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White pine blister rust (WPBR) is an exotic disease threatening five-needle pines in North America. In spite of its relatively recent introduction, some five-needle pines such as sugar pine (Pinus lambertiana) have developed both complete (major) gene resistance and partial (quantitative) resistance to WPBR. While significant effort has been dedicated to clone and locate the position of the major gene of WPBR resistance in sugar pine, the genetic basis of quantitative resistance remains largely unknown in all Strobus pines. In this work, we took a preliminary approach to identify potential genotype × phenotype associations using the results of long-term survival and symptoms of infection in both experimental and applied breeding populations. Our study found significant associations between several genes and WPBR disease symptoms such as normal active cankers and blights, important symptoms in the development of partial resistance. No significant associations were found with percentage of survival, probably due to the complex inheritance of the disease and long time to infection. With this study, we hope to lay the ground for further genome-wide association studies using large phenotypic data sets in sugar pine and other Strobus pines.

Premise of research. Plant sexuality evolves in response to genetic and ecological pressures that shape mating systems and floral traits. Comparing such systems and traits within phylogenies can show evolutionary trends in reproduction and floral morphology without the problems posed by the nonindependence of species. We compared sexual systems in seven species of the monophyletic genus Ariocarpus to elucidate major differences in floral morphology and potential relationships between biogeographic rarity and reproductive traits. We hypothesized that floral morphology would be linked to outcrossing rates and that deviations from strict outcrossing and reduced fertility would be present in rare species.Methodology. In one population per species, floral biology was detailed to characterize breeding systems, and mating systems were determined through pollination treatments. Discriminant analysis was used to identify floral traits that separate flowers into species. Phylogenetically independent contrasts were ...

†Background and Aims Four species of Pinus subsection Australes occur in the Caribbean Basin: P. caribaea, P. cubensis, P. maestrensis and P. occidentalis. This study analyses the phylogeography of these species to assess possible colonization events from Central America to the islands and subsequent population expansions during glacial periods driven by both drier climate and larger emerged land areas. †Methods Allele size data were obtained for plastid microsatellites for 314 individuals from 24 populations, covering the distribution range of subsection Australes in the Caribbean Basin. †Key Results In total, 113 plastid haplotypes were identified. The highest genetic diversity was found in populations of P. caribaea. Overall, Caribbean Basin populations fit the isolation by distance model. Significant phylogeographical structure was found (RST ¼ 0.671 . permuted RST ¼ 0.101; P , 0.0001). The haplotype network and a Bayesian analysis of population structure (BAPS) indicated different Central American origins for P. caribaea var. bahamensis and P. caribaea var. caribaea plastids, with Central America populations in northern and south-eastern groups. Sudden expansion times for BAPS clusters were close to three glacial maxima. †Conclusions Central America contains ancestral plastid haplotypes. Population expansion has played a major role in the distribution of genetic diversity in P. caribaea var. hondurensis. Two colonization events gave rise to the P. caribaea var. bahamensis and P. caribaea var. caribaea lineages. Plastid variation in the eastern species (P. cubensis, P. maestrensis and P. occidentalis) evolved independently from that in P. caribaea var. caribaea. Incomplete lineage sorting between P. cubensis and P. maestrensis is apparent. Inferred expansion times for P. caribaea var. bahamensis and for the eastern lineages correspond to glacial maxima, whereas those for P. caribaea var. hondurensis correspond to the beginning of the temperature decrease that led to Marine Isotope Stage 8.

The identity of genes causally implicated in the development and evolutionary origin of reproductive characters in gymnosperms is largely unknown. Working within the framework of plant evolutionary developmental biology, here we have cloned, sequenced, performed phylogenetic analyses upon and tested the expression patterns of LEAFY/FLORICAULA and NEEDLY orthologs in reproductive structures from selected species of the conifer genera Picea, Podocarpus, and Taxus. Contrary to expectations based on previous assessments, expression of LFY/FLO and NLY in cones of these taxa was found to occur simultaneously in a single reproductive axis, initially overlapping but later in mutually exclusive primordia and/or groups of developing cells in both female and male structures. These observations directly affect the status of the "mostly male theory" for the origin of the angiosperm flower. On the other hand, comparative spatiotemporal patterns of the expression of these genes suggest a complex genetic regulatory network of cone development, as well as a scheme of functional divergence for LFY/FLO with respect to NLY homologs in gymnosperms, both with clear heterochronic aspects. Results presented in this study contribute to the understanding of the molecular-genetic basis of morphological evolution in conifer cones, and may aid in establishing a foundation for gymnosperm-specific, testable evo-devo hypotheses.

Pinus pseudostrobus and Pinus montezumae are closely related species. They belong to the subsection Ponderosae, with a wide geographical distribution in Mexico and Central America. Morphological, biochemical, and anatomical information suggests that these species can form hybrids in natural populations. In this study, molecular (chloroplast microsatellites) and morphological markers were studied in 13 natural populations of these species to test the existence of introgressive hybridization, infer its dynamics, and describe the phylogeographic structure of the populations. Using analytical methods of population genetics, as well as Bayesian inference and coalescent approach, we show that putative hybrid populations are more similar to P. pseudostrobus than to P. montezumae and that these populations had the highest estimates of morphological and genetic variation. Furthermore, a greater introgression rate was observed from P. montezumae to putative hybrid and P. pseudostrobus populations. We showed that ge...

PREMISE OF STUDY: Bisexuality (male and female function in one structure) has been reported as a key innovation of angiosperms. Although there are several reports of "teratological" bisporangiate (bisexual) cones in gymnosperms, there have been none on the viability of their ovules and pollen. Analyses of the development and arrangement of female and male structures on bisporangiate cones of Pinus johannis enables us to gain insight on the origin of bisexuality in seed plants, for both angiosperms and gymnosperms. METHODS: Viability of bisporangiate cones was assayed by performing manual crosses and using anatomical and histological methods. KEY RESULTS: We determined that bisporangiate cones of P. johannis produce functional pollen and ovules. Male and female organs occupy basal and apical positions, respectively, the same positions found in almost all bisporangiate strobili in gymnosperms and bisexual flowers in angiosperms. CONCLUSIONS: The viability and spatial distribution of female and male organs of bisporangiate cones and their frequent occurrence in gymnosperms suggest a common mechanism in all seed plants for the production of bisporangiate structures. This idea is further supported by the presence of homologous genes for sexual organ identity in gymnosperms and angiosperms as reported by other authors. The lack of bisporangiate structure in gymnosperms may be primarily due to selection to avoid inbreeding rather than to genetic constraint.

The present dataset comprises 36,931 SNPs genotyped in 46 maize landraces native to Mexico as well as the teosinte subspecies Zea maiz ssp. parviglumis and ssp. mexicana. These landraces were collected directly from farmers mostly between 2006 and 2010. We accompany these data with a short description of the variation within each landrace, as well as maps, principal component analyses and neighbor joining trees showing the distribution of the genetic diversity relative to landrace, geographical features and maize biogeography. High levels of genetic variation were detected for the maize landraces (HE = 0.234 to 0.318 (mean 0.311), while slightly lower levels were detected in Zea m. mexicana and Zea m. parviglumis (HE = 0.262 and 0.234, respectively). The distribution of genetic variation was better explained by environmental variables given by the interaction of altitude and latitude than by landrace identity. This dataset is a follow up product of the Global Native Maize Project, an initiative to update the data on Mexican maize landraces and their wild relatives, and to generate information that is necessary for implementing the Mexican Biosafety Law. Keywords: Maize, Teosinte, Maize SNP50K BeadChip, Mexican landraces, Proyecto Global de Maíces Nativos