, coupled with morphological and molecular studies, have halved the number of species and elucidated new ingroup and outgroup relationships. The recent sequencing of the potato genome has greatly accelerated investigation of all aspects of potato biology and allows us to address new questions not conceivable before. The purpose of this review is to provide a historical overview and update since 1990 of the systematics, diversity, genetics, domestication, evolution, and breeding of Solanum section Petota that will serve as a reference for the next generation of studies in the potato.

Managing Colorado Potato Beetle Insecticide Resistance: New Tools and Strategies for the Next Decade of Pest Control in Potato

Neonicotinoid insecticides have been the most common management tool for Colorado potato beetle, Leptinotarsa decemlineata (Say), infestations in cultivated potato for nearly 20 yr. The relative ease of applying neonicotinoids at planting coupled with inexpensive, generic neonicotinoid formulations has reduced the incentive for potato growers to transition from these products to other mode of action (MoA) groups for early-season L. decemlineata control. Continuous use of neonicotinoids has resulted in resistant L. decemlineata populations in some production areas of the eastern United States. Continued reliance on neonicotinoids will accelerate L. decemlineata resistance development and result in additional insecticide inputs to manage these populations. Resistance management recommendations for L. decemlineata have focused on rotation of insecticides within the growing season. Growers using at-plant neonicotinoids for early-season L. decemlineata control are encouraged to rotate MoAs for later generations to delay resistance development. Although this short-term insecticide rotation has likely prolonged the utility of neonicotinoid insecticides, reducing reliance on a single MoA soil application at planting will improve the longevity of newer, more reduced-risk alternatives. The objectives of this article are twofold: 1) to provide a review of the current status of L. decemlineata neonicotinoid resistance, and 2) to propose long-term resistance management strategies that arrange reduced-risk MoA groups into several, multiyear sequences that will maximize L. decemlineata control and reduce the probability for resistance development. This recommendation maintains practical and economical approaches for L. decemlineata control, but limits reliance on any single MoA group to minimize selection pressure for resistance development.

An updated conventional- and a novel GM potato late blight R gene differential set for virulence monitoring of Phytophthora infestans

Late blight is an important disease in potato that is caused by the oomycete Phytophthora infestans. In the past, Solanum demissum late blight resistance (R) genes were introgressed into cultivated potato (Solanum tuberosum). Eleven of these resistant plants were selected to characterize the virulence spectrum of individual P. infestans isolates and to monitor the dynamics of virulence in P. infestans populations. These plants are referred to as the Mastenbroek and Black differential sets. It has long been assumed that each differential plant contained one single R gene. In the current study and previous studies, however, most Mastenbroek differential plants were shown to harbor multiple R gene(s), which blurs virulence typing of late blight isolates. In order to acquire more accurate virulence profiles, we extended the Mastenbroek differential set with Solanum spp. plants harboring reduced R gene complexity and with plants containing recently identified R genes from related but different Solanum species. In addition, a differential set of ten Genetically Modified (GM) plants harboring single late blight R genes in the same genetic background (Desiree). By analyzing the virulence spectra of recently collected isolates using both newly described differential sets, we found that the GM Desiree differential set was more accurate for isolate virulence typing than the conventional (extended) differential set. Besides, the GM Desiree differential set was shown to be useful as trap plants to isolate novel P. infestans strains and to monitor virulence towards particular R genes in P. infestans populations `on site´. Legislative restrictions are, however, limiting the use of the GM Desiree differential set.

Challenges and prospects of endosperm balance number in potato (Solanum tuberosum) improvement

Endosperm Balance Number (EBN) is a genome-specific ploidy, which is not necessarily equivalent to the chromosome ploidy. The EBN is the ‘effective ploidy’ that determines crossability in Solanum species. It varies from 1 to 4 and the two Solanum species are crossable if they have the same EBN so that maternal to paternal ratio of EBN in the endosperm is 2:1. However, a number of significant exceptions to this rule have been observed in potato (Solanum tuberosum L.). EBNs have been experimentally assigned to a number of Solanum species after crosses with standard species whose EBN was arbitrarily established. Neither specific genes nor the molecular basis of EBN have been established in potato, but 2-3 unlinked loci with equal additive effects are known to determine the EBN in Solanum species. EBN acts as a powerful isolating mechanism in the sexual reproduction of Solanum species. EBN incompatibility played an important role in the speciation of polyploids from diploids, complementing the role of 2n gametes in the polyploidy evolution of potato species. EBN has great predictive value for planning interpsecific crosses in potato. EBN of a species can be modified through sexual or somatic polyploidization. This has facilitated the transfer of useful disease and pest resistance genes from 1 EBN and 2EBN wild species to 4EBN cultivated potatoes. Besides direct, indirect gene transfer through bridge species from otherwise incompatible Solanum species has been accomplished for improving cultivated potatoes. The concept, inheritance and role of EBN in speciation, and its prospects in potato varietal improvement are reviewed in this paper. The problems associated in transfer of useful traits from wild species to cultivated potatoes due to EBN barriers are also highlighted.

Heterosis Breeding in Potato

Cultivated potato Solanum tuberosum is a tetraploid and exhibits heterosis due to multi-allelic gene action. Selfing in potato leads to inbreeding depression for a number of characters including fertility and tuber yield. An increase in heterozygosity and multi-allelic loci results in more tuber yields. A number of strategies exist to maximize heterozygosity in potato. This paper reviews the effectiveness of various strategies including selection of parents based on genetic diversity, breeding at diploid level, analytical breeding schemes, use of 2n gametes, sexual polyploidization and somatic hybridization in increasing heterozygosity. Semi-cultivated and wild species of potato are rich in genes for not only resistance to diseases and pests, but also for production of heterotic progenies. Heterosis observed on the use of Andigena, Neo-Tuberosum, S. phureja, S. stenotomum and other species in potato breeding is described. The constraints in exploitation of wild species and limitations of heterosis breeding are also analysed. It is concluded that pre-breeding of wild species for adaptability and early maturity and elimination of the undesirable tuber characters can go a long way in overcoming the existing yield barriers in potato breeding.

Gene Flow between Potato Cultivars under Experimental Field Conditions in Argentina

Wild and cultivated potatoes form a polyploid series with 2n = 2x to 2n = 6x (x = 12). In nature, they are separated by external and/or internal hybridization barriers that, when incomplete, provide opportunities for gene flow and introgression. Isolation distances estimated in one environment are not necessary extrapolable. As a starting point for pollen-mediated gene flow risk assessment in potatoes, an experiment was set up in the field in one of the major potato growing area in Argentina, with two pollen-pistil compatible tetraploid commercial cultivars with differential molecular marker patterns. The field design consisted of a 10 × 10 m central square with the pollen donor, surrounded by circles with a male sterile pollen recipient, set every 10 m up to 40 m. The crop was managed as a perennial, and data were recorded over 2 years. Seeded berries were obtained in both years at 30 and 40 m away from the center; all of them contained hybrid seeds as revealed by electrophoretic profiles. We consider that a minimal required isolation distance of 100 m or more would be more suitable for preventing undesirable gene flow in the area.

Environmental fate of soil applied neonicotinoid insecticides in an irrigated potato agroecosystem.

Since 1995, neonicotinoid insecticides have been a critical component of arthropod management in potato, Solanum tuberosum L. Recent detections of neonicotinoids in groundwater have generated questions about the sources of these contaminants and the relative contribution from commodities in U.S. agriculture. Delivery of neonicotinoids to crops typically occurs as a seed or in-furrow treatment to manage early season insect herbivores. Applied in this way, these insecticides become systemically mobile in the plant and provide control of key pest species. An outcome of this project links these soil insecticide application strategies in crop plants with neonicotinoid contamination of water leaching from the application zone. In 2011 and 2012, our objectives were to document the temporal patterns of neonicotinoid leachate below the planting furrow following common insecticide delivery methods in potato. Leaching loss of thiamethoxam from potato was measured using pan lysimeters from three at-plant treatments and one foliar application treatment. Insecticide concentration in leachate was assessed for six consecutive months using liquid chromatography-tandem mass spectrometry. Findings from this study suggest leaching of neonicotinoids from potato may be greater following crop harvest in comparison to other times during the growing season. Furthermore, this study documented recycling of neonicotinoid insecticides from contaminated groundwater back onto the crop via high capacity irrigation wells. These results document interactions between cultivated potato, different neonicotinoid delivery methods, and the potential for subsurface water contamination via leaching.

The Tvv1 retrotransposon family is conserved between plant genomes separated by over 100 million years

Combining several different approaches, we have examined the structure, variability, and distribution of Tvv1 retrotransposons. Tvv1 is an unusual example of a low-copy retrotransposon metapopulation dispersed unevenly among very distant species and is promising for the development of molecular markers. Retrotransposons are ubiquitous throughout the genomes of the vascular plants, but individual retrotransposon families tend to be confined to the level of plant genus or at most family. This restricts the general applicability of a family as molecular markers. Here, we characterize a new plant retrotransposon named Tvv1_Sdem, a member of the Copia superfamily of LTR retrotransposons, from the genome of the wild potato Solanum demissum. Comparative analyses based on structure and sequence showed a high level of similarity of Tvv1_Sdem with Tvv1-VB, a retrotransposon previously described in the grapevine genome Vitis vinifera. Extending the analysis to other species by in silico and in vitro approaches revealed the presence of Tvv1 family members in potato, tomato, and poplar genomes, and led to the identification of full-length copies of Tvv1 in these species. We were also able to identify polymorphism in UTL sequences between Tvv1_Sdem copies from wild and cultivated potatoes that are useful as molecular markers. Combining different approaches, our results suggest that the Tvv1 family of retrotransposons has a monophyletic origin and has been maintained in both the rosids and the asterids, the major clades of dicotyledonous plants, since their divergence about 100 MYA. To our knowledge, Tvv1 represents an unusual plant retrotransposon metapopulation comprising highly similar members disjointedly dispersed among very distant species. The twin features of Tvv1 presence in evolutionarily distant genomes and the diversity of its UTL region in each species make it useful as a source of robust molecular markers for diversity studies and breeding.

M6: A Diploid Potato Inbred Line for Use in Breeding and Genetics Research

M6 (Reg. No. GP-1, BS 228) is a diploid self-compatible inbred line of the potato wild relative Solanum chacoense. It is a vigorous, homozygous breeding line derived by self-pollinating the diploid wild potato relative S. chacoense for seven generations. While most wild Solanum species are self-incompatible, this clone is homozygous for the dominant self-incompatibility inhibitor gene Sli. In addition, it is homozygous for 90% of single-nucleotide polymorphism markers in the Infinium Array developed by the SolCAP consortium. M6 is vigorous and both male and female fertile, producing seeds in crosses to diploid cultivated and wild potato germplasm. These traits enable us to systematically develop diploid inbred lines, which was not possible in potato breeding until the discovery of Sli. M6 produces tubers under both short and long photoperiods, unlike other wild potato relatives. In addition, M6 has several desirable traits, including high dry matter content, good chip processing quality, and resistance to soft rot and Verticillium wilt. M6 is being used to develop recombinant inbred line populations.

Ploidy level and molecular phylogenic relationship among novel Ipomoea interspecific hybrids

Interspecific hybridization can be used to broaden the genetic base, generate novel species, postulate genetic relationships, and to introgress elite alien genes. However, interspecific hybridizations using wild parents outside the Ipomoea section Batatas are very difficult and have not been much studied. We used an improved hybridization technology to generate three novel interspecific hybrids by crossing Ipomoea batatas (L.) Lam.&amp;nbsp;&amp;times; I. hederacea Jacq., I. batatas (L.) Lam. &amp;times; I. muricata (L.) Jacq., and I. batatas (L.) Lam. &amp;times; I. lonchophylla J.M. Black. The ploidy level of the interspecific hybrids was determined by flow cytometry. The cross, I. batatas&amp;nbsp;&amp;times; I. hederacea, yielded the first artificial pentaploid Ipomoea hybrid ever. The other two hybrids, I. batatas &amp;times; I. hederacea and I. batatas &amp;times; I. muricata were tetraploid. The first two hybrids showed normal storage roots, a significant improvement in the storage roots of currently existing interspecific Ipomoea hybrids. AFLP (Amplified Fragment Length Polymorphism) molecular markers were used to explore the genetic relationship of these three novel interspecific hybrids with three other natural diploid, tetraploid, and hexaploid species of the Ipomoea section Batatas. Cluster analysis of AFLP bands showed that these three new interspecific hybrids were closely related to cultivated sweet potato (I. batatas/L./Lam.), which indicated that these novel hybrids can be used as an interspecific bridge to transfer alien genes from wild to cultivated species.

Transcriptional expression of seven key genes involved in steroidal glycoalkaloid biosynthesis in potato microtubers

Red light (10–12 lx) has been shown to induce the accumulation of steroidal glycoalkaloids (SGA) in potato (Solanum tuberosum) tubers. This study was to analyse the impact of genotypes, red light illumination and duration of incubation on SGA biosynthesis at the transcriptional level. The microtubers of wild species S. chacoense and cultivated potato varieties Shepody, Favorita, Longshu-3 and Zhuangshu-3 were tested. After 24 h incubation in the dark, the genes coding for hydroxymethylglutaryl coenzyme A reductase (hmg1, hmg2) and squalene synthase (pss1) remained relatively stable in S. chacoense and Longshu-3. The gene coding for vetispiradiene synthase (pvs1) was significantly induced in Favorita and Longshu-3. The expressions of sgt1 (solanidine galactosyl transferase) and sgt3 (rhamnosyltransferase) were induced in all tested varieties except S. chacoense. The transcript abundance of hmg1, hmg2, sgt1 and sgt3 was increased with red light illumination and incubation duration, but pvs1 was decreased. The results imply a feedback regulation system at the transcriptional level in SGA biosynthesis during red light illumination.

Effect of Insecticide Management History on Emergence Phenology and Neonicotinoid Resistance in &lt;I&gt;Leptinotarsa decemlineata&lt;/I&gt; (Coleoptera: Chrysomelidae)

Emergence phenology and fitness attributes of several Colorado potato beetle, Leptinotarsa decemlineata (Say), populations were measured under field and greenhouse conditions. Anecdotal observations by producers and pest managers in many locations of the upper Midwest increasingly suggested that select populations of Colorado potato beetle were emerging over a longer period in the spring and were less sensitive to systemic neonicotinoids in cultivated potato. These changes in emergence phenology may be related to changes in systemic insecticide concentration over time. Specifically, a prolonged period of adult emergence in the spring increases the potential of low-dose chronic exposure to systemic neonicotinoid insecticides in potato. In 2010 and 2011, our objectives were twofold: 1) establish a common garden experiment to compare the emergence phenology of Colorado potato beetle populations uniquely managed with variable insecticide inputs, and 2) measure postdormancy fitness of emerged adult beetles from among these selected populations. Cumulative adult emergence was modeled with logistic regression. Results from this study found no clear evidence for direct relationships between phenology and management history or resistance. Differences in reproductive capacity, sex ratio, and body size were apparent in some instances. However, these results did not uniformly correspond to one specific form of potato pest management tested here. In this study, long-term reliance on systemic insecticides for Colorado potato beetle control did not serve as a strong predictor for variable life history for selected populations in Wisconsin.

Pollen-mediated gene flow from a commercial potato cultivar to the wild relativeS. chacoenseBitter under experimental field conditions in Argentina

The common potato, Solanum tuberosum ssp. tuberosum (tbr, 2n = 4x = 48; 4EBN), has many closely related wild tuber-bearing species. Around 28 to 35 of them spontaneously grow in Argentina overlapping, in some areas, with the crop and/or experimental transgenic potatoes. Although it is well proven that hybridization barriers in potatoes can be incomplete, information on gene flow between cultivated and wild germplasm is scarce. Thus, a gene flow field experiment with a circular array was set up in Balcarce, Argentina, in 2009, and evaluated over two seasons. The tetraploid tbr cultivar Huinkul MAG and one compatible cloned genotype of the related wild potato S. chacoense Bitter (chc, 2n = 2x = 24; 2EBN), which produced 2n eggs, were used, respectively, as pollen donor and receptor. Berries with hybrid seeds - as revealed by ploidy and RAPD profiles - were obtained in one season, at 30 m from the pollen donor. These results reinforce others previously obtained with the same pollen donor and a male sterile tbr cultivar in a similar array, pointing out to the need of increasing isolation distances in areas of overlap between cultivated and wild potato germplasm to prevent or minimize undesirable pollen-mediated gene flow.

Application of a PCR-Based Cytoplasm Genotyping Method for Phylogenetic Analysis in Potato

We previously developed five polymerase chain reaction-based markers (T, S, SAC, D, and A) to distinguish potato cytoplasms into six types (M, P, A, W, T, and D). As the applicability of this genotyping method for phylogenetic studies had been questioned, we applied this method to species distantly related to cultivars (four accessions of two tomato species, and 176 accessions of 29 Solanum species). The T marker uncovered two insertions, which, along with a unique S marker band, supported independency of series Piurana. The A and D markers generated unique bands to A- and D-type cytoplasms, respectively, but the SAC marker generated a similar banding pattern to the cytoplasms of both cultivated and their distantly related species. Consequently, while the cytoplasm type definition is validated only among cultivated potatoes and their closely related wild species, the developed markers, with the exception of the SAC marker, could provide useful phylogenetic information.