**Session IV -- Physiology, Ecology and Production -- Poster IV-2**

**Do Cereals Differ in Grain Weight Stability?**

C. Mariano Cossani^1^, Roxana Savin ^1^, and Gustavo A. Slafer
^1,\ 2,\*^

^1^Department of Crop and Forest Sciences, University of Lleida, Centre
UdL-IRTA, Av. Rovira Roure 191, 25198, Lleida, SPAIN, ^2^ICREA
(Catalonian Institution for Research and Advanced Studies,
[www.icrea.es](http://www.icrea.es/)) \*Corresponding author: Email:
slafer@pvcf.udl.cat

The frequently large variability in grain yields that occurs under
Mediterranean environments often determines conservative strategies by
farmers (Sadras *et al*., 2002). In dryland agricultural systems of
Catalonia (Spain), as well as in many other Mediterranean regions,
farmers usually grow a barley monoculture in drought-prone areas. This
is based on the assumption that barley yields are more stable than those
of other cereals (see arguments in Cossani *et al.,* 2007). Although
grain number dominates grain weight in yield determination (e.g.
Peltonen-Sainio *et al.,* 2007), grain weight still varies and in
conditions prone to terminal stresses yield stability might be
associated to a more stable determination of grain weight. Thus it might
be hypothesized that grain weight of barley would be more stable than
other cereals to changes due to availability of resources and
interannual variation in weather. As the barley most commonly used in
the region is a 2-row type, this would also emphasize the hypothesis as
grain size is supposedly more uniform in 2-row barley than in other
small-grain cereals. To test the hypothesis, we compared grain growth
dynamics and the consequent grain weight of barley, durum wheat and
bread wheat in a wide range of conditions (irrigation x fertilization)
in three different growing seasons in Catalonia, and expanded the
comparison to oats with data from the literature. Experiments were
conducted on actual farmer's paddocks at or near Agramunt, province of
Lleida (Catalonia, north-eastern Spain) during, 2004/05, 2005/06 and
2006/07. Treatments consisted in sowing wheats (durum and bread) and
barley under different combinations of water (rainfed or irrigated) and
N fertilization treatments. We frequently sampled grains during the
whole postanthesis period and grain filling curves for each particular
condition were fitted. The R^2^ of these curves were 0.76 in one case or
always higher than 0.81. The parameters of the curves provided detailed
information on rate of grain growth, its effective duration and final
grain weight for each individual condition.

Regardless of the soundness of both elements supporting the hypothesis,
the experimental data evidenced that barley grain weight is not more
stable than durum or bread wheat. The variability was 14.7 to 30.9%,
16.9 to 24.7% and 2.41 to 11.7% for barley, durum and bread wheat,
respectively. This might be the cause for the lack of experimental
support to the assumption that barley is more adequate than wheat for
Mediterranean dryland systems. Although oats were not included in the
experiment, reviewing the literature it seems clear that whenever oats
grain weight responses to environmental changes was compared to
responses of other cereals, barley did respond more markedly: oats would
have a quite conservative grain weight determination, like wheat does.

Regarding the determinants behind the differential stabilities of grain
weight in barley and wheat, it seems that the changes in both grain
filling rate (mg~DM~ grain^-1^ \[ºC d\]^-1^) and effective duration of
grain filling (ºC d) were concurrently responsible of the grain weight
responses to management/year.

*We do acknowledge that reported work was funded by EU INCO-MED project
WatNitMED*

Cossani, C.M., Savin, R., Slafer, G.A., 2007. Ann. Appl. Biol.,
151:167--173

Passioura; J.B., 2002. Funct. Plant Biol., 29: 537--546.

Peltonen-Sainio, P., Kangas, A., Salo, Y., Jauhiainen, L., 2007. Field
Crops Res., 100:179-188.

Sadras*, V.O., Roget, D., Krause, M.*, 2002. Agric. Syst., 76: 929--948.