Plant genetics

Australian species of Chara L. sect. Charopsis (Kütz.) Leonh. are revised. Multivariate analysis supports recognition of four species: Chara braunii C.C.Gmel., C. evanida Casanova, C. karolii Casanova and C. muelleri (A.Braun) F.Muell. These taxa are described and illustrated, and a key is provided.

The perception of African nightshades (Solanum section Solanum) as “healthy” foods, supported by documentation of their high nutritional
and medicinal benefits, has led to a sudden and steady upsurge in their consumption, demand and monetary value in Africa and
most parts of South-East Asia. However, due to very low leaf yields, production of these vegetables remains on small-scales, resulting in
acute shortages and escalating prices, especially in urban areas. Apart from local variants or landraces selected in some regions where
these plants are utilized as food and/or medicinal plants, there are no improved cultivars developed through conventional plant breeding
techniques. Species belonging to this section, generally referred to as “Solanum nigrum-complex” are predominantly autogamous, favouring
production of many small fruits and seeds, which compete with leaves for photosynthates. S. nigrum-complex constitutes a polyploid
series, with diploid (2n=2x=24), tetraploid (2n=4x=48), hexaploid (2n=6x=72) and rarely, octoploid (2n=8x=96) species, a trait that can be
exploited for cultivar development. This review outlines the possible evolutionary mechanisms and modes of origin of the polyploids,
breeding strategies to produce heteroploids such as triploid (2x=3x=36), pentaploid (2n=5x=60) and heptaploid (2n=7x=84) from existing
or induced polyploids and envisaged advantageous properties of the novel polyploids or heteroploids over their wild-type progenitors.
With few exceptions, heteroploidy is known to cause sterility or highly reduced fertility of both pollen and ovules. The African nightshade
heteroploid series would putatively be male- and female-sterile, thus eliminating fruit- and seed-set and enhancing leaf productivity.

The chromosome number of 21 species belonging to 9 Angiosperm families from Paraguay are given. We report for the first time the chromosome number for the following species: Enhydra anagallis (n=12), Cuphea campylocentra (2n=16), Cuphea micrantha (2n=16) and Cuphea pterosperma (2n=48). We added a new chromosome number for Cuphea glutinosa (2n=34).

Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipit...

Question: Malus sylvestris is considered an endangered tree species in Central Europe. Hybridization with Malus domestica poses a serious threat to the genetic integrity of the wild species. Here we investigate whether M. sylvestris and the hybrid M. domestica × sylvestris occur in the same habitat or have different ecological niches and whether M. sylvestris is threatened by displacement by the hybrid.
Location: Northern Bavaria.
Methods: Taxon delimitation was accomplished using six genetic microsatellite markers and 613 Germany-wide references of M. sylvestris and 75 cultivars. To determine differences in the ecological niches between M. sylvestris and hybrids, light availability for the trees was estimated via gap fractions in hemispherical photographs. Soil particle size fractions and pH values were determined for each horizon.  Vegetation relevé data were collected, and mean Ellenberg indicator values calculated. For habitat differences, means in combination with frequency patterns of the parameters were compared, and logistic models and detrended correspondence analysis (DCA) of community data were calculated.
Results: Genetic markers identified 22 M. sylvestris and 11 hybrid specimens, meaning that in the study area the wild taxon is much more frequent than the hybrid. Ecological site differences between M. sylvestris and its hybrid with M. domestica were best explained by light availability, pH and mean Ellenberg moisture value. In contrast to the
ecological demands of the hybrid, Malus sylvestris tolerated wet soil and flooding and even somewhat shadier conditions in the later successional stages. DCA revealed that differences in the composition of the plant communities in which the taxa were found were primarily driven by soil moisture.
Conclusions: Our data suggested different ecological niches, which are appropriate to reduce the risk of replacement of M. sylvestris by the hybrid M. domestica × sylvestris. Hence, these findings provide important implications for a more targeted planning of in-situ conservation strategies of M. sylvestris genomes with low levels of admixture and help to protect plant communities suitable for the threatened wild apple.

Following a phylogenetic analysis using morphology, Pittosporum is here monographed and recircumscribed as a monophyletic genus, by including the small genus Citriobatus and by excluding a new genus, described in the accompanying paper as Auranticarpa. Within Australia and its associated territories, 20 species are now recognised in Pittosporum, including the four from Citriobatus, three of which are given new combinations (P. spinescens, P. lancifolium and P. multiflorum). Citriobatus linearis requires a new name (P. viscidum). Four species are reinstated or confirmed at species level (P. angustifolium, P. ligustrifolium, P. nativitatis and P. wingii), and P. trilobum is described for the first time.

Callitris Vent. is the most speciose of the Southern Hemisphere genera of Cupressaceae, occupying a diverse range of habitats within Australia and New Caledonia and is closely allied to Actinostrobus Miq. and the monotypic New Caledonian genus Neocallitropsis Florin. Results of phylogenetic analyses of 18S–26S rDNA internal transcribed spacer region sequences for representatives of 12 of the 18 currently recognised species of Callitris, two of the three Actinostrobus species and the single known species of Neocallitropsis help to clarify major lineages and relationships in this group. ITS data provide strong evidence against the monophyly of Callitris as currently circumscribed, with the strongest evidence being for the inclusion of the New Caledonian monotypic species Neocallitropsis pancheri (Carriere) de Laubenfels. This species shares a close relationship with C. sulcata (Parl.) Schltr. Three representatives of Actinostrobus are monophyletic and are placed in a polytomy with C.�...