Solanum bill-hookeri: New wild potato species from Peru

There is presented the original diagnosis ofSolanum bill-hookeri from the series Tuberosa (Sect. Petota), a new wild tuber-bearing diploid (2n=2x=24) species from Peru, named in honor of Dr. William J. Hooker.     

Solanum sawyeri,a new wild potato species from the Peruvian tropics

During my ongoing study of the systematics of the Peruvian wild tuberbearing Solanums I have reviewed some rare and interesting collections made in the past which previously had seemed very difficult to classify correctly. After reviewing and comparing some of these specimens with other collections gathered in the main herbaria of U.S.A. and Europe, I am convinced of the existence of some still undescribed species such as the one I am presenting here under the name ofSolanum sawyeri in honor of Dr. Richard Leander Sawyer, promoter and founder of The International Potato Center located at Lima, Peru. Solanum sawyeri, is acclimated to the warm humid tropics of Southern Peru. It grows in forests of the low land regions of the Eastern province of Urubamba in the Department of Cusco and thereafter might serve as a source of breeding material for those who want to select potato cultivars for the low land tropics. This species belongs to the series Tuberosa with 2n = 2× = 24 chromosomes.     

Solanum antacochense,a new wild Peruvian species

The largest concentration of wild tuber-bearingSolanums in the Western Hemisphere is located in the Andean region of Perú. However, in spite of the many potato collecting expeditions which have carried out extensive field work in the past, there still remain new species to be presented to science for the first time.Solanum antacochense, from the series tuberosa, a diploid species (2n = 2x = 24 chromosomes) native to Perú described here, is one of them.     

Wild potato collecting expedition in Southern Peru (Departments of Apurímac, Arequipa, Cusco, Moquegua Puno, Tacna in 1998: Taxonomy and new genetic resources

Peru has 103 taxa of wild potatoes (species, subspecies, varieties, and forms) according to Hawkes (1990; modified by us by a reduction of species in theSolanum brevicaule complex) and including taxa described by C. Ochoa since 1989. Sixty-nine of these 103 taxa (67% ) were unavailable from any of the world’s genebanks and 85 of them (83%) had less than three germplasm accessions. We conducted a collaborative Peru (INIA), United States (NRSP-6), and International Potato Center (CIP) wild potato (Solanum sect.Petota) collecting expedition in Peru to collect germplasm and gather taxonomic data. This is the first of a series of planned expeditions from 1998–2002. We collected from February 18 to April 18, 1998, in the southern departments of Apurímac, Arequipa, Cusco, Moquegua, Puno, and Tacna. We made 57 germplasm collections, including 14 taxa that are the first available as germplasm for any country (Solanum aymaraesense, S. chillonanum, S. incasicum, S. megistacrolobum subsp.megistacrolobum f. purpureum, S. longiusculus, S. multiflorum,S. pillahuatense, S. sawyeri, S. sandemanii, S. tacnaense, S. tarapatanum, S. urubambae, S. velardei, S. villuspetalum), and two additional taxa that are the first available for Peru but with germplasm from Bolivia (S. megistacrolobum subsp.toralapanum, S. yungasense). Collections also were made for the rare taxaS. acroscopicum, S. buesii, S. limbaniense, andS. santolallae. Our collections suggest the following minimum synonymy may be needed for Peruvian potatoes:S. sawyeri as a synonym ofS. tuberosum;S. hawkesii andS. incasicum as synonyms ofS. raphanifolium;S. multiflorum andS. villuspetalum as synonyms ofS. urubambae.     

Solanum neovavilovii: A new wild potato species from Bolivia

Regions such as Mexico, where important sources of resistance to late blight of potato have been found, have also been widely explored for wild potatoes. In contrast, Bolivia has received little attention. Although more than 50 names have been published for wild species from Bolivia, a great majority of these only constitute synonyms. Nevertheless, our exploratory work shows that finding new species is still possible in the isolated and remote localities of this country as demonstrated by the present new species,Solarium neovavilovii (Sect. Petota), dedicated to the great Russian scientist Nicolai I. Vavilov. Solatium neovavilovii is a diploid species (2n = 2x = 24 chromosomes) and belongs to the Conicibaccata series. Its preferred habitat is in thickets of “Ceja de Selva,” an ecological formation which is humid, cold, and frequently foggy, typical of the eastern region of the Andes. Its type locality has an altitude of 3000 m. This species is closely related toSolanum limbaniense Ochoa from south east Perú.     

Solanum bombycinum,a new tuber-bearing tetraploid species from Bolivia

It is probable that the wild potatoes from Bolivia are the least known of all the Andean region. Although approximately 50 species have been described from this country since Dunal, 1852, a great majority of these are synonyms. Nevertheless, in some remote and unexplored regions of Bolivia, it is still possible to find new material, as demonstrated by the new species described herein. Solanum bombycinum was found in the north-northwest part of the Department of La Paz, Province of Caupolican, at an altitude of 2000 m, living among shrubby woods in a humid lowland tropic. This wild species constitutes a particularly interesting discovery, as it represents the southern most species from South America described to date for the series Conicibaccata, and, furthermore, because its ploidy level is 2n = 4x = 48 chromosomes in a series usually having 2n = 2x = 24.     

Species relationships between a wild tetraploid potato species,Solanum acaule bitter, and its related species as revealed by rflps of chloroplast and nuclear DNA

Solanum acaule Bitter is a wild, disomic tetraploid potato species widely distributed in the South America. In this study, species relationships between eight accessions ofS. acaule and 108 accessions of 27 morphologically closely related species were investigated using chloroplast and nuclear DNA RFLPs. Chloroplast DNA types were determined for most of the accessions based on restriction digestion patterns of entire chloroplast DNA. C type chloroplast DNA was common inS. acaule andS. albicans (a hexaploid derivative fromS. acaule), which was also found inS. megistacrolobum, S. sanctae-rosae,S. raphanifolium, and several other Peruvian species in seriesTuberosa. Nuclear DNA was analyzed by Southern hybridization with 31 single-copy RFLP probes. One hundred and thirty-four bands were scored, from which a UPGMA dendrogram was constructed to show overall similarities among accessions.Solanum acaule andS. albicans (andS. demissum) formed a cluster with a high similarity, and then, this group was clustered withS. megistacrolobum andS. sanctae-rosae. The resulting cluster was well separated from other clusters. Thus, we suggest that an initial tetrasomic tetraploid arose from eitherS. megistacrolobum orS. sanctae-rosae. Interestingly, a Mexican hexaploid speciesS. demissum showed the closest similarity toS. acaule andS. albicans, suggesting that they shared a common ancestry.     

Taxonomy and new collections of wild potato species in Central and Southern Peru in 1999

Peru contains about half of the described wild potato taxa, and many of these are not yet preserved in genebanks. This paper reports results of the second of a series of five planned collecting expeditions to Peru. Collections were made in the central Peruvian departments of Ancash, Huancavelica, La Libertad, and Lima, from March 8 to April 25,1999. They follow collections in 1998 in the southern Peruvian departments of Apurimac, Arequipa, Cusco, Moquegua, Puno, and Tacna. We collected 101 germplasm accessions, including first germplasm collections of the following 22Solanum taxa:Solanum amayanum, S. anamatophilum, S. arahuayum (lost in germplasm increase),S. augustii, S. bill- hookeri, S. cantense, S. chavinense, S. chomatophilum var. subnivale, S. chrysoflorum, S. gracilifrons, S. hapalos um, S. huarochiriense, S. hypacrarthrum, S.jalcae, S. moniliforme, S. multiinterruptum f. longipilosum, S. multiinterruptum var. machaytambinum, S. peloquinianum, S. rhombilanceolatum, S. simplicissimum, S. taulisense (lost in germplasm increase), andS. wittmackii. In addition, new collections were made of the under-collected speciesS. hastiforme (three collections). The above taxonomy is that used in planning our expedition, that we compare to a new treatment of Peruvian wild potatoes published by C. Ochoa in 1999. This paper reports the collection and new species identifications of the 1999 collections, and germplasm conservation and survival of the 1998 and 1999 collections. In addition, chromosome counts are provided for 134 accessions from the 1998 and 1999 expeditions, including first reports forS. chomatophilum var. subnivale (2n = 2x = 24),S. megistacrolobum subsp.purpureum (2n = 2x = 24), andS. multiinterruptum var.multiinterruptum f.albiflorum (2n = 2x = 24); we also report the first triploid count of an accession ofS. immite.     

Frost resistant potato hybrids viaSolanum acaule,Bitt. Diploid-Tetraploid crosses

Solanum juzepczukii Buk. andSolanum curtilobum Juz. et Buk. are two important primitive cultivated species of potato which are planted in the highlands of Peru and Bolivia. Little natural variation exists within these species. Crosses were made to artificially recreate these species using tetraploid cultivated potatoes as female parents and triploids derived from acaule-diploid crosses as males. The new hybrids were tetraploid (2n = 48) with a high degree of heterosis and variability, and several potential cultivated clones possessing valuable characters such as yield, earliness, frost tolerance and good tuber type were selected.     

Germplasm transfer from the wild tetraploid speciesSolanum acaule bitt. to the cultivated potato,S. tuberosum L. using 2N eggs

Solanum acaule Bitt. (acl ¹, 2n=4x=48 and 2n=6x=72) is a wild potato species in which resistance to adverse biotic and abiotic agents has been found. The tetraploid subspeciesacaule andaemulans cannot be easily crossed with the common potato,S. tuberosum L. Grouptuberosum (tbr, 2n=4x=48) because the development of the endosperm in the hybrid seed is abnormal. Since 4xacl behaves as a diploid in intra and interploidy crosses, it was postulated that the hybridization barrier withtbr could be overcome if the wild species produced 2n gametes. One hundred and ninety-seven plants of 4xacl (22 introductions) were screened for pollen of heterogeneous size; only two plants produced this type of pollen, with 3% and 5% of pollen in the large class, respectively. On the other hand, 427 plants (47 introductions) were screened for 2n eggs through controlled crosses withtbr. Forty-one plants (13 introductions) produced 219 berries of which 46 contained at least one plump seed. Seed from berries with low seed set gave rise to hexaploid hybrids possibly through the functioning of 2n eggs from 4xacl. A sample of these hybrids was successfully backcrossed as female parents totbr, giving rise to 5x BC₁ progenies. These BC₁ progenies could be easily back-crossed totbr, yielding tetraploid or near tetraploid BC₂ plants.     

A new wild potato mutant inSolanum stoloniferum Schltdl. Lacking purple pigment

A sample ofSolanum stoloniferum Schltdl. (reclassified fromSolanum fendleri A. Gray), PI 620874, was collected by the authors from a previously undocumented site in the Patagonia Mountains of southern Arizona in September 2001. When original seed was grown at the US Potato Genebank, two of 25 seedlings produced white flowers. Upon closer inspection they were found to be completely without purple pigmentation on the tubers, stems, and underside of leaves—a characteristic previously unknown in this species and rare in wild potato overall.Solanum stoloniferum, like other species of series Longipedicellata (LON), is a disomic tetraploid. Results of crossing trials were consistent with the most simple genetic explanation for this phenotype: a recessivep allele at the P locus, making the mutant (pp pp), or “Purple-less” abbreviated “P-less.” P-less plants were testcrossed with nearly 200 other LON populations originating across the U.S.A. and Mexico to make BC1 generations that had either one-half or one-quarter P-less seedlings. Surprisingly, about one-third of the populations, and from widely distributed origins, produced one-half P-less progeny, indicating that they also possess the recessive allele on one genome. Since this mutant has not been confirmed as an allele at the original P locus, its designation with the same allele symbols in this report (P andp) is provisional. This discovery of the widespreadp allele in LON and P-less mutants could provide a simple, unambiguous seedling marker for study of gene flow and dispersion, pollinator behavior in the wild, gene expression interactions between homeologous genomes, and chromosome pairing control.     

Solanum serratoris: a new wild ecuadorian potato species

A new wild Ecuadorian tuber-bearing species ofSolanum,S. serratoris (SeriesTuberosa, Sect.Petota is described and illustrated. This species from the eastern-Andean region of provincia Morona-Pastaza has been named in honor of Dr. Richard L. Sawyer, founder of the International Potato Center, Lima, Peru.     

Tracking the R Mc1 Gene for Resistance to Race 1 of Columbia Root-Knot Nematode (Meloidogyne chitwoodi) in Three Mexican Wild Potato Species with Different Ploidies

Resistance to Columbia Root-knot nematode was discovered in three wild species in a polyploidy series, Solanum bulbocastanum (2n?=?2x), .S. fendleri (2n?=?4x), and S. hougasii, 2n?=?6x, respectively. After several generations of introgression into the cultivated gene pool, a single dominant monogene conditioning resistance to root propagation of race 1 of CRKN was theorized to be acting in breeding lines derived from each species. Coincidently, sequence tagged sites (STS) and cleaved amplified polymorphic site (CAPS) markers that associated with resistance with S. bulbocastanum were found to be informative in other segregating breeding populations regardless of the source of the gene. The utility of the markers across ploidies suggests that the original gene and genome of S. bulbocastanum or a modern derivative, is present in S. fendleri and S. hougasii. In this polyploidy series, knowledge that the S. bulbocastanum genome is the original source of useful genes guides future germplasm surveyors to search first and most intensively in the primitive Mexican diploid species that may have served as the contributor of a genome to descendants harboring this genome at higher ploidies.     

Solanum burtonii,a new wild potato species from Ecuador

Before 1960 knowledge of the wild potato species from Ecuador was very limited. We knew only three tuber bearing species:Solanum paucijugum Bitt.,S. pichinchense Bitt. et Sodiro andS. solisii Hawkes. However, during the last two decades information has increased greatly with the researches of Donovan S. Correll and the writer. So, to the aforementioned species we must addS. albornozii, S. cyanophyllum, S. regularifolium, S. suffrutescens andS. minutifoliolum found by Correll;S. calacalinum, S. correlli andS. tundalomense discovered by me. With this opportunity, I present another new wild potato species from Ecuador,Solarium burtonii, named in honor of Prof. Dr. W. Glynn Burton as a recognition to his outstanding contributions in the field of potato physiology.     

Solanum sect. petota in Guatemala; Taxonomy and genetic resources

There are five wild potato species in Guatemala:Solanum agrimonifolium,S. bulbocastanum,S. clarum,S. demissum, andS. morelliforme. We conducted a collecting expedition there from September 11 to November 5, 1995. The goals of the expedition were to gather field data for taxonomic studies of the five species of Guatemalan wild potatoes and to collect potato germplasm. Our 43 true seed collections nearly quadruple the available wild potato germplasm for Guatemala, provide germplasm from most previously known localities, and add new ones. We provide a systematic treatment of Guatemalan wild potatoes, geographic and logistical data for collecting wild potatoes in Guatemala, statistics on human population growth and deforestation to help explain decline of wild potato populations, recommend areas for future collecting, and suggest two areas as in-situ reserves for wild potatoes     

Solanum irosinum,new Peruvian tuber bearing species resistant toPhytophthora infestans

The greatest variety of tuberiferousSolanums of the Western Hemisphere is found in the Peruvian Andes, where, in spite of extensive explorations, new material is still found, such as the species which is here presented under the name ofSolanum irosinum. This is a diploid species; that is, it has 2n = 2x = 24 chromosomes and belongs to the Conicibaccata series. It could be used as a new source of breeding because it offers great resistance to attacks byPhytophthora infestans, the most serious disease of potato crops in the world.     

Weed hosts of the tobacco rattle virus in Idaho

The corky ringspot disease of potato (Solanum tuberosum) caused by the tobacco rattle virus (TRV) is a serious problem in certain Idaho localities. To investigate natural TRV sources, weeds and plants from rotation crops were randomly collected from six fields with a history of corky ringspot symptoms. Transmission trials, Ouchterlony agar double-diffusion tests, and electron-microscopy showed evidence of TRV in three Idaho counties (Fremont, Ada, and Canyon). Inoculations were made from 27 species and TRV was recovered from the roots of three:Solanum nigrum, Brassica campestris, andErodium cicutarium. Solanum nigrum was the most consistent source of TRV and it generally incited the severest symptoms onNicotiana tabacum (Samsun NN). The results show thatS. nigrum, besides being an important wild host of TRV, may be a useful naturallyoccurring bait plant for detection of TRV in field soils.     

Progress in Mapping and Cloning Qualitative and Quantitative Resistance Against <Emphasis Type="Italic">Phytophthora infestans</Emphasis> in Potato and Its Wild Relatives

Cultivated potato is susceptible to many pests and pathogens, none of which is more of a threat to potato agriculture than the late blight disease, caused by the oomycete Phytophthora infestans (Mont.) de Bary. To date all efforts to thwart this most adaptive of pathogens have failed, and early attempts to deploy ‘R genes’ introgressed from the wild Mexican hexaploid Solanum demissum ended in abject failure. With the advent of facile gene mapping and cloning, allied to knowledge of plant resistance gene structure, renewed efforts are leading to mapping and isolation of new sources of late blight resistance in potato wild species, many of which are being performed under the auspices of the BIOEXPLOIT project (Sub-project 2). We document recent advances in late blight resistance gene mapping and isolation, and postulate how these genes, allied to knowledge of pathogen effectors and their recognition specificity, may greatly enhance our chances of halting the progress of late blight disease in potato crops worldwide.     

Selection and Validation of an AFLP Marker Core Collection for the Wild Potato Solanum microdontum

Solanum microdontum is a diploid potato species with features that make it a good model for research into management and use of germplasm in the genebank. Its taxonomic status is unambiguous and it is in the taxonomic series of wild species closest to cultivated forms. It is represented by about 100 populations in the genebank—not too many for comprehensive evaluation, yet not too few to make prioritization of the most valuable populations worthwhile. This species is also particularly rich in desirable traits, often exhibiting very broad segregation. We here report use of DNA markers for selection of a core set of populations, and assessing whether that core captures populations with the most desirable evaluation results for economic traits. DNA was extracted from bulks of 27 plants from each of 94 populations to generate AFLPs. A total of 1,741 informative loci were detected. AFLP loci were treated as though they were traits, with the banded condition considered to be the desired state to include in a core set. At least one band unique to a population was present in 45 populations, and these 45 populations together captured 98 % of all bands. Adding another 14 populations for a core of 59 populations captured 100 % of bands. This core set was assessed for whether it encompassed those populations known to have useful traits, including nutritional and quality components; and disease, stress and pest resistances. As with AFLP bands, 25 of 26 of the most desirable phenotypic traits were also found in populations in the core set of 59 populations. The most desirable status of 3 traits is lost by selecting a core of 45 populations. We conclude that these core sets would be a rational starting point when prospecting for new useful traits in microdontum.