Fusarium head blight (FHB) remains a devastating disease in bread wheat (Triticum aestivum L.) and other small grains. Genetic resistance to FHB is a complex trait; in addition to active physiological resistance, plant developmental and morphological traits may indirectly affect disease progression and provide a passive mechanism of resistance. In this study, we investigated the relationship between FHB type II resistance and spike architecture traits in a recombinant inbred line (RIL) population of bread wheat. Disease resistance traits were FHB severity at 21 days post inoculation (dpi) and area under the disease progress curve (AUDPC). Spike architecture traits measured were rachis length, spike density, number of spikelets per spike, florets per spike and florets per spikelet.
The RIL population showed significant variation for all traits. Heritability values were moderate to high for FHB severity (0.69) and AUDPC (0.63) and high for the spike architecture traits (0.74 - 0.92). FHB severity and AUDPC showed a moderate and significant association with the number of florets per spike (r = 0.38 and r = 0.31, respectively) and with the number of florets per spikelet (r = 0.28 and r = 0.27, respectively), reflecting a greater spread of the fungus in spikes with higher floret number. These results suggest that the number of florets per spike and the number of florets per spikelet should be considered in FHB resistance breeding efforts, because selection of lines with higher number of florets could lead to a correlated selection response towards increased FHB levels under field conditions.