Ashrafuzzaman, Md.: Exploring ethylenediurea (EDU) as an ozone biomonitoring and screening tool for rice (Oryza sativa L.). - Bonn, 2018. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-52891
@phdthesis{handle:20.500.11811/7386,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-52891,
author = {{Md. Ashrafuzzaman}},
title = {Exploring ethylenediurea (EDU) as an ozone biomonitoring and screening tool for rice (Oryza sativa L.)},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2018,
month = dec,

note = {Tropospheric ozone concentrations are rapidly rising in many developing parts of the world, thereby threatening food security. Therefore, breeding for adapting rice varieties is essential in Asia, especially in the Indian subcontinent, to cope with ozone stress and to secure staple food supply. Genotypic variation can play a key role in successful ozone tolerance/resistance breeding. However, ozone impact evaluation on crops and field screening experiments in these highly ozone affected areas are scarce, as the establishment of field-based ozone fumigation facilities can be technically challenging or very expensive. Alternatively, ethylenediurea (EDU) has been proposed as a chemical applied as a foliar spray to assess the effects of ozone in large-scale field experiments. However, little has been known about its confounding effects on rice in the absence of ozone, and the protection mechanisms against ozone phytotoxic effects. Therefore, a series of agronomic and physiological experiments were performed including transcriptomics (RNA-Seq) and scanning electron microscopy (SEM), to test the suitability and feasibility of EDU as a future ozone biomonitoring tool for field crops. Four different treatments, (i) control (below the damage threshold level, 40 ppb), (ii) control+EDU, (iii) ozone (average 77 to 108 ppb for 7 h day-1), and ozone+EDU were assigned to rice genotypes ranked a priori in terms of ozone tolerance. Application of EDU did not affect plants in the absence of ozone, but it alleviated negative effects of ozone on plant morphology, leaf symptom formation, spectral reflectance indices such as the normalized difference vegetation index (NDVI), SPAD value, lipid peroxidation, photosynthetic parameters, panicle number, spikelet sterility as well as biomass and grain yields in the sensitive genotypes. RNA-sequencing and SEM were conducted using the Bangladeshi high yielding rice variety BR28 which was highly affected by ozone (37 percent grain yield reductions) and showed consistent recovery by EDU applications. Transcriptome profiling revealed that several thousand genes responded to ozone treatment, but almost none responded to EDU application. The dominant trend of significant interactions between ozone treatment and EDU application for the ozone responsive genes was the ozone mediated up-regulation mitigated by EDU application. These transcriptional patterns suggested that EDU did not enhance stress defense pathways in plants, but rather acted as a surface protectant against upstream physiological stress reactions. Additional experiments indicated that EDU might have ozone degrading properties due to abiotic chemical interactions between ozone and EDU. Further, SEM image analyses displayed the presence of EDU deposits on treated leaf surfaces. We further demonstrated that EDU application did not alleviate the reaction of plants to a number of other abiotic stresses i.e. iron toxicity, zinc deficiency and salinity. In conclusion, EDU is a surface protectant that specifically mitigates ozone stress without interfering with the plants' stress response systems. These properties, together with its ease of application, make it very suitable for biomonitoring and screening studies of ozone damage to field crops in developing countries.},
url = {https://hdl.handle.net/20.500.11811/7386}
}

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