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Robert L. Jarret, Jason Bolton and L. Brian Perkins

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Josh B. Henry, Penelope Perkins-Veazie, Ingram McCall and Brian E. Whipker

Phosphorus (P) deficiency commonly results in the development of red-to-purple coloration in plant foliage, typically attributed to anthocyanins. Betacyanins are a red pigment found in some plant species that do not produce anthocyanins, including Alternanthera sp. This study was conducted to investigate the effects of P nutrition on the betacyanin concentration and subsequent foliar coloration of ‘Purple Prince’, ‘Brazilian Red Hots’, and ‘Little Ruby’ alternanthera (Alternanthera brasiliana). The purpose of this study was to determine whether P fertilization management could enhance the coloration and aesthetic appeal of alternanthera. Custom fertilizers provided P concentrations of 0, 2.5, 5, 10, and 20 mg·L−1 P. One-half of the plants from each P concentration were restricted to 0 mg·L−1 P 1 month after transplant to determine whether adequate size could be attained before withholding P. Differences in P response were observed among cultivars for hue, betacyanin content, and plant size. Concentrations ≤5 mg·L−1 P resulted in plants that were more compact in terms of plant height and diameter, had deeper red foliage coloration, and greater foliar betacyanins compared with plants grown with greater P concentrations. Plants initially grown with 5 or 10 mg·L−1 P attained marketable size before P restriction and developed more red pigmentation compared with plants grown with P for the remaining duration of the study. Regression analysis demonstrated height was maximized with 3 to 8 mg·L−1 P, diameter with 4.1 to 8.4 mg·L−1 P, and branching with 10.0 mg·L−1 P. Foliar betacyanin concentrations were greatest in plants grown without P, reaching 269 mg/100 g fresh weight, whereas plants grown with 10 or 20 mg·L−1 P were 95% less (averaged ≈13 mg/100 g fresh weight). This study demonstrates that P restriction can benefit the aesthetic appeal of alternanthera and provides the first confirmation that P nutrition is associated with betacyanin accumulation.

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Robert L. Jarret, Elizabeth Baldwin, Brian Perkins, Rod Bushway and Kelly Guthrie

Fruit of 40 genotypes of Capsicum frutescens L. from the US Department of Agriculture/Agricultural Research Service Capsicum germplasm collection were analyzed for a variety of fruit quality parameters, including fruit size, weight, and concentrations of capsaicinoids, sucrose, glucose, fructose, malic acid, and total acid equivalents. Fruit weight ranged from 0.23 g fresh weight to 4.04 g fresh weight (average 1.05g). Fruit length/width ranged from 1 to 8.0 (average, 3.61). Capsaicin concentrations ranged from 34 to 350 mg·100 g−1 fresh weight (average, 135 mg·100 g−1 fresh weight). Sucrose concentrations ranged from 0.28 to 1.0 g·100 g−1 (average, 0.6 g·100 g−1 fresh weight). Total sugar extracts ranged from 0.73% to 2.6% (average, 1.55%). Malic acid concentrations and total acid equivalents ranged from 0.62 to 2.29 g·100 g−1 fresh weight (average, 2.07 g·100 g−1 fresh weight) and 0.97 to 3.31 g·100 g−1 (average, 1.87 g·100 g−1) respectively. These data demonstrate an approximate 4 to 14-fold range in values for the characteristics examined, suggesting the presence of sufficient variability for these traits within this species to support the development of germplasm enhanced for specific or multiple fruit quality attributes.