Genetic dissection of resistance to abiotic and biotic stresses in durum wheat

This thesis was aimed to investigate the genetic response to abiotic and biotic stresses in durum wheat (Triticum turgidum L. var. durum), a cultivated tetraploid subspecies used for the production of pasta, couscous and various types of bread. Two research areas were focused: i) the high-throughput phenotyping (HTP) to detect novel drought tolerance quantitative trait loci (QTL) clusters and ii) the Kompetitive Allele Specific Polymerase chain reaction (KASP) marker development for the genetic dissection of Furarium head blight (FHB) resistance. Concerning the first area, I investigated drought adaptive traits on durum wheat elite accessions at Maricopa Agricultural Center (University of Arizona, US) which provided the experimental field and the high-throughput phenotyping platforms. The genome-wide association study (GWAS) detected thirty-one QTL clusters for two or more drought adaptive traits unrelated to the major loci responsible for phenology and plant height. Twelve of them overlapped with the major QTL for grain yield and related traits previously reported in studies carried out across a broad range of soil moisture availability and field drought conditions in wheat. Concerning the second area, I investigated two plant materials: i) 130 durum wheat accessions artificially inoculated with Fusarium culmorum and F. graminearum species and evaluated for incidence (INC), severity (SEV), FHB index, Fusarium-damaged kernels (FDK) and deoxynivalenol (DON) content; ii) 165 F6 recombinant inbred lines (RILs) from the cross between the cultivars Simeto and Levante evaluated for SEV using FG as inoculum. The genetic dissection led to sixteen QTL clusters, in part unrelated to the phenology and unknown in bread wheat, from which specific loci significantly influenced DON content. The haplotype analysis allowed me to validate KASP Single Nucleotide Polymorphisms (SNPs) suitable for marker-assisted selection (MAS) programs and to select cultivars for resistance/tolerance to DON content and other FHB traits

Carbon Isotope Composition and the NDVI as Phenotyping Approaches for Drought Adaptation in Durum Wheat: Beyond Trait Selection

High-throughput phenotyping platforms provide valuable opportunities to investigate biomass and drought-adaptive traits. We explored the capacity of traits associated with drought adaptation such as aerial measurements of the Normalized Difference Vegetation Index (NDVI) and carbon isotope composition (δ13C) determined at the leaf level to predict genetic variation in biomass. A panel of 248 elite durum wheat accessions was grown at the Maricopa Phenotyping platform (US) under well-watered conditions until anthesis, and then irrigation was stopped and plot biomass was harvested about three weeks later. Globally, the δ13C values increased from the first to the second sampling date, in keeping with the imposition of progressive water stress. Additionally, δ13C was negatively correlated with final biomass, and the correlation increased at the second sampling, suggesting that accessions with lower water-use efficiency maintained better water status and, thus, performed better. Flowering time affected NDVI predictions of biomass, revealing the importance of developmental stage when measuring the NDVI and the effect that phenology has on its accuracy when monitoring genotypic adaptation to specific environments. The results indicate that in addition to choosing the optimal phenotypic traits, the time at which they are assessed, and avoiding a wide genotypic range in phenology is crucial

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity