الفهرس 
Effects of drought on morphological characteristics:
Plant material and growth conditionsOnly 14 pages are availabe for public view
 |  | from | 153 |  |  |
| | | from | 153 | | |
Abstract
Physiological and molecular responses of some rice genotypes to drought stress and the role of some microorganisms in rice tolerance to drought stress Rice is an essential food. It supplies more than three billion people with about 65% of their daily calorie intake. To meet the expected consumption by the year 2025, rice production must be increased by 60%. About 30% of freshwater for agricultural crops worldwide was used for rice cultivation. In Egypt, the competition among the limited water resources could escalate worsely. To overcome the water limitation problems in Egypt, exploring ways of reducing water used in rice production is major strategic importance for sustainable agricultural production under water deficient condition. Water deficit affects plant photosynthesis, morphology, physiology, biochemical and molecular reaction of plant and yield. Also affects the expression patterns of many genes as a response of control plant reaction. Plant growth promoting rhizobacteria (PGPRs) can directly stimulate micro nutrient uptake and influence phytohormone homeostasis, or indirectly enhance the plant defense system toward biotic and abiotic stresses and improve soil structure and texture. Genome responses to stress are varied, so gene expression studies are important tools to understand and contrasting the holistic responses of an organism to their ecosystem. This study was conducted on four rice genotypes Orabi3, Vandana, IR64 and Giza177 at Genetics Department, Faculty of Agriculture, Tanta University. The aim of study: Reducing the rice consumption rate of water is desirable strategy to overcome water limitation problem in Egypt. In accordance with this strategy, the purpose of this study was to: 1- Investigate the differential responses of four rice genotypes under drought stress conditions on various morphological, physiological and biochemical parameters and on the molecular genetical level at three different growth stages. 2- Evaluate soil biological activities by estimation of microbial population density (bacteria, fungal and actinomycetes) and soil enzymatic activities under the tested conditions. 3- Isolate and identify the screened drought tolerant endophytic bacteria, and characterize the isolates for their functional traits associated with plant growth promotion and induced systemic tolerance. 4- Evaluate the potential application of the artificial inoculation by three selected endophytic bacteria on one sensitive rice genotype (to enhance abiotic stress tolerance) by studying the morphological, physiological, biochemical and molecular responses under drought stress. Materials and methods First experiment This experiment was designed to screen the differential responses of 4 rice genotypes under drought stress through three growth stages in respect to the role of soil microbial activity associated with the studied genotypes. The germinated seeds were placed in pots (25 cm diameter and 35 cm height). The pots were irrigated up to water holding capacity of the soil. The drought stress treatment began after 10 days of planting. Irrigation of stressed plants was applied at about 65% of SWC of control treatment (field capacity). This investigation involved many determinations: Morphological parameters; this included: • Shoot and root Lengths • Fresh and dry weights of shoot and root • Numbers of tillers Physiological and biochemical parameters; this included: • Lipid peroxidation (MDA), • Electrolyte leakage (EL) • Total proteins Molecular analysis • RNA extraction and cDNA synthesis • Differential display reverse transcription polymerase chain reaction (DD-RT-PCR) was used to detect differential responses of studied genotypes at different growth stages under drought stress. Yield parameters included • Numbers of panicles, • Weight of 1000 seeds • Production of plant Soil biological activities included: Population density of microbial involved: • Bacteria, fungal and actinomycetes. Soil enzymatic activities involved • Dehydrogenase • Nitrogen cycling enzyme (urease and Nitrogenase) • Alkaline phosphatase Isolation of endophytic bacteria • Screening drought tolerant bacteria • Extraction of DNA, PCR amplification and 16S rRNA gene sequencing • Morphological and cultural characteristics • Production of IAA • Exopolysaccharides production • Phosphate solubilization