Received: 9 October, 2009. Accepted: 10 December, 2010. Invited Mini-Review The Americas Journal of Plant Science and Biotechnology ©2010 Global Science Books Relationships of Carbohydrate and Nitrogen Content with Strawberry Transplant Vigor and Fruiting Pattern in Annual Production Systems Daniel S. Kirschbaum 1* • Kirk D. Larson 2 • Steve A. Weinbaum 2 • Theodore M. DeJong 2 1 Instituto Nacional de Tecnología Agropecuaria (INTA). EEA Famaillá. Ruta Prov. 301, Km 32. (4132) Famaillá, Tucumán. Argentina 2 Department of Plant Sciences, University of California Davis. One Shields Ave., Davis, CA 95616. USA Corresponding author: * dkirschb@correo.inta.gov.ar ABSTRACT In strawberry (Fragaria x ananassa Duch.), fruit production systems based on leafless, bare-root transplants, successful plant establish- ment is dependent on crown/root reserves for the formation of new feeder roots and new leaves. Successful stand establishment, early fruiting, and sustained high productivity in strawberry have been correlated with total nonstructural carbohydrate (TNC) reserves. However, nitrogen (N) reserves have largely been overlooked. The importance of root carbon and N has been highlighted in studies focused on growth of perennial plants, where apparently growth and fruiting in spring are determined primarily by N reserves. In temperate fruit trees, protein would be the main form of N storage and the predominant storage amino acid would be arginine. This could be the case of strawberries, which share many of the general characteristics of temperate fruit trees. In this frame, the concept that confers a primary role to TNC over any other reserve nutrient in strawberry needs to be reconsidered. The N cycling process in strawberries remains largely unknown; however, emerging research lines suggest a key function of N in early fruit production of fresh-dug strawberry transplants, questioning the importance of TNC as the unique storage compounds involved in plant vigor. _____________________________________________________________________________________________________________ Keywords: Fragaria x ananassa Duch., starch, chilling, plant maturity, fruit production, stand establishment, foliar applied nitrogen, nursery CONTENTS INTRODUCTION........................................................................................................................................................................................ 98 THE BROAD PICTURE ............................................................................................................................................................................. 99 INVOLVEMENT OF INITIAL PLANT TOTAL NONSTRUCTURAL CARBOHYDRATES LEVELS IN VIGOR AND FRUITING PATTERN OF STRAWBERRY PLANTS ................................................................................................................................................. 100 NITROGEN RESERVES IN STRAWBERRY RUNNER PLANTS: A WORLD TO BE EXPLORED.................................................... 101 CONCLUDING REMARKS ..................................................................................................................................................................... 102 REFERENCES........................................................................................................................................................................................... 102 _____________________________________________________________________________________________________________ INTRODUCTION All highly productive strawberry (Fragaria x ananassa Duch.) regions of the world utilize annual planting systems, in which plantations are completely renewed each autumn using freshly dug transplants. Due to use of annual plan- tings, nursery transplant production and quality are impor- tant considerations, and highly specialized strawberry trans- plant nurseries have been developed to supply quality trans- plants worldwide. The concept of quality involves trueness to type of the cultivar, plant maturity, transplant size, extent of physical damage, and phytosanitary condition. Due to the high cost of annual planting, fruit growers require trans- plants physiologically balanced at the time of digging, medium to large size and free of physical damage and pests and diseases (Roudeillac and Veschambre 1987; Galletta and Bringhurst 1990; Faedi and Baruzzi 2003). Strawberry short-day cultivars go through several developmental stages (Guttridge 1969; Taylor 2002; Darnell et al. 2003). In a model suggested by Durner and Poling (1988), axillary buds differentiate into stolons (runners) when exposed to long photoperiods, axillary buds form branch crowns when the photoperiod decreases, and floral induction takes place when plants are exposed to very short days. Because of this developmental sequence, commercial runner plant nurseries often are located at relatively high latitudes (HL > 40° N lat.) and/or at high elevations (HE). High-latitude sites have longer photoperiods than low lati- tude sites in summer and this enhances daily photosynthesis and runner plant production. High-elevation sites, as well, have lower summer temperatures than low elevation sites (Ruan et al. 2009). Thus, HL combined with HE, ensures runner plant exposure to decreasing temperatures and photoperiod in the nursery prior to digging in early/mid- autumn (Shaw 2004). Strawberry transplants are exposed to several stresses between the time of nursery digging and after planting in the fruiting field. These stresses affect plant vigor and can cause economic losses to strawberry growers, either by death of plants (shortly after planting) or reduced vigor and decreased productivity over an entire season (Larson and Shaw 2002). In California, the largest strawberry transplant producer in the world, plant leaves are mechanically mowed immedi- ately prior to digging the nursery. Plants are then dug using ®