The effects of the application of the chemical thinner Armothin® on fruit set, yield and quality of Japanese plum (Prunus salicina Lindl.) cv. ‘Fortune’ were studied during two seasons in Central Chile (34.56°S, 71.5°W). Trees were sprayed with Armothin® at 0.5%, 1% and 2% concentrations. All thinning treatments reduced the fruit set and fruitlet number (fruitlets/50 cm of branch). Armothin® at 2% conc. was the most aggressive treatment, drastically reducing the fruit set from 85.9% and 82.9% of the control and crop load to unprofitable levels during both seasons. Chemical thinning treatments at the two lowest concentrations (0.5 and 1%) did not significantly alter the crop load compared with the unsprayed control during both study seasons. Thinning costs were reduced (Armothin® 0.5%, 25.0% and 21.5% of the control treatment and Armothin® 1%, 24.6% and 24.1% of the control, during the first and second season, respectively). In general, chemical thinning increased the fruit size and total soluble solids content (TSS). Taking into account the effects on thinning, crop load, fruit quality and thinning costs, Armothin® 1% and Armothin® 0.5% are the most advantageous treatments in the case of this study.
Rosaceae fruit trees are characterized by gametophytic self-incompatibility, with their production typically requiring artificial pollination or pollination tree is required in production. Both of these solutions cause reductions in production efficiency, and self-incompatibility has become a major issue in agricultural biology, and as such, has been extensively studied. In this review, we discuss the relationship between S-RNase content in the style and self-incompatibility, and the role of the SLF gene in stamen-determining factor. Considering mutations in self-compatibility-related genes and self-compatibility in polyploid fruit trees, we discuss the potential mechanisms of self-incompatibility. Based on a preliminary study of the role of pollen tube Ca2+ gradients in self-incompatibility in Pyrus, we propose a new mechanistic model of self-incompatibility taking into account the effect of Ca2+. We also discuss the potential for hormone regulation to be used to control selfincompatibility in Rosaceae fruit trees.