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  • Author or Editor: D. Kester x
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Abstract

Shoot invigoration and rooting potential of hard-to-root ‘46-1 Mazzard’ sweet cherry (Prunus avium L) was progressively increased during six consecutive subcultures when cocultured with easy-to-root ‘Colt’ (P. avium × P. pseudocerasus). Similar results were produced with gibberellic acid at a concentration range of 0.1 to 0.25 mg·liter−1, but rooting depended on transfer to a GA3-free medium. It is suggested that the invigoration and enhanced rooting involved rejuvenation of the mature ‘46-1 Mazzard’ to a more juvenile phase.

Open Access

Abstract

Leaf resistance (r1) in fully exposed leaves of bud-failure (BF) sensitive subclones of 2 almond (Prunus amygdalus Batsch) cultivars was much greater than in leaves of non-BF-sensitive (normal) subclones of these cultivars. The differences in resistance were evident at ambient temperatures between 26° and 38°C, and temperatures of fully exposed leaves on BF-sensitive plants exceeded ambient temperature and averaged 5° higher than leaf temperature of normal plants. The difference between BF-sensitive and normal subclones was not apparent below 25° or above 39°. Increase in resistance preceded the development of abnormal growth patterns characteristic of the BF syndrome, and these differences may serve to identify BF sensitivity at incipient stages of the syndrome. Stress is accentuated in BF-sensitive clones between 26° and 38° because transpirational cooling is suppressed; however, the physio-chemical basis of BF sensitivity remains obscure.

Open Access

Abstract

Exposure of growing shoots to high temperature resulted in symptom expression of noninfectious bud-failure, a “genetic disorder” in almond Prunus amygdalus Batsch, whereas lower temperature prevented expression. Exposure of the normal phase of the disorder to high temperature gradually induced symptom expression.

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

Harvesting seed of ‘Manzanillo’ olive (oleo europaea L.) at the end of October, when embryo growth was complete, gave optimum germination and extended storage life with lower germination rates and shorter storage life before or after this date. Optimum germination occurred at 15°C for whole seed and 25° for excised embryos; both grew faster at 25° after germination. Seed and excised embryos germinated equally well in light or dark.

Open 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

Pollen tube growth in the styles following self- and cross-pollination was studied in self-incompatible ‘Ne Plus Ultra’ almond (Prunus amgdalus Batsch) and 5 unnamed self-fertile almond selections derived from back-cross hybridization with peach (P. persica (L.) Batsch).

Self-incompatibility of ‘Ne Plus Ultra’ was expressed morphologically by failure of all tubes to grow through the style, failure of many tubes to penetrate the style, presence of swollen pollen tube ends and retrogression with time at higher temperatures. Rates of pollen tube growth in self-fertile selections was consistently less than after cross-pollination, but the ratios of self/cross varied. Thus, selections ranged from those approaching selfincompatibility to those approaching self-compatibility.

Optimum temperatures for ‘Ne Plus Ultra’ were 15°C when selfed and 25° when crossed. For the self-fertile selections selfed, it was 25° for all but one, which was 15°. When crossed, it was always 25°. One selection showed a high degree of ovule under-development independent of self-compatibility.

Open Access

Abstract

Shoots of ‘Nonpareil’, ‘Jordanolo’ and their hybrid progenies expressing bud-failure symptoms grew more vigorously and longer than those of normal plants. Viability of lateral buds decreased on abnormal shoots during the summer prior to bud failure, whereas those on normal shoots retained their viability. On abnormal shoots there was an increasing trend of bud-failure from the basal portion to the shoot tip. When propagated in a control nursery, buds collected from trees growing in a warmer area exhibited more bud-failure than those from a cooler zone. When shoots collected over the season from the above trees were treated with potassium salt of gibberellic acid, the inhibition of budbreak was proportional to hormone concentration; the treatment resulted in fewer bud breaks in abnormal shoots than normal ones. Bioassays of extracts from shoot apices from normal and abnormal shoots revealed large variation in hormonal levels.

Open Access

Abstract

Vegetative buds from ‘Nonpareil’ almond trees affected by noninfectious bud-failure with (BF) and without (non-BF) symptoms were compared to plants without noninfectious bud-failure (normal). Samples were collected every 2 weeks from June until the following March to establish seasonal trends in weight and abscisic acid (ABA) and gibberellins (GA). Increases in bud fresh and dry weight occurred during July and August, followed by progressive dehydration up to the end of September. These changes were accompanied first by an increase in ABA and GA-like activity, and then a decrease in both hormones. During the remainder of the year (October to January) bud weight increased gradually and ABA and GA were low. Buds from BF and non-BF plants increased in weight in July and August, but much less than the normal. ABA levels were much less than from the normal, but the GA activity was comparable to normal. BF symptom development is characterized by lower production of ABA during the critical July-Aug. period. A disruption of the normal rest induction and recovery pattern was also hypothesized.

Open Access
Authors: , , and

Abstract

Comparative anatomical studies of vegetative buds from normal and failure prone (BF) ‘Nonpareil’ almond showed no anatomical difference in the buds, except reduced size in buds on severely affected BF trees, until early August to mid-September. The sequence of microscopically visible degenerative processes in shoot apices of BF trees is: l) breakdown of the outer tunica layer, 2) disorganized proliferation of the corpus: and, 3) the differentiation of layers of cells in the sub-apical region delimiting the potentially necrotic tissues of the apex. Subsequent abscission of affected buds occurs depending upon the extent of the necrosis. Growth was observed from 13% of buds from BF trees budded onto peach seedling rootstock, 38% of buds from non-BF trees grafted at the same time, and 95% of buds from normal plants. The scion buds had been collected and grafted in October, when internal anatomical symptoms were apparent. In general, the number of failing buds and the severity of the internal symptoms increased acropetally. Buds from BF trees attained maximum size by early June and thereafter decreased in size due to dessication.

Open Access