Fusarium Graminearum Infection in the Morphological Components of Wheat Spikes

Fusarium head blight caused by Fusarium graminearum (Schwabe) has caused significant losses in the wheat crop in North America, which has led to extensive greenhouse and field screening of cultivars and germ plasm for FHB resistance. The single floret inoculation system is commonly used to rate the spread of fungal hyphae in the spike by monitoring visible infection of spikelets to determine Type II resistance. Preliminary studies of this system in our laboratory have shown that these visual ratings of inoculated spikelets may be poorly associated with the F. graminearum occurring in infected components the same individual spikelets. Our data has also shown that fungal movement in the spike occurs in three ways; localization around the point of inoculation (PI), movement both up and down the spike from the PI and movement primarily downward from the PI. This objective of this research is to use the single floret inoculation system to relate visual spike and spike let infection across a wide range of cultivars to F. graminearum infection in individual components of all spikelets. The movement of fungal hyphae into the various components of the spike will be evaluated following inoculation at various locations on the spike. These experiments will allow us to closely evaluate the method of single floret inoculation and possibly improve the accuracy of the visual rating system for spikelet infection. It should provide definitive information of the movement of fungal hyphae to various morphological components of the wheat spike across a wide range of cultivars. This research is relevant to the goals of the Scab Initiative because it proposes to develop more accurate methods of assessing FHB infection, thus improving the efficiency of breeding for FHB resistance.