Genetic incompatibilities resulting from interactions between two loci represent a potential source of postzygotic barriers and may be an important factor in evolution when they impair the outcome of interspecific crosses. We show that, in crosses between strains of the plant Arabidopsis thaliana, loci interact epistatically, controlling a recessive embryo lethality. This interaction is explained by divergent evolution occurring among paralogs of an essential duplicate gene, for which the functional copy is not located at the same locus in different accessions. These paralogs demonstrate genetic heterogeneity in their respective evolutionary trajectories, which results in widespread incompatibility among strains. Our data suggest that these passive mechanisms, gene duplication and extinction, could represent an important source of genetic incompatibilities across all taxa.
Stolon is an elongated, two-node, vegetative, axillary shoot, which supports the ramet (rooted rosette) until it is completely independent on its own roots. The reciprocal capacity of the ramets, in a single runner chain, to sustain the growth and share locally abundant resources or to tolerate a local stress, is still in debate. This capacity may play an important role for improving nursery plant production and for better understanding the natural clonal multiplication. To describe strawberry stolon action, in plant-to-plant relationship, bare-rooted Camarosa ramets, joint in couples by their own stolons (generally, second and third ramet in a runner chain) were transplanted in two pots. The couples of ramets were treated in a factorial experiment with decortication (peeling a 2-mm ring of bark from the stolon), removal of root system or glyphosate application to one of the two ramets. In the studied system, the older ramet was referred as mother and the other as daughter. The two ramets were very similar in age and seem to act with a very limited hierarchic prevalence of the mother. When the root system of one ramet was eliminated, leaf number and chlorophyll content had a very slight decrease, independently in the mother ramet or in the daughter. The decortication did not reduce water integration, in any group of plants, but limited assimilate allocation towards the daughter ramet when the mother ramet had a severe root cut (not vice versa). The glyphosate action resulted localized in the sprayed ramet, which reduced chlorophyll content within 2 days and expired after 4 days.
Olive micropropagation is nowadays possible but knowing if it induces juvenile traits and how juvenility, vigor and fruit productivity are affected is pivotal. Three trials were carried out during micropropagation and afterwards in the field. Three varieties were characterized during multiplication in vitro, after several subcultures. ‘Arbequina’ revealed higher shoot miniaturization than ‘Coratina’ and ‘Frantoio’, and likely-juvenile shoots with three or four leaves per node. The ‘Arbequina’ trees obtained from two- and three-leaves-per-node in vitro plantlets were compared to cuttings in the field. Two years after planting, flower-differentiated shoots were found in the apical part of the canopy in all tested trees while in this position the ramification was more intense on three-leaves-per-node trees. Architecture of ‘Arbequina’ trees from micropropagation and cuttings was finally characterized in a high-density commercial grove. Micropropagated trees showed a well distributed and deep root system, a regular conical shape of the canopy, a higher number of primary branches, and a reproductive ability equivalent to cuttings. In conclusion, some juvenile traits and vigor may appear in vitro and last after ex vitro acclimation, but no more than two years in the field.
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