8th INTERNATIONAL WHEAT CONFERENCE

The gRAIN C:N RATIo AS AN eARLy deTeRmINANT
of The gRAIN NITRogeN CoNCeNTRATIoN
IN CoNTRASTINg WheAT CuLTIVARS uNdeR dIffeReNT
eNVIRoNmeNTAL CoNdITIoNS
L. Gabriela Abeledo1, 3 , Ignacio Alzueta1 ,
1, 2, 3
Daniel J. Miralles
1 Departamento de Producción Vegetal,
2 IFEVA, Facultad de Agronomía, Universidad de Buenos Aires, Av. San Martín 4453,
C1417DSE, Buenos Aires, Argentina.
3 CONICET, Buenos Aires, Argentina.
E-mail Address of presenting author: abeledo@agro.uba.ar
The grain nitrogen concentration (GNC) is one of the primary determinants of wheat
quality and wheat breeding consistently increased grain yield, but this process was in
parallel with a significant reduction in GNC. Under water and nutritional potential conditions,
actual photosynthesis is the most important source of assimilates during grain
filling; while the main source of nitrogen (N) to the grains is the N accumulated before
anthesis and that is remobilized to the grains during the grain filling period. The size of
the source (i.e. leaf area and leaf photosynthetic capacity), together with the remobilization
of assimilates, determine the capacity of the crop to provide assimilates to the
growing grains, while the number of grains and its potential size determine the potential
capability of the crop to demand assimilates. In spite of wheat is considered a sink limited
crop with low source (carbon) limitation during grain filling, different evidences showed
a significant nitrogen limitation during that period. The aim of the present work was to
assess comparatively the carbon and nitrogen accumulation in the grains in contrasting
wheat cultivars grown under a wide range of environmental conditions. Two experiments
were carried out at the Experimental Field of the Faculty of Agronomy of the University
of Buenos Aires (34º 35’ S, 58º 29’ W). The first experiment consisted of a factorial
combination of: (i) a traditional and low-yielding cultivar (Buck Manantial, Bman) and
a modern and high-yielding cultivar (Klein Chajá, Kcha), (ii) two sowing dates, and (iii)
two soil N levels at sowing (70 and 160 kg N ha -1 ). The second experiment comprised the
factorial combination of: (i) three cultivars of different baking quality (Baguette Premium
13, Buck 75 Aniversario, Klein Chajá), (ii) two soil N levels at sowing (70 and 170 kg N
ha -1 ), and (iii) two N levels of N during post-anthesis (control or fertilized with 30 kg N
ha -1 at anthesis). Both experiments were carried out under water potential conditions,
and were arranged following a split-split-plot design with three replications per treatment.
From anthesis onwards, two main shoot spikes per treatment were harvested at
least twice weekly to study dry matter and nitrogen (Kjeldahl method) dynamics. The rate
and duration of grain weight and nitrogen accumulation during the grain filling period
were estimated using a bi-linear model. Considering both experiments, grain weight at
maturity ranged from 27 to 42 mg per grain. Variations in final grain weight were mainly
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