J. Voltas et al., Genotype by environment interaction for grain yield and carbon isotope discrimination of barley in Mediterranean Spain, AUST J AGR, 50(7), 1999, pp. 1263-1271
Carbon isotope discrimination (Delta) has been found to be either positivel
y or negatively related to grain yield of small grain cereals when grown in
contrasting environments. In order to clarify a possible association betwe
en grain yield of barley (Hordeum vulgare L.) and Delta of mature kernels,
five 6-rowed and five 2-rowed barley cultivars were evaluated in 22 rainfed
environments of northern Mediterranean Spain. Analyses of variance suggest
ed that the genotypic Delta values were more consistent across environments
than the genotypic yields. Genotypexenvironment (GxE) interaction for grai
n yield was further explored by fitting an AMMI (additive main effects and
multiplicative interaction) model. The first 2 multiplicative axes were fou
nd significant. The AMMI2 model provided more accurate estimates of genotyp
ic yields within environments than the conventional unadjusted means across
replicates. AMMI2 estimates were used for input into cluster analysis, gro
uping environments that ranked genotypic yields similarly. Three major grou
ps were obtained, with average yields of 2.42 t/ha (cluster I), 3.06 t/ha (
cluster II), and 5.16 t/ha (cluster III). The genotypic ranking for Delta d
id not vary substantially across clusters, but it changed for grain yield.
The average genotypic yields in the low-yielding cluster I ranked opposite
to those in the high-yielding cluster III, suggesting the existence of a cr
ossover point at an intermediate yield level. The association between grain
yield and Delta for genotypic means within clusters was variable. In clust
er I, yield and Delta tended to be negatively related, whereas they were po
sitively related in clusters II and III. Genotypes with lower Delta, i.e. w
ith higher transpiration efficiency, performed better in low-yielding envir
onments (mostly those grouped in cluster I). On the contrary, a high genoty
pic Delta was of advantage in medium (cluster II) and high-yielding environ
ments (cluster III). This observation supports the assumption that drought
tolerance and high yield potential under non-limiting growing conditions ma
y be antagonistic concepts in barley. Genotypic means for kernel number per
m(2) and Delta were consistently and positively related within clusters, s
uggesting that a constitutively high Delta may have been driven by a large
genotypic reproductive sink. The convenience of using nas a selection crite
rion in areas exhibiting a considerable GxE interaction for grain yield is
discussed.