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James A. Taylor, John-Paul Praat and A. Frank Bollen

Harvester-mounted yield sensors have prompted many investigations into the amount of spatial variability present in grain, cotton, viticulture, and some mechanically harvested horticultural crops (usually vegetable crops). Investigations into the

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Mirko Siragusa, Fabio De Pasquale, Loredana Abbate, Letizia Martorana and Nicasio Tusa

at genetic improvement. Currently in Sicily, there are several lemon landraces with interesting agronomic traits, but little information is available about their genetic variability. Until now, Sicilian lemon characterization has been done only

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Yeun-Kyung Chang, Richard E. Veilleux and Muhammad Javed Iqbal

hybrids for market demands. Despite the economic importance of Phalaenopsis , the genetic potential of Phalaenopsis has not been fully exploited. An assessment of genetic variability is important for the use of genetic resources and for determining

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Rolland Agaba, Phinehas Tukamuhabwa, Patrick Rubaihayo, Silver Tumwegamire, Andrew Ssenyonjo, Robert O.M. Mwanga, Jean Ndirigwe and Wolfgang J. Grüneberg

variability in a given population ( Abinasa et al., 2011 ). The objective of this study was to estimate genotypic means, variance components, broad sense heritability, GCV, PCV, and correlations for yield components [i.e., SRFY, SRDY, VNY, FBY, and harvest

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Peter J. Stoffella and Mike F. Fleming

Cabbage [Brassica oleracea L. (Capitata Group) cv. Bravo] transplants were grown on raised beds at Fort Pierce, Fla., during Fall 1987 and 1988. Plants were spaced at 8, 15, 23, 30, and 38 cm within rows or populations equivalent to 123,000, 61,500, 41,000, 30,800, and 24,600 plants/ha. Individual root weights, total plant weights, and core length increased linearly as within-row spacing (WRS) increased in both experiments. Untrimmed head weights, trimmed head weights, head height, head width, and core width increased quadratically as WRS increased in both experiments. Head shape and core index did not differ among WRS in either experiment, except for a quadratic increase in the head height: bead width ratio (head shape) as WRS increased in the 1988 experiment. Coefficients of variability (cv) for most measured variables decreased as WRS increased, indicating a reduction in plant-to-plant variation. Optimum marketable cabbage head size (>1 kg) and lower plant-to-plant variation (cv < 20%) were obtained at WRS of 23 cm or wider. However, trimmed cabbage yields decreased linearly as WRS increased in both experiments. In this study, a lower plant population (WRS > 23 cm) was more conducive to a once-over cabbage harvest since plant-to-plant variation in head size and other yield and quality characteristics was reduced.

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Abe Shegro Gerrano, Patrick Olusanmi Adebola, Willem Sternberg Jansen van Rensburg and Sonja Louise Venter

, however, requires information on the genetic variability that exists among available germplasm. Information on the genetic heritability and genetic advance of the targeted traits is also important for efficient selection. This study was therefore carried

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Hongfei Jiang, Jack D. Fry and Steve C. Wiest

Microclimates can vary significantly across a golf course, and directly influence turf irrigation requirements. The objective of this study was to quantify the extent of this variability in water demand, and evaluate the accuracy of weather station—generated evapotranspiration (ET) estimates for determining irrigation need for one Kansas golf course. Evaporation was measured using black Bellani plate atmometers placed on four golf tees and near the weather station at the Manhattan Country Club, Manhattan, Kans., in 1995 and 1996. Evaporation was measured On a total of 62 precipitation-free summer days in 1995 and 1996. Probably because the weather station was situated over nonirrigated turf, evaporation at the weather station was up to 22% higher than that at locations on tees. Evaporation varied by >20% among tees. Evaporation on a north-facing slope was 8% lower than that on a level surface or south-facing slope. Weather station—estimated empirical ET (Penman model) was consistently higher than ET estimated from atmometer evaporation, particularly when ET was >4 mm·day-1. Superintendents should be aware of the potential variability in water demand across a golf course, and that weather-station ET estimates may differ from turf ET primarily because of microclimatic differences and potential inaccuracies in the empirical model employed by the weather station to estimate turf ET.

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Amanda Wiberg, Richard Koenig and Teresa Cerny-Koenig

There is extensive variability in physical and chemical properties among brands of retail potting media. The purpose of this study was to assess variability in seed germination and plant growth responses among and within brands. Twenty-four different brands of media, and multiple bags of five brands, were purchased at nine retail stores. Tomato (Lycopersicon esculentum) seeds were germinated in 11 different brands of media and in media from different bags of four of the same brands. Marigold (Tagetes erecta) and petunia (Petunia×hybrida) were grown to flowering in 10 brands of media. Germination varied significantly among media brands and among bags of one of the brands. Plant performance also varied significantly, with several of the brands producing plants with few flowers, long times to flowering, and low shoot and root dry weights even though all treatments received uniform applications of a complete fertilizer solution three times per week. Few relationships could be discerned between individual physical and chemical properties of the media and plant performance. Results indicate improvements in quality among brands and quality control within brands are needed in the retail potting media industry. Quality assessment tools emphasizing plant performance could improve overall media quality.

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Michael W. Courtney and Don La Bonte

Sweetpotato [Ipomœa batatas (L.) Lam.] is a major subsistence crop in southern Africa, where iron and zinc deficiency in humans is an important health problem. A cultivar of sweetpotato that is suited for subsistence farming in this region and that is high in iron and zinc could be an important means of combatting these deficiencies. As part of a program of the HarvestPlus program, under the auspices of the International Potato Center (CIP) to develop such a cultivar, we are working to identify the high and low range of iron and zinc in sweetpotato cultivars grown throughout the world by testing a number of cultivars for these nutrients. Subsidiary objects include determining the heritability of iron and zinc levels and surveying the variability in the levels of these nutrients from root to root on the same plant, from plant to plant of the same cultivar, from the proximal to the distal end of a given root, and from cambium to cortex. For the roughly 80 cultivars in the genotypic variability study, results showed a three-fold difference between the high- and low-yielding cultivars on a fresh weight basis and a two-fold difference on a dry weight basis, for both iron and zinc.

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Maria Susana Lopes, Duarte Mendonça, Kristina M. Sefc, Fabíola Sabino Gil and Artur da Câmara Machado

A collection of 130 olive samples, originating from diverse areas in Europe and corresponding to 67 different cultivars denominations, was genotyped at 14 microsatellite loci. In total, 135 alleles with a mean number of 9.6 alleles per locus were detected. All but 30 accessions showed unique genotypes. Several cases of synonymy listed in the FAO database of olive germplasm could not be confirmed, as different allelic profiles were obtained from putatively synonymous cultivars. The existence of homonyms or mislabeled samples in olive germplasm collections was evidenced by allele differences of up to 60% between samples of the same denomination. An allele-sharing phenogram of the analyzed genotypes revealed several cultivars with high levels of intra-varietal polymorphism, as well as cultivar families consisting of closely related cultivars with similar denominations. Our work shows that the current designations of olive cultivars fall short of describing the genetic variability among economically important plant material. A thorough investigation of the existing variability will prove of major importance for both management and economic production of olive trees.