Fusarium head blight resistance measured by type II inoculation method among UK wheat cultivars and investigations into the relationship with anthers trapped and anthers retained

Abstract

There is a paucity of information on the relationship between anthers and Type II expression of Fusarium Head Blight resistance (measured by point inoculation of a spikelet and observing disease spread over the wheat spike). Twenty-nine UK commercial wheat varieties were evaluated for the expression of Type II resistance. Anther extrusion was measured by counting the number of spikelets with anthers trapped between the lemma and palea (anthers trapped). In five spikelets where trapped anthers were not observed, the number of spikelets with anthers contained within the spikelet was counted (anthers retained). There was variation in expression in the expression of Type II resistance (p < .001), anthers trapped (p < .001) and anthers retained (p < .001). Anthers trapped and anthers retained were not correlated with each other, indicating both should be considered independently. Later maturity correlated with great resistance in the AHDB Type I resistance ratings but to greater susceptibility to point inoculations (Type II). Consistent with previous literature higher numbers of anthers trapped to increase susceptibility to FHB Type I. However, the relationships were reversed for the expression of resistance measured by point inoculation within the spikelet, where anthers trapped between the lemma and palea reduced susceptibility to Type II point inoculation (p < .01). This suggests a benefit of releasing some pollen from within the spikelet for this inoculation method. Similarly, anthers retained contributed to increased Type II susceptibility (p < .05), potentially providing substrates within the spikelet inoculation site aiding fungal growth, but correlated to greater Type I resistance (p < .05) indicating the anthers are hidden from initial infection on the outside of the spikelet, particularly under low infection pressure. While preliminary, this work suggests that variation in anthers trapped, anthers retained and maturity date may increase Type II expression of resistance and could relate to increased Type I FHB susceptibility.