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.

A living mulch system can provide beneficial biodiversified phytocoenoses and spatial competition against weeds; however, it may also compete for water with the main cultivated crop under Mediterranean climate conditions. Strawberries employed as living mulch in a rain-fed hill vineyard of central Italy were evaluated for two years through a participative approach involving the farmer. A local wild strawberry was propagated by stolons to obtain small plantlets easily uprooted after the summer and then transplanted to a one-year-old vineyard. The densities of two and four strawberry plants per grapevine were compared with no living mulch in a randomized complete block design. A horizontal blade weeder was used once a year in all treatments. The results showed that strawberries as living mulch plus application of a blade weeder avoided the need for further soil tillage and assured a full soil cover during winter for both initial planting densities. The strawberry living mulch did not alter the grapevine transpiration during an incident of water stress in summer. Moreover, the yield per vine and the grape quality were comparable with those of the soil without living mulch. The growth of strawberry mulch was relevant in the area surrounding the vines. Furthermore, the living mulch guaranteed a constant soil cover reducing the risk for soil erosion while increasing the vineyard’s biological diversity. This may imply a higher resilience.

Recently, several studies on olive fruit growth have focused on circadian monitoring as an important orchard management tool. The olive fruit growth trend is described by double sigmoid model with four growth phases, where the third phase spans from the end of pit hardening to initial fruit maturation, and the last phase includes olive maturation up to fruit drop. Environmental factors play an important role in fruit growth, with vapor pressure deficit (VPD) being a keystone factor. Our experiment was designed to hourly monitor olive (Olea europaea L. cv. ‘Frantoio’) fruit transversal diameter from approximately initial pit hardening (II Phase), extension (III Phase) until harvest time (IV Phase) in the attempt to determine whether fruit growth dynamically responds to environmental variables such as diurnal VPD change in different stages of fruit development. Automatic extensimeters were applied in open field and VPD was calculated from data of our weather station. Throughout the experiment period, the circadian model of fruit growth showed two steps: shrinkage and expansion. Almost in all days of the third phase of fruit growth, daily response of transversal diameter to VPD formed complete clockwise hysteresis loops. During the fourth phase of fruit growth, with increasing fruit maturation, the complete clockwise hysteresis loop experienced some abnormality. At the fourth stage of fruit growth there were incomplete and partial clockwise hysteresis loops. We conclude that hysteresis can be employed to detect the shift between the end of the third phase (cell expansion) and the beginning of the fourth phase (fruit maturation) of fruit growth. The disappearance of the complete clockwise hysteresis loop and the substitution with incomplete, or partial clockwise hysteresis loops was observable only in the fourth stage of fruit growth. These results can be valuable for any smart fruit management of olive fruit production.