Agricultura Pesca y Alimentación, 1988 ) led to an increasing demand for ‘Albariño’ grapes and to the substitution of low-quality cultivars and the hybrids they produced (then typical of post-Phylloxera Galicia) by ‘Albariño’. Because no clonal selection had
Abstract
Data on 15 traits collected from 30 walnut selections were analyzed for changes in relation to both clone and rootstock age. Data collection began at first flowering (age 3 or 4) and continued annually for up to 28 years on each clone. Significant correlations were found between seasonal timing of the expression of phenological traits and clone age. The general trend was towards earlier leafing, bloom, and time of nut maturity as the clone aged. Correlations with rootstock age were lower than with clone age for phenological traits. Shell and kernel trait expression was more highly correlated with rootstock age than clone age, suggesting that changes may be due to vigor and other effects of grafting rather than aging per se. Estimates of the age of stabilization for phenological traits ranged between 9 and 18 years from germination. It is suggested that changes in leafing, bloom, and nut maturity dates be considered prior to commercial release of walnut cultivars.
The term “clone” is a key biological term that designates a number of horticultural situations. In breeding, many cultivars are designated as clones, originating from consecutive vegetative propagation from individuals within a seedling population, from individual plants of a clone exhibiting “bud mutations,” and, more recently, from genetic engineering and biotechnology. Extensive vegetative propagation of a limited numbers of clones in modern horticultural systems has been accompanied by systemic incorporation by serious pathogens (viruses, viroids, phytoplasmas, etc.), and in some cases by horticultural deterioration (e.g., noninfectious bud-failure in almonds). Control of these problems in clonal propagation is achieved by 1) propagation source selection 2) maintenance of the source in a registered foundation block under protected conditions and 3)multipli-cation in controlled “mother blocks” or “increase blocks” from which commercial material is distributed after a minimum of consecutive generations of vegetative propagation. This system is the basis for Registration and Certification programs and “clean stock” in general. In many crops the selected propagation source is a single plant, its progeny constitutes a “clone,” and the new entity is given a unique name or number. To distinguish this “new” clone from the “original” clone, the designation of FOUNDATION CLONE is suggested. Biological and horticultural significance is illustrated in almond (Prunus dulcis).
Thyme (Thymus vulgaris L) is an important medicinal and aromatic plant used in nutrition, pharmaceutical and cosmetic industries. The main objective of this investigation was to elucidate the influence of different growning conditions on photosynthesis, chlorophyll contnet and leaf water potential in two different thyme clonal selections. Pot experiments were conducted in a greenhouse with three different soil water levels (50, 70 and 90% by weight), under supplementary lighting and natural lighting. Photosynthetic rate was positively related to soil water level and supplementary lighting. Under both light treatments, photosynthesis was found to be highest at 70% soil water level. “Selection 1” showed higher rates of photosynthetsis than “Selection 2”. “Selection 1” had slightly higher leaf water potential than “selection 2” under all growing conditions. Leaf water potential was found to be much higher for both selections grown without supplementary lighting than the variants grown under supplementary light. The mean chlorophyll content of “Selection 1” grown under supplementary lighting was found to be higher than “Selection-2” under all soil water levels (50 % 70% and 90%). There was a clear difference in leaf color between plants grown under the two light levels. This research was partially supported by Matol Botanical International.
Eight individual potatoes, exhibiting a wide range of quality characteristics, were cloned at the Texas A&M Vegetable Improvement Center, College Station, Tex., in order to produce a large number of slips for field trials. Leaf photosynthetic light response for six of these clonal selections was determined during a greenhouse experiment conducted at the Texas A&M Univ. Agricultural Research and Extension Center at Overton, Tex. Photosynthesis data were fit to a rectangular hyperbola in order to estimate light saturated leaf photosynthetic rate (Amax), quantum efficiency (QE), and dark respiration rate (Rd). Significant differences (P ≥ 0.05) were detected in all three of these parameter estimates among the six clonal selections. Parameter estimates ranged from 23.4 to 28.8 μmol (CO2) m-2·s-1, 0.056 to 0.071 mol (CO2)/mol (photons), and –0.9 to –2.0 μmol (CO2) m-2·s-1 for Amax, QE, and Rd, respectively. However, these differences were not clearly related to quality characteristics determined for these clones in field trials.
cultivars and experimental selections will provide turfgrass breeders and managers with a greater selection pool. In addition, it is important to determine the effectiveness of subjective and nondestructive evaluation parameters for plant salinity tolerance
Suspension cultures of grape hybrids (Vitis spp.) were used to select cold tolerant cell lines. The cultured cells were subjected to selection pressures by cooling at 2° C/h to various temperatures below the average lethal temperature (LT50) of the cell population. The cold tolerant lines were selected based on the distribution of lethal temperatures in the population. The small fractions of cells which were more cold tolerant than the LT50 of the population were enriched by many selection cycles. After two selection cycles, the cold tolerant lines of all three cultivars survived -9 and -9.6°C (LT50), whereas the control population survived between -2.5 and -3.2°C. The increased cold tolerance in selected lines was due to shifts in the frequency and distribution of lethal cell injury in the selected population as compared to the unselected control.
Eight and seven clones, respectively selected within the olive cultivars `Arbequina' and `Manzanilla de Sevilla', were studied by means of randomly amplified polymorphic DNA (RAPD) and amplified fragment-length polymorphism (AFLP) markers. Two clones of `Arbequina', C3 and C12, showed polymorphism with respect to the standard cultivar by means of both markers. In fact, about 33.6% RAPD bands and 9.2% AFLP bands were polymorphic for these clones. This high level of polymorphism and the presence of a high percentage of bands absent in `Arbequina' suggest their possible origin as `Arbequina' seedlings. The dendrogram obtained by both molecular markers also supports the hypothesis of a seedling origin of these clones as they clustered separately from the original cultivar and the rest of monomorphic clones at low values of similarity. Also within the `Manzanilla de Sevilla' group, two clones (31 and 44) showed diversity with respect to the standard cultivar; 4.5% RAPD and 6.3% AFLP markers were polymorphic for these genotypes while all the other clones didn't show any difference with the standard `Manzanilla de Sevilla'. RAPD and AFLP markers effectively revealed intracultivar variability due to gametic or multiple mutational events, while the detection of other kind of differences such as eventual single mutations remains uncertain and requires further investigation.
appreciated by the Israeli population, various selections were made in the country expected to be more responsive to intensification. “Clonal” propagated plants of these selections were distributed by the nurseries to many of the new intensive olive orchards
been involved in pecan cultivar testing for over 93 years ( Worley and Mullinix, 1994 ). More recently, it has been a testing location for the National Pecan Advanced Clone Testing System (NPACTS). This system tests advanced pecan selections from the