Breeding for Fusarium head blight (FHB) resistance and lower deoxynivalenol (DON) in barley has been challenging due to substantial genotype by environment interactions, lack of QTL with large effects, and associations with agro-morphological traits (e.g. late flowering, tall plant height, and two row spike morphology) which are generally considered avoidance mechanisms rather than true genetic resistance. The dominant classes of barley grown in the U.S. are spring six-row and two-row with the latter becoming more favored by the malting and brewing industries. Increased interest in developing winter barley for regions that have traditionally produced spring barley is spurred by the need to develop more sustainable cropping systems. Similarly, there is increased interest in developing naked (or hulless) barley for human food, animal feed, and malting, particularly for organic production systems. As growers and end-users explore these other barley classes, we recognized their potential to impact DON contamination. For example, two-row barley is often observed to be lower in disease compared to six-row barley and mapping studies often link spike type with FHB resistance. Similarly, DON is known to accumulate in the hull of barley and therefore the loss of the hull in naked barley could also reduce DON. Additionally, fall-sown winter barley matures earlier than spring sown barley and this modified timing of plant development could reduce the risk of DON contamination. While there are many considerations that affect the extent to which two-row, naked, or winter barley, should be deployed on the landscape, it would be desirable to quantify the specific advantage these types of barley have in mitigating DON contamination. We used data from the North American Barley Scab Evaluation Nursery from the years 2007 – 2017 in which multiple breeding programs submitted two-row and six-row elite breeding lines to evaluate for FHB and DON. We developed and tested near isogenic lines for the nud locus to quantify the effect of hull loss on DON concentration. Lastly, we compared fall-planted and spring-planted facultative barley lines to determine the effect of phenological development on DON. These studies indicate that altered spike morphology, hull loss, and fall-planting reduce DON levels by 18%, 48%, and 66%, respectively.

This work was supported by the USDA-ARS U.S. Wheat Scab Initiative, USDA-NIFA OREI, and the American Malting Barley Association. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the USDA USWBSI.