No abstract

The work was performed in the I. V. Michurin Federal Scientifi c Center (Tambov region, Russia) in 2015-2018. The fruits of Sinap Orlovsky variety with high susceptibility to bitter pit, medium – to superfi cial scald and CO2 -skin injuries were used. The main post-harvest strategy of protecting fruits from bitter pit (BP) is storage in a controlled atmosphere (CA), short-term low oxygen storage (10 days, O2<1 %) reduces losses from scald and BP, but does not provide protection from diseases of varieties with high susceptibility; post-harvest treatment with ethylene biosynthesis inhibitor (1-MCP) provides protection from scald, but has an ambiguous effect on the development of BP, and may increase the degree of disease appearance. The purpose of the research is the development of innovative technology of managing of bitter pit and other post-harvest pathological diseases. In the experiment, the control and 1-MCP-treated fruits were stored at 0 + 1 °C under regular (RA) and controlled atmosphere (CA) conditions: CA-1 (CO2 – 1.2-1.5 %, O2 – 1.2-1.5 %), CA-2 (СО2<0.1 %, О2 – 1.2-1.5 %), under conditions of short (10 days) post-harvest impact of controlled factors: temperature 18-20 °С, О2 – 1.2-1.5 %, CO2<0.1 % and further storage in regular atmosphere (LO2 ). Ethylene, α-farnesen and its oxidation products (CТ281), phenolic compounds were determined in fruits, losses from bitter pit, scald, CO2 -skin injuries, quality (fi rmness) were estimated. 1-MCP-treatment ensured a low level of ethylene and CT281 accumulation in fruits, protection from scald, preservation of fi rmness in all variants of fruit storage, with maximum effi ciency of variants CA-2, CA-1 and LO2 . Fruit protection from bitter pit was provided by CA-2 technology, a signifi cant reduction of losses – LO2 . When using the technology of CA-2, losses from CO2 -skin injuries, noted in the conditions of CA-1, were excluded. The maximum efficiency of protection of fruits from BP, scald, CO2 -injuries is provided by the developed technology CA-2 (CO2<0.1 %, O2 — 1.2-1.5 %).

Chemical thinning of apple ovaries in intensive orchards is highly relevant. This farming practice reduces manual labour, decreases  the  fructification  interval and improves apple quality. Growth regulators, including alpha-aphthylacetic acid,  also  reduce preharvest fruit drop allowing for an optimal harvest capacity. The research aimed to study the impact of different alpha-naphthylacetic acid application rates on ovary thinning  and preharvest  fruit drop. Assays were conducted in 2019—2020  in a  leached-chernozem experimental apple orchard of the Michurin Federal Research Centre  in Tambov Region. Assay 1 studied the treatment impact on apple tree thinning at rates 100, 200, 300 and 400 ml/ha in 8—12 mm fruits, assay 2 (treatment 2 weeks prior to expected harvest) —  on reducing preharvest apple drop at rates 200, 300 and 400 ml/ha. The treatments significantly reduced the number of ovaries in the Zhigulevskoe/62-396 cultivar and increased mean apple fruit weight. Such increase was an important yield-rising factor in the 300 and 400 ml/ha treatments. Alpha-naphthylacetic acid treatments in 8—12 mm fruits had a significant lowering impact on total leaf nitrogen content. The treatments also induced a significant reduction in preharvest apple fruit drop, with the best effect at rate 300 ml/ha. No explicit impact of alpha-naphthylacetic acid on fructification interval was observed in the study period.

The work was carried out at the Federal Research Center named after I.V. Michurin (Tambov region, Russia) in 2019, using fruits cv. Honeycrisp with a high susceptibility to bitter pit (BP), low temperature breakdown (LTB) and soft scald (SS). Studied fruits were grown at commercial orchards from 6 regions of the Central Federal District (Moscow, Tula, Lipetsk, Kursk, Belgorod, Voronezh). The aim of the research was to assess the influence of meteorological factors of different growing regions on the susceptibility of fruits to physiological diseases during storage. The maximum susceptibility to BP is observed for fruits from the Southern region of the Central Federal District (Kursk, Voronezh, Belgorod regions) with high air temperatures (> 25 °C) and moisture deficit (HTC <0.7) during the growing season. The fruits from the Northern region of the Central Federal District (Moscow, Tula regions) with low air temperatures (minimum temperatures <10 °C) and sufficient moisture supply during the growing season (HTC > 1) are characterized by the maximum susceptibility to SS and LTB. An intermediate position is occupied by the Lipetsk region, where the risks of BP, SS and LTB development are quite high. Stressful agronomic factors such as young age of plantations (1-2 years of fruiting), low yield, strong pruning, etc. can cause the development of BP regardless of growing region, with higher risks of disease development under stressful meteorological conditions.

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.