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.