Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2013
Publication Date: N/A
Interpretive Summary: Unpredictable crop loss due to vivipary (i.e., premature germination of nuts while still on the tree) is a major profit-limiting problem for certain pecan (Carya illinoinensis) farming operations. There is need to better understand the cause of vivipary and for orchard management tools and strategies enabling better control over the incidence of vivipary. We found that the incidence of vivipary is influenced by nitrogen fertilization and irrigation practices, at least in part through their influence on production of abscisic acid, a germination inhibiting plant hormone. This work provides the basis for modifying nitrogen and water management strategies to enable better control over crop loss due to vivipary and gives insight into the physiology of the malady.
Technical Abstract: Preharvest sprouting, or vivipary, of pecan (Carya illinoinensis) nuts results in substantial loss of nut yield and quality; thus, there is need for greater understanding of this malady and the influence of orchard management factors. A field study assessing the influence of irrigation (water) and nitrogen (N) management on ‘Cheyenne’ found that relatively high soil moisture and exposure to high soil N during mid- and late-summer increases the incidence of vivipary. Other field studies assessing the influence of abscisic acid (ABA) on vivipary, by treating developing fruit with either ABA or a metabolic inhibitor of ABA anabolism (i.e., fluridone) found that in ‘Sumner’ and ‘Oconee’ ABA exposure reduces the incidence of vivipary whereas exposure to the ABA inhibitor increases vivipary. Fluridone exposure also increases seed germination. These findings indicate that orchard water and N management can substantially influence vivipary in commercial orchards and that this influence is at least partially due to the effects of tree water and N status on ABA metabolism within the developing seed. Reassessment of orchard water and N status during kernel filling and nutritional status of metalloenzymes involved in the synthesis of ABA should lead to an improved vivipary management strategy.