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Simple sequence repeat (SSR) enriched libraries for five groups of tropical perennial plants with edible fruits and shoots were prepared and sequenced in a GS-FLX Roche 454: sapodilla (Manilkara zapota (L.) P. Royen), lychee (Litchi chinensis Sonn.), mangosteen (Garcinia mangostana Linn. and G. cochinchinensis (Lour.) Choisy), rambutan (Nephelium lappaceum L.), and bamboo (Bambusa vulgaris Schrad. ex J.C. Wendl and Guadua angustifolia Kunth). For SSR development, these species were organized by their common names in five groups. A total of 3870 SSR primer sets were designed, using capillary electrophoresis 1872 nuclear SSRs were tested on 4 to 10 DNA samples within each plant group, that is 384 loci for each of the four groups of fruit trees and 336 loci for the bamboo group. Only 7.9% of the primers tested did not result in amplification. All 1872 SSRs are provided, we highlight 178 SSRs (between 26 and 47 per group) considered top-quality polymorphic SSRs that amplified all the samples, had strong fluorescence signal, presented no stutters and showed minimum non-specific amplification or background fluorescence. A total of 66,057 contig sequences were submitted to GenBank Database. Markers presented here will be useful not only for conservation efforts in banks of germplasm, but also for in-depth analysis of population genetics which usually requires evaluation of large number of loci.

The genetic basis of general plant vigor is of major interest to food producers, yet the trait is recalcitrant to genetic mapping because of the number of loci involved, their small effects, and linkage. Observations of heterosis in many crops suggests that recessive, malfunctioning versions of genes are a major cause of poor performance, yet we have little information on the mutational spectrum underlying these disruptions. To address this question, we generated a long-read assembly of a tropical japonica rice (Oryza sativa) variety, Carolina Gold, which allowed us to identify structural mutations (>50 bp) and orient them with respect to their ancestral state using the outgroup, Oryza glaberrima. Supporting prior work, we find substantial genome expansion is the sativa branch. While transposable elements (TEs) account for the largest share of size variation, the majority of events are not directly TE-mediated. Tandem duplications are the most common source of insertions and are highly enriched among 50-200bp mutations. To explore the relative impact of various mutational classes on crop fitness, we then track these structural events over the last century of US rice improvement using 101 resequenced varieties. Within this material, a pattern of temporary hybridization between medium and long-grain varieties was followed by recent divergence. During this long-term selection, structural mutations that impact gene exons have been removed at a greater rate than intronic indels and single-nucleotide mutations. These results support the use of ab initio estimates of mutational burden, based on structural data, as an orthogonal predictor in genomic selection.Significance StatementSome crop varieties have superior performance across years and environments. In hybrids, harmful mutations in one parent are masked by the ancestral alleles in the other parent, resulting in increased vigor. Unfortunately, these mutations are very difficult to identify precisely because, individually, they only have a small effect. In this study, we use long-read sequencing to characterize the entire mutational spectrum between two rice varieties. We then track these mutations through the last century of rice breeding. We show that large structural mutations in exons are selected against at a greater rate than any other mutational class. These findings illuminate the nature of deleterious alleles and will guide attempts to predict variety vigor based solely on genomic information.

The genetic basis of general plant vigor is of major interest to food producers, yet the trait is recalcitrant to genetic mapping because of the number of loci involved, their small effects, and linkage. Observations of heterosis in many crops suggests that recessive, malfunctioning versions of genes are a major cause of poor performance, yet we have little information on the mutational spectrum underlying these disruptions. To address this question, we generated a long-read assembly of a tropical japonica rice (Oryza sativa) variety, Carolina Gold, which allowed us to identify structural mutations (>50 bp) and orient them with respect to their ancestral state using the outgroup, Oryza glaberrima. Supporting prior work, we find substantial genome expansion in the sativa branch. While transposable elements (TEs) account for the largest share of size variation, the majority of events are not directly TE-mediated. Tandem duplications are the most common source of insertions and are highly enriched among 50-200bp mutations. To explore the relative impact of various mutational classes on crop fitness, we then track these structural events over the last century of US rice improvement using 101 resequenced varieties. Within this material, a pattern of temporary hybridization between medium and long-grain varieties was followed by recent divergence. During this long-term selection, structural mutations that impact gene exons have been removed at a greater rate than intronic indels and single-nucleotide mutations. These results support the use of ab initio estimates of mutational burden, based on structural data, as an orthogonal predictor in genomic selection., Author summary Some crop varieties have superior performance across years and environments. In hybrids, harmful mutations in one parent are masked by the ancestral alleles in the other parent, resulting in increased vigor. Unfortunately, these mutations are very difficult to identify precisely because, individually, they only have a small effect. In this study, we use long-read sequencing to characterize the entire mutational spectrum between two rice varieties. We then track these mutations through the last century of rice breeding. We show that large structural mutations in exons are selected against at a greater rate than any other mutational class. These findings illuminate the nature of deleterious alleles and will guide attempts to predict variety vigor based solely on genomic information.

Aflatoxin contamination in peanut seeds is still a serious problem for the industry and human health. No stable aflatoxin resistant cultivars have yet been produced, and given the narrow genetic background of cultivated peanuts, wild species became an important source of genetic diversity. Wild peanut seeds, however, are not abundant, thus, an effective method of screening for aflatoxin accumulation using minimal seeds is highly desirable. In addition, keeping record of genetic fingerprinting of each accession would be very useful for breeding programs and for the identification of accessions within germplasm collections. Results: In this study, we report a method of screening for aflatoxin accumulation that is applicable to the small-size seeds of wild peanuts, increases the reliability by testing seed viability, and records the genetic fingerprinting of the samples. Aflatoxin levels observed among 20 wild peanut species varied from zero to 19000 ng.g-1 and 155 ng.g-1 of aflatoxin B1 and B2, respectively. We report the screening of 373 molecular markers, including 288 novel SSRs, tested on 20 wild peanut species. Multivariate analysis by Neighbor-Joining, Principal Component Analysis and 3D-Principal Coordinate Analysis using 134 (36 %) transferable markers, in general grouped the samples according to their reported genomes. The best 88 markers, those with high fluorescence, good scorability and transferability, are reported with BLAST results. High quality markers (total 98) that discriminated genomes are reported. A high quality marker with UPIC score 16 (16 out of 20 species discriminated) had significant hits on BLAST2GO to a pentatricopeptide-repeat protein, another marker with score 5 had hits on UDP-D-apiose synthase, and a third one with score 12 had BLASTn hits on La-RP 1B protein. Together, these three markers discriminated all 20 species tested. Conclusions: This study provides a reliable method to screen wild species of peanut for aflatoxin resistance using minimal seeds. In addition we report 288 new SSRs for peanut, and a cost-effective combination of markers sufficient to discriminate all 20 species tested. These tools can be used for the systematic search of aflatoxin resistant germplasm keeping record of the genetic fingerprinting of the accessions tested for breeding purpose. Fil: Arias, Renee S.. National Peanut Research Laboratory; Estados Unidos Fil: Sobolev, Victor S.. National Peanut Research Laboratory; Estados Unidos Fil: Massa, Alicia N.. National Peanut Research Laboratory; Estados Unidos Fil: Orner, Valerie A.. National Peanut Research Laboratory; Estados Unidos Fil: Walk, Travis E.. National Peanut Research Laboratory; Estados Unidos Fil: Ballard, Linda L.. Usda Agricultural Research Service; Estados Unidos Fil: Simpson, Sheron A.. Usda Agricultural Research Service; Estados Unidos Fil: Puppala, Naveen. New Mexico State University Las Cruces; México Fil: Scheffler, Brian E.. Usda Agricultural Research Service; Estados Unidos Fil: de Blas, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Seijo, José Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina

The USDA–ARS Tropical Agriculture Research Station (TARS) is responsible for conserving germplasm of a number of important agricultural crop species. Its banana (Musa spp.) collection is comprised of diploid, triploid, and tetraploid accessions of cultivated, ornamental, wild, and synthetic hybrid accessions. To estimate genetic diversity, identify gaps, determine integrity, and generate clonal reference multilocus DNA profiles for a total of 175 accessions in the collection, a set of 22 microsatellite markers developed in the framework of the Generation Challenge Program (www.generationcp.org/, accessed 30 June 2014) by Centre de Cooperation Internationale en Recherche Agronomique pour le Developpement and recommended by the Global Musa Genomics Consortium were screened with an additional 15 reference DNA samples. Twenty-one of the 22 microsatellite markers amplified well and generated a total of 302 alleles with an average number of 14.4 alleles per locus. In general, profiles were reproducible and consistent for the 21 loci when clonal field and tissue culture plants were compared with reference samples. The average number of alleles and gene diversity estimates demonstrated substantial genetic diversity in the collection. Principal coordinate and cluster analyses grouped accessions in the collection according to their ploidy level and genomic compositions. Markers that were used in the study distinguished accessions to the subgroup level and identified mislabeled accessions, notably in the tissue culture collection where phenotypic differences are difficult to observe. The accessions and fingerprint profiles for the TARS collection are available through the USDA National Plant Germplasm System, Germplasm Resource Information Network (GRIN-Global) database

Transmissible colistin resistance in the form of an mcr-1 -gene-bearing plasmid has been recently reported in Enterobacteriaceae in several parts of the world. We report here the completed genome sequence of an Escherichia coli strain isolated from swine in the United States that carried the mcr-1 gene on an IncI2-type plasmid.

Breadfruit (Artocarpus altilis, Moraceae) is a traditional staple crop in Oceania and has been introduced throughout the tropics. This study examines important germplasm collections of breadfruit and its closest wild relatives and aims to (1) characterize genetic diversity, including identification of unknown and duplicate accessions, (2) evaluate genetic structure and hybridization within the breadfruit complex, and (3) compare utility of microsatellite markers to previously reported amplified fragment length polymorphism (AFLP) and isozyme markers in differentiating among cultivars. Data for 19 microsatellite loci were collected for 349 individuals (representing 255 accessions) including breadfruit (A. altilis), two wild relatives (Artocarpus camansi and Artocarpus mariannensis), and putative hybrids (A. altilis × A. mariannensis). Accessions were of mixed ploidy and regional origin, but predominantly from Oceania. Microsatellite loci collectively had a polymorphic information content (PIC) of 0.627 and distinguished 197 unique genotypes sorted into 129 different lineages, but a single genotype accounts for 49 % of all triploid breadfruit examined. Triploid hybrids and diploid A. altilis exhibited the highest levels of diversity as measured by allele number and gene diversity. Most accessions (75 %) of unknown origin matched either a known genotype or lineage group in the collection. Putative hybrids all had genetic contributions from A. mariannensis but ranged in the level of genetic contribution from A. altilis. Microsatellite markers were found to be more informative than isozyme markers and slightly less informative, with regard to accession discrimination, than AFLP markers. This set of microsatellite markers and the dataset presented here will be valuable for breadfruit germplasm management and conservation.

Premise of the study: Chloroplast microsatellite loci were characterized from transcriptomes of Artocarpus altilis (breadfruit) and A. camansi (breadnut). They were tested in A. odoratissimus (terap) and A. altilis and evaluated in silico for two congeners. Methods and Results: Fifteen simple sequence repeats (SSRs) were identified in chloroplast sequences from four Artocarpus transcriptome assemblies. The markers were evaluated using capillary electrophoresis in A. odoratissimus (105 accessions) and A. altilis (73). They were also evaluated in silico in A. altilis (10), A. camansi (6), and A. altilis × A. mariannensis (7) transcriptomes. All loci were polymorphic in at least one species, with all 15 polymorphic in A. camansi. Per species, average alleles per locus ranged between 2.2 and 2.5. Three loci had evidence of fragment-length homoplasy. Conclusions: These markers will complement existing nuclear markers by enabling confident identification of maternal and clone lines, which are often important in vegetatively propagated crops such as breadfruit.

Premise of the study: Microsatellite loci were isolated and characterized from enriched genomic libraries of Artocarpus altilis (breadfruit) and tested in four Artocarpus species and one hybrid. The microsatellite markers provide new tools for further studies in Artocarpus. Methods and Results: A total of 25 microsatellite loci were evaluated across four Artocarpus species and one hybrid. Twenty-one microsatellite loci were evaluated on A. altilis (241), A. camansi (34), A. mariannensis (15), and A. altilis × mariannensis (64) samples. Nine of those loci plus four additional loci were evaluated on A. heterophyllus (jackfruit, 426) samples. All loci are polymorphic for at least one species. The average number of alleles ranges from two to nine within taxa. Conclusions: These microsatellite primers will facilitate further studies on the genetic structure and evolutionary and domestication history of Artocarpus species. They will aid in cultivar identification and establishing germplasm conservation strategies for breadfruit and jackfruit.