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Università degli Studi di Milano (2015)

GENETIC DISSECTION OF DEVELOPMENTAL TRAITS IN BARLEY (HORDEUM VULGARE) - ITALY IRAN

VERDERIO, GABRIELE

Titre : GENETIC DISSECTION OF DEVELOPMENTAL TRAITS IN BARLEY (HORDEUM VULGARE) - ITALY IRAN

Auteur : VERDERIO, GABRIELE

Université de soutenance : Università degli Studi di Milano

Grade : Tesi di dottorato 2015

Résumé
Barley (Hordeum vulgare) ranks in fourth place among cultivated cereals for worldwide production and is a recognized model organism for genetic and genomic studies in the Triticeae tribe, which includes wheats (Triticum species) and rye (Secale cereale). Root and shoot architecture traits are key factors in plant performance, competition with weeds, adaptation and stress responses thus having an important impact on yield and yield stability. Breeders have proposed hypothetical optimal morphological parameters to improve production in relation to different environmental conditions. Leaf size and orientation are determinants of canopy transpiration and radiation interception e.g. in dry and sunny Mediterranean environments reduced size and erect orientation of the leaves can reduce water loss by transpiration and allow deeper light penetration into the canopy. Tillering influences crop performance, biomass and grain production, e.g. a reduction in tillering compensated by an increase dimension and number of kernels per spike could be a strategy of adaptation to dry climates. A reduction in plant height and an augment in stem thickness is connected to lodging resistance. Root system extension is connected to the ability of the plant to reach water. The objectives of this project were to dissect genetic variability for shoot and root morphological traits in barley, identifying genomic regions and characterizing genes controlling these traits, and exploring how different traits influence each other. To this end, two approaches were undertaken depending on the trait(s) under study : • the first exploited natural variation in a panel of modern and old European barley cultivars to carry out association mapping of flowering date, stem diameter, spike fertility, leaf dimension, plant height, tillering and root extension (Chapters 2 and 3) ; • the second was to characterize the ontogenetic basis of increased tillering using as a case study the many-noded dwarf6.6 (mnd6.6) high tillering barley mutant (Chapter 4). In the first approach, we focused on winter barley because of its agronomic interest in the Mediterranean area, where genetic improvement of drought tolerance is particularly important. We analyzed a panel of 142 European winter barley cultivars (67 two-rowed and 75 six-rowed) with a view to conduct a genome wide association scan (GWAS) for shoot and root architecture traits in two separate sets of experiments. To this end, genotyping data for 4,083 SNPs were available from previous projects of which 2,521 mapped on the POPSEQ barley reference map. PCoA results indicated the existence of two major sub-populations in our germplasm panel, corresponding to two-rowed and six-rowed barley cultivars. In order to study shoot developmental traits (Chapter 2) the panel was phenotyped during the growing season 2012-2013 in a field trial at Fiorenzuola d’Arda, Piacenza, Italy. The experimental scheme consisted in 3 replicates (each being a plot of 24 well spaced plants) in randomized blocks. For selected traits data were integrated and analyzed together with those coming from a parallel field trial that was carried out at the University of Shiraz, Iran (data courtesy of Dr. Elahe Tavakol). Flowering date (FD) and leaf width (LW) were measured in both Italy and Iran, leaf length (LL) was measured only in Iran, plant height (PH), spike length (SL), number of fertile rachis node per spike (NFRN) tillering (T) and (SD) were measured only in Italy.

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