EMU DSpace – Eesti Maaülikooli digitaalarhiiv
Digitaalarhiiv EMU DSpace kogub, säilitab ja loob ligipääsu Eesti Maaülikooli liikmeskonna poolt loodud või Eesti Maaülikooli vastutusvaldkondadega seotud teadustöödele toetamaks maaülikooli konkurentsivõimet ja teadmistepõhist ühiskonna arengut. Digitaalarhiivi haldab Eesti Maaülikooli raamatukogu.
Valdkonnad DSpace's
Valige valdkond, et selle kogusid sirvida.
- Institute of Forestry and Engineering (MMI)
- Institute of Agricultural and Environmental Sciences (PKI)
- Institute of Veterinary Medicine and Animal Sciences (VLI)
- Publications
- Units
Hiljutised sisestused
The impact of straw application on growth dynamics and proline accumulation in drought-stressed rice
(Estonian University of Life Sciences, 2025) Ria, R.P.; Kartika, K.; Lakitan, B.; Sulaiman, F.; Meihana, M.
The frequent occurrence of unpredictable extreme droughts necessitates investigating measures to mitigate their impacts, as drought may occur at any growth phase of rice. This study evaluated the efficiency of straw applications to conserve soil moisture and mitigate the negative effect of drought stress on rice in tropical riparian wetlands. Rice straw was applied as organic matter (S1) and as mulch (S2) and then subjected to drought stress during early vegetative (D1), late vegetative (D2), and generative (D3) phases. The result of this study showed that the utilization of straw slowed down the water loss through evaporation as indicated by soil moisture. However, both rice straw applications, organic matter and mulch, were inefficient in maintaining the optimum plant growth when the soil moisture declined to < 10%. Drought stress at the early vegetative phase reduced the number of leaves by 63.68%, the number of tillers by 50.58%, and the total leaf area by 72.36%. Drought stress at the early vegetative phase also delayed flowering time for 11 days. Meanwhile, drought stress during the generative phase reduced the number of filled spikelets by 45.18% and increased sterile spikelets to 247.05%, which significantly reduced the yield. Plants that experienced drought stress during the vegetative and generative phases eventually increased the proline content by about 10 times (18.47 mmol g-1) compared to unstressed plants (1.62 mmol g-1). Straw mulching is recommended for mild to moderate droughts, but additional methods are needed to maintain soil moisture below 10%.
Toxicity of insecticides for adults of Diceraeus melacanthus Dallas, 1851 (Hemiptera: Pentatomidae) in three exposure modes
(Estonian University of Life Sciences, 2025) Vieira, E.C.S.; Ávila, C.J.; Vieira, M.C.S.; Silva, P.G.
Phytophagous stink bugs are considered the important pest in second-crop corn cultivation in Brazil, especially when they occur during the early stage of plant development. This study aimed to evaluate the efficiency of insecticides in controlling adults of the Diceraeus melacanthus (Dallas, 1851) stink bug when applied separately in three different modes of exposure. The treatments were evaluated in three modes of exposure of insecticides to D. melacanthus adults as described below: direct contact (direct application of the insecticide to the insects); tarsal contact (exposure through their walking on the treated surface) and ingestion (contact through their feeding on previously treated fresh bean pods). Mortality was assessed at 1, 5, 24 and 48 hours post-exposure. We observed that the percentage of accumulated mortality of D. melacanthus adults was significant through direct contact with chemical treatments. However, if the target insect does not receive direct spraying on its body, indirect contact through its tarsus walking on the treated surface can guarantee a significant final mortality of the stink bugs. In addition, although the mode of exposure through ingestion has shown low mortality, it may also contribute to the final mortality of stink bugs in the field depending on the chemical treatment applied to the crop.
Assessment of new citrus hybrid rootstocks to salinity at the early seedling stage under greenhouse conditions
(Estonian University of Life Sciences, 2024) Majji, M.; Chetto, O.; Talha, A.; Bouaaza, G.; Beniken, L.; Benkirane, R.; Benyahia, H.
The citrus industry in arid areas is largely constrained by the salinity of irrigation water and soil. This study was conducted to determine how six novel citrus hybrid rootstocks will respond to salinity at the seedling stage. Three different NaCl concentrations, 0, 2, and 5 g L-1, were added to the half-concentrated Hoagland solution (corresponding to 1.3 (control), 4 and 9 dS m-1, respectively). Three-month-old seedlings grown in greenhouse conditions and transplanted in plastic pots were used. After two months of stress, different responses from the rootstocks and salt levels were observed. The addition of NaCl to the irrigation solution considerably decreased the fresh and dry weight and leaf chlorophyll content. Additionally, the proline content, soluble sugar, and the leaf chloride content increase with the increase in salinity. Our findings demonstrated that the hybrid Poncirus Trifoliata× Citrus reshni Hort. ex Tan. (V5) H6 is salt-sensitive, accumulating a high leaf chloride level of 46.92 mg g-1 of dry matter and a low chlorophyll content of 1.12 mg g-1 of fresh matter associated with signs of leaf toxicity, leading to poor fresh and dry weight. Although hybrid Poncirus Trifoliata× Citrus reshni Hort. ex Tan. (V1) H2 is thought to be salt-tolerant, it accumulates 38.88 mg g-1 of dry-matter leaf chloride and 1.72 mg g-1 of fresh-matter chlorophyll content.
Preliminary study of microplastics in bottled and tap water in Estonia
(Estonian University of Life Sciences, 2024) Meitern, Annika Joy; Neilant, Keith; Raamets, Jane
Microplastics (MPs) are a growing environmental concern due to their widespread occurrence and potential harmful impacts on ecosystems and public health. This preliminary study -assesses the prevalence of MPs in bottled and tap water in Estonia and reviews related research in the field. The study aimed to evaluate the occurrence of MPs and understand the potential influence of the water source and packaging material on water properties. The study encompassed 12 different bottled water products from 9 Estonian brands and tap water samples from Tallinn and Tartu. All the tested water samples contained MPs, predominantly fibers, with blue and transparent being the most common colors. The packaging material, bottle caps, or the water source did not influence the number of MPs found in bottled water. Interestingly, water packaged in glass bottles contained a higher count of MPs than in plastic bottles and tap water. The study underscores the need for further research to determine the sources of contamination.
Factors affecting beekeeping sustainability: pathogen spread, diagnostics and queen breeding
(Estonian University of Life Sciences, 2025) Naudi, Sigmar; Mänd, Marika (advisor); Karise, Reet (advisor); van der Steen, Jozef (opponent)
ABSTRACT. The decline of pollinators is a global issue caused by diseases, parasites, poor nutrition, pesticides, habitat loss, and climate change. The honeybee (Apis mellifera Linnaeus) is a vital pollinator that helps maintain ecosystem balance and ensure food security. Although the number of managed bee colonies has increased in recent decades, beekeepers continue to face various challenges, including the spread of diseases, the impact of pesticides, and bee health issues. This doctoral theses focuses on identifying several of these threats, investigating major bee diseases, the effects of pollutants, their interactions, and developing potential protection methods.
The study assessed the prevalence of the pathogenic microsporidians Nosema apis and N. ceranae in Estonian and Latvian apiaries. The results revealed that in cooler climates, the recently discovered N. ceranae is beginning to replace N. apis, which may lead to differences in the nature, spread, and control of the disease. Additionally, it was found that the simultaneous presence of both pathogens in bees increases infection levels, indicating a synergistic interaction. Research on Paenibacillus larvae, the pathogen responsible for American foulbrood, highlighted the hidden nature of the disease and its spread's dependence on bee density and climatic conditions. The use of qPCR technology proved effective for early disease detection, helping to reduce the severity and extent of infections.
To ensure the sustainability of beekeeping, it is crucial that queen bees are healthy and their development is not disrupted. Studies on the fungicide active ingredient tebuconazole showed that, while the substance accumulates in beeswax, its transfer to other hive matrices, including royal jelly and developing bees, is minimal. This suggests the presence of a so-called barrier system within the colony that limits potential exposure to contaminants. However, further research is needed to understand the internal movement of pollutants within the hive and their long-term effects. Additionally, the impact of Nosema species on queen bees was investigated, revealing that infected royal jelly caused only minimal developmental disturbances in queens. Future studies should further analyze the effects of pathogens on different members of the bee colony.