Soil organic carbon (SOC) fractions and soil enzyme activities were effective indicators to represent C changes under different plant densities (PD) and nitrogen (N) application levels, which influenced crop yield in turn. The aim of the experiment was to investigate the impact of PD and N application levels on soil productivity. The experiment conducted in the North China Plain included three plant densities: 1) PD1 - 60,000 plants ha-1, 2) PD2 - 67,500 plants ha-1, and 3) PD3 - 75,000 plants ha-1, and three N application levels: 1) N0 - 0 kg ha-1 N, 2) N1 - 220 kg ha-1 N, and 3) N2 - 290 kg ha-1N. Maize (Zea mays L.) grain yield was higher when N was applied at the N1 and N2 application levels each year. Obviously, the grain yield and its components at the N1 and N2 application levels showed no difference at each PD, and vice versa. Plant densities and N fertilisation rates significantly affected the content of SOC, microbial biomass C (MBC), and dissolved organic C (DOC). Ranged from 1.85 to 1.98 mg d g-1, the sucrase activity was larger in the treatment with a high PD and N fertilisation rate. Higher PD yielded the increase of grain yield (GY) by 19.38%, while the kernel number per ear (KN) and the 1,000-kernel weight (TKW) were decreased by 7.81% and 9.03%, respectively. In addition, the grain yield and yield components were dramatically increased at the N2 application level. The SOC content and its fractions and the sucrase activity were also increased with the PD and N fertilisation rate.These results indicated that the optimum PD and N fertilisation rates were benefits for increasing the grain yield and soil C storage. Considering both soil parameters and grain yield, the PD of 75,000 plants ha-1 and the N fertilisation rate of 220 kg ha-1 N were benefits for crop production and soil sustainability.
Living mulch is the most natural soil cover in the orchard; however, competition with grasses creates stressful conditions for fruit crops.The reaction of plants to stress can be determined by the activity of antioxidant enzymes and the content of lipid peroxidation products in plant tissues.The reaction of trees to coexistence with living mulch (natural grasses that were mowed four times during the growing season) was studied in an organic sweet cherry (Prunus avium L.) orchard with chestnut, sandy soil in the warm and arid conditions of Southern Steppe of Ukraine.The aim of the research was to determine how the living mulch (compared to bare fallow) affects the activity of antioxidant enzymes and the content of malondialdehyde (MDA) in sweet cherry fruits at different stages of fruit development.It was determined that living mulch significantly increased the activity of ascorbate peroxidase (by 21-52%), polyphenol oxidase (by 22-42%), and peroxidase (26-34%) in the tissues of sweet cherry fruits.The MDA content was significantly higher in sweet cherry fruits produced under living mulch (compared to the fruits of a bare fallow management system) only at the stage of partial reddening in 2018 (by 41%) and at the stage of stone hardening in 2019 (by 58%).At the picking maturity stage, no significant difference between the treatments of the experiment was found, which indicates the successful overcoming of oxidative stress caused by competition with natural grasses.
Fusarium wilt, caused by Fusarium oxysporum, is considered one of the essential diseases of strawberries.The importance of nutrient supply against Fusarium infection has been studied, while the severity of Fusarium wilt under nutrient deficiency remains unknown.The effect of F. oxysporum on strawberries under calcium (Ca), iron (Fe), and zinc (Zn) deficiency was studied.As plant material, the strawberry (Fragaria × ananassa Duch) cultivar 'Albion' was used.After growth for two months in the nutrient solution, plants were exposed to Ca, Fe, or Zn deficiency conditions (except control).Next, the plants were exposed to mineral deficiency conditions for two months.Finally, a group of non-deficient (control) and mineral-deficient plants were subjected to Fusarium infection.Disease development and severity were monitored over three weeks.At the end of the experiment, the highest plant decline index was found under Ca deficiency followed by Fe and Zn ones.Fusarium infection caused a decrease in the chlorophyll concentration.Nutrient deficiency or Fusarium infection decreased cell expansion.Fusarium + Ca deficiency decreased xylem conduit diameter.Fusarium + Ca deficiency decreased theoretical stem hydraulic conductivity, while other treatments increased the value.According to the results, the Fusarium wilt severity was higher under Ca deficiency.The results of the experiment suggest that the strawberry growers must deal with Ca deficiency in Fusariuminfected plants.
This study aimed to evaluate the impact of environmental and genetic factors on the yield, starch, and dry matter content in tubers of potato (Solanum tuberosum L.) cultivars belonging to different maturity groups considering cultivars diversity according to SSR markers.Twenty-four very early, early, medium, and late potato cultivars were evaluated.Field experiments were conducted in 2018-2020 in two locations: Forest Steppe and Forest zones of Ukraine.The SSRs analysis was carried out in 2021 using eight markers: STM0019, STM3009, STM2005, STM2028, STM3012, STM3023, STM5136, and STM5148.During this study, it was found that the growing zone and the year weather conditions had the greatest influence on the potato tuber yield -54% and 24%, while the effect of the cultivar genotype on the tuber yield was 8%.It was found that the cultivar genotype and the year weather conditions had the greatest influence on the potato tuber dry matter content -36% and 30%, respectively.The impact of cultivar genotype on the starch content was 31%, while the influence of the year weather conditions reached 21% and the growing zone 3%.Based on the distribution of alleles obtained by SSR markers, the majority of the very early ('Riviera', 'Prada', 'Duma', and 'Vzirets') and one of the early ('Zhytnytsia') tested potato cultivars were included in one cluster group.It was revealed that the 416 bp allele was identified by the STM5148 marker mainly in the very early potato cultivars, and the 424 bp allele was detected only in the very early and early ones.The study of SSRs and their associations with maturity can be considered as a reliable and rapid method for potato genotyping to find favourable combinations of alleles.Thus, to increase the nutritional value and productive potential of potatoes by developing and improving the main elements of cultivation technology, the biological characteristics of the potato cultivars in the agricultural and climatic conditions of Ukraine should be taken into account.
Salinity in soil and irrigation water has negative effects on plant morphology, physiology, and biochemical processes. In this study, an experiment was conducted to investigate the effect of two plant growth-promoting rhizobacteria (PGPR) Bacillus subtilis and Pseudomonas fluorescens on sweet basil (Ocimum basilicum L.) growing under salinity stress: 0 (control, without NaCl), 50, and 100 mM NaCl. Increasing salinity significantly decreased plant height, root length, aboveground and root biomass, and photosynthetic pigment content. However, bacterial inoculation reduced the negative effects of salinity. Both antioxidant enzyme activity and antioxidant metabolites were affected by salinity and PGPR inoculation. The activity of catalase was the highest in P. fluorescens-inoculated plants at 100 mM NaCl (0.084 U g-1 FW). The highest activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) was observed in B. subtilis-inoculated plants at 100 mM NaCl (2.83 and 0.61 U g-1 FW, respectively), and the highest percentage of essential oils (EOs) was found in plants inoculated with B. subtilis under 50 mM NaCl (0.87%). The results of gas chromatography-mass spectrometry (GC-MS) showed the main constituents of the basil EOs in all treatments were oxygen-containing monoterpenes. The highest content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) (as indicators of stress conditions) was related to non-inoculated plants at 100 mM NaCl (2.675 nmol g-1 FW and 0.8525 mu g g-1 FW, respectively). The highest level of nitrate reductase activity was observed under non-saline conditions and in B. subtilis-inoculated plants: 4.33 mu mol NO2 h-1 g-1 FW. Increasing salinity significantly decreased glutamine synthetase (GS) activity and total protein content in leaves. According to the main effect of inoculation, the highest glutamine synthetase activity and protein content was found in P. fluorescens-inoculated plants: 6.065 mu mol GHA mu g-1 protein h-1 and 31.77 mg g-1 FW. The highest concentration of proline was found at 100 mM NaCl along with P. fluorescens inoculation (6.27 mu g g-1 FW). These results indicate a positive effect of PGPR on plant salt stress and physiology.
