Polyploidization has played a key role in plant breeding and crop improvement. Although its potential to increase biomass yield is well described, the effect of polyploidization on biomass composition has largely remained unexplored. Here, we generated a series of Arabidopsis (Arabidopsis thaliana) plants with different somatic ploidy levels (2n, 4n, 6n, and 8n) and performed rigorous phenotypic characterization. Kinematic analysis showed that polyploids developed slower compared to diploids; however, tetra- and hexaploids, but not octaploids, generated larger rosettes due to delayed flowering. In addition, morphometric analysis of leaves showed that polyploidy affected epidermal pavement cells, with increased cell size and reduced cell number per leaf blade with incrementing ploidy. However, the inflorescence stem dry weight was highest in tetraploids. Cell wall characterization revealed that the basic somatic ploidy level negatively correlated with lignin and cellulose content, and positively correlated with matrix polysaccharide content (i.e. hemicellulose and pectin) in the stem tissue. In addition, higher ploidy plants displayed altered sugar composition. Such effects were linked to the delayed development of polyploids. Moreover, the changes in polyploid cell wall composition promoted saccharification yield. The results of this study indicate that induction of polyploidy is a promising breeding strategy to further tailor crops for biomass production.

Pyrus species display a gametophytic self-incompatibility (GSI) system that actively prevents fertilization by self-pollen. The GSI mechanism in Pyrus is genetically controlled by a single locus, i.e., the S-locus, which includes at least two polymorphic and strongly linked S-determinant genes: a pistil-expressed S-RNase gene and a number of pollen-expressed SFBB genes (S-locus F-Box Brothers). Both the molecular basis of the SI mechanism and its functional expression have been widely studied in many Rosaceae fruit tree species with a particular focus on the characterization of the elusive SFBB genes and S-RNase alleles of economically important cultivars. Here, we discuss recent advances in the understanding of GSI in Pyrus and provide new insights into the mechanisms of GSI breakdown leading to self-fertilization and fruit set. Molecular analysis of S-genes in several self-compatible Pyrus cultivars has revealed mutations in both pistil- or pollen-specific parts that cause breakdown of self-incompatibility. This has significantly contributed to our understanding of the molecular and genetic mechanisms that underpin self-incompatibility. Moreover, the existence and development of self-compatible mutants open new perspectives for pear production and breeding. In this framework, possible consequences of self-fertilization on fruit set, development, and quality in pear are also reviewed.

There is an urgent need for novel, efficient and environmentally friendly strategies to control apple scab (Venturia inaequalis), for the purpose of reducing overall pesticide use. Fructans are recently emerging as promising “priming” compounds, standing out for their safety and low production costs. The objective of this work was to test a fructan-triggered defense in the leaves of apple seedlings. It was demonstrated that exogenous leaf spraying can reduce the development of apple scab disease symptoms. When evaluated macroscopically and by V. inaequalis-specific qPCR, levan-treated leaves showed a significant reduction of sporulation and V. inaequalis DNA in comparison to mock- and inulin-treated leaves, comparable to the levels in fosetyl-aluminum-treated leaves. Furthermore, we observed a significant reduction of in vitro mycelial growth of V. inaequalis on plates supplemented with levans when compared to controls, indicating a direct inhibition of fungal growth. Variations in endogenous sugar contents in the leaves were followed during priming and subsequent infection, revealing complex dynamics as a function of time and leaf ontogeny. Our data are discussed in view of the present theories on sugar signaling and fructan-based immunity, identifying areas for future research and highlighting the potential use of fructans in apple scab management in orchards.

The acquisition of a single chromosome set by gametes generated during sexual reproduction depends on cohesion proteins that are protected by a phosphatase enzy