Bud Union Research Articles

TREE TRAINING PROCEDURES FOR HIGH-DENSITY SWEET CHERRY PRODUCTION ON VIGOROUS ROOTSTOCKS

Sweet cherries produce vigorous upright growth from Apr.-Sept. and are slow to bear in California. Our tree training objectives include earlier bearing, easier harvesting, high productivity of good quality fruit. `Bing' cherry on mazzard and mahaleb rootstock were planted in 7 blocks and trained 6 ways. One group was headed 12-18 inches above the bud union and 4 branches were retained at the 1st dormant pruning. Lateral buds were treated with promalin at bud-break to induce lateral shoot formation. Trees were spring-summer pruned to reduce terminal growth. At the second dormant pruning, strong shoots were removed and lateral shoots were treated with promalin to induce spur formation. Trees were treated likewise through the 3rd dormant season and produced a fair crop in the 4th season. Central leader trees were created by tying/weighting limbs, dormant and summer pruning, and retaining less vigorous limbs as well as utilizing promalin. Slow growing trees tended to bear fruit more rapidly. Both training methods yielded fruit in the 4th season while traditional pruning procedures produced few fruit. Data and procedures will be presented to document these practices.

CHARACTERIZATION OF GROWTH AND METAL-BINDING CONSTITUENTS OF TWO CITRUS CELL CULTURE LINES

Citrus blight is an extremely complex decline disorder of unknown etiology, Zinc accumulates in the phloem of the tree 40-50 cm above the bud union 1-3 years prior to visible symptoms of blight (foliage wilt and twig dieback). This is accompanied by Zn deficits in the leaves. A Zn-binding peptide (ZBP) purified from citrus phloem tissue accounts for a symptomatic redistribution of Zn from the canopy to the trunk phloem. ZBP is found in blight and healthy trees and is therefore a normal component of cellular metabolism. To further understand ZBP's role in metabolism two citrus cell culture lines which were selected based on their susceptibility to blight have been characterized as to their growth under Zn treatments as well as Cu and Cd. In addition, their complement of metal-binding constituents is being determined.

Response of buds ofCitrus sinensis(L.) Osbeck inserted into rootstock stems to exogenous growth substances

Abstract Buds of ‘Valencia’ orange implanted in ‘Troyer Citrange’ rootstocks remain dormant for variable periods. A range of growth substances was applied either to the buds before implantation or through a wick following bud union with the stock in an attempt to promote rapid budburst. Soaking the buds in solutions before budding caused the death of some buds, particularly with gibberellic acid solutions. 6-benzylaminopurine promoted earlier budburst in most circumstances and may be helpful in nursery practice; other growth substances produced variable results.

Acer rubrum Cultivars for the South

Nine budded Acer rubrum cultivars were evaluated from 1980-1988 for fall color, growth rate and bud union incompatibility. Fall foliar coloration was consistent with 'Autumn Flame', Tilford', 'Gerling', and 'Bowhall', but not with 'Red Sunset'. With the exception of 'Red Sunset', bud union incompatibility has occurred with all cultivars, especially 'Bowhall', 'Scarlet Sentinel', and 'Schlesingeri'. Annual height growth of these cultivars averaged 50-69 cm, with the exception of 'Autumn Flame' which averaged 40-45 cm a year. 'Armstrong', a fastigiate form, grew 60-65 cm annually. Two seedling selections, from south Alabama and Tennessee, were compared with the cultivars. Height and caliper growth of the seedlings were similar to most cultivars.

Calculating Canopy Area of Citrus Trees and Surface Area of Fruits

We encountered the problem of calculating the approximate surface area of a citrus tree in the process of developing a plot design for a mature citrus grove with unequal tree size. The objective of our experiment was to observe the impact of alternative cultural and pest management practices on fruit yield. Fruit yield for the year prior to experimental maniupulation is one parameter that has been used in selecting replications in such experiments (Parker and Batchelor 1932, Parker 1942, T. W. Embleton, personal communication). A second useful measurement is trunk diameter at a specified distance above the bud union (Embleton and Jones 1973). In our experiment, neither of these parameters were wholly satisfactory. Fruit yield in the prior year was somewhat variable due to low fruit set. In addition, a winter frost which had occurred shortly after planting resulted in considerable trunk deformation, dieback, and regrowth such that trunk diameter measurements were variable for similar sized trees and thus suspect as indicators of tree size and production. Citrus tree canopies are quite dense and the majority of foliar growth and fruit production occurs near the exterior surface of the tree. Because of the dense tree canopy, we hypothesized that the external canopy surface area of the tree would be proportional to the effective leaf surface area of the tree with regards to light interception and photosynthesis. In fact, Jahn (1979) showed that the canopy area ratio (leaf area/external canopy surface area) was fairly constant for 9 varieties of citrus and that this ratio was linearly related to penetration of photosynthetically active radiation. Thus, we considered canopy surface area to be a reasonable covariate (in addition to prior year fruit yield) upon which to base our experimental design. Derivation of a formula for canopy surface area depends upon tree shape. A simple solution is obtained when tree shape is assumed to approximate that of a half sphere. Canopy surface area (SA) is given by (1) assuming tree height (a) equal to canopy base across-row radius (b) and within-row radius (c) (see Fig. 1). Allen and McCoy (1979) assumed a spherical tree shape when modeling the thermal environment of the citrus rust mite on citrus fruit. The use of a more complex shape, in their case, would have led to somewhat intractable mathematics. In many cases, however, tree height and radius are dissimilar, tree height often approaches three diameter (twice the radius).

A decline-like disorder of pear in Greece: Pear decline or scion—Rootstock incompatibility?

Several pear orchards in Northern Greece exhibit a severe decline-like disorder without a clear etiology. An anatomical study of pear trees budded on quince indicated a distinct necrotic layer at the bud union. Breaking trees at the point of union revealed a clean and smooth surface of breakage. Measurements of the stem perimeter at, above and below the bud union showed that in most trees the scion was thicker than the rootstock, indicating differences in growth rate between scion and rootstock. All results favour the suggestion that the decline-like symptoms in the orchards investigated were caused by graft incompatibility.

Heavy Soil and Bud Union Crease with Some Grapefruit Clones Limit Use of Swingle Citrumelo Rootstock

Abstract Ten-year tests in 8 locations in the Lower Rio Grande Valley showed that grapefruit (Citrus paradisi Macf.) trees on Swingle citrumelo [C. paradisi x Poncirus trifoliata (L.) Raf.] rootstock grew very poorly on heavy clay soil; trees on sour orange (C. aurantium L.) were much less affected. Trees propagated from a single mother tree of an old-line red grapefruit selection on Swingle citrumelo were stunted and had severe bud union crease, whereas trees propagated from a nucellar California Experiment Station (CES) #3 ‘Redblush’ source were large and productive. Old-clone trees on sour orange also were smaller than CES #3 ‘Redblush’ trees, but showed no bud union crease.

Growth of Mechanically Planted Nectarines Planted at Various Depths1

Abstract High-budded trees of nectarine [Prunus persica (L.) Batsch] that were mechanically planted with the bud union as a depth guide resulted in poorer growth when compared to those planted with the crown roots within 5 cm of the surface. Deeper-planted trees had smaller leaves and less total increase in trunk cross-sectional area, and were more susceptible to the formation of air pockets around their bases.

Performance and compatibility of ‘Muscat Gordo Blanco’ grape on eight rootstocks

In a soil not previously planted with vines, ‘Muscat Gordo Blanco’ (= ‘Gordo’) grafted on to 8 rootstocks did not significantly increase the 7-year cumulative yield compared to own-rooted (control) vines despite the increased vigour (pruning-weight) given by some rootstocks. ‘Gordo’ on 1613 rootstock had the maximum cumulative yield, but this was only 8% greater than control. Growth of vines on rootstocks 62–66 was the most vigorous as judged by trunk circumference. During the course of the trial a number of vines on ‘Salt Creek’ (‘Ramsey’) died and others declined markedly due to graft-incompatibility. Surviving vines yielded 40% less than control due to fewer and smaller bunches. They also had lower Brix and pruning-weight and smaller trunk circumference. Symptoms of Legno riccio virus were observed below the bud union on ‘du Lot’ and 420 A rootstocks, and yield of vines on ‘du Lot’ was lower than control. Due to their poor performance, grafting ‘Gordo’ on ‘Ramsey’ and ‘du Lot’ rootstocks is not recommended. In soil not previously planted with vines, ‘Gordo’ clones on their own roots are the most economical and best to use.

The effect of prunus necrotic ringspot virus on field‐grown roses

SUMMARYThe effect of prunus necrotic ringspot virus (PNRSV; cherry serotype) on field‐grown maiden rose bushes cv. Fragrant Cloud was assessed in two trials during 1979 and 1980. PNRSV delayed the onset of flowering, reduced the size and number of blooms and increased the proportion of deformed flowers but had no effect on flower pigmentation or scent. Autumnal leaf‐fall was generally earlier in diseased bushes, which lacked vigour and re‐established less readily after transplanting. Although all healthy plants conformed to the British Standards Institution specifications for maiden bush roses, c. half of diseased plants were sub‐standard because the total diameter of the shoots produced at the bud union was less than 20 mm.The significance of these results is discussed in relation to the commercial production of field‐grown rose bushes in the UK.

Phloem Zinc Accumulation in Citrus Trees Affected with Blight1

Abstract Zn content was higher in trunk bark (cambium to outer scrapings) than in the adjacent wood in healthy and blight-affected sweet orange (Citrus sinensis (L.) Osb.) and grapefruit (C. paradisi MacF.) trees. Zn levels were elevated in trunk bark and wood of blight-affected trees on rough lemon (C. limon (L.) Burnt, f.) rootstock, whereas affected seedling trees or trees on ‘Cleopatra’ mandarin (C. reticulata Blanco) rootstock that were tested had high Zn levels only in the bark. Bark Zn content was much higher above the bud union than below in blight affected trees on rough lemon or trifoliate (Poncirus trifoliata (L.) Raf.) rootstocks, but Zn content was high above the bud union in healthy trees only on rough lemon rootstock. The inner half of the bark, an area representative of the active secondary phloem, had much more Zn than the outer half of the bark or the most recently developed xylem. The outer half of the bark served as a barrier against outside contamination. Accumulation of Zn in wood occurred only when the phloem Zn was high.

Effect of Training Young Lemon Trees for Limb-shaker Mechanical Harvest on Yield and Tree Trunk Growth1

Abstract Three year old lemon trees [C. limon (L.) Burm f.] were selectively pruned to form a 3- to 4-scaffold branch structure for limb shaker harvesting. Yield was reduced 16 kg per tree and trunk circumference 10 cm above the bud union was reduced 5.3 cm per tree over a 6-year period. Training was completed with minimal production loss.

Foam Sprays of Plant Growth Regulating Chemicals on Rose Shoot Development at Cutback1

Abstract Expanded foam sprays of (2-chloroethyl)phosphonic acid (ethephon), 6-(benzylamino)-9-(2-tetrahydropyran-yl)-9H-purine (PBA), and 6-benzylamino purine (BA) at 1000 and 2000 ppm applied at plant cutback increased the total number of flowering stems per plant and the number of stems from axillary buds within 30 cm of the bud union, compared with conventional sprays of the same chemicals and concentration. Sprays of plant growth regulators were most effective when applied at cutback, with less benefit from treatments 3 weeks before cutback or 1 or 3 weeks after cutback. No chemical or method of application effectively promoted shoot development from the bud union.

The Effect of Plant Growth Regulating Chemicals on Rose Shoot Development from Basal and Axillary Buds1

Abstract 2,3,5-triiodobenzoic acid (TIBA), (2-chloroethyl) phosphonic acid (ethephon), 6-(benzylamino) - 9 - (2-tetrahydropyran-yl) - 9 H-purine (PBA), and N6 benzyl adenine (N6BA) were applied to greenhouse rose cvs. Red American Beauty, Forever Yours, Mary DeVor and Jack Frost as sprays, lanolin paste, and in solutions in floral foam. Axillary shoot development was significantly increased when PBA and N6BA were applied as sprays, in paste or in solutions in floral foam. The most significant response was obtained when the chemical solutions were absorbed from floral foam cubes attached to a cutback rose cane. Most of the axillary buds broke dormancy when the growth regulating chemicals were applied by this method, however, many of the developing buds stopped growth before becoming shoots. Chemicals PBA and N6BA significantly increased the development of flowering and blind shoots for all rose clones. Plant growth regulating chemicals, methods of application, and concentrations favorable for the development of axillary shoots had no comparable effect on basal shoots developing from the rose bud union.

Anatomy of the Bud Union in Mango (Mangifera indica L.)1

Abstract Details of mango (Mangifera indica L.) stem anatomy and formation of the bud union were observed in 4 combinations of 2 scions and 3 stocks chip budded at 5 stages of stock growth from first flush to 1 year old. ‘Haden’, ‘Saigon’, and ‘Turpentine’ stems of equivalent age and growth rate were indistinguishable anatomically. Four stages in formation of the bud union were: pre-callus, where 4 days after budding only a wound periderm was present; callus, where 8 days after budding proliferation from tissues mainly near the cambium resulted in firm attachment of the components; cambial bridge, where 12 days after budding cambial layers from stock and scion formed a bridge and vascular tissues were differentiated within 36-48 days; and, the healed union, where after 6-8 months several cylinders of new tissues were present and the lateral shift of the scion to align with the stock had begun.

Promotion of Leaf Abscission of Deciduous Nursery Stock with 2-Chloroethylphosphonic Acid1

Abstract Work with 2-chloroethylphosphonic acid (Ethrel)3 over a two year period to stimulate leaf abscission of deciduous nursery stock showed that this chemical has potential for this purpose. Satisfactory rates for apples were generally 3 applications of 2000 ppm at weekly intervals. ‘Italian’ prune required two applications of 2000 ppm. Single applications of 500 ppm and 1000 ppm were sufficient for ‘Bartlett’ pear trees and Prunus mazzard cherry seedlings respectively. A 5 or 10 ppm NAA spray two weeks prior to Ethrel application materially reduced the effect of Ethrel. Combining NAA with Ethrel in the same application had less effect than a pre-spray but still often reduced leaf abscission. Combining 5 and 10 lbs. urea/100 gal with Ethrel occasionally increased abscission. ‘Elberta’ peaches were killed back almost to the bud union with single applications of 2000 ppm Ethrel and serious bud damage occurred on ‘d'Anjou’ pear at 4000 ppm. Apple, prune, and cherry were not damaged by 4000 ppm.

Control of Meloidogyne Javanica in Potato Tubers and M. Hapla in the Roots of Young Rose Bushes By Means of Heated Water

Water temperatures of between 46°C and 47.5°C with an immersion period of 2 hrs, killed all stages of M. javanica contained within moderately to severely blistered potato tubers, without adversely affecting subsequent sprouting of the tubers during a 3 months storage period. Immersion of the roots of dormant rose bushes to just below the bud union, for 60 min in water heated to 45.5°, killed all eggs and larvae of M. hapla, without adversely affecting the subsequent growth of a vigorous floribunda and a non vigorous hybrid tea variety budded on vigorous thornless Mexican Briar rootstocks.

Starch Level in the Trunk as a Measure of Compatibility Between Stock and Scion in Citrus

SummaryStudies were carried out on the assumption that incompatibility and dwarfness of budded citrus trees result from impaired carbohydrate movement through the bud union. During autumn and winter, carbohydrates move from the tree tops to the roots and accumulate there as starch. The starch level can therefore serve as a measure of this movement.This study included seven rootstock varieties all budded with Shamouti orange scion. Unbudded rootstocks were included for purposes of comparison.The starch level was determined in the winter at three locations along the trunk, below and above the bud union.No clear indication was found of impaired carbohydrate movement through the bud union of stock-scion combinations showing very low growth vigour.The starch level in bark and wood in the rootstock portion of trunks of budded trees was found to be negatively correlated with tree size. This indicates that the level of starch in the trunk results from the growth vigour of the tree and is not a factor which affect...

Double-working of Satsuma orange. II

A strain of Satsuma orange (Citrus unshiu) was rebudded on three different strains of Satsuma oranges, Yuzu (C. junos), and Tachibana (C. tachibana) in September, 1939. These interstocks had been budded on trifoliate orange (Poucirus trifoliata) rootstocks in September, 1937. The scion was the same strain as one of the interstocks of Satsuma. In April, 1959, these double-worked trees were all dug out and every part of them was weighed. The effects of the interstocks on the tree growth, fruit quality and yields for the ten years after the previous report were investigated. The results of the present experiments are summarized as follows: 1. The interstock of a dwarf Satsuma strain (Nods) showed less vigor of the top, less yield, and less growth of rootstock than those of a vigorous one (Tanikawa). These tendencies have become more conspicuous as the age of tree increased. 2. The tree growth and yield on the interstocks of the Satsuma strains other than the one used as the scion were less than those of the trees on Satsuma interstock of the same strain as the scion. 3. The Satsuma top on Tachibana interstock showed rather vigorous growth and larger cropping, while that on Yuzu interstock showed the poorest growth and the least cropping, and the trifoliata stock in this combination also showed very poor growth. The older the trees the more differences there were. 4. There were hardly any differences among the plants with different interstocks in the size, the coloring time, and the quality of fruit, excepting that plants with Yuzu interstock produced somewhat small fruits. 5. It was shown that the scion and the interstock had united well and the united part had uniformly grown on the interstock of three Satsuma strains. However, a marked swelling at the base of scion was seen on Tachibana interstock, while the scion on Yuzu interstock was more slender than the interstock itself. 6. When the bark of the trunk was removed, the woody tissue of Noda strain (one of the Satsuma interstocks) showed a distinct fissure at the bud union between the interstock and the rootstock, and then, the fissure splitted rather deep as the wood dried up. The other four interstocks showed no distinct symptoms at the bud union, although a marked overgrowth of the trifoliata rootstock had been seen in all tested trees, as usual. 7. All the interstocks of Tachibana and some of Yuzu showed a distinct stem-pitting like the symptom of tristeza at the part of interstock, but it was supposed to have no direct relation with the vigor of the tree.

Anatomy of bark of bud union, trunk, and roots of quick-decline-affected sweet orange trees on sour orange rootstock

This paper concerns the sequence of anatomical changes occurring in sweet orange trees on sour orange rootstock after infection by quick decline. The primary symptom is necrosis of sieve tubes below the bud union. This symptom is followed by degeneration of the older sieve tubes above the union, accelerated cambial activity, and other reactions of a secondary nature.