Are obligatory apomicts invested in the pollen tube transmitting tissue? : comparison of the micropyle ultrastructure between sexual and apomictic dandelions (Asteraceae, Lactuceae)

With the exception of the sunflower, little information concerning the micropyle ultrastructure of the family Asteraceae is available. The aim of our study was to compare the micropyle structure in amphimictic and apomictic dandelions. Ultrastructural studies using buds and flowers during anthesis have been done on the micropyle of the sexual and apomictic Taraxacum. In all of the species that were examined, the micropylar canal was completely filled with ovule transmitting tissue and the matrix that was produced by these cells. The ovule transmitting tissue was connected to the ovarian transmitting tissue. The micropyle was asymmetrical because the integument epidermis that forms the transmitting tissue was only on the funicular side. There was a cuticle between the obturator cells and epidermal cells on the other side of integument. The micropylar transmitting tissue cells and theirs matrix reached the synergid apex. The cytoplasm of the transmitting tissue cells was especially rich in rough endoplasmic reticulum (ER), dictyosomes, and mitochondria. No major differences were detected between the micropyle structure of the amphimictic and apomictic species; thus, a structural reduction of obturator does not exist. The ovule transmitting tissue is still active in apomictic dandelions despite the presence of the embryo and endosperm. Differences and similarities between the micropyle structure in the Asteraceae that have been studied to date are discussed

Allelic Diversity of Acetyl Coenzyme A Carboxylase accD/bccp Genes Implicated in Nuclear-Cytoplasmic Conflict in the Wild and Domesticated Pea (Pisum sp.)

Reproductive isolation is an important component of species differentiation. The plastid accD gene coding for the acetyl-CoA carboxylase subunit and the nuclear bccp gene coding for the biotin carboxyl carrier protein were identified as candidate genes governing nuclear-cytoplasmic incompatibility in peas. We examined the allelic diversity in a set of 195 geographically diverse samples of both cultivated (Pisum sativum, P. abyssinicum) and wild (P. fulvum and P. elatius) peas. Based on deduced protein sequences, we identified 34 accD and 31 bccp alleles that are partially geographically and genetically structured. The accD is highly variable due to insertions of tandem repeats. P. fulvum and P. abyssinicum have unique alleles and combinations of both genes. On the other hand, partial overlap was observed between P. sativum and P. elatius. Mapping of protein sequence polymorphisms to 3D structures revealed that most of the repeat and indel polymorphisms map to sequence regions that could not be modeled, consistent with this part of the protein being less constrained by requirements for precise folding than the enzymatically active domains. The results of this study are important not only from an evolutionary point of view but are also relevant for pea breeding when using more distant wild relatives.Peer reviewe

New chromosome counts and genome size estimates for 28 species of Taraxacum sect. Taraxacum

The species-rich and widespread genus Taraxacum F. H. Wiggers, 1780 (Asteraceae subfamily Cichorioideae) is one of the most taxonomically complex plant genera in the world, mainly due to its combination of different sexual and asexual reproduction strategies. Polyploidy is usually confined to apomictic microspecies, varying from 3x to 6x (rarely 10x). In this study, we focused on Taraxacum sect. Taraxacum (= T. sect. Ruderalia; T. officinale group), i.e., the largest group within the genus. We counted chromosome numbers and measured the DNA content for species sampled in Central Europe, mainly in Czechia. The chromosome number of the 28 species (T. aberrans Hagendijk, Soest & Zevenbergen, 1974, T. atroviride Štěpánek & Trávníček, 2008, T. atrox Kirschner & Štěpánek, 1997, T. baeckiiforme Sahlin, 1971, T. chrysophaenum Railonsala, 1957, T. coartatum G.E. Haglund, 1942, T. corynodes G.E. Haglund, 1943, T. crassum H. Øllgaard & Trávníček, 2003, T. deltoidifrons H. Øllgaard, 2003, T. diastematicum Marklund, 1940, T. gesticulans H. Øllgaard, 1978, T. glossodon Sonck & H. Øllgaard, 1999, T. guttigestans H. Øllgaard in Kirschner & Štěpánek, 1992, T. huelphersianum G.E. Haglund, 1935, T. ingens Palmgren, 1910, T. jugiferum H. Øllgaard, 2003, T. laticordatum Marklund, 1938, T. lojoense H. Lindberg, 1944 (= T. debrayi Hagendijk, Soest & Zevenbergen, 1972, T. lippertianum Sahlin, 1979), T. lucidifrons Trávníček, ineditus, T. obtusifrons Marklund, 1938, T. ochrochlorum G.E. Haglund, 1942, T. ohlsenii G.E. Haglund, 1936, T. perdubium Trávníček, ineditus, T. praestabile Railonsala, 1962, T. sepulcrilobum Trávníček, ineditus, T. sertatum Kirschner, H. Øllgaard & Štěpánek, 1997, T. subhuelphersianum M.P. Christiansen, 1971, T. valens Marklund, 1938) is 2n = 3x = 24. The DNA content ranged from 2C = 2.60 pg (T. atrox) to 2C = 2.86 pg (T. perdubium), with an average value of 2C = 2.72 pg. Chromosome numbers are reported for the first time for 26 species (all but T. diastematicum and T. obtusifrons), and genome size estimates for 26 species are now published for the first time

Classic (extensive) orchards in Croatia

Hrvatska ima vrlo povoljne pomoekološke uvjete za uzgoj voćaka. Tradicija uzgoja voćaka duga je više stoljeća, a voćke su se uzgajale na gotovo svim seoskim gospodarstvima, te dijelom i u urbanim sredinama. Intenzivan uzgoj voćaka počeo se značajnije širiti polovinom prošlog stoljeća. Intenzivan uzgoj je u određenoj mjeri potisnuo interes za klasičnim, ali se postojeći voćnjaci visokostablašica uglavnom nisu krčili već su u većoj mjeri bili zapušteni. U novije vrijeme klasični voćnjaci ponovno postaju aktualni. Njihova uloga očituje se u očuvanju genetske raznolikosti, kako voćnih vrsta, tako i biljaka općenito. Posebna vrijednost tih voćnjaka očituje se u očuvanju tipičnog krajobraza ruralnih sredina, te kao osnove sustava organske proizvodnje voća i voćnih prerađevina. U ukupnim površinama voćnjaka u Hrvatskoj, intenzivni (plantažni) voćnjaci zauzimaju 24%, a preostali dio od oko 21.800 ha otpada na klasične voćnjake. U pojedinim županijama udio klasičnih voćnjaka je značajno veći, pa primjerice u Krapinsko-zagorskoj, Karlovačkoj, Varaždinskoj, Primorsko-goranskoj i Ličko-senjskoj županiji klasični voćnjaci visokostablašica zauzimaju više od 95% površina pod voćem. Među voćnim vrstama najviše se na klasičan način uzgajaju trešnje (92,0%), zatim slijede: orah (90,0%), šljiva (89,9%), marelica (87,2%), kruška (75,4%), višnja (73,4%), dok je značajno niži udio breskve i nektarine (53,3%), i najniži jabuke (43,2%).Croatia has very favourable ecological conditions for growing fruit trees. The tradition of growing fruit trees has a long history, and fruit was cultivated at almost all farms, and partly in the urban areas. Intensive cultivation of fruit trees began to expand significantly from the middle of last century. Intensive farming to some extent pushed interest for the classic growing system and the existing classic orchards were generally not managed properly and were largely neglected. In recent years, the classic orchards made again become current. Their role is reflected in the preservation of genetic diversity, both fruit species, and plants in general. The special value of these orchards is reflected in the preservation of the typical landscape of rural areas, as well as the basics of organic production of fruits and fruit products. In respect of the total acreage of orchards in Croatia, intensive (plantation) orchards occupy 24%, and the remaining part of about 21 800 ha are traditional orchards. In some counties, the share of traditional orchards is significantly higher, so for example in Krapinsko-zagorska, Karlovačka, Varaždinska, Primorsko-goranska and Ličko-eenjska, where classic orchards occupy more than 95% of the area under the fruit. Among the fruit species mostly traditionally grown are cherries (92.0%), followed by: nut (90.0%), plums (89.9%), apricots (87.2%), pears (75.4%), cherries (73.4%), while a significantly lower share is that of peaches and nectarines (53.3%), and the lowest are apples (43.2%)

Research gaps and challenges in the conservation and use of North American wild lettuce germplasm

The North American crop wild relatives (CWR) of lettuce (Lactuca L.) represent an underexplored pool of genetic diversity of potential value to breeding programs. The 10 species belong to three different groups: a native clade including at least six allotetraploid species [L. biennis (Moench) Fernald, L. canadensis L., L. floridana (L.) Gaertn., L. graminifolia Michx., L. hirsuta Muhl. ex Nutt., and L. ludoviciana (Nutt.) Riddell], a diploid clade with one species [L. tatarica (L.) C. A. Mey. subsp. pulchella (Pursh) Stebbins], and a clade related to the cultivated taxon (L. sativa L.) with three non‐native species (L. saligna L., L. serriola L., and L. virosa L.). In this review, we examine the role of herbarium and genebank holdings in taxonomic and other foundational studies, as well as for germplasm exploration and use. We compile the state of knowledge on the ranges of lettuce CWR in North America, modeling the potential distributions of the species and assessing their ex situ and (for native species) in situ conservation status. We categorize seven of the species as high priority for further conservation and three as medium priority, with none currently considered low priority or sufficiently conserved. Further, we review morphological, phenological, genetic diversity, and pest and disease information with regard to North American species. We conclude by outlining the critical gaps and describing a way forward for addressing challenges in the conservation and use of North American wild lettuce germplasm

PCoA 3D plot.

<p>Principal coordinate analysis (based on Jaccard’s similarity coefficient) of 96 apomictic <i>Taraxacum</i> individuals. For taxon abbreviations see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041868#pone.0041868.s001" target="_blank">Table S1</a>.</p

Multilocus estimates of <i>F-</i> and <i>R-</i>statistic for all six microsatellite loci for studied apomictic <i>Taraxacum</i> accessions.

***<p>– significant value, P<0.001.</p

Character compatibility test for studied apomictic <i>Taraxacum</i> accessions.

<p><i>N</i>, number of samples; <i>NG</i>, number of genotypes; <i>MIC</i>, matrix incompatibility count; <i>E</i>, number of genotypes left at <i>MIC</i>  = 0. For taxon abbreviations see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0041868#pone.0041868.s001" target="_blank">Table S1</a>.</p