High regrowth of potato crop wild relative genotypes after cryogenic storage.

Potatoes are consumed by millions of people and are the survival food in several countries. Cultivated varieties of potato (Solanum tubersosum L.) are results of selection and crossing of many wild species. Only 8-13% of wild potato species used for food are preserved by either in situ or ex situ methods. The U.S. National Potato Germplasm Collection maintains over 5900 accessions, of which 75% are crop wild relatives (CWR). The objective of the study was to investigate regrowth of cryogenically stored clonal propagules (shoot tips) of selected CWR accessions maintained in the collection. Sixty-nine accessions from 30 Solanum species and six accessions that are not yet assigned to a species were cryopreserved by a droplet vitrification method at the NLGRP. The post cryopreservation regrowth varied from 40 to 100% (average 68%) but was not significantly different between the tested accessions. Regrowth of six accessions tested after 10 years of cryogenic storage was between 35 and 90% (average 66%) and was significantly different from their initial regrowth (average 87%); the largest viability loss was in S. condolleanum; but for the other five accessions the regrowth was between 45 and 90% (average 72%) and suggested at least 10 years of successful storage in LN was possible. Twelve potato wild species cryopreserved in this study were reported in literature as important for developing cultivated varieties for changed weather conditions.

Evidence for human-caused founder effect in populations of Solanum jamesii found at archaeological sites: I. Breeding experiments and the geography of sexual reproduction.

PREMISE: Plant domestication can be detected when transport, use, and manipulation of propagules impact reproductive functionality, especially in species with self-incompatible breeding systems. METHODS: Evidence for human-caused founder effect in the Four Corners potato (Solanum jamesii Torr.) was examined by conducting 526 controlled matings between archaeological and non-archaeological populations from field-collected tubers grown in a greenhouse. Specimens from 24 major herbaria and collection records from >160 populations were examined to determine which produced fruits. RESULTS: Archaeological populations did not produce any fruits when self-crossed or outcrossed between individuals from the same source. A weak ability to self- or outcross within populations was observed in non-archaeological populations. Outcrossing between archaeological and non-archaeological populations, however, produced fully formed, seed-containing fruits, especially with a non-archaeological pollen source. Fruit formation was observed in 51 of 162 occurrences, with minimal evidence of constraint by monsoonal drought, lack of pollinators, or spatial separation of suitable partners. Some archaeological populations (especially those along ancient trade routes) had records of fruit production (Chaco Canyon), while others (those in northern Arizona, western Colorado, and southern Utah) did not. CONCLUSIONS: The present study suggests that archaeological populations could have different origins at different times-some descending directly from large gene pools to the south and others derived from gardens already established around occupations. The latter experienced a chain of founder events, which presumably would further reduce genetic diversity and mating capability. Consequently, some archaeological populations lack the genetic ability to sexually reproduce, likely as the result of human-caused founder effect.

Single Nucleotide Polymorphism (SNP) markers associated with high folate content in wild potato species.

Micronutrient deficiency, also known as the hidden hunger, affects over two billion people worldwide. Potato is the third most consumed food crops in the world, and is therefore a fundamental element of food security for millions of people. Increasing the amount of micronutrients in food crop could help alleviate worldwide micronutrient malnutrition. In the present study, we report on the identification of single nucleotide polymorphism (SNP) markers associated with folate, an essential micronutrient in the human diet. A high folate diploid clone Fol 1.6 from the wild potato relative Solanum boliviense (PI 597736) was crossed with a low/medium folate diploid S. tuberosum clone USW4self#3. The resulting F1 progeny was intermated to generate an F2 population, and tubers from 94 F2 individuals were harvested for folate analysis and SNP genotyping using a SolCap 12K Potato SNP array. Folate content in the progeny ranged from 304 to 2,952 ng g-1 dry weight. 6,759 high quality SNPs containing 4,174 (62%) polymorphic and 2,585 (38%) monomorphic SNPs were used to investigate marker-trait association. Association analysis was performed using two different approaches: survey SNP-trait association (SSTA) and SNP-trait association (STA). A total of 497 significant SNPs were identified, 489 by SSTA analysis and 43 by STA analysis. Markers identified by SSTA were located on all twelve chromosomes while those identified by STA were confined to chromosomes 2, 4, and 6. Eighteen of the significant SNPs were located within or in close proximity to folate metabolism-related genes. Forty two SNPs were identical between SSTA and STA analyses. These SNPs have potential to be used in marker-assisted selection for breeding high folate potato varieties.

Antiproliferative activity and cytotoxicity of Solanum jamesii tuber extracts on human colon and prostate cancer cells in vitro.

Some tuber-bearing wild potato species are reportedly higher in potential health-promoting traits, such as antioxidant activity (AOA) and total phenolic content (TP), than commercial cultivars; therefore, they could be used as parental material in breeding for high AOA and TP. However, using wild species might result in progenies that are toxic for human consumption because of the presence of high total glycoalkaloids (TGAs) and other unknown compounds. Therefore, wild potato accessions should be screened for cytotoxicity before their introduction into breeding programs. The objective of this study was to investigate antiproliferative activity and cytotoxicity of tuber extracts from 15 Solanum jamesii accessions on human HT-29 colon and LNCaP prostate cancer cell lines in vitro. Also, correlations among AOA, TP, TGA, and antiproliferative activity were determined. The tuber extracts significantly inhibited proliferation of HT-29 and LNCaP cell lines and were not cytotoxic to the cells compared to the control (DMSO). The antiproliferative activity exhibited by tuber extracts was not due to necrosis, because the amount of lactate dehydrogenase (LDH) released from cells incubated with the extracts was not significantly different from that released from cells incubated without extracts (control). Colon cancer cells were more responsive to tuber extract treatment than prostate cancer cells. In both HT-29 and LNCaP cells, there were no observable significant correlations between antioxidant activity (DPPH and ABTS) and inhibition of cell proliferation or between TP and cell proliferation inhibition. Also, glycoalkaloids did not exhibit significant correlations with the inhibition of cancer cell proliferation. Findings of this study show that S. jamesii accessions probably pose no cytotoxic effects when used as parental material in improving the nutritional value of potato cultivars. Correlation results, along with cell proliferation data, suggest that not only the compounds measured in this study but also other bioactive compounds present in the matrix acting additively or synergistically may be more responsible for the antiproliferative effects of potato tuber extracts than higher concentrations of a single or group of compounds.

The R1 resistance gene cluster contains three groups of independently evolving, type I R1 homologues and shows substantial structural variation among haplotypes of Solanum demissum.

Cultivated and wild potatoes contain a major disease-resistance cluster on the short arm of chromosome V, including the R1 resistance (R) gene against potato late blight. To explore the functional and evolutionary significance of clustering in the generation of novel disease-resistance genes, we constructed three approximately 1 Mb physical maps in the R1 gene region, one for each of the three genomes (haplotypes) of allohexaploid Solanum demissum, the wild potato progenitor of the R1 locus. Totals of 691, 919 and 559 kb were sequenced for each haplotype, and three distinct resistance-gene families were identified, one homologous to the potato R1 gene and two others homologous to either the Prf or the Bs4 R-gene of tomato. The regions with R1 homologues are highly divergent among the three haplotypes, in contrast to the conserved flanking non-resistance gene regions. The R1 locus shows dramatic variation in overall length and R1 homologue number among the three haplotypes. Sequence comparisons of the R1 homologues show that they form three distinct clades in a distance tree. Frequent sequence exchanges were detected among R1 homologues within each clade, but not among those in different clades. These frequent sequence exchanges homogenized the intron sequences of homologues within each clade, but did not homogenize the coding sequences. Our results suggest that the R1 homologues represent three independent groups of fast-evolving type I resistance genes, characterized by chimeric structures resulting from frequent sequence exchanges among group members. Such genes were first identified among clustered RGC2 genes in lettuce, where they were distinguished from slow-evolving type II R-genes. Our findings at the R1 locus in S. demissum may indicate that a common or similar mechanism underlies the previously reported differentiation of type I and type II R-genes and the differentiation of type I R-genes into distinct groups, identified here.