P-414 - Characterizing hosts and non-hosts of Fusarium noneumartii to assess impacts and inform rotation methods in California annual cropping systems

In the last decade, Fusarium Stem Rot and Decline (FRD), primarily caused by Fusarium noneumartii (FN), has become a major yield loss-driver of processing tomatoes in California. FN is also known to cause decline and rot of potato but the host range across rotated annual crops is otherwise unclear. In greenhouse studies, FN caused canopy decline in sunflower, potato, and cilantro (80-100% of plants), reducing cilantro dry weight by 50% (P < 0.03 vs. controls), and external tap root rot of carrot (78% of plants)—all likely yield-impacting symptoms. Further, safflower, pepper, garbanzo, fava, vetch and hemp developed a cryptic internal stem rot (55-100% of plants) with no significant biomass or canopy health impacts (P > 0.05).  Corn, cotton, garlic, onion, melon, alfalfa, spinach, parsley, broccoli, barley, and wheat did not develop symptoms, indicating potential use as non-host crop rotations. In warm season field studies, all putative hosts developed FN-associated stem rot (30-70% of plants); however, in cool season field studies no putative hosts developed symptoms, nor was FN recovered from healthy stem tissue (n = 15). All putative non-hosts tested in field studies did not develop symptoms. Further studies are underway to evaluate potential for FN to asymptomatically colonize putative non-hosts. These studies suggest that F. noneumartii may be driving yield losses in several previously unrecognized crops; identification of putative non-hosts provides a foundation to develop effective crop rotation methods which minimize soil propagule accumulation.