Fruit Nurseries Research Articles

DEVELOPMENT OF APPLE TREES, BENCH-GRAFTED ACCORDING TO THE METHOD OF CROWN FORMATION IN THE FRUIT NURSERY

To obtain a high yield production in the first year after apple tree plantation establishments and a quicker reimbursement of the considerable capital investments, it is done only in case of using grafted fruit trees on dwarf rootstock with formed crown base in the fruit nursery. The aim of the investigations made is to improve the up-to-date technology in the apple crowned planting material productivity, produced by the method of bench grafting in perfected copulation with detached branches. The investigations were leaded at “Codru-ST” Ltd., where it was established a fruit-growing nursery called “Fruit Nurseries” Ltd. The objects for study served the varieties Golden Delicious Reinders, Jonagored and Idared, grafted on the M 9 rootstock. For grafting were used the marcottes with the diameter of 10 mm and virus free grafted branches imported from Holland. The bench grafting was made in February, and the graft’s place was tied with a special film, and then paraffined. The obtained grafts had been stratified in refrigerator at a temperature of +40C. The plantation in the field was realized in the second part of April. The distance of plantation is 90x35 cm. In the second field of the fruit nursery, in spring, the annual grafting stem is shortened at 75 cm from the graft’s place. There were studied three methods in order to have the crown base formed. These methods are: V1 – traditional method (with 3-4 branches on the base); V2 – traditional method + periodical apical leaf remove at the main axle, 4 times at an interval of 5-7 days without hurting the final bud-fruit; V3 – traditional method + application of physiological active substances to stimulate the sylleptic shoots growth on the axle. As a physiological active substance was used the preparation Ecostim with a concentration of 0,25 mg to 1 liter of water. At the end of the first period of vegetation in the first field of the fruit nursery, the investigations demonstrated that the graft height, depending on the variety, was 114 cm (Idared), and 122 cm (Jonagored); the diameter at 10 cm above the graft’s place is of 10,1-10.9 mm.

CROWNED APPLE TREE DEVELOPMENT IN THE NURSERY AND THEIR BEHAVIOUR IN THE ORCHARD IN THE FIRST TWO YEARS AFTER PLANTATION

The investigations were made in the fruit nursery o f the joint stock company Fruit Nurseries. It was studied the production technology of apple trees of knip-baum type and their later development in a superintensive orchard of the farm I. Sitari. There were studied the varieties Idared, Golden Del icious Reinders, Jonagold Boerekamp Early Queen, Granny Smith, Jonagored, Gloster and Campion grafted on the M 9 rootstock. It was established that the grade of striking of th e bench grafts of the varieties from the first fiel d of fruit nursery was 96,0-99,0 %, the scions' height was 94- 126 cm. In the second field the obtained results co rrespond to the first category of the actual standards and h ave the tree height of 166-189 cm, trunk diameter - 16,5-17,2 mm, the quality of sylleptic shoots - 4,5-11,0 piec es/tree and to the average length of the apple tree s. The first obtained yield in the orchard in the first year aft er plantation was 0,16-1,30 t/ha, in the second yea r, depending on the variety, was 4,80-11,60 t/ha.

Effects of applied ABA on growth cessation, bud dormancy, cold acclimation, leaf senescence and N mobilization in apple nursery plants

SummaryCommercial tree fruit nurseries can promote aggressive tree growth by adding greater amounts of N than is necessary. Although this practice may produce the largest stock possible, it often causes physiological problems such as delays in growth cessation, bud dormancy development, and cold acclimation, especially in late apple cultivars. In this study, abscisic acid (ABA) was applied to Fuji/M.26 apple (Malus domestica Borkh.) nursery plants that had been growing into the late season with a high N supply. We tested the hypothesis that exogenously applied ABA enhances growth cessation and that this is related to the improvement of bud dormancy development and cold acclimation. We also studied the effects on leaf senescence and mobilization of leaf N into perennial woody tissues. In September 1996, ABA at 1000.mg l-1 plus 0.1% Tween 80 was sprayed twice, at 7.d intervals. ABA treatment significantly enhanced shoot growth cessation and advanced the early stages of bud endodormancy development; these effects were closely related. Maximum growth cessation and bud dormancy were attained in mid-December similarly in both control and ABA treatments. In early November, stem cold hardiness measured by the electrolyte leakage method was significantly greater in the ABA-treated plants than in the controls, but was similar in late December. This indicated that cold acclimation was related to the depth of bud endodormancy development. N mobilization from the senescing leaves into perennial woody tissues was significantly enhanced by ABA treatment. Therefore, autumnal increases in total-N and soluble-protein concentrations were significantly higher in the ABA-treated plants (especially in the stem bark), but both control and ABA-treated plants reached similar maximum levels later when plants were completely defoliated.

311 Seed Treatments, Rootstock Cultivar, and Environment Affect Peach Seed Germination

Poor peach seed germination can be a problem for commercial tree fruit nurseries. Even standard rootstocks such as Lovell and Nemaguard do not always have high germination rates. New seed-propagated rootstocks under development, such as Guardian peach rootstock, often are selected for their field traits, with nursery characteristics being of secondary importance. Guardian rootstock is derived from bulked open-pollinated seed from a number of F1 seedling selections. Germination of Guardian bulked seed has been poor. Four pre-stratification cold treatments were given to four 100-seed lots each of Lovell, Nemaguard, and 10 Guardian selections prior to planting each year (1994 to 1998) in a Cecil sandy loam at Musser Fruit Research Center near Clemson, S.C. Treatments included taking dry, refrigerated seed that were harvested in August and soaking 100-seed seedlots in 1500 mL perlite and 400 mL distilled water for 0 (no soaking), 2, 4, 6, and 8 weeks at 6 °C before sowing (typically early November). All treatments consisted of 25 seeds per replicate (4 reps/year) per rootstock or selection and were sowed the same day. The experiment was analyzed as a blocked split plot design with duration of stratification the whole-plot and seedlot the sub-plot. Number of emerged seedlings were counted weekly starting in January of each year. There were significant differences between stratification treatments, seedlots and years. The 6-week pre-stratification had the highest germination over 5 years and like the 8-week treatment advanced the average germination date by 20 to 30 days. Nemaguard (65%), Lovell (64%), and Guardian 3-17-7 (60%) had the best germination percent across all treatments and years, with SL2891 (42%) slightly less. All other selections averaged less than 25%. Year-to-year variation was large, indicating strong environmental influences on seed germination despite the pre-stratification treatments.

Collar Rot and Wilt of Yellow Passion Fruit in Venezuela.

Surveys were conducted to determine the occurrence of diseases of yellow passion fruit (Passiflora edulis f. flavicarpa) in plantations located in the central states of Aragua, Carabobo, Guarico, Miranda, and Yaracuy, Venezuela, from 1991 to 1998. Plants in both commercial plantations and passion fruit nurseries were symptomatic for wilt and reddish-brown collar rot. Symptomatic tissues were surface-disinfected and plated on PARPH medium (1). Phytophthora parasitica was frequently isolated from diseased tissues, and pathogenicity tests were conducted with the fungus under greenhouse conditions. Passion fruit seedlings were grown in pots containing a 1:1 (vol/vol) steamed soil/sand mixture, one plant per pot. Five-millimeter-diameter plugs of P. parasitica isolates were grown on clarified V8 agar. Three-month-old seedlings were wounded with a sterile scalpel in the collar region. Wounded and unwounded plants were inoculated with 10 ml of zoospore suspension (105 spores per ml) or sterile water (control). Fifty plants were evaluated per treatment, and the experiment was repeated. Wounded and unwounded seedlings inoculated with zoospores developed chlorosis and collar necrosis after 15 days. Seedling mortality reached 50% 1 month after inoculation, and the fungus was reisolated from symptomatic tissues. This is the first report of P. parasitica causing collar rot and wilt of yellow passion fruit in Venezuela. Reference: (1) S. N. Jeffers and S. B. Martin. Plant Dis 70:1038, 1986.

608 PB 252 DEFOLIATION OF TREE FRUIT NURSERY STOCK

Many tree fruit nurseries are limited to fall digging of deciduous nursery stock. Since trees may not defoliate naturally for timely digging, these nurseries may wish to defoliate chemically, which would be less expensive than hand-stripping and may more closely simulate natural leaf abscission. Consequently, test chemicals were applied with hand sprayers at commercial nurseries in central Washington State using single or double applications 1 wk apart. In 1992 on 7 apple cultivars and one pear, 500 ppm NPA + 150 ppm Ethrel significantly enhanced defoliation. Defoliation at 1000 ppm NPA was not superior to that at 500 ppm, and two applications were generally no better than one. However, in 1993, two applications were often more effective than one, and the addition of Ethrel to NPA generally enhanced defoliation if the combination of NPA + Ethrel was applied twice. Alanap and NPA were generally equally effective as defoliants. The addition of Ethrel to Alanap enhanced defoliation in only 3 of 9 cultivars, and then generally only when sprayed twice. Alanap + Ethrel was as effective with Alanap at 300 ppm as with Alanap at 500 ppm Ethrel by itself seldom increased defoliation.

Prunus Stem Pitting

Abstract Prunus stem pitting disease was first described and recognized as a specific, infectious disease in 1967 and is now known to affect a number of Prunus species. Apricot trees affected by stem pitting show stunted terminal growth and chlorotic, drooping leaves that curl upward and lengthwise. The lower trunk may become enlarged at ground level or below with very thick, spongy bark. Removal of the bark from the affected lower trunk reveals pits and grooves on the woody cylinder. Wood pitting begins below ground, then gradually spreads into the roots and the trunk above ground. Stem pitting is caused by certain strains of the tomato ringspot virus. The causal agent is soil‐borne and also graft transmissible but is not uniformly distributed through infected trees. Naturally infected apricot trees may show a slow decline, or rapid dieback of the terminal growth. The severity of symptoms is determined by the cultivar and the strain of tomato ringspot virus. Control measures for Prunus stem pitting should include: use of propagation material from healthy trees and rogueing of pitted trees in nurseries and orchards. Repeated use of infested nursery sites for stone fruit nurseries should be avoided

Fruit Nursery Practices.

It is a well-established fact that the success of fruit-growing industry is mainly dependent upon the fruit nurseries. Nurserymen not only determine the fruit wealth and fruit quality of a region but also influence to a conside- rable extent the economic condition of fruit farming. A large class of the public naturally look upon the nurserymen for guidance on a variety of matters such as the selection of orchard sites, selection of kinds and varieties of fruits and the proper orchard cultural practices. This aspect of the nurserymen's duties are considered so important in some parts of the world that the issue of periodic publications replying to enquiries and organisa- tion of demonstrations and exhibitions are being done through a permanent and important branch of each of the various leading horticultural nursery establishments. Many countries of the world proudly point out the research work carried out entirely by some of the reputed nursery firms, particularly in the sphere of originating new varieties either by breeding or through selection of bud sports, which form in some fruits a fertile source of improve- ment, for or through the proper selection of propagating material. Trading with spurious plants under wrong names and with fanciful claims is unfortu- nately not an unknown feature of the Indian fruit nursery trade.