Keeping ability of apple fruits of new cultivars under different storage technologies

The fruits of new apple cultivars bred by the FSBSI “Federal Scientific Center named after IV Michurin”, adapted to the stressful weather conditions of the Central Black Earth Region of Russia, were used. During storage of control and 1-MCP-treated fruits of 5 studied apple cultivars in air (regular atmosphere: CO2 = 0.03%, O2 = 21%), modified atmosphere (O2 = 16-19%, CO2 = 1.5-5.0%) and controlled atmosphere with ultra-low oxygen content (O2 = 1.2-1.5%, CO2 = 1.2-1.5%), the following main diseases were identified: for cv. Uspenskoye – scald, bitter pit, breakdown; for cv. Fregat - bitter pit, breakdown, CO2-skin injury. Development of several diseases at the same time is also possible (CO2-skin injury + bitter pit, bitter pit + breakdown); for cv. Flagman - scald, bitter pit, breakdown, scald + bitter pit; for cv. Bylina - CO2-skin injury, bitter pit, breakdown, soft scald; for cv. Vympel - CO2-skin injury. Maximum storage efficiency was shown by fruits cv. Vympel stored under CA + 1-MCP technology. Data on the keeping ability of apple fruits of the studied cultivars allow developing high-precision varietal storage technologies.

Summer Pruning, an Eco-Friendly Approach to Controlling Bitter Pit and Preserving Sensory Quality in Highly Vigorous Apple cv. ‘Reinette du Canada’

Summer pruning reduces vegetative growth in apple trees, but it could have an impact on fruit quality. This study analyzed the effects of summer pruning as an eco-friendly pre-harvest alternative to chemical growth regulation inputs on instrumental and sensory quality of highly vigorous apple cv. ‘Reinette du Canada’, which has been awarded with a Protected Designation of Origin label in two environments. The results showed that summer pruning affected the mineral content of the fruit. Summer pruning reduced bitter pit, but it did not negatively affect fruit weight nor any other instrumental characteristic during storage. Moreover, sensory quality or degree of liking were not affected by summer pruning. Thus, summer pruning could be an eco-friendly pre-harvest alternative to chemical treatments to improve quality in global terms of ‘Reinette du Canada’ apple cultivar, regardless of the location. This technique contributed to the decrease of bitter pit incidence, but did not decrease sensory quality nor degree of liking.

Accumulation of Abnormal Amyloplasts in Pulp Cells Induces Bitter Pit in Malus domestica

Apple bitter pit primarily occurs during fruit ripening and storage; however, its formation mechanism remains unclear. Although it is considered that Ca2+ deficiency causes metabolic disorders in apples, there have been few studies on the mechanism of the bitter pit from the perspective of cell structure. At the fruit ripening stage, the fruit with a bitter pit on the tree was taken as the research material. In this study, the microscopic observation revealed numerous amyloplasts in the pulp cells of apples affected with bitter pit, but not in the healthy pulp. Furthermore, the results of fluorescence staining and transmission electron microscopy (TEM) revealed that the bitter pit pulp cells undergo programmed cell death (PCD), their nuclear chromosomes condense, and amyloplast forms autophagy. The cytoplasmic Ca2+ concentration in the healthy fruits was lowest near the peduncle, followed by that in the calyx, whereas it was highest at the equator. In contrast, the cytoplasmic Ca2+ concentration in apple fruits showing bitter pit disorder was lowest near the peduncle and highest in the calyx. Moreover, the cytosolic Ca2+ concentration in the flesh cells of apples with the bitter pit was much lower than that in the healthy apple flesh cells; however, the concentration of Ca2+ in the vacuoles of fruits with the bitter pit was higher than that in the vacuoles of healthy fruits. In summary, bitter pit pulp cells contain a large number of amyloplasts, which disrupts the distribution of Ca2+ in the pulp cells and causes PCD. These two processes lead to an imbalance in cell metabolism and induce the formation of a bitter pit.

‘Honeycrisp’ Bitter Pit Response to Rootstock and Region under Eastern New York Climatic Conditions

There are still unknown factors at play in the causation of bitter pit in ‘Honeycrisp’ as well as in other apple varieties. To investigate some of these factors, we conducted a survey of 34 ‘Honeycrisp’ orchard blocks distributed across two disparate production regions in eastern New York State, representing a variety of rootstocks, over three growing seasons. Weather, soil, horticultural traits, fruit quality traits, pick timing, leaf and peel minerals were evaluated for their impact on bitter pit (BP) incidence; factors were further evaluated for their interaction with region and rootstock. ‘Honeycrisp’ trees on B.9 rootstock were smaller but with comparable terminal shoot growth when compared to those on M.26 and M.9 rootstocks. B.9 fruits, which had similar fruit size to M.26 and M.9 and had good fruit quality at harvest and after storage, were much less likely to express bitter pit symptoms compared to M.9 and M.26 rootstocks. Not all traits evaluated individually correlated significatively with bitter pit incidence after a period in storage. Depending on rootstock and region, the correlation could be significant in one situation, with no correlation at all in another. In this study, peel Mg/Ca ratio and peel Ca correlated with BP for all three rootstocks, with the strongest correlations associated with the M.9 clones. These same traits correlated with BP for both regions. Pick timing had a significant influence on BP incidence following storage, with later picks offering better bitter pit storage performance. While excessively large fruits, those in the 48 and 56 count size categories, were found to be highly susceptible to BP regardless of rootstock, B.9 BP fruit susceptibility for smaller sizes was found to be size neutral. A PLSR prediction model for each rootstock and each region showed that different variables correlated to BP depending on the situation. Thus, the results could suggest that in addition to the variables considered in this study, there are other less studied factors that can influence the expression of BP symptoms. We strongly suggest that rootstock BP performance be considered a critical parameter when planning a commercial ‘Honeycrisp’ orchard and be evaluated in rootstock breeding and development programs prior to wide commercial release.

Potential of VIS/NIR spectroscopy to detect and predict bitter pit in ‘Golden Smoothee’ apples

Aim of study: A portable VIS/NIR spectrometer and chemometric techniques were combined to identify bitter pit (BP) in Golden apples.Area of study: WorldwideMaterial and methods: Three different classification algorithms – linear discriminant analysis (LDA), quadratic discriminant analysis (QDA) and support-vector machine (SVM) –were used in two experiments. In experiment #1, VIS/NIR measurements were carried out at postharvest on apples previously classified according to 3 classes (class 1: non-BP; class 2: slight symptoms; class 3: severe symptoms). In experiment #2, VIS/NIR measurements were carried out on healthy apples collected before harvest to determinate the capacity of the classification algorithms for detecting BP prior to the appearance of symptoms.Main results: In the experiement #1, VIS/NIR spectroscopy showed great potential in pitted apples detection with visibly symptoms (accuracies of 75–81%). The linear classifier LDA performed better than the multivariate non-linear QDA and SVM classifiers in discriminating between healthy and bitter pitted apples. In the experiment #2, the accuracy to predict bitter pit prior to the appearance of visible symptoms decreased to 44–57%.Research highlights: The identification of apples with bitter pit through VIS/NIR spectroscopy may be due to chlorophyll degradation and/or changes in intercellular water in fruit tissue.