Photosynthetic heat tolerance in wheat: Evidence for
genotype-by-environment interactions
Abstract
High temperature stress inhibits wheat photosynthetic processes and
threatens wheat production. Photosynthetic heat tolerance (commonly
measured as Tcrit – the critical temperature at
which incipient damage to photosystem II occurs) in wheat genotypes
could be improved by exploiting genetic variation and
genotype-by-environment interaction (GEI) for this trait. Flag leaf
Tcrit of a total of 54 wheat genotypes were
evaluated in 12 thermal environments over three years in Australia using
linear mixed models for assessing GEI effects. Nine of the 12
environments had significant genotypic effect and highly variable
broad-sense heritability (H2 ranged from 0.15 to
0.75). Tcrit GEI was variable, with 55.6% of the
genetic variance across environments accounted for by the factor
analytic model. Mean daily growth temperature preceding anthesis was the
most influential environmental driver of Tcrit
GEI, suggesting varied scales of biochemical, physiological, and
structural adaptations to temperature requiring different durations to
manifest at the thylakoid membrane and leaf levels. These changes help
protect or repair photosystem II upon exposure to heat stress. To
support current wheat breeding, we identified genotypes superior to
commercial cultivars commonly grown by farmers, and showed that there is
potential for developing genotypes with greater photosynthetic heat
tolerance.