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Ilhami Tozlu, Charles L. Guy, Ouinvin Cai and Gloria A. Moore

There is wide variation in Citrus and related genera in tolerance to cold and salt stress. While Poncirus trifoliata (L.) Raf. is an important rootstock for cold regions, it is salt sensitive. C. grandis (L.) Osb., on the other hand, is cold sensitive, but is relatively salt hardy. We are attempting to map genes (quantitative trait loci, QTLs) influencing salt and cold tolerance in Cirrus, using a BC1 population from [C. grandis × (C. grandis × P. trifoliata)]. As a first step, 2 year old containerized replicates of individual BC1 progeny plants have been salinized with 30 mM NaCl over a 9 month period under greenhouse conditions. Growth response under saline conditions, as evaluated by plant height and node number, varied significantly between individual progeny. Concentrations of 11 macro- and micro-elements, including Na and Cl, in leaf and root tissues were also determined. Ultimately, this data will be analyzed in conjunction with our current linkage map of this population, which consists of more than 200 marker genes, in order to map QTLs for salt tolerance.

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Dustin P. Meador, Paul R. Fisher, Philip F. Harmon, Natalia A. Peres, Max Teplitski and Charles L. Guy

The objective was to analyze the physical, chemical, and biological water quality in horticulture irrigation systems in 24 ornamental plant greenhouses and nurseries in the United States. At each greenhouse or nursery, water was collected from up to five points (“Sample Types”) which included 1) “Source” from municipal or private well supplies, 2) “Tank” from enclosed storage containers, 3) “Subirrigation” from water applied to crops in ebb-and-flood systems, 4) “Furthest Outlet” that were irrigation emitters most distant from the Source, and 5) “Catchment Basin” from open outdoor retention areas. On average, Source water had the highest physical and microbial quality of Sample Types including the highest ultraviolet (UV) light transmission at 86%, lowest total suspended solids (TSS) at 3.1 mg·L−1, and lowest density of aerobic bacteria with 1108 cfu/mL of water. Average quality of recycled water from Subirrigation or Catchment Basins did not meet recommended levels for horticultural irrigation water for UV transmission (68% to 72% compared with recommended 75%), microbial counts (>100,000 cfu/mL compared with recommended <10,000 cfu/mL), and chemical oxygen demand (COD) (48.2 to 61.3 mg·L−1 compared with recommended <30 mg·L−1). Irrigation water stored in Tanks or applied at Furthest Outlets had lower physical and biological water quality compared with Source water. Level of aerobic bacteria counts highlighted a risk of clogged microirrigation emitters from microbial contaminants, with highest bacteria levels in recirculated irrigation water. The physical, chemical, and microbial water quality results indicate a need for more effective water treatment to improve biological water quality, particularly with recirculated irrigation.