the kernel market, while nuts of ‘Lewis’ and ‘Willamette’ could also be sold in-shell. Although climatic adaptation is rarely a concern in the major production areas, expansion of hazelnut plantings into marginal areas will require the development of
Absence or long delay of budbreak, also known as prolonged dormancy, is the most important symptom during incomplete dormancy. Budbreak number was evaluated to quantify seedling response to chilling and selection on excised and intact 1-year-old apple (Malus ×domestica Borkh.) seedlings under controlled and natural environmental conditions. Indices based on: 1) the number and distribution of budbreak (prolonged dormancy grade = PDG); 2) the number of buds breaking, including shoot length with increased budbreak as part of the calculation (prolonged dormancy index = PDI); and 3) budbreak number per 100-cm shoot (NB) were tested in association with budbreak time (TB). The indices expressed the effects of cold treatments that induce earlier and higher numbers of budbreak. PDI and NB, but not PDG, identified families with increased budbreak. Seedlings with high PDG and NB were also associated with families in which high chill requiring parents were used, indicating that TB as pre-selection criterion may fail to identify seedlings with increased budbreak. Response to pre-selection for increased budbreak using PDG could be verified with the PDS and NB indices in seedlings and seedling clones. The NB of intact 1-year-old shoots under natural conditions is recommended as a pre-selection criterion against prolonged dormancy in suboptimal winter conditions.
Genetic variation in chilling requirement was investigated over three growth periods using clonal progenies of six apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] families derived from crosses of high and low chill requiring cultivars. Two quantitative measurements related to chilling requirement, viz., the time of initial budbreak (vegetative and reproductive) and the number of breaking buds over a specified time interval, were used as evaluation criteria. Genetic and environmental variances of the traits are presented as intra-class correlation coefficients for clones within and between families. For budbreak time, reproductive and vegetative, broad-sense heritability averaged around 75% and 69% respectively, indicating a high degree of genetic determination in this material. For budbreak number, moderate to low genetic determination was found with broad-sense heritabilities around 30%. Estimates of genetic components of variance between families were generally very low in comparison to the variance within families and predict potentially favorable responses to truncation selection on the traits within these progeny groups. Analysis of the data showed that distribution of budbreak time is typical of quantitative traits with means distributed closely around midparent values. Skewed distributions towards low budbreak number were obtained in varying degrees in all families.
analogous climatic adaptation, were clustered at the upper part of the dendrogram, whereas old European cultivars appear at the bottom. The two most distant cultivars, Josif Mahomet and Missionary Hybrid, were very different from the rest (with a similarity
crop quality and productivity ( Thomashow, 1999 ). Fruit breeding efforts have recently focused on the development of cultivars with broader climatic adaptation (such as increased freezing tolerance for the northern regions), disease and pest resistance
resistance from C. americana is a challenge for reaching breeding objectives, which expand beyond disease resistance and include kernel traits, yield, and climatic adaptation. Several recent studies have begun to shed light on the inheritance of EFB
Abstract
Temperate zone (deciduous) fruit crops are cultivated largely in areas far removed from their center of origin. Selection and breeding have improved climatic adaptation in these perennial crops. Current breeding programs are attempting to broaden this adaptation by developing cultivars with high mid-winter cold tolerance, late blooming to avoid spring freezes, and increased disease resistance. The attainment of these and other breeding objectives will recessitate the use of noncommercial exotic germplasm. The range of these fruits also is being extended to the subtropics and tropical highlands through selection and breeding. It is only through genetic manipulation that more productive and adapted plant materials are likely to be developed. Germplasm centers are needed to maintain and provide the array of genetic variability necessary for continued scion and rootstock improvement.
Abstract
The principal area of apple (Malus domestica Borkh.) production in Brazil is in the south in the states of Santa Catarina, Rio Grande do Sul, and Paraná. In these states, apples are grown using modern technology, and trees are propagated on size-controlling rootstocks (1). Apple production areas are limited because present cultivars have inadequate climatic adaptation and a high level of susceptibility to fungal diseases, including apple scab [Venturia inaequalis (Cke.) Wint.], powdery mildew [Podosphaera leucotricha (Ell. & Ev.) Salm.], and bitter rot [Glomerella cingulata (Ston.) Spauld & Schrenk] (2). There is a need to develop early ripening cultivars that would make it possible to reduce the cost of chemical protection against diseases and also reduce the length of time that late-maturing apples must be stored until the beginning of the next summer's harvest.
. Flowers of ‘Razz’ highbush blueberry. Fig. 3. Fruit of ‘Razz’ highbush blueberry. ‘Razz’ is suitable for production in areas where highbush is typically grown. It may have broad climatic adaptation like ‘Bluecrop’, but has not been tested outside of New
( Fisher, 1957 , 1958 ). This species combines multiple desirable features: drought and pest tolerance, flower heads with showy yellow ray florets, wide climatic adaptation (USDA Hardiness Zones 3 to 9), and a long season of bloom typically lasting several