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Hongzhan Huang, James Harding, and Thomas Bvrne

The effects of long-term genetic improvement are measured by selection response predicted from estimates of narrow-sense heritability. However, changes of population mean must be partitioned into genetic and environmental components-in order to accurately estimate selection response.

A long-term selection experiment for cut-flower yield in the Davis population of gerbera (Gerbera hybrida, Compositae) was conducted for sixteen generations. Breeding value was estimated for individual plants in the population using Best Linear Unbiased Prediction (BLUP). Genetic change was calculated from breeding values of individual plants in each generation. The results of this study indicate: the long-term selection experiment was successful and necessary for genetic improvement. Genetic change over sixteen generations was 33 flowers. Mean breeding values increased monotonously with an “S” shape pattern. Environmental effects fluctuated from generation to generation. Cut-flower yield in the Davis population of gerbera will continuously respond to selection.

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Yiran Yu, James Harding, and Thomas Famula

Additive genetic components of variance and narrow-sense heritabilities were estimated for flowering time and cut-flower yield for generations 8-13 of the Davis population of gerbera, using the least squares (LS) and restricted maximum likelihood (REML)

methods. Estimates of heritability for flowering time were 0.54 and 0.50 using REML and LS, respectively, indicating a close agreement between the two methods. However, estimates of heritability for cut-flower yield were 0.30 and 0.46 from REML and LS. This may result from the fact that cut-flower yield was selected in each generation; flowering time was not. Realized heritability for cut-flower yield was estimated to be 0.26 which agreeded more closely with the heritability estimated from REML. The advantages of REML, and its applications in the estimation of components of genetic variance and heritability of plant populations are discussed.

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Dave Llewellyn, Katherine Schiestel, and Youbin Zheng

were similar for each plot. A t test (data not shown) comparing supplemental PPFD within each treatment (n = 60) indicated no treatment differences ( P = 0.26) and an overall mean supplemental PPFD of 55.9 ± 0.47 µmol·m −2 ·s −1 . Cut-flower yield

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Roxana Myers, Brian Bushe, Cathy Mello, Joanne Lichty, Arnold Hara, Koon-Hui Wang, and Brent Sipes

burrowing nematode populations and 2) increasing cut flower yields. Materials and methods Trial 1. A field trial was conducted at a commercial anthurium farm in Hilo, HI, with a 2-year-old established planting of ‘Starlight’ anthurium inside a shadehouse

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Michael A. Ortiz, Krystyna Hyrczyk, and Roberto G. Lopez

have reported that shading plants grown in the field using a 55% shadecloth increases stem length but consequently reduces cut flower yield ( Armitage, 1991 ). These results suggest that the generalization that indicates lower DLI results in reduced

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Yiran Yu, James Harding, and Thomas Byrne

Genetic components of variance and heritability of flowering time were estimated for five generations of the Davis Populationof Gerbera hybrids, Composite, Estimates of narrow-sense heritability averaged 0.50 and broad-sense heritability averaged 0.77 using the NCII design. Narrow-sense heritability was also estimated with two models of parent-offspring regression, resulting in average heritability of 0.49 and 0.51. Estimates of components of variance indicated that the major genetic effect controlling flowering time is additive. However, the dominance component accounted for 28% of the total variance; the environmental component was only 23%. Flowering time is negatively correlated with cut-flower yield. The phenotypic coefficient was –0.34; genetic correlations were –0.47 when estimated from the NCII design, and –0.72 when estimated from the parent-off-spring method. A practical model was constructed to assess the efficiency of indirect selection for cut-flower yield using flowering time as a marker trait. The advantages of indirect selection accruing from increased population size and reduced generation time are discussed.

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Yiran Yu, James Harding, and Thomas Byrne

Genetic components of variance and heritability of flowering time were estimated for five generations of the Davis Populationof Gerbera hybrids, Composite, Estimates of narrow-sense heritability averaged 0.50 and broad-sense heritability averaged 0.77 using the NCII design. Narrow-sense heritability was also estimated with two models of parent-offspring regression, resulting in average heritability of 0.49 and 0.51. Estimates of components of variance indicated that the major genetic effect controlling flowering time is additive. However, the dominance component accounted for 28% of the total variance; the environmental component was only 23%. Flowering time is negatively correlated with cut-flower yield. The phenotypic coefficient was –0.34; genetic correlations were –0.47 when estimated from the NCII design, and –0.72 when estimated from the parent-off-spring method. A practical model was constructed to assess the efficiency of indirect selection for cut-flower yield using flowering time as a marker trait. The advantages of indirect selection accruing from increased population size and reduced generation time are discussed.

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Douglas A. Hopper

One-year-old plants of four cut rose (Rosa hybrida L.) cultivars were grown under either natural or supplemental irradiance for 4 months during the winter in Colorado. Supplemental irradiance with high-pressure sodium (HPS) lamps was supplied at 100 μmol·m–2·s–1 for 10 h each night during off-peak electrical use periods. Total cut flower yield, stem length, and fresh weight of individual flowers were recorded. The number of flowers produced and fresh weight increased for all cultivars under the supplemental irradiance treatment. Flower count, stem length, and fresh weight showed significant differences among the four 4-week production periods; production differences were promoted through pinches of two stems per plant to time for holiday peaks. When production was highest, stem length and fresh weight were lower, most likely due to redistribution of the limited carbohydrate pool during the winter.

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Joseph DeFrank, Tadashi Higaki, and Joanne Imamura

Yield components of 4 anthurium cultivars over a 2 year harvest period were determined. The varieties are `Ozaki' (red color-OZ), `Nitta' (orange-NT), `Kozohara' (dark red-KZ) and `Marian Seefurth' (pink-MS). The herbicide treatments are: diuron (1.1 kg ai/ha) every 3 months (DN); granular formulation of oxyfluorfen (2%) and oryzalin (1%) (3.4 kg ai/ha) in an alternating 3 month cycle with diuron (1.1 kg ai/ha) (OO). Black polypropylene mulch (PM) is the non-chemical control treatment. Yield components include: total cut flower yield, mean stem length and mean flower size (spathe width × length). Total flower yield was not significantly affected by weed control treatments. Yield ranking was: MS>KZ=NT>OZ. A significant interaction was recorded for stem length and flower size. OZ stem length was unaffected by weed control treatments while the others showed variations dependent on treatments. KZ and OZ flower size was not affected by weed control treatments, however, herbicide treatments did reduce flower size of MS and NT. Weed control ranking was: PM=00.>DI.

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Raul I. Cabrera, Richard Y. Evans, and J. L. Paul

Nitrogen leaching losses of 21, 40 and 49% were measured from container-grown `Royalty' roses irrigated for one year with nutrient solutions containing 77, 154 and 231 mg N/l. There were no significant differences in number of flowers per plant or dry matter per plant. The N present in the harvested flowers accounted for 43, 27 and 17% of the N applied for the 77, 154 and 231 mg N/l treatments, respectively.

Plants receiving 154 mg N/l at leaching fractions of 0.1, 0.25 and 0.5 had corresponding N leaching losses of 22, 38 and 56%. In this experiment, however, the 0.5 leaching fraction produced yields significantly higher than those of the 0.1 and 0.25 treatments. The N recovered in the harvested flowers accounted for 28, 25 and 19% of that applied to the 0.1, 0.25 and 0.5 treatments, respectively.

The results of these studies suggest that modifications in current irrigation and fertilization practices of greenhouse roses would result in a considerable reduction of N leaching losses and enhance N fertilizer use efficiency, without loss of cut flower yield and quality.