3.2 Yield components
Spikes per m2 and kernels per spike were reduced by
waterlogging treatments (Fig. 3). WL1-3 reduced spikelet per
m2. No death of tillers was recorded for WL4, as this
treatment was applied after ear emergence (spikelets per
m2 were not affected). WL2 caused the highest spike
number reduction across genotypes (average decline of 37%). All
treatments reduced kernels per spike except WL1 and WL2 for Westminster.
WL4 caused the greatest reduction in kernels per spike for all genotypes
(except TAMF169) by increasing numbers of infertile spikelets.
Waterlogging that occurred relatively early in crop phenology (WL1, WL2,
WL3) led to an increase in 1000-kernel weight of Franklin, Macquarie+
and Westminster. In contrast, waterlogging in later crop development
stages (WL4) reduced 1000-kernel weight by more than 50%. These results
indicated that yield penalty was primarily associated with either (1)
plant survival and reduced tillering when waterlogging was applied at
early growth stages or (2) with reduced
spikelet
fertility and grain filling when waterlogging was applied at ear
emergence. An extreme example is that none of the Franklin plant
survived under WL3 thus led to 100% yield reduction.
To better understand how waterlogging affected 1000 kernel weight,
further measurements were conducted on grain size. Waterlogging reduced
grain length for all barley genotypes except for Franklin, where grain
length increased by 5% in WL1 and 10% in WL2 (Fig. 4). In contrast
with grain length, all waterlogging treatments except WL4 increased
grain width and grain thickness. WL4 reduced grain width across
genotypes, with an average reduction of 20%. Similarly, grain thickness
in Planet, Macquarie, Macquarie+ and TamF169 was reduced, decreasing by
5%, 11%, 13% and 14%, respectively, compared with the controls.