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Abstract

The original ‘Brooks’ cherry (Prunus avium L.) seedling was evaluated at the Wolfskill Ranch of the University of California, Davis from 1970 to 1985. Clones of the original seedling have been evaluated for fruit quality in Contra Costa County since 1978 and in Fresno County at the University's Kearney Agricultural Center since 1981. ‘Brooks’ registered its most outstanding performance at the Kearney Field Station.

Open Access

Abstract

Three new cultivars of almond [Prunus dulcis (Mill) D.A. Webb syn. P. amygdalus Batch] are released for distribution. ‘Solano’ has a high-quality kernel and could be grown in combination with ‘Nonpareil’ for simultaneous bloom and sequential harvest. ‘Sonora’ has a high-quality kernel, blooms earlier than ‘Nonpareil’, and could be used as a substitute for or in combination with ‘Ne Plus Ultra’ and ‘Peerless’. ‘Padre’ is a high-yielding, late-blooming cultivar that could be planted together with or as a substitute for the ‘Mission’.

Open Access

Abstract

Fruits of ‘Delicious’ apple (Malus domestica Borkh.) were grown under differing radiant flux densities (rfd 400 700 nm) from 45 days post-bloom until harvest. The rfd 400 700 nm affected red fruit color, soluble solids, starch content and size, but not firmness, pH or total acidity at harvest or after 105 days of storage at −0.5°C. Levels of rfd 400 700 nm sufficient to enhance red color development in red sports of ‘Delicious’ were not necessarily sufficient to insure flesh quality.

Open Access

A replicated rootstock trial for almond was established in 1986 in the central San Joaquin Valley, a major almond growing area for this most widely planted tree crop in California. `Nonpareil', the major cultivar in California, was used for this trial with `Fritz' grown as the pollenizing cultivar. Two standard rootstocks for almond, `Nemaguard' and `Lovell' peach, were compared to two newer peach-almond hybrid rootstocks, `Bright's' and `Hansen'. After eight years both hybrid rootstocks produced significantly larger trees than the peach rootstocks, based on trunk cross-sectional area. Trees on hybrid rootstocks frequently produced greater yields than those on peach rootstocks; although, differences were not always significant. However, there were generally no significant differences in production per trunk cross-sectional area (yield efficiency). Thus, increased production by trees on hybrid rootstock was the result of larger tree size and not an inherent increase in productive efficiency of the tree itself. Since trees on hybrid rootstock should be planted further apart than those on peach, production per hectare should not be significantly increased, at least under good growing conditions as represented in this trial.

Free access

Boron(B) deficiency in almond (Prunus dulcis Mill.) is characterized by leaf tip scorch, leaf drop, twig dieback, brown gummy areas in the endocarp, and embryo abortion followed by nut drop in May. Additional symptoms revealed by our work include failure of flowers to set nuts and lateral bud drop. Lack of production in part or in all of the free canopy causes spurs to elongate leading to a “willow twig” symptom on the small fruitwood. This can be confused with the nonproductive “bull” syndrome or with virus bud failure (ABFV or PRSV). Comparative leaf, pericarp, or kernel analysis in May gave a better indication of low B than did leaf analysis in August. In August, analyzing the hulls (mesocarp and exocarp) gave better separation between deficient and adequate trees than did leaf, kernel, or shell analysis. B critical levels for almond leaves should be re-evaluated since deficiency symptoms occur at currently accepted “adequate” levels.

Free access

Six cross-incompatibility groups, which contain most of commercially important California almond cultivars [Prunus dulcis (Mill.) D.A. Webb, syn. Prunus amygdalus Batch], and their self-incompatibility (S) allele genotypes are identified. Incompatibility groups include `Mission' (SaSb), `Nonpareil' (ScSd), and the four groups resulting from the `Mission' × `Nonpareil' cross: (SaSc), (SaSd), (SbSc), and (SbSd), as represented by `Thompson', `Carmel', `Merced' and `Monterey', respectively. All seedlings from the `Mission' × `Nonpareil' cross were compatible with both parents, a result indicating that these two cultivars have no alleles in common. Crossing studies support a full-sib relationship for these progeny groups and the origin of both parents from common germplasm. Cultivars in these six groups account for ≈ 93% of present California production, a result demonstrating a limited genetic base for this vegetatively propagated tree crop.

Free access

Abstract

Establishment, shoot proliferation, root induction, and transplanting stages were accomplished with Prunus avium × P. cerasus cv ‘Colt’, ‘Dwarf Mahaleb’ (P. mahaleb L) (both vegetatively propagated rootstock cultivars) and seedling Mazzard sweet cherry (P. avium L) ‘46-1 Mazzard’, (P. avium L.), a clonal rootstock seed tree, could be established and multiplied by the same procedure. However, no rooting was obtained. Limited rooting was possible with seedling Mazzard trees < 3 years in age. It was concluded that the limiting factor in ‘46-1 Mazzard’ rooting was the mature status of the source material.

Open Access

In 1979 a Nonpareil-Price almond orchard, was planted 2.2m × 6.7m (270 trees/acre). Four pruning treatments were imposed on the hedgerow planting at the end of the first year. 1. Interplanted: Trees trained to 3 scaffolds then standard pruned 2nd-6th years. Alternate trees were whisked back during 7th and 8th years and whisked trees removed after 9th year. 2. Permanent Hedge: Trees trained to 3 scaffolds and standard pruned throughout. 3. Two Scaffold Hedge: Heavy 2nd and 3rd year training required to form 2 main scaffolds growing into the row middles then standard pruned. 4. Unpruned Hedge: Trees trained to 3 scaffolds then no further pruning. Treatment with alternate trees whisked back had 15% reduced yield each year following whisking. Removing these heavily pruned alternate trees at the 9th year then reduced yields an additional 30%. Now, three years after removal, yield still lags by 18%. Accumulating six years yield data shows no differences between the three treatment maintained as hedgerows. However, whisking and removing alternate trees resulted in 2000 lbs less yield over the 6 year period.

Free access

Abstract

Ground application of urea increased yields of ‘Nonpareil’ almond (Prunus amygdalus Batsch) by increasing the number of flowers per tree rather than by increasing blossom receptivity and percentage fruit-set. Hand pollination of flowers on caged limbs indicated that blossom receptivity declined between 3 and 6 days after anthesis.

Open Access

Noninfectious bud-failure (BF) is a genetic disorder in almond, associated with nursery source selection. Previously (Kester, PASHS, 1968), the latent potential for BF (BFpot) was shown to be heritable but its phenotypic expression (BFexp) varied among individual seedlings of a populations as a function of age. Vegetative propagation perpetuates BFpot of individual propagules (Kester and Asay, JASHS, 1978b) but the subsequent age of BFexp within individual plants is a function of accumulated exposure to high summer temperature and growth (Kester and Asay, JASHS 1978a). A recent 7-year “somatic heritability” study of 12 commercial nursery sources (Kester et al., HortScience 1998abst) portrays the total range of variability of BFpot and BFexp within the entire `Carmel' almond clonal population and includes a pattern of BF increase in consecutive vegetative propagation cycles that mimics patterns produced by phase change (i.e., juvenile > mature) phenomena (Hartmann et al., 1997). Although phase change potential is heritable in seedling populations, phase change expression is not (Kester, HortScience 1983). Furthermore phase changes can be reversed under particular conditions during consecutive vegetative propagations (Hartmann et al., 1997). In contrast, evidence shows that BF produces permanent changes in genotype that are heritable and irreversable. High correlations exist between BFpot of individual source blocks, individual trees and individual budsticks and the age and severity of BFexp in progeny trees. The apparent continuous change in BFpot and BFexp within clones appears to be the pattern of expression of different populations of increasingly defective (?) somatic cells that result from consecutive sequences of change during annual cycles of growth and generations of vegetative propagation.

Free access