Local adaptation and genotype by environment (G×E) interactions affect the
expression of phenotypes in crop species. An investigation on the
interplay between adaptation and G×E on sorghum heterosis phenotypes is
lacking. To address this question, a set of 112 diverse grain sorghum
hybrids and their 22 inbred parents of local and exotic origins,
representing the primary female and male heterotic groups, were tested in
five contrasting sorghum growing environments across two years in
Queensland, Australia. Plant height, days to flowering, seed yield, grain
weight, and grain number were measured and used in the estimation of
heterosis. Mid parent heterosis for yield ranged from -25 to 217% and was
highly influenced by grain number. In contrast to observations in maize
the magnitude of heterosis for yield was not associated with site mean.
Striking differences were observed in heterosis in hybrids from locally
developed inbred parents compared with hybrids that were developed from
exotic inbred parents developed in other countries. Heterosis in the
latter combination was higher on average across all the test environments
for the majority of traits. We hypothesise maladaptive phenotypic
plasticity in the exotic parents contributed to the observed differences
in heterosis estimates. These data confirm that heterosis estimates in
sorghum must be obtained and interpreted in relevant genetic and
environmental contexts. Breeders in developing countries with low sorghum
hybrid seed uptake will find these insights useful when selecting hybrids
for broader adaptation, improving efficiency of their breeding programs.