This study evaluated the applicability of remote sensing instrumentation for site- specific management of abiotic and biotic stress on cotton grown under a center pivot. Three different irrigation regimes (100%, 75%, and 50% ETc) were imposed on a cotton field to 1) monitor canopy temperatures of cotton with infrared thermometers (IRTs) in order to pinpoint areas of biotic and abiotic stress, 2) compare aerial infrared photography to IRTs mounted on center pivots to correlate areas of biotic and abiotic stress, and 3) relate yield to canopy temperatures. Pivot-mounted IRTs and IR camera were able to differentiate water stress between the irrigation regimes, however, only the IR camera was effectively able to distinguish between biotic (cotton root rot) and abiotic (drought) stress with the assistance of groundtruthing. The 50% ETc regime had significantly higher canopy temperatures, which were reflected in significantly lower lint yields when compared to the 75% and 100% ETc regimes. Deficit irrigation up to 75% ETc had no impact on yield, indicating that water savings were possible without yield depletion.

Agronomic and physiological traits associated with drought adaptation were assessed within the Seri/Babax recombinant inbred line population, derived from parents similar in height and maturity but divergent in their sensitivity to drought. Field trials under different water regimes were conducted over three years in Mexico and under rainfed conditions in Australia. Under drought, canopy temperature (CT) was the single-most drought-adaptive trait contributing to a higher performance (R2= 0.71, p<0.0001), highly heritable (h2= 0.65, p<0.0001) and consistently associated with yield phenotypically (r= -0.75, p<0.0001) and genetically [R(g)= -0.95, p<0.0001]. CT epitomises a mechanism of dehydration avoidance expressed throughout the growing season and across latitudes, which can be utilised as a selection criteria to identify high-yielding wheat genotypes or as an important predictor of yield performance under drought. Early response under drought, suggested by a high association of CT with estimates of biomass at booting (r= -0.44, p<0.0001), leaf chlorophyll (r= -0.22,p<0.0001) and plant height (r= -0.64, p<0.0001), contrast with the small relationships with anthesis and maturity (averaged, r= -0.10, p<0.0001), and with osmotic potential (r= -0.20, p<0.0001). Results suggest that the ability to extract water from the soil under increasing soil water deficit is a major attribute of drought adaptation. Ample genetic variation and significant transgressive segregation under drought suggested a polygenic governance feasible of dissection via molecular markers of CT and associated physiological and agronomic traits. Bulked segregant analysis of selected secondary traits was utilised as an alternative to complete genome mapping, due to a low polymorphism (27%) within the cross and limited chromosomic linkage of loci. The assessment of the extremes of expression in a genotypic subset with a composite molecular database of 127 markers (PCR-based and AFLPs) allowed evaluation of the three hexaploid wheat genomes and coverage of all chromosomic groups, except 3D. One-way analysis of variance indicated significant associations of loci explaining phenotypic variance under drought and rainfed conditions, of 20-70% in Mexico and 20-45% in Australia (F>5.00, p<0.05). Significant loci were established in both latitudes for all physiological and agronomic traits assessed via BSA, with CT being the trait with the most numerous associations (in Mexico, 34 loci; in Australia, 24). Results demonstrate an efficient development of molecular markers associated to physiological traits under specific soil water conditions in Mexico and Australia, and suggest further genomic and transcriptomic studies be conducted for unravelling the complex relationship between drought adaptation and performance under drought. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1284279 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

In the Mediterranean area water is a scarce natural resource and periods of drought are frequent. It is then important to increase water use efficiency of irrigated crops. In order to achieve this, one promising option is regulated deficit irrigation (RDI). RDI consists in reducing water application during stages of crop development when yield and fruit quality have low sensitivity to water stress. Full irrigation is provided during the rest of the season to maintain production and fruit quality at adequate levels (Behboudian and Mills, 1997). In citrus, flowering and fruit set are sensitive periods to water restrictions, because water stress during this period increases fruit drop (Ginestar and Castel 1996). The more appropriate phenological period for applying water restrictions seems to be the summer period providing that water applications returned at full dosage sufficiently before harvest in order to allow for compensation in fruit growth (Cohen and Goell 1988). Previous work by González-Altozano and Castel (1999) showed the feasibility of applying RDI in 'Clementina de Nules' and identified threshold values of plant water stress that allowed water savings of about 10-20% without any detrimental effect on yield or fruit size. It would be desirable now to study the extrapolation of these results to commercial orchards of citrus and assess the use of RDI in different citrus cultivars. Two RDI strategies (RDI-1, irrigated at 50% of crop evapotranspiration (ETc) during summer and; RDI-2, irrigated at 35% ETc during the same period to RDI-1) will be compared with a control treatment irrigated at full requirements. As the level of water stress reached by trees is the important factor when RDI strategies are applied, the study of accurate water stress indicators for citrus is also needed. Thus, during the period of water restrictions the use of sap flow and canopy temperature measurements, obtained by thermal imaging or by means of fixed infrared thermometer sensors, will be assessed and compared to classical methods like stem water potential and stomatal conductance. / Ballester Lurbe, C. (2013). Regulated deficit irrigation in citrus: agronomic response and water stress indicators [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28582 / TESIS / Premios Extraordinarios de tesis doctorales

As average global temperatures rise, cool-season C3 turfgrasses, such as the most commonly grown Kentucky bluegrass (Poa pratensis L.; KBG), struggle to tolerate extreme summer heat and increase their water consumption. Hybrid Bermudagrass (Cynodon dactylon [L.] Pers. × Cynodon transvaalensis Burtt Davy; HBG) is a warm-season C4 grass that may be increasingly suited for northern ecosystems traditionally classified as transition or cool-season climate zones. Glasshouse and field studies were conducted to compare HBG and KBG water use. The objective of the glasshouse study was to evaluate plant health and growth for two HBG cultivars (‘DT-1’ and ‘NorthBridge’) compared to a blend of KBG cultivars in all combinations of deficit, moderate, and high irrigation at optimum or short mowing height. The study was conducted in a glasshouse at Provo, UT, USA from 2020-2021. Grass was grown in pots arranged in a randomized complete block, full factorial design, with four replications of each treatment. The moderate KBG was also significantly different from both high and deficit for verdure and for the last half of NDVI. The objective of the field study was to evaluate two HBG cultivars (‘Tahoma 31’ and ‘Latitude 36’) compared to a blend of KBG cultivars for water loss and canopy health, temperature, and growth when subjected to deficit, moderate, and high irrigation. The study was arranged in a randomized complete block, full factorial design with three replications per treatment, and was conducted at Provo, UT, USA throughout the summer of 2021. In both the glasshouse and field trials, the deficit irrigated KBG consistently scored lower for NDVI and visual turf quality than all other treatments, including moderate and high KBG. This same trend was seen in the field study for percent cover. Although not observed in the glasshouse trial, it was observed in the field trial that the different irrigation levels of HBG resulted in no significant differences for any measurements but the HBG regularly scored better than KBG. The canopy temperatures of deficit irrigated KBG were also higher than all other treatments on most dates. The shoot mass, thatch mass, and total biomass of KBG were significantly less than either HBG cultivar. In the glasshouse trial it was observed that all deficit grasses were significantly lower than the other irrigation treatments and HBG had significantly deeper roots than KBG, although these results were not seen in the field trial. The data suggest that irrigation needs will be less for HBG than KBG and that HBG could provide a water-saving turfgrass alternative to KBG in semi-arid, cool-season regions with increasing water scarcity.