ARS | Publication request: WILD OAT (AVENA FATUA L.) SEED PHENOLICS AND POLYPHENOL OXIDASE: POTENTIAL ROLES IN SEED LONGEVITY AND RESISTANCE TO DECAY

Submitted to: Phenol Conference
Publication Type: Abstract Only
Publication Acceptance Date: August 17, 2006
Publication Date: November 1, 2006
Citation: Fuerst, P.E., Gallagher, R.S., Kennedy, A.C., Anderson, J.V. 2006. WILD OAT (AVENA FATUA L.) SEED PHENOLICS AND POLYPHENOL OXIDASE: POTENTIAL ROLES IN SEED LONGEVITY AND RESISTANCE TO DECAY. Phenol Conference.

Technical Abstract: Wild oat seeds can survive in a dormant state for five to seven years in cultivated soils. Long-term survival requires both dormancy and resistance to decay. Phenolic compounds and polyphenol oxidase (PPO) have been implicated in plant defense, although their interactions remain obscure. We have characterized several factors that may influence seed decay resistance in the highly dormant wild oat line, M73. The wild oat hull (lemma and palea) is the major reservoir of both soluble and insoluble seed phenolics while both the hull and caryopsis have substantial PPO activity. Therefore the hull may employ biochemical mechanisms of decay resistance. The most abundant phenolic acids of the hull were identified as insoluble forms of ferulic, caffeic, and p-coumaric acids using GC/MS. Western blot analysis indicated the presence of one major PPO isoform in the caryopsis and three PPO isoforms in the hull. Caryopsis PPO activity increased 50 to 100% compared to the control when wild oat caryopses were incubated with Fusarium isolates that cause decay. Caryopsis PPO activity increased 50% when intact seeds were incubated on the most virulent isolate, F. avenaceum WF223a, suggesting that this particular pathogen readily breached the physical and biochemical barrier of the hull. In contrast, PPO activity decreased 25% when caryopses were incubated on Pythium ultimum, a root pathogen that did not readily cause seed decay. Results indicate that dormant wild oat seeds are responsive to their biotic environment and that phenolics and PPO may play significant roles in wild oat seed longevity in the soil.