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  • Author or Editor: Thomas Byrne x
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Abstract

Shoots of ‘Cara Mia’ rose (Rosa hybrida L.) arising from buds higher on the parent shoot become salable more quickly than those arising from lower buds. Those developing above the 10th or below the 6th true leaf are shorter, of smaller diameter and weigh less. Shoot development is also strongly influenced by shoot diameter at the point of origin. Larger parent shoots give rise to shoots that become salable more quickly, are longer, weigh more, and are larger in diameter than those from smaller parent shoots. Buds from larger-diameter shoots are of larger diameter and have more leaf primordia than those from smaller-diameter shoots, but the diameter of their apical dome is not greater.

Open Access

Abstract

Twenty-nine Japanese-type plum clones were assayed for isozymic variability for eight enzyme systems. Glutamate dehydrogenase (GDH), leucine amino-peptidase (LAP), malate dehydrogenase (MDH), phosphoglucose isomerase (PGI), phosphoglucomutase (PGM), and peroxidase (PX) showed variability among the plums surveyed. 6-phosphogluconate dehydrogenase (6PGD) and triosephosphate isomerase (TPI) were not variable. Isozymic characterization uniquely identified 38% of the clones. The remainder separated into groups of two to three clones that were distinguishable using vegetative morphological characteristics. Reported parentage of five out of nine plums examined was not consistent with their isozymic genotypes.

Open Access

Abstract

Seven enzyme systems were examined in 69 apricot [Prunus armeniaca L. and P. mandshurica (Maxim.) Koehne] clones. Three enzymes (6-phosphogluconate dehydrogenase, phosphoglucose isomerase, and phosphoglucomutase) were polymorphic at five loci. Only seven clones were characterized uniquely by their isozyme phenotypes and 56% fell into two of the 15 phenotypic groups found. Isozyme variability in apricot was greater than in peach, but less than that reported in plum or almond.

Open Access

Abstract

Statistics were developed to measure the relative importance of genotype × environmental (GE) interactions. Estimates indicate that as much as half of the genetic variance for cut-flower yield in the Davis Population of Gerbera may be attributable to GE interactions. The bias this causes in broad-sense heritability estimates averaged 10.3% ± 2.97% for single-factor interactions; 15.6% ± 3.52% for 2-factor interactions, and 26.8% ± 3.45% for 3-factor interactions. The mean unadjusted broad-sense heritability for cut-flower yield in the same experiments was 37.1% ± 6.54%. Therefore, response equations that do not take interaction bias into account will overestimate selection potential.

Open Access

Abstract

Flower bud initiation of herbaceous peony (Paeonia L.) may start soon after the current year’s flower anthesis in June; buds continue to develop until the onset of dormancy in the fall. Flower formation, days to harvest, foliage senescence, and dormancy are unaffected by photoperiod. Flower bud dormancy can be broken by storage of dormant plants for a minimum of 4 weeks at 5.6°C after which they may bloom in the greenhouse in 8 to 10 weeks. Increasing storage time to 6 weeks or reducing the temperature to 1° increases the total number of shoots that grow after forcing.

Open Access

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.

Free access

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.

Free access

Inbreeding depression is found in most flower crops. Limited population size can cause inbreeding even in outcrossed populations. The Davis population of Gerbera hybrida has been selected for increasing flower yield for 15 generations. The mean yield per plant of the population has been increased from 14.2 to 28.0 flowers per winter six-month period. In each generation 23 to 80 selected parents have been crossed at random. Inbreeding coefficients were estimated from the pedigrees of each of the 6199 plants in the 16 generations. The inbreeding level in this population was found to increase in each generation and currently is 16.5%. Mean yield and inbreeding per family have a statistically significant negative correlation in generations 13 to 16. The results indicate that inbreeding is increasing in this randomly outcrossed population because of its finite number of parents, and that yield is reduced by 3.9 flowers per six-month due to inbreeding.

Free access

Abstract

A series of diploid plum (Prunus salicina Lindl. and hybrids), apricot (P. armeniaca L.), and plum × apricot (plumcot) clones were surveyed for six enzyme systems to identify a biochemical marker system for plumcots. Peroxidase (EC 1.11,1.7) was the best marker for identifying plum × apricot hybrids. The other systems contained plum or apricot specific alleles useful in verifying hybrid parentage of first or later generation derivatives.

Open Access

The development of gerbera (Gerbera jamesonii H. Bolus ex. Hooker) as a floricultural crop is traced from its collection as a botanical novelty in South Africa to its establishment as a commercial crop in the 1930s. The origin of the cultivated germplasm, G. jamesonii and G. viridifolia (DC) Schultz- Bipontinus, is discussed, as well as breeding work that occurred in Europe and the United States. The contributions of the two species to the cultivated germplasm is unknown. Early breeding in Europe was conducted by RI. Lynch at the Cambridge Botanic Gardens in England, R. Adnet at La Rosarie in Antibes, France; and by C. Sprenger in Italy. In the United States, early work was done at estates in New Jersey by Herrington and Atkins, and by the commercial growers Jaenicke and the J.L. Childs' Seed Co. Establishing the cold hardiness of the crop for temperate climates was an early goal of horticulturists and breeders. Much of the cultivated germplasm can be traced to material that passed through Cambridge and Antibes.

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