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Yi Tan, Baisha Li, Yi Wang, Ting Wu, Zhenhai Han, and Xinzhong Zhang

heritability of BRR was estimated using the data from the 78 hybrid trees. Theoretically, the phenotypic value can be determined by the genotype and environment. Here, the phenotypic variance ( S ) was calculated as the hybrid population total variance. The

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M. Joseph Stephens, Peter A. Alspach, Ron A. Beatson, Chris Winefield, and Emily J. Buck

fruit size. Although all yield components interact with environmental influences to produce total yield, from a breeding point of view, there are key components that are likely to be better correlated with yield and are more heritable. We found few

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John R. Stommel and Robert J. Griesbach

.0, whereas the most orange fruit had a value near 0.5. The leaf color data were transformed using the formula R + B-G. Using transformed data, the blackest leaves had a value near 60, whereas the greenest leaves had a value near 4. Heritability

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Roberto Hauagge and James N. Cummins

Abbreviations: CR, chilling requirement; CU, chill unit; GDH, growing degree hours; H 2 , heritability; I 50 , index of bud activity; OP, open-pollinated. 1 Present address: IAPAR-lnstituto Agronômico do Paraná, P.O. Box 2301, Curitiba, PR, Brazil

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Cecilia E. McGregor, Vickie Waters, Tripti Vashisth, and Hussein Abdel-Haleem

of inheritance, heritability, and the possible candidate genes are all unknown for this crop. These factors are critical impediments to efficient breeding of watermelon cultivars in a changing environment, and especially for the United States where

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Dennis Ray, Steven Smith, and Mark Hurlburt

Lettuce (Lactuca Sativa L.) seeds imbibe water but most fail to germinate, This phenomenon now termed “thermodormancy” is prevalent in arid and semiarid climates like the southwest desert regions, Inheritance studies of thermodormancy were performed in two lettuce cultivars, Dabora (Dutch butterhead) and PI 251245 (a plant introduction from Egypt). Dabora will germinate up to 27 C and PI 251245 up to 36C. Reciprocal crosses were made. Pericarp color was used as a marker to determine successful crosses. Dabora X PI 251245 was used to estimate the heritability of thermodormancy by germinating seed from 10 F3 families and 160 F4 families at “high” temperatures.

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Linda Wessel-Beaver and J.W. Scott

Abbreviations: G × E, genotype × environment; h 2 , heritability. 1 Professor. 2 Associate Professor. Florida Agricultural Experiment Station Journal Series no. R-02374. This research was supported in part by the U.S. Dept. of Agriculture under CSRS

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Creighton Gupton and James Spiers

To determine whether manganese tolerance in rabbiteye blueberry (Vaccinium ashei Reade) is heritable, a 10-parent diallel cross was produced. A 250 ppm Mn solution (200 ml/plant) was applied to a sand culture, of the progeny daily. Visual ratings (1 - dead plant - 13 - no Mn toxicity symptom) were made after 6 weeks. Shoot weight and Mn content of leaves were determined. Narrow-sense heritability estimates (h2) were 0.45±0.28 for Mn content, 0.49±0.27 for visual ratings, and 0.37± 0.21 for shoot weight. The genetic correlation between neither shoot weight nor visual rating and Mn content (0.11 and -0.15, respectively) was very high; however, the correlation between shoot weight and visual ratings (1.00) was extremely high. This suggests that visual ratings provide an estimate of Mn effects on plans equal to objective measurements of shoot weight. Though h2 estimates for Mn content and visual ratings were similar, the lack of genetic correlation between the traits indicates that tolerance to Mn toxicity is independent of Mn content. The high h2 for visual ratings suggests mass selection as the method of choice for improving Mn tolerance in a rabbiteye blueberry population.

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Verónica Raga, Guillermo P. Bernet, Emilio A. Carbonell, and Maria J. Asins

hybrids included in both treatments in all years ( InfoStat, 2004 ). Considering rootstocks as a random effects factor, broad-sense heritability (H 2 ) was estimated for all traits evaluated in 2008 only for nucellar rootstocks (repetitions) derived from

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Creighton L. Gupton and Barbara J. Smith

A study was conducted to determine if blackberry cultivars Humble, Rosborough, and Brazos transmit rosette (incited by Cercosporella rubi) resistance and to estimate heritability (h2). Plants of parents and offspring involving these cultivars were rated for rosette severity on a whole plant basis from 0 = no rosette to 7 = all buds infected or plant dead. An estimate of h2 was computed by regression of cross means on parental means. The mean rosette severity rating of plants from crosses was always intermediate between the cultivar and other parents. Only `Humble' transmitted enough rosette tolerance to be usable although `Rosborough' crosses were more tolerant than the other parents. The h2 estimate of 0.48 was fairly high but low variability among parents other than `Humble' would suggest little progress from mass selection.