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Riccardo Lo Bianco, Mark Rieger, and She-Jean S. Sung

Terminal portions of `Flordaguard' peach roots [Prunus persica (L.) Batsch] were divided into six segments and the activities of NAD+-dependent sorbitol dehydrogenase (SDH), sorbitol oxidase (SOX), sucrose synthase (SS), soluble acid invertase (AI), and soluble neutral invertase (NI) were measured in each segment 10, 15, and 20 days after seed germination. The same type of experiment was conducted with terminal portions of `Flordaguard' and `Nemaguard' peach shoots except that one of the six segments consisted of the leaflets surrounding the apex. Independent of the age of individual roots, activities of SDH and AI were consistently highest in the meristematic portion and decreased with tissue maturation. In shoots, AI was the most active enzyme in the elongating portion subtending the apex, whereas SDH was primarily associated with meristematic tissues. A positive correlation between SDH and AI activities was found in various developmental zones of roots (r = 0.96) and shoots (r = 0.90). Sorbitol and sucrose contents were low in roots regardless of distance from tip, while sucrose showed a decreasing trend with distance and sorbitol, fructose, and glucose increased with distance from the meristem in shoots. Activity of SDH in internodes, but not apices, correlated with shoot elongation rate of both cultivars, whereas activities of other enzymes did not correlate with shoot elongation rate. We conclude that AI and SDH are the predominant enzymes of carbohydrate catabolism and the best indicators of sink growth and development in vegetative sinks of peach.

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Michael W. Smith, Charles T. Rohla, and Niels O. Maness

. Pearson's coefficients of correlation were calculated for crop load and return bloom with nonstructural carbohydrates, K, and organically bound N. Results and Discussion The percentage of current season shoots flowering was negatively related to

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Christopher S. Cramer and Todd C. Wehner

Increased fruit yield in slicing cucumber (Cucumis sativus L.) has been difficult to achieve since yield is quantitatively inherited with low heritability. From 1981 to 1993, four slicing cucumber populations differing in their genetic diversity (wide, medium, elite, and `Beit Alpha') were advanced through six to ten cycles of modified half-sib recurrent selection. The objectives of this research were to determine 1) the fruit yield and yield component means; 2) the correlations between yield components, between yield traits, and between components and yield; and 3) the change in means and correlations with selection for improved yield of four slicing cucumber populations. In 1994 and 1995, four families were randomly selected from three cycles (early, intermediate, and late) from each population and self-pollinated. Thirty plants from each S1 family were evaluated in 3.1-m plots in Spring and Summer 1995 and 1996 at the Horticultural Crops Research Station in Clinton, N.C. Plants were harvested and data were collected on number of branches per plant and nodes per branch, proportion of pistillate nodes, fruit set and shape, and total, early, and marketable yield. When averaged over all populations, seasons, and years, fruit yield and quality increased with selection while yield components remained unchanged with selection. Fruit yield and components differed between populations, seasons, and years. Most correlations between yield components and between yield components and fruit yield were weak, and strong correlations varied between populations, seasons, and yield components. Indirect selection of proportion of pistillate nodes has potential for improving yield for certain population-season combinations. Selection weakened many strong correlations between yield components and between yield and components. Changes in correlations often did not correspond with changes in trait means. Based on this research, selection for yield components would not be advantageous for improving fruit yield in all slicing cucumber populations. Additional yield components, yield component heritability, and better component selection methods need to be determined before component selection can be used to improve fruit yield.

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Valdomiro A.B. de Souza, David H. Byrne, and Jeremy F. Taylor

Thirteen peach [Prunus persica (L.) Batsch] fruit characteristics were investigated for 3 years, 1993, 1994, and 1995, in College Station, Texas, to determine heritability, genetic and phenotypic correlations, and predicted response to selection. Seedlings of 108 families resulting from crosses among 42 peach cultivars and selections were used in the evaluations. A mixed linear model, with years treated as fixed and additive genotypes as random factors, was employed to analyze the data. Best linear unbiased prediction (BLUP) was used to estimate fixed effects. Restricted maximum likelihood (REML) was used to estimate variance components, and a multiple trait model was used to estimate genetic and phenotypic covariances between traits. Genetic and phenotypic correlations ≥0.65 and <0.30 were considered strong or very strong and weak, respectively. Date of ripening, fruit development period (FDP) and date of full bloom had the highest heritability (h2) estimates, 0.94, 0.91, and 0.78, respectively. Fruit cheek diameter and titratable acidity (h2 = 0.31) were the traits with the lowest estimates. Fruit development period, fruit blush, and date of ripening had the highest predicted selection responses, whereas fruit suture, fruit cheek, L/W12 (ratio fruit length to average fruit diameters), and fruit tip had the lowest values. Most genetic correlations were ≥0.30 and were, in general, much higher than the corresponding phenotypic correlations. All four measures of fruit size were genetically and phenotypically very strongly correlated. Important genetic correlation estimates were also observed for date of ripening with FDP (ra = 0.93), date of ripening and FDP with fruit blush (ra = -0.77, ra = -0.72), SS (percent soluble solids) (ra = 0.63, ra = 0.62) and TA (ra = 0.55, ra = 0.64), and SS with TA (ra = -0.56). Direct selection practiced solely for early ripening and short FDP is expected to have a greater effect on correlated traits than direct selection for early bloom and large fruit mass.

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Valdomiro A.B. de Souza, David H. Byrne, and Jeremy F. Taylor

Seedlings of 108 families from crosses among 42 peach [Prunus persica (L.) Batsch] cultivars and selections were evaluated for six plant characteristics in 1993, 1994, and 1995. The data were analyzed by using a mixed linear model, with years treated as fixed and additive genotypes as random factors. Best linear unbiased prediction (BLUP) was used to estimate fixed effects. Restricted maximum likelihood (REML) was used to estimate variance components, and a multiple trait model was used to estimate genetic and phenotypic covariances among traits. The narrow-sense heritability estimates were 0.41, 0.29, 0.48, 0.47, 0.43, and 0.23 for flower density, flowers per node, node density, fruit density, fruit set, and blind node propensity, respectively. Most genetic correlations among pairs of traits were ≥0.30 and were, in general, much higher than the corresponding phenotypic correlations. Flower density and flowers per node (ra = 0.95), fruit density and fruit set (ra = 0.84) and flower density and fruit density (ra = 0.71) were the combinations of traits that had the highest genetic correlation estimates. Direct selection practiced solely for flower density (either direction) is expected to have a greater effect on fruit density than direct selection for fruit density.

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Hyun-Hee Han*, Yong-Koo Kim, and Jae-Young Lee

The nitrogen contents of leaves were the same on the first measurement of 9 May 2003 and the date was immediately prior date to application of different training angles to the one-year-old shoots grown during the previous year. However, the nitrogen content began to be different according to training angles as early as 8 days after the training of one-year-old branches. The 90° branch showed higher nitrogen content on the eighth date from the training application against 120° or non-trained slanting branch. The 90° branch continuously demonstrated larger nitrogen contents on 23 May and 2 June against non-trained branch. While, the 120° branch began to show the tendency of larger nitrogen content compared with slanting branches from 23rd May which was 2 weeks from training, and this difference continued up to 2 June 2003. The chlorophyll (SPAD value) of the leaves trained to 120° and 90° were the same at the time of initial training was applied on 9t May 2003, but a significant reduction of the chlorophyll (SPAD value) was found as early as eighth date from the first training date and this difference was reduced to be the same on the date of 2 weeks after the initial training date, but the chlorophyll (SPAD value) became different again on 2 June 2003. Correlations between chlorophyll contents (SPAD value) and photosynthetic rates influenced by training angles were highly positive in 90° training and in 120-degree training than non-training. Additionally, the correlations between the specific leaf weight and chlorophyll contents (SPAD value) were highly positive in 120° training than in 90° training or non-training.

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Stefano Macolino, Matteo Serena, Bernd Leinauer, and Umberto Ziliotto

-soluble carbohydrates (WSC), or water soluble non-structural carbohydrates represent a subgroup of TNC. A positive correlation has been reported between TNC and freezing tolerance in turfgrasses ( Di Paola and Beard, 1992 ; Fry et al., 1993 ; Rogers et al., 1975

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Javier Sanzol and Timothy P. Robbins

interspecific backcross of Lycopersicon esculentum × L. hirsutum : Linkage analysis and a QTL study of sexual compatibility factors and floral traits Genetics 147 861 877 Bošković, R. Tobutt, K.R. 1996 Correlation of

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Bill B. Dean

Asparagus is a unique crop in that the yield of the crop is entirely dependent on the storage of carbohydrates from the previous season. The number of spears produced is determined by the number of buds on underground rhizomes and the size of each spear is related to the size of the bud from which it originates. Growth of spears begins in the spring when some minimal temperature is reached in the soil. We have determined that the minimum temperature for spear growth is 10°C (50°F) and that temperatures in excess of 35°C (95°F) inhibit growth. Using data from growth response to temperature experiments, we have compared the accumulative effects of hourly temperatures preceding harvest to subsequent yields. There was a significant effect of the number of hours above 10°C for the 24 hours preceding harvest and the yield obtained. Yield of spears cycled over an 11-day period which correlated to an eleven day weather cycle determined from the heat unit accumulations. Heat unit and yield cycles for seven cultivars over a 4-year period will be discussed.

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J.M. Alonso, J.M. Ansón, M.T. Espiau, and R. Socias i Company

Almond (Prunus amygdalus Batsch.) blooming date is determined by the temperatures during the dormancy period, from the onset of endodormancy to just before blooming. In this work we have developed a model, based on several years data, to estimate the mean transition date from endodormancy to ecodormancy in 44 almond cultivars covering the whole range of almond bloom, through the significance of correlation coefficients between the temperatures occurring during dormancy and the date of full bloom. The estimation of this date for each cultivar has allowed the calculation of its chill and heat requirements. It was found that most cultivars have chilling requirements between 400 and 600 chill units, whereas the span of heat requirements was wider, from 5500 to 9300 growing degree hours Celsius. Some cultivars show high chilling requirements and low heat requirements whereas others show opposite requirements. These differences confirm the wide almond adaptability to different climatic conditions and offer the possibility of being utilized in breeding programs. The good fit shown by the application of this model in the prediction of bloom time may sustain its application in chilling and heat requirement estimation in other fruit species if blooming dates and climatic data for several years are available.