Tropical, Coastal Aquifer Management - A Case Study

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Exploring combined stress incited disease dynamics of chickpea x dry root rot interation

Dry root rot (DRR) of chickpea caused by Rhizoctonia bataticola (Rb) has become an emerging threat to chickpea production. Under field conditions, the disease becomes highly aggressive, coincides with higher temperatures and decrease in soil moisture content (SMC). Thus establishing a sound relation between various climatic factors and DRR is necessary to design a rational strategy for combating this disease. Hence, the present study aims to quantify the roles of temperature, soil moisture and Rb as combined stress for causing infection and subsequent disease progression in chickpea. The results proved that a significant relationship exists between the biotic and abiotic elements in predisposing chickpea to DRR. Out of two temperatures (25°C and 35°C) and two soil moisture content (60% and 80% SMC) tested, the combination of high temperature (35°C) and low SMC (60%) was successful in inciting early disease symptoms in the chickpea cultivars tested. The disease severity based on percent susceptibility index (derived from modified 0-9 rating scale) and percent loss in root biomass also provided similar insights, where plants grown under the above combination displayed higher degree of root rot than the combination of low temperature (25°C) and high SMC (80%). A high positive correlation was observed between disease severity, temperature at 35°C and SMC at 60%, whereas, a negative correlation was realized for temperature at 25°C and SMC at80%. Results of the real-time qPCR based absolute quantification for fungal propagules present in the root tissues sampled at different time points also corroborated with the above finding

Temperature and Soil Moisture Stress Modulate the Host Defense Response in Chickpea During Dry Root Rot Incidence

Dry root rot caused by the necrotrophic phytopathogenic fungus Rhizoctonia bataticola is an emerging threat to chickpea production in India. In the near future, the expected increase in average temperature and inconsistent rainfall patterns resultant of changing climatic scenarios are strongly believed to exacerbate the disease to epidemic proportions. The present study aims to quantify the collective role of temperature and soil moisture content (SMC) on disease progression in chickpea under controlled environmental conditions. In our study, we could find that both temperature and soil moisture played a decisive role in influencing the dry root rot disease scenario. As per the disease susceptibility index (DSI), a combination of high temperature (35 C) and low SMC (60%) was found to elicit the highest disease susceptibility in chickpea. High pathogen colonization was realized in chickpea root tissue at all time-points irrespective of genotype, temperature, and SMC. Interestingly, this was in contrast to the DSI where no visible symptoms were recorded in the roots or foliage during the initial time-points. For each time-point, the colonization was slightly higher at 35 C than 25 C, while the same did not vary significantly with respect to SMC. Furthermore, the differential expression study revealed the involvement of host defense-related genes like endochitinase and PR-3-type chitinase (CHI III) genes in delaying the dry root rot (DRR) disease progression in chickpea. Such genes were found to be highly active during the early stages of infection especially under low SMC

The Interactions Between Rapeseed Lipoxygenase and Native Polyphenolic Compounds in a Model System

The focus of the present research was to study inhibition of lipoxygenase activity by rapeseed native polyphenols and the interactions between those compounds and the enzyme. The enzyme and polyphenolic compounds (polyphenols, phenolic acids) were extracted from rapeseed (Brassica napus) varieties Aviso and PR45DO3. The total phenolic compounds concentration in tested rapeseed was 1,485–1,691 mg/100 g d.m. (dry matter) and the free phenolic acids content in both rapeseed varieties was about 76 μg/100 g d.m. The isolated proteins showed lipoxygenase activity. Prooxidant properties of phenolic compounds in the presence of lipoxygenase and linoleic acid were observed rather in the case of extracts containing a relatively high concentration of miscellaneous polyphenols. Antioxidant properties were recorded in the case of phenolic acid extracts which contain only 1.4–1.9% of phenolics present in raw phenolic extracts. We propose that the prooxidant effect of phenolic compounds comes from quinone and oxidized polyphenols formation. The observed antioxidant activity of phenolic acid extracts is probably due to their ability to scavenge free radicals formed from linoleic acid. However, reduction of lipoxygenase ferric to ferrous ions, which prevent the activation of the enzyme and inhibited its activity, was also observed

PARAMETRIC STUDIES ON THE ADVANCING INTERFACE IN COASTAL AQUIFERS DUE TO LINEAR VARIATION OF THE FRESH-WATER LEVEL

The transient motion of the freshwater-seawater interface in coastal aquifers due to a constant lowering of freshwater levels at inland locations is simulated using a sharp-interface, finite-element model. The performance of the numerical model is compared with a Hele-Shaw model. The numerical model is then used to perform parametric studies on an advancing interface that considers hypothetical cases over a wider range of possible conditions. The advancement of the interface was found to be dependent on the rate, location, and period of freshwater level variations. A seaward moving freshwater divide is formed by the lowering of the freshwater level. When the advancing interface crosses the seaward moving divide, aggressive intrusion is likely because of the reversed freshwater gradient existing landward of the divide. A safe zone for the freshwater extraction can be determined based on the movement of the interface and the freshwater divide

Transient effect of battery of injection wells on seawater intrusion

The transient effect of battery of injection wells on seawater intrusion into coastal confined aquifers is analyzed using a quasi-three-dimensional areal finite-element model derived based on the sharp interface approach. Linear triangular elements are used to discretize the domain The validity of the model is tested using the theoretical solutions and experimental results. The model is then used to carry out detailed parametric studies on the efficacy of battery of injection wells in controlling seawater intrusion. Hypothetical cases over a wide practical range are considered for this purpose. In the study, the motion of the interface is tracked for different combinations of the well spacing, injection rate, and the duration. Relationships are established between the key parameters in nondimensional forms, which have wider practical application. The injection wells are found to be effective in controlling the intrusion over a longer period of operation, running into several years. Reduction of intrusion up to 60-90% is achievable under favorable conditions. A specific example is solved to illustrate the usefulness of the results