Current trends in population growth suggest that global food production is
unlikely to satisfy future demand under predicted climate change scenarios.
Therefore, further improvements on wheat yield potential will be essential to
meet future food demand. Thus, to further raise wheat grain yield it is critical to
understand the physiological basis of grain number per m2 determination. Yield
responsiveness to resource availability is usually related to grain number per m2
in most of grain crops, such as durum wheat. Under Mediterranean conditions,
wheat yields vary widely, mainly in response to erratic rainfall, but it has been
proposed that part of this variability may be reduced through nitrogen (N)
management. Wheat yield responses to N fertilisation are usually related to
those of grains per m2, which in turn is the consequence of processes related to
floret development (floret initiation followed by floret death/survival) during stem
elongation. However, there are almost no studies published relating floret
primordia generation and survival in response to increases in N availabilities in
wheat. Understanding the dynamics of floret primordia development as a
physiological determinant of grain setting can be relevant to further increase
grain yield in wheat. The focus of this thesis was to study the effects of N
availability and the differences among modern cultivars (and, in some cases,
combined with availability of other resources) on dynamics of floret
development and survival determining the fate of these primordia and the
generation of grain number in durum wheat.
Six experiments were conducted (4 semi-controlled and 2 field conditions)
during four consecutive growing seasons at Catalonia, NE Spain, with a
combination of different N and water availabilities and contrasting modern
durum wheat cultivars.
Across all experiments, yield responsiveness to N was, in general, related to
grain number increases as an indirect response to N through its effect on
increasing growth. This is not only based on the fact that the relationship of
grain number with spike dry matter was not improved if spike N were used
instead, but also on the fact that detillering did increased grain number through
the same relationships to spike dry matter. Also, improved spike fertility was
due to both producing more fertile florets (in response to N and water or to the
removal of competing shoots) and to reduce the percentage of failure of fertile
florets in becoming grains. Responsiveness of the number of fertile florets was
determined by a developmental response of floret primordia, which under high
resource availability conditions continued developing normally in some distal
florets of the spikelets, at any position of the spike, whilst in more stressful
conditions their development stopped. Genotypic variation in fruiting efficiency
was found for modern durum wheat cultivars and there was a tendency for
some cultivars to have higher values of fruiting efficiency in most of the
environments. Differences in fruiting efficiency were responsible for genotypic
differences in grain number. A functional negative relationship was found
between grain weight and fruiting efficiency, revealing a trade-off related to
spike growth per floret developing normally.
| Identifer | oai:union.ndltd.org:TDX_UDL/oai:www.tdx.cat:10803/104605 |
| Date | 27 February 2012 |
| Creators | Ferrante, Ariel |
| Contributors | Slafer, Gustavo A., Savin, Roxana, Universitat de Lleida. Departament de Producció Vegetal i Ciència Forestal |
| Publisher | Universitat de Lleida |
| Source Sets | Universitat de Lleida |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | 177 p., application/pdf |
| Source | TDX (Tesis Doctorals en Xarxa) |
| Rights | info:eu-repo/semantics/openAccess, ADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs. |
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