Many traditional drought assessments are conducted based on climate and hydrologic data. The availability and precision of data limit the spatial and temporal resolution and accuracy of derived drought indices. In this study, Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) were generated from Moderate Resolution Imaging Spectroradiometer (MODIS) products. The VCI was derived from Normalized Difference Vegetation Index (NDVI) that was calculated with near infrared and visible red band reflectance from MOD09Q1. The TCI was derived from land surface temperature (LST) product MOD11A2. The VCI and TCI were then combined with reference to the vegetation coverage information from MOD44B to generate the modified Vegetation Health Index (VHI). The modified VHI was applied to quantify the intensity of drought that took place in Illinois from 2000 to 2012. The results showed that the modified VHI identified the major droughts that occurred in Illinois from 2000 to 2012, especially the extreme one taking place in 2012. Moreover, the modified VHI led to the spatial distributions and temporal trends of drought severity, which were overall similar to those from the U.S. Drought Monitor (USDM) maps, but had more detailed spatial variability and much higher spatial resolution. The modified VHI also differentiated the drought impacts between the vegetated and non-vegetated areas, being a lack of the original VHI. Thus, the modified VHI takes advantage of spatially continuous and timely data from satellites and can be applied to conduct the monitoring and detection of drought intensity at local, regional, and national scales. The modified VHI can effectively synthesize the drought information of LST and NDVI to differentiate the effects of land use and land cover (LULC) types and provide the detailed spatial variability of drought intensity and thus enhance the understanding of relationship between drought condition and LULC types.

A series of experiments was carried out in the Department of Agriculture, University College of North Wales, Bangor, during October 1987 to September 1989. The purpose of these was to study the effects of water stress and salinity stress at different stages on long (Norman), medium (Fenman) and short duration (Wembley) wheat varieties in different environments. Effects of water stress were tested in large pots in different types of soil. Effects of salinity were tested by growing plants in solution culture. In both experiments water stress and salinity stress were imposed at three major stages, tillering to stem extension (TL-SE), stem extension to booting (SE-BG) and booting to maturity (BG-MT). These were tested in each variety in comparison with a control of each variety. Growth measurements, leaf number and area, stem area, shoot number, plant height, nitrogen %, nitrogen uptake, dry weight per plant were determined at the end of each stage. Soluble carbohydrates were determined at anthesis. This was done to find out how much these growth measurements were decreased during each stress period. Yield and yield components were determined at harvest. In these experiments the long duration variety took a long time in growth during TL-SE, in comparison to mid winter and spring wheat varieties. The long duration variety gave a higher plant, more straw dry weight production and more leaf number than the short duration variety. The long duration variety also gave a higher yield than the medium and short duration varieties, due to larger ears, more spikelets vi per ear, more grain number per ear and more grain number per spikelet. All varieties experienced higher temperatures and longer days during SE-BG and BG-MT in both experiments. The lengths of these stages therefore showed smaller variation between varieties. In water stress experiments the mixed peat-soil used in Experiment 2 dried out quicker than the normal field soil used in Experiment 1. The upper portion of the soil was dried before the lower portion of the soil during the stress period. With water stress at SE-BG and BG-MT the soil dried out quicker in both years. Gypsum blocks were used to give readings of water stress. with water stress at BG-MT the soil was completely dried out after the third week, in all varieties, due to higher plant height, higher temperature and more evaporation. Because of this water stress at BG-MT resulted in a short duration for ripening. In both water stress Experiments 1 and 2, in all varieties all water stress treatments decreased the growth measurements, decreased yield and yield components. In Norman water stress at TL-SE had a long stress period due to slow growth processes during cold winter. However, this stage had a similar effect on yield in Norman, Fenman and Wembley. In both water stress experiments in all varieties, water stress at SE-BG caused the largest reductions in growth measurements, because at this stage the plant had the greatest leaf area and temperature was higher, although the period of stress was only a few weeks. However, water stress at BG-MT caused the greatest decreases in yield. This stage showed the greatest vii decreases in yield and yield components, due to small grain size, fewer fertile spikelets, small size of ear, earlier leaf senescence, short duration for ripening, higher temperature, lack of soluble carbohydrate for grain f~lling from stem and pollination problems at anthesis time. In both salinity Experiments 1 and 2, all varieties had a larger green leaf area, more tillers and all varieties were much stronger after stem extension than in the water stress experiments due to the solution culture teChnique. Norman was more strong than the other varieties because of its long period grown in solution culture. Salinity at TL-SE was more damaging than other stages in all varieties. Salinity at TL-SE decreased the growth measurements, such as leaf area, stem area, plant height, dry weight per plant. Because of the growth measurement reduction, grain weight per plant, grain number per plant, grain number per ear, grain number per fertile spikelet and fertile spikelet per ear were decreased by salinity at this stage. Salinity at SE-BG and BG-MT also decreased growth measurements, decreased grain yield and yield components. Salinity at BG-MT decreased grain yield and yield components more than salinity at SE-BG. In Experiment 2 in all varieties with salinity at BG-MT plants were harvested a few days before other stages and the control. Norman was more sensitive with salinity at TL-SE than the other varieties because of its long period grown under salt stress. Norman was much stronger with salinity at SE-BG. Norman gave lower yield, yield components at BG-MT than other varieties at this stage.

A field study was conducted at ARC - Grain Crops Institute, Potchefstroom Experimental Farm and at Taung Crop Production Center during 2006/07 summer growing season. Twenty sorghum genotypes were planted in two separate blocks, under full irrigation and rain fed conditions with plot size of 4 rows x 5 m x 0.9 m giving a density of 55 555 plants ha-1. The experiment was laid out in a randomised complete block design replicated three times. The irrigated block received scheduled irrigation from planting until maturity, while the rain fed block received irrigation prior to germination only. Agronomic traits measured were plant height, stem diameter, biomass, flowering date, panicle exertion, panicle length, leaf area, grain yield, and thousand seed mass at Potchefstroom and Taung experiments. Drought susceptibility index (DSI) was quantified using the formula: DSI = [1 - (Ydi/ Ypi)]/ [1 - (YD/YP)] and %yield reduction (%YR) was calculated using the formula: %YR = (Ypi –Ydi)/ Ypi x 100. Significant variations among genotypes with regard to grain yield (GYLD), plant height (PH), panicle length (PL), biomass (BM), stem diameter (SD), panicle exertion (PEx), and 1000 seed mass (TSM) were observed at Potchefstroom under rain fed conditions, while under irrigated conditions significant variations were only observed for GYLD, PH, PL, BM, days to 50% flowering (DF), SD, leaf area (LA), PEx and TSM. At Potchefstroom genotypes varied significantly with regard to PH, PL, BM, DF, SD, LA, PEx and TSM under rain fed conditions, while under irrigated conditions genotypes varied with all traits measured with exception of harvest index (HI) and relative water content (RWC). At Potchefstroom, soil water deficits significantly affected GYLD, PH, HI, PEx and RWC, while at Potchefstroom soil water deficits significantly affected GYLD, PH, SD, LA, PEx, TSM and RWC. Genotypes varied with their level of resistance/ susceptibility to soil water deficits at both Potchefstroom and Taung. Some remarkable correlations among traits measured were observed under rain fed and irrigated conditions and across the treatments at both Potchefstroom and Taung. At Potchefstroom, significant correlation was only observed between drought susceptibility index (DSI) and PH under rain fed conditions, while at Potchefstroom negative and significant correlation was only observed between DSI and GYLD under rain fed conditions. At Potchefstroom, GYLD under rain fed significantly related to GYLD under irrigated conditions and across the treatments. However, GYLD under irrigated conditions significantly related to GYLD across the treatments. At Potchefstroom, GYLD under rain fed conditions significantly correlated with GYLD across soil water regimes, while GYLD under irrigated conditions significantly correlated with GYLD across the treatments. Genotypes that exhibited the combination of high yield potential and resistant traits were recommended. Genotypes that exhibited high resistant traits with low yield potential were recommended for breeders to incorporate those traits into susceptible genotypes with high yield potential. / Dissertation (MInstAgrar)--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21058号 / 工博第4422号 / 新制||工||1687(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 堀 智晴, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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<p>  </p> <p>Rice (<em>Oryza sativa</em> L.) is a staple crop consumed globally. Increased variability in rainfall in much of the world is a predicted consequence of climate change and drought is predicted to be a major cause for concern for rice production. One approach to mitigating water-deficit stress is integrating beneficial (drought-tolerance) loci from wild rice donors into elite rice cultivars. Bi-parental interspecific chromosome segment substitution lines (CSSLs) and near introgression lines (NILs) are genetic resources that contain genetic introgressions from wild rice but are otherwise genetically identical to the cultivated parent, known as the recurrent parent. For this study, 12 CSSLs and NILs were selected for having wild rice introgressions on chromosomes two and five, previously shown to be beneficial under field conditions. In the current work, these lines were evaluated under water-deficit conditions for their potential of serving as future pre-breeding material. The recurrent parents, Cybonnet and Jefferson, two U.S. cultivars adapted to the Southern Rice Belt, were additionally included in this study as controls. In total, three trials took place: two at Purdue University under controlled environments (West Lafayette, Indiana) and one in the field at the Dale Bumpers Rice Research Center (Stuttgart, Arkansas). Traits such as yield components, gas exchange, leaf water content, leaf water potential and chlorophyll fluorescence were measured during predawn and midday timepoints. Results from the three trials did not show consistent genotype rankings in yield component traits, which was expected due to the different ways in which water-deficit treatments were approached (continuous water-deficit application versus transient drought and recovery). While many of the CSSLs outranked Cybonnet in mean values, none were significantly different, likely due to low replication. Despite not having identified superior genotypes, the yield component, physiology, and high-throughput phenotyping datasets published here can provide the foundation to address future questions about physiological linkages and methodology development associating high-throughput data with ground-truth measurements. All data associated with this work are publicly available through Purdue University Research Repository.</p>

Drought is one of the most widespread and least understood natural phenomena. Many indices using multiple data types have been created, and their success at identifying periods of extreme wetness and dryness has been well documented. In recent years, researchers have begun to assess the potential of total water storage (TWS) anomalies in drought monitoring method- ologies. The Gravity Recovery and Climate Experiment (GRACE) provides temporally and spatially consistent TWS measurements across the globe, and studies have shown GRACE TWS anomalies are suited to identify drought. GRACE TWS is used with MODIS-derived normalized difference veg- etation index (NDVI) and NOAA/NWS precipitation data to create a new drought index, the Merged-dataset Drought Index (MDI). Each dataset corre- lates with a different type of drought, giving robustness to MDI. MDI is based on dataset deviations from a monthly climatology and is objective and easy to calculate. MDI is studied across Texas, which is broken into five dataset- defined sub-regions. Multiple drought events are identified from 2002 - 2014, with the most severe beginning in October 2010. A new drought severity clas- sification scheme is proposed based on MDI, and it is organized to match the current US Drought Monitor Classification Scheme. MDI shows strong correlation with existing drought indices, notably the Palmer Drought Severity Index (PDSI). MDI consistently identifies droughts in different sub-regions of Texas, but shows better performance in regions with large GRACE TWS signals. MDI performance is enhanced through a weighting scheme that relies more on GRACE TWS. Even with this scheme, MDI and PDSI exhibit occasional behavioral differences. Drought analysis using MDI shows for the first time that GRACE data provides information on a sub-regional scale in Texas, an area with low signal amplitudes. Past studies have shown TWS capable of identifying drought, but MDI is the first index to quantitatively use GRACE TWS in a manner consistent with current practices of identifying drought. MDI also establishes a framework for a future, completely remote-sensing based index that can enable temporally and spatially consistent drought identification across the globe. This study is useful as well for establishing a baseline for the necessary spatial resolution required from future geodetic space missions for use in drought identification at smaller scales. / text

The response of cassava (Manihot esculenta Crantz) to water stress was studied in two distinct sites (Tucson, Arizona and Santander de Quilichao, Colombia). A third experiment was conducted in Palmira, Colombia to evaluate the relationship between photosynthesis, relative humidity and yield of cassava cultivars HCol 1684. Plants stressed after 2 months of growth in Tucson reduced growth by reducing leaf formation, expansion and leaf area. Reductions in LAI due to stress imposed to MCol 1684 in Quilichao were attained by reducing leaf expansion rates and leaf formation in plants stressed after 3 months of age. Plants stressed later increased leaf fall and did not reduce leaf formation. Stress reduced dry matter production in all cultivars, especially when given to young plants. Stress also altered the patterns of dry matter partitioning in 3-month-old plants of MCol 1684, but not in those stressed at 6 months. Transpiration and diffusive conductances of MCol 1684 were reduced after 40 days of stress. These parameters were correlated to photosynthesis and leaf temperatures for non-stressed plants, and additionally with relative humidity in the plants stressed after 3 months of growth. Interestingly, leaf temperatures were lower in stressed plants of MCol 1684, which suggests that stressed cassava plants can avoid excessive heating caused by stomatal closure simply changing leaf orientation and increasing reflectance. Leaf water potential was slightly reduced by stress in Tucson except for MVen 218. Stressed plants of MCol 1684 in Quilichao showed lower values of (L) than those of non-stressed plants after 30-40 days of treatment, suggesting an adaptation of stressed plants acquired during the stress period. The effects of air humidity on stomatal functioning of MCol 1684 seems to be strong as suggested by the dependence of transpiration, conductances and photosynthesis on relative humidity.

The continuum of western North American hydroclimate during the last millennium is analyzed here using instrumental records, proxy data, and global climate model (GCM) simulations. We find that variance at long timescales (low frequencies) is generally more substantial than variance at short timescales (high frequencies). We find that local sources of autocorrelation (e.g., soil moisture storage) likely explain the tendency for variance to increase from monthly to interannual timescales, but that variance at longer timescales requires remote climate sources of variability. Our analysis of global climate model data indicates that at least one fully coupled GCM can reproduce the characteristics of the continuum on short (interannual) and long (multicentury) timescales, but that proxy spectra and GCM spectra disagree about the amount of variance present on intermediate (decadal to centennial) timescales. Since instrumental records, as well as multiple independent types of paleoclimate records, provide evidence that variance increases with timescale at these frequencies, and because numerical experiments indicate that local autocorrelation is not a likely source of variance at these timescales, we argue that climate model simulations underestimate the full range of low-frequency drought variability. Moreover, the models may also underestimate the risk of future megadroughts, which we attempt to quantify using a new method that combines frequency information from observational data with projections of 21st century hydroclimate. Our results indicate that the risk of a severe, decadal-scale drought during the coming century is at least 1-in-10 for most of the US Southwest, and may be as high as 1-in-3. These findings should be incorporated into adaptation and mitigation strategies to cope with regional climate variability and climate change.

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. November 2016, Johannesburg. / Drought stress is one of the major limitations to crop production worldwide and has been predicted to become more severe in the future due to global climate change. Research has often been focused on genetic engineering to improve the tolerance of plants to abiotic and biotic stresses. Plant growth-promoting rhizobacteria (PGPR) are an alternative mechanism to improve the tolerance of plants to many stresses and is crucial for developing and third world countries. In this study, Helianthus annuus was inoculated with Pseudomonas koreensis and subjected to drought stress. The germination and growth characteristics, leaf water content, leaf electrolyte leakage and leaf area, substrate water content, phenolic compounds and proline concentration, root bacterial counts, as well as recovery and regrowth, were compared between uninoculated and inoculated plants. In addition, the phosphatase activity, siderophore and indole-3-acetic acid (IAA) production, as well as growth at -0.73 MPa was compared between P. koreensis and P. fluorescens. It was found that inoculated plants were significantly taller plants and had a larger leaf area; and had significantly higher phenolic and proline concentration and a higher colonised root surface under drought stress. However, inoculation negatively affected germination and chlorophyll fluorescence. These plants also had a lower substrate water content under drought stress. P. koreensis outperformed P. fluorescens in all parameters studied, except for growth under osmotic stress. It can be concluded that P. koreensis generally improves the drought stress tolerance of H. annuus, however, further investigations are needed to determine the reasons for some of the negative effects. / LG2017