Direct evidence for crossover and chromatid interference in meiosis of two plant hybrids (Lolium multiflorum×Festuca pratensis and Allium cepa×A. roylei)

Crossing over, in addition to its strictly genetic role, also performs a critical mechanical function, by bonding homologues in meiosis. Hence, it is responsible for an orderly reduction of the chromosome number. As such, it is strictly controlled in frequency and distribution. The well-known crossover control is positive crossover interference which reduces the probability of a crossover in the vicinity of an already formed crossover. A poorly studied aspect of the control is chromatid interference. Such analyses are possible in very few organisms as they require observation of all four products of a single meiosis. Here, we provide direct evidence of chromatid interference. Using in situ probing in two interspecific plant hybrids (Lolium multiflorum×Festuca pratensis and Allium cepa×A. roylei) during anaphase I, we demonstrate that the involvement of four chromatids in double crossovers is significantly more frequent than expected (64% versus 25%). We also provide a physical measure of the crossover interference distance, covering ~30-40% of the relative chromosome arm length, and show that the centromere acts as a barrier for crossover interference. The two arms of a chromosome appear to act as independent units in the process of crossing over. Chromatid interference has to be seriously addressed in genetic mapping approaches and further studies

Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus

Alien introgressions introduce beneficial alleles into existing crops and hence, are widely used in plant breeding. Generally, introgressed alien chromosomes show reduced meiotic pairing relative to the host genome, and may be eliminated over generations. Reduced pairing appears to result from a failure of some telomeres of alien chromosomes to incorporate into the leptotene bouquet at the onset of meiosis, thereby preventing chiasmate pairing. In this study, we analysed somatic nuclei of rye introgressions in wheat using 3D-FISH and found that while introgressed rye chromosomes or chromosome arms occupied discrete positions in the Rabl’s orientation similar to chromosomes of the wheat host, their telomeres frequently occupied positions away from the nuclear periphery. The frequencies of such abnormal telomere positioning were similar to the frequencies of out-of-bouquet telomere positioning at leptotene, and of pairing failure at metaphase I. This study indicates that improper positioning of alien chromosomes that leads to reduced pairing is not a strictly meiotic event but rather a consequence of a more systemic problem. Improper positioning in the nuclei probably impacts the ability of introgressed chromosomes to migrate into the telomere bouquet at the onset of meiosis, preventing synapsis and chiasma establishment, and leading to their gradual elimination over generations

How alpine heathlands response to the snow cover change on the ski slope? Long-lasting ski slope impact case study from the Hrubý Jeseník Mts (Central Europe)

The distribution and duration of snow cover are important variables that affect ecosystem processes in the alpine zone. The establishment of ski resorts dramatically change their surrounding environment and ski slopes represent significant anthropogenic impact in the mountains. We assessed the changes in environmental factors, phenology, growth, and reproductive performance of bilberry (Vaccinium myrtillus), a dominant species of alpine heathlands, caused by a “nature-friendly” managed ski slope (i.e., without artificial snow and machine grading) at permanent plots established on the ski slope under operations (inside the ski slope) and on an unaffected control area (outside the ski slope). A lower mean temperature and a shorter time of great temperature fluctuation during snow melting, a longer time span of snow cover, and a higher snow water equivalent were observed inside the ski slope compared to outside it. Due to changed environmental conditions, the beginning of growth was postponed, and a delay in phenological development was observed in the bilberry at the ski slope. However, bilberry ripened both inside and outside the ski slope in a similar period and showed similar cover and even higher flower and fruit densities inside the ski slope compared with natural surroundings. The persistence of bilberry was not deteriorated and its performance was even better inside the ski slope. On the ski slope, managed snow cover can reduce the potential vegetation shifts due to expected impact of the climate warming. That should be taken into account in conservation and management planning

Biology and Yield of Rocket (<i>Eruca sativa</i> Mill.) under Field Conditions of the Czech Republic (Central Europe)

Five rocket (Eruca sativa (L.) Mill.) varieties and accessions were cultivated under field conditions in the Czech Republic (Central Europe) and subsequently studied for variation in morphology and yield. Two cultivation techniques (treatments) were tested during the growing seasons in 2010 and 2011: directly sown seeds in the field and plantlets cultivated in a glasshouse and later transplanted to the field. There were analysed four morphological parameters of the leaf rosette (leaf shape in outline, leaf margin, leaf apex and leaf colour), marketable yield, nonmarketable parts, and rosette radius. Plants from plantlets transplanted to the field in spring terms (April) yielded a substantially higher marketable yield and had a higher rosette radius in contrast to plants from directly sown seeds. Conversely, for the summer terms (late August, September) the direct sowing technique produced higher marketable yield in comparison with plantlets treatment. Plants cultivated from directly sowed seeds reached a marketable yield on average from 15 to 60 g per plant while transplanted plants produced on average from 10 to 49 g per plant. It is evident that cultivation of rocket under field conditions of the Czech Republic is possible and provides, when using the appropriate sowing term, more or less stable yields of marketable parts. Details on variation in yield parameters of individual varieties and accessions are presented

Anthropogenic and natural disturbances increase local genetic diversity in an early spring geophyte (Ficaria verna Huds)

Gefördert im Rahmen des Projekts DEA