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Summary: The origin of sweetpotato, a hexaploid species, is poorly understood, partly because the identity of its tetraploid progenitor remains unknown. In this study, we identify, describe and characterize a new species of Ipomoea that is sweetpotato's closest tetraploid relative known to date and probably a direct descendant of its tetraploid progenitor.We integrate morphological, phylogenetic, and genomic analyses of herbarium and germplasm accessions of the hexaploid sweetpotato, its closest known diploid relative Ipomoea trifida, and various tetraploid plants closely related to them from across the American continent.We identify wild autotetraploid plants from Ecuador that are morphologically distinct from Ipomoea batatas and I. trifida, but monophyletic and sister to I. batatas in phylogenetic analysis of nuclear data.We describe this new species as Ipomoea aequatoriensis T. Wells & P. Muñoz sp. nov., distinguish it from hybrid tetraploid material collected in Mexico; and show that it likely played a direct role in the origin of sweetpotato's hexaploid genome. This discovery transforms our understanding of sweetpotato's origin. See also the Commentary on this article by Särkinen et al., 234: 1107–1108. [ABSTRACT FROM AUTHOR]

The in trust sweetpotato collection housed by the International Center of Potato (CIP) is one of the largest assemblages of plant material representing the genetic resources of this important staple crop. The collection currently contains almost 6,000 accessions of Ipomoea batatas (cultivated sweetpotato) and over 1,000 accessions of sweetpotato crop wild relatives (CWRs). In this study, the entire cultivated collection (5,979 accessions) was genotyped with a panel of 20 simple sequence repeat (SSR) markers to assess genetic identity, diversity, and population structure. Genotyping and phenotyping of in vitro plantlets and mother plants were conducted simultaneously on 2,711 accessions (45% of the total collection) to identify and correct possible genetic identity errors which could have occurred at any time over the thirty plus years of maintenance in the in vitro collection. Within this group, 533 accessions (19.6%) had errors in identity. Field evaluations of morphological descriptors were carried out to confirm the marker data. A phylogenetic tree was constructed to reveal the intraspecific relationships in the population which uncovered high levels of redundancy in material from Peru and Latin America. These genotypic data were supported by morphological data. Population structure analysis demonstrated support for four ancestral populations with many of the accessions having lower levels of gene flow from the other populations. This was especially true of germplasm derived from Peru, Ecuador, and Africa. The set of 20 SSR markers was subsequently utilized to examine a subset of 189 accessions from the USDA sweetpotato germplasm collection and to identify and reconcile potential errors in the identification of clones shared between these collections. Marker analysis demonstrated that the USDA subset of material had 65 unique accessions that were not found in the larger CIP collection. As far as the authors are aware, this is the first report of genotyping an entire sweetpotato germplasm collection in its entirety. [ABSTRACT FROM AUTHOR]

Members of the highly polyphagous Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) species complex cause major crop damage by feeding and by transmitting plant viruses. The Middle East-Asia Minor 1 (MEAM1) of the B. tabaci complex is by far the most problematic whitefly affecting crops including cultivated watermelon (Citrullus lanatus ; Cucurbitaceae: Cucurbitales). Watermelon cultivars share a narrow genetic base and are highly susceptible to whiteflies. We studied the potential of C. ecirrhosus , a perennial desert species that can be hybridized with C. lanatus , as a source of whitefly resistance for cultivated watermelon. The results of this study indicate that C. ecirrhosus offers resistance (although not total) against the MEAM1 B. tabaci based on, at least, antibiosis and antixenosis. Whitefly performance concerning developmental survival, body size attainment, and nonpreference were suppressed on C. ecirrhosus compared with the watermelon cultivar 'Sugar Baby'. Also, our olfactometer results indicated that the adults were less attracted to leaf volatiles of C. ecirrhosus. Although there is a pungent odor associated with the leaves of C. ecirrhosus , the leaf volatiles had no toxic effect on adult whitefly survival as compared with cultivated watermelon. We also demonstrated that plants of C. ecirrhosus can be clonally propagated from vine cuttings of the parent plant. Using traditional breeding procedures, C. ecirrhosus was hybridized with C. lanatus and viable F1 and F2 seeds were produced. This is the first report of pest resistance in C. ecirrhosus. This wild species offers a source of resistance against whiteflies for the improvement of cultivated watermelon. [ABSTRACT FROM AUTHOR]

Sweetpotato (Ipomoea batatas) plays a critical role in food security and is the most important root crop worldwide following potatoes and cassava. In the United States (US), it is valued at over $700 million USD. There are two sweetpotato germplasm collections (Plant Genetic Resources Conservation Unit and US Vegetable Laboratory) maintained by the USDA, ARS for sweetpotato crop improvement. To date, no genome-wide assessment of genetic diversity within these collections has been reported in the published literature. In our study, population structure and genetic diversity of 417 USDA sweetpotato accessions originating from 8 broad geographical regions (Africa, Australia, Caribbean, Central America, Far East, North America, Pacific Islands, and South America) were determined using single nucleotide polymorphisms (SNPs) identified with a genotyping-by-sequencing (GBS) protocol, GBSpoly, optimized for highly heterozygous and polyploid species. Population structure using Bayesian clustering analyses (STRUCTURE) with 32,784 segregating SNPs grouped the accessions into four genetic groups and indicated a high degree of mixed ancestry. A neighbor-joining cladogram and principal components analysis based on a pairwise genetic distance matrix of the accessions supported the population structure analysis. Pairwise F ST values between broad geographical regions based on the origin of accessions ranged from 0.017 (Far East – Pacific Islands) to 0.110 (Australia – South America) and supported the clustering of accessions based on genetic distance. The markers developed for use with this collection of accessions provide an important genomic resource for the sweetpotato community, and contribute to our understanding of the genetic diversity present within the US sweetpotato collection and the species. [ABSTRACT FROM AUTHOR]

The United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Plant Genetic Resources Conservation Unit in Griffin, GA maintains the United States germplasm collection for Ipomoea spp. (Convolvulaceae). During 2012-2014, 737 sweetpotato, Ipomoea batatas (L.) Lam., plant introductions (PI) were acquired as tissue-culture plantlets and then acclimated to greenhouse conditions at the USDA, ARS, U. S. Vegetable Laboratory (USVL), Charleston, SC. Single plants were transferred to plastic-covered plant beds to produce cuttings for replicated field trials. Storage roots were harvested from 690 PIs grown in the field and 695 PIs grown in pots. Color coordinates were obtained for each PI using a tristimulus colorimeter. Hue angle values (h*) ranged from 8.2° to 88.3° (x¯ = 54.9°) for the periderm (peel or skin) of field-grown storage roots (n = 690 PIs) and − 9.4° (= 350.6°) to 96.2° (x¯ = 51.3°) for pot-grown roots (n = 695 PIs). The red-green coordinate (a*) ranged from 0.8 to 30.7 (x¯ = 12.8) for the periderm of field-grown roots and − 2.0 to 44.9 (x¯ = 16.1) for pot-grown roots. The yellow-blue coordinate (b*) ranged from 2.8 to 33.1 (x¯ = 19.4) for the periderm of field-grown roots and − 7.4 to 38.1 (x¯ = 19.3) for pot-grown roots. Color saturation (chroma, C*) ranged from 13.7 to 35.8 (x¯ = 24.9) for the periderm of field-grown roots and 14.9-45.5 (x¯ = 29.3) for pot-grown roots. Lightness (white-black, L*) ranged from 32.6 to 81.7 (x¯ = 54.6) for the periderm of field-grown roots and 32.1-88.2 (x¯ = 64.0) for pot-grown roots. Hue angles ranged from − 13.1° (= 346.9°) to 100.9° (x¯ = 80.9°) for the stele (flesh) of field-grown storage roots (n = 672 PIs) and − 29.9° to 103.5° (x¯ = 81.6°) for pot-grown roots (n = 676 PIs); a* ranged from − 5.6 to 35.0 (x¯ = 8.0) for the stele of field-grown roots and − 6.0 to 41.0 (x¯ = 7.6) for pot-grown roots; and b* ranged from − 7.7 to 56.1 (x¯ = 34.6) for the stele of field-grown roots and − 12.6 to 56.1 (x¯ = 31.8) for pot-grown roots. C* ranged from 12.7 to 65.8 (x¯ = 37.2) for the stele of field-grown roots and 8.9-65.7 (x¯ = 34.5) for pot-grown roots; and L* ranged from 27.8 to 91.1 (x¯ = 77.7) for the stele of field-grown roots and 28.2-91.9 (x¯ = 80.4) for pot-grown roots. There were significant relationships between stele color (h*) and percent dry matter, with orange stele having a significantly lower % dry matter (x¯ = 25.6%, n = 183) compared with roots with cream/white stele (x¯ = 30.8%, n = 373). There appears to be wide genetic diversity for root color characteristics for the United States sweetpotato germplasm collection. [ABSTRACT FROM AUTHOR]

Scanning electron and light microscopy were used to examine pollen of the currently recognized species (and forms) within the genus Citrullus (Cucurbitaceae). Materials examined included: C. lanatus (Thunb.) Matsum. & Nakai, the citron (C. amarus Schrad.), the egusi [C. mucosospermus (Fursa) Fursa], C. colocynthis (L.) Schrad., C. rehmii De Winter, C. ecirrhosus Cogn., and the gemsbok cucumber [C. naudinianus (Sond.) Hook. f.]- also referred to in the literature as Acanthosicyos naudinianus (Sond.) C. Jeffrey. Pollen of all species were similar in shape differing slightly in their polar (P) and equatorial (E) axes and P/E. In general, all were characterized as prolate and tricolpate with a small polar area and reticulate ornamentation. Flow cytometry revealed C values for the taxa examined as ranging from 0.8 to 1.04 pg DNA per 2C nuclei. A mutant affecting pollen ornamentation was identified in PI 482261, a C. amarus citron from Zimbabwe. Pollen ornamentation on PI 482261 was rugulate. An examination of 15 additional accessions from neighboring areas in Zimbabwe revealed a second rugulate type in PI 482312, while the remaining 14 C. amarus accessions were reticulate. Successful hybridizations were made between C. colocynthis (PI 652554) and C. naudinianus (GRIF 14032), and between C. rehmii (PI 670011) and C. naudinianus (GRIF 14032). The F1 hybrids of both crosses were extremely vigorous and exhibited some characteristics (i.e., branching and storage root formation) associated with the male parent. Other characteristics such as tendril length and shape, and leaf size and shape, were intermediate between the parents. To date, the interspecific F1 hybrids have produced only shrunken (nonviable) pollen. [ABSTRACT FROM AUTHOR]

Crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas] have the potential to contribute to breeding objectives for this important root crop. Uncertainty in regard to species boundaries and their phylogenetic relationships, the limited availability of germplasm with which to perform crosses, and the difficulty of introgression of genes from wild species has constrained their utilization. Here, we compile geographic occurrence data on relevant sweetpotato wild relatives and produce potential distribution models for the species. We then assess the comprehensiveness of ex situ germplasm collections, contextualize these results with research and breeding priorities, and use ecogeographic information to identify species with the potential to contribute desirable agronomic traits. The fourteen species that are considered the closest wild relatives of sweetpotato generally occur from the central United States to Argentina, with richness concentrated in Mesoamerica and in the extreme Southeastern United States. Currently designated species differ among themselves and in comparison to the crop in their adaptations to temperature, precipitation, and edaphic characteristics and most species also show considerable intraspecific variation. With 79% of species identified as high priority for further collecting, we find that these crop genetic resources are highly under-represented in ex situ conservation systems and thus their availability to breeders and researchers is inadequate. We prioritize taxa and specific geographic locations for further collecting in order to improve the completeness of germplasm collections. In concert with enhanced conservation of sweetpotato wild relatives, further taxonomic research, characterization and evaluation of germplasm, and improving the techniques to overcome barriers to introgression with wild species are needed in order to mobilize these genetic resources for crop breeding. [ABSTRACT FROM AUTHOR]

* Premise of the study: Morning glories are an emerging model system, and resolving phylogenetic relationships is critical for understanding their evolution. Phylogenetic studies demonstrated that the largest morning glory genus, lpomoea, is not monophyletic, and nine other genera are derived from within lpomoea. Therefore, systematic research is focused on the monophyletic tribe Ipomoeeae (ca. 650-900 species). We used whole plastomes to infer relationships across Ipomoeeae. * Methods: Whole plastomes were sequenced for 29 morning glory species, representing major lineages. Phylogenies were estimated using alignments of 82 plastid genes and whole plastomes. Divergence times were estimated using three fossil calibration points. Finally, evolution of root architecture, flower color, and ergot alkaloid presence was examined. * Key results: Phylogenies estimated from both data sets had nearly identical topologies. Phylogenetic results are generally consistent with prior phylogenetic hypotheses. Higher-level relationships with weak support in previous studies were recovered here with strong support. Molecular dating analysis suggests a late Eocene divergence time for the Ipomoeeae. The two clades within the tribe, Argyreiinae and Astripomoeinae, diversified at similar times. Reconstructed most recent common ancestor of the Ipomoeeae had blue flowers, an association with ergot-producing fungi, and either tuberous or fibrous roots. * Conclusions: Phylogenetic results provide confidence in relationships among Ipomoeeae lineages. Divergence time estimation results provide a temporal context for diversification of morning glories. Ancestral character reconstructions support previous findings that morning glory morphology is evolutionarily labile. Taken together, our study provides strong resolution of the morning glory phylogeny, which is broadly applicable to the evolution and ecology of these fascinating species. [ABSTRACT FROM AUTHOR]

Data on intra-specific variability for seed oil content, physical characteristics and fatty acid composition in Cucurbita moschata and Cucurbita argyrosperma are lacking in the scientific literature. We examined 528 genebank accessions of C. moschata and 166 accessions of C. argyrosperma – which included members of both subsp. argyrosperma and subsp. sororia – for seed oil content, oil physical characteristics and fatty acid composition. The oil of both species had near-identical viscosities, viscosity indices, colour and oxidative stabilities while the oil of C. argyrosperma had a slightly higher pour point, cloud point, percentage of free fatty acids and acid value when compared with C. moschata. Mean oil content values of the two species were similar at 28.7 ± /2.7 and 29.8 ± /2.6% for C. moschata and C. argyrosperma, respectively. The mean seed oil content of C. argyrosperma subsp. argyrosperma var. palmeri (32.1%) was significantly higher than that of the other taxa examined. The average (mean) percentage of total seed weight attributable to the kernel was 77.2% in C. moschata (n= 34) and 74.5% in C. argyrosperma (n= 46). The percentage of total seed weight attributable to the hull was correlated with seed oil content, in both species. Linoleic was the predominant fatty acid in all the samples analysed. Means for individual fatty acids in C. moschata were linoleic 48.5%, oleic 22.6%, palmitic 20.7% and stearic 7.5%. Means for individual fatty acids in C. argyrosperma were linoleic 47.3%, oleic 27.5%, palmitic 16.5% and stearic 8.0%. [ABSTRACT FROM AUTHOR]

Various methods to synthesize capsinoids (the nonpungent analogs of capsaicinoids) from precursor molecules have been reported. Capsinoids are also naturally present, at typically low concentrations, in the fruit of many Capsicum species and genotypes. However, they are also present in the fruit of select genotypes at high concentrations. The fruit of high-capsiate genotypes represents a commercial source of these compounds. To date, no method has been published that efficiently extracts and purifies capsinoids from Capsicum fruit in a rapid and simple bulk process. This study evaluated the efficacy of various organic solvents for the extraction of capsinoids from dried Capsicum annuum fruit. Among the organic solvents evaluated, pentane appeared to provide a good combination of both recovery and purity. A subsequent liquid/liquid extraction step, utilizing pentane and acetonitrile, resulted in 26.3% (wt/wt) capsiate and 19.4% (wt/wt) dihydrocapsiate for a combined capsinoids yield of 45.7% (wt/wt). A third step, involving a rapid hp20ss chromatography column using a water/acetonitrile gradient, resulted in a combined capsinoids yield of 96.6% (wt/wt). [ABSTRACT FROM AUTHOR]

The nucleotide sequences of 16S rDNAs (coding for the small subunit ribosomal RNAs) were used to identify Xylella fastidiosa, a nutritionally fastidious plant pathogenic bacterium. The near-complete 16S rDNAs from nine strains of Xyl. fastidiosa, including seven pathotypes and one strain of Xanthomonas campestris pv. campestris, were amplified through PCR with two conserved primers (forward primer 5′-AGA GTT TGA TCC TGG CTC AG-3′ and reverse primer 5′-AAG GAG GTG ATC CAG CC-3′) and sequenced. The 16S sequences were compared with all eukaryote and prokaryote DNA entries in GenBank database. A Xyl. fastidiosa 16S rDNA sequence, M26601, was determined to be the most similar to all the near-complete (1537 bp) and partial 5′ end sequences from Xyl. fastidiosa, but not those from the Xanthomonas strain. A 20-bp oligonucleotide (5′-TTG GTA GTA ATA CCA TGG GT-3′) was found to be highly characteristic of Xyl. fastidiosa. Since the 16S rDNA of Xyl. fastidiosa strains are highly homologous and characteristically different from other bacteria, including the most closely related Xanthomonas, 16S rDNA sequences can be used as signature characters to identify this bacterium. [ABSTRACT FROM AUTHOR]

Pierce's disease (PD, Xylella fastidiosa) of grapevine is the primary pathogen limiting vinifera grape production in Florida and other regions of the southeastern United States. Quick and accurate detection of PD strains is essential for PD studies and control. A unique random amplified polymorphic DNA (PD1-1-2) was isolated from a PD strain from Florida. Fragment PD1-1-2 was cloned, sequenced, and found to be 1005 bp in length. PCR primers were designed to utilize these sequence data for PD strain detection. One primer set (XF176f–XF954r) amplified a 779-bp DNA fragment from 34 PD strains including seven pathotypes of X. fastidiosa, but not from strains of Xanthomonas campestris pv. campestris, Xan. vesicatoria or Escherichia coli. A second primer set (XF176f and XF686r) amplified a 511-bp fragment specific to 98 PD strains, but not from strains of citrus variegated chlorosis, mulberry leaf scorch, oak leaf scorch, periwinkle wilt, phony peach, or plum leaf scald. Sequence analysis indicated that RAPD fragment PD1-1-2 contains a Ser-tRNA gene. The PD-specific region includes a TaqI restriction site (TCGA) and is 150 bp downstream of the Ser-tRNA gene. [ABSTRACT FROM AUTHOR]

Discs of cortical and perimedullary tissue from tubers of potato (Solanum tuberosum L. cv. Superior) formed adventitious shoots when cultured on a medium containing Murashige and Skoog's salts, myo-inositol, 100 mg/l; folic acid, 0.5 mg/l: D-biotin, (0.05 mg/l; gibberellic acid (GA3), 0.5 mg/l; thiamine HCl, 0.1 mg/l; glycine, 2.0 mg/l; pyridoxine HCl, 0.5 mg/l; nicotinic acid, 0.5 mg/l; sucrose, 25 g/l; casein hydrolysate, 1 g/l Bacto agar, 9.0 g/l; and a cytokinin [N6-benzylaminopurine (BAP), N6-γ,γ-dimethylallylaminopurine (2iP), or N6-furfurylaminopurine (kinetin)]. Discs of pith tissue either failed to survive or produced callus but did not undergo morphogenesis. Cytokinin was essential for explant survival, while BAP at 3.0 mg/l was most efficacious in promoting shoot initiation. Auxin was not essential for shoot initiation or development; however, a low concentration (0.03 mg/l) of α-naphthaleneacetic acid (NAA) stimulated both explant survival and the number of shoots produced per disc. Indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA) did not stimulate shoot initiation. GA3 was essential for both shoot initiation and subsequent shoot development. The highest incidence of morphogenesis (over 100 shoots in 12 weeks) occurred from tuber discs cultured at 18°C constant and under a photon flux density of 60 μE m-2s-1. No difference in regenerative ability was found in explants taken from source tubers stored for 0 to 20 weeks at 4°C. A histological examination indicated that shoots developed from small clusters of meristematic cells which were initiated from within small protuberances on the surface of the tuber disc 3 weeks after transfer. [ABSTRACT FROM AUTHOR]

Presents information on a study pertaining to triploid genome of plantain (Musa spp., AA group) to analyze the genetic constitution of tetraploid hybrids in order to characterize the nature of the gametes from which they were derived. Reasons for its considered intractable to genetic improvement; What were the reasons given for the analyzation; Details on the methods used; Results of the study.

Two loofah (Luffa) species, the ridge gourd (Luffa acutangula (L.) Roxb.) and the sponge gourd (L. cylindrica (L.) M. Roem.; syn. L. aegyptiaca), are cultivated widely in Asia by smallholder famers. Both species have significant economic and nutritional importance. However, Tomato leaf curl New Delhi virus (ToLCNDV) and downy mildew (DM) caused by Pseudoperonospora cubensis are important biotic constraints to loofah production throughout Asia. Loofah landrace-derived breeding lines, developed at the World Vegetable Center (WorldVeg), were evaluated at the WorldVeg East and Southeast Asia Research and Training Station, Kasetsart University, Kamphaeng Saen, Thailand—where natural epidemics of ToLCNDV and DM regularly occur. The lines were also evaluated for other commercially important horticultural traits such as days to 50% staminate and pistillate flowering, fruit color, fruit bitterness, and market segment classification. Thirteen and 59 lines of ridge gourd and sponge gourd, respectively, were determined to be resistant to both ToLCNDV and DM. These lines covered all market segments of loofah and exhibited variability for all of the evaluated horticultural traits. The results of these evaluations and their implications on loofah breeding are discussed. [ABSTRACT FROM AUTHOR]

Background: Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, storage roots have evolved numerous times. The primary goal of this study is to understand whether this was through parallel evolution, where species use a common genetic mechanism to achieve storage root formation, or through convergent evolution, where storage roots in distantly related species are formed using a different set of genes. Pairs of species where one forms storage roots and the other does not were sampled from two tribes in the morning glory family, the Ipomoeeae and Merremieae. Root anatomy in storage roots and fine roots was examined. Furthermore, we sequenced total mRNA from storage roots and fine roots in these species and analyzed differential gene expression. Results: Anatomical results reveal that storage roots of species in the Ipomoeeae tribe, such as sweetpotato, accumulate starch similar to species in the Merremieae tribe but differ in vascular tissue organization. In both storage root forming species, more genes were found to be upregulated in storage roots compared to fine roots. Further, we find that fifty-seven orthologous genes were differentially expressed between storage roots and fine roots in both storage root forming species. These genes are primarily involved in starch biosynthesis, regulation of starch biosynthesis, and transcription factor activity. Conclusions: Taken together, these results demonstrate that storage roots of species from both morning glory tribes are anatomically different but utilize a common core set of genes in storage root formation. This is consistent with a pattern of parallel evolution, thus highlighting the importance of examining anatomy together with gene expression to understand the evolutionary origins of ecologically and economically important plant traits. [ABSTRACT FROM AUTHOR]