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- Author or Editor: James N. Cummins x
Rootstock influence on tree architecture may be seen in a variety of expressions. Above ground effects include canopy volume and shape, crotch angles, branch display angles, relative distribution of long shoots and spurs, internode length, relative distribution of fruit buds and spurs, and trunk taper. Below the graft union, effects include relative distribution of fine vs. coarse roots, total root mass, and numbers, nature and distribution of burrknots. Many of these phenomena are indirect effects that stare from induction of fruiting by the rootstock, e.g., early fruit production induced by the rootstock will result in reduced canopy volume, reduced aboveground total mass, flatter branch display angles, and reduced root mass. The rootstock also plays a major role in the duration of shoot extension growth; by influencing the production of growth regulators in the shoot tip, the rootstock indirectly influences the inhibit ion of lateral buds and therefore the production of feathers.
Abstract
Orchard production systems have experienced rapid and dramatic changes over the past 3 decades in both the techniques and geno-types used. We expect this rate of change to accelerate in the future. As production costs escalate, the demand will become ever stronger for systems providing early, heavy, reliable yield fo high-quality, easy-to-harvest fruit. These systems must, however, be reasonably priced and durable. The grower will be less able to afford tree losses, whether due to biotic, climatic, or edaphic hazard, and will need to economize on use of machinery and chemical pesticides. Growth regulators will be employed only where there are effective, economically justified, and environmentally acceptable.
Isozymes of six enzyme systems extracted from 13 apple (Malus domestica Borkh.) rootstocks were separated electrophoretically on a horizontal starch gel. Each rootstock was clearly distinguished by its unique isozyme banding patterns. All the rootstocks were distinguishable using only two of the enzyme systems, phosphoglucomutase and 6-phosphogluconate dehydrogenase, both of which exhibited considerable isozyme polymorphism.
Spininess is characteristic of many Malus species, especially American crabapple and Malus baccata L. Spininess often is present on rooted stoolshoots of commercial apple rootstocks (M.9, M.26, MM.111, and MM.106) and some rootstocks from the Geneva Breeding Program. This undesirable characteristic makes liner production costly and laborious. It is estimated that the cost of manual removal of spines amounts to ≈20% to 25% of total production costs. To counteract spininess, the stoolshoots of excessive spiny rootstock selections [74R5M9-760 (T/1), 74R5M9-707 (T/2), and 75R5M9BR-521 (T/3)] were chemically treated while growing at stoolbed. Chemical treatments consisted of single sprays of nontranslocated growth regulators Tamex (a.i. butralin) or Tamex AG (a.i. butralin + fatty alcohols C8- C10), and commercial auxin formulation (Tre-Hold A-112). Tamex AG and A-112 at applied rates brought about some phytotoxicity effects while Tamex did not. On average, Tamex application (1000, 2000, and 4000 ppm) reduced spine number to ≈80%, 68%, and 84% of T/1, T/2, and T/3 control plants, respectively. However, Tamex at 4000 ppm reduced the number of spines to 57% and 60% of control T/2 and T/3 plants, respectively, without any detrimental side effects. A parallel greenhouse experiment is being performed using commercial M.26 and Geneva 30 apple rootstocks.
Abstract
Tomato ringspot virus (TmRSV) was consistently detected in myrobalan (Prunus cerasifera) and in 8 other plum rootstocks that exhibited prune brownline (PBL) symptoms at the graft unions. The infected rootstocks included Prunus domestica cvs. St. Julien A, Brompton, Ackermanpflaume, and Pershore and 6 seedling lines of P. cerasifera. Own-rooted ‘Stanley’ prune trees remained free of natural infection by TmRSV for 14 years on a site where 36% of the ‘Stanley’ trees on other rootstocks became infected. Mortality among TmRSV-infected trees on myrobalan stocks was higher than among infected trees on P. domestica roots. Own-rooted ‘Stanley’ trees are suggested for extensive commercial trial in areas infected with TmRSV.
Abstract
Tomato ringspot virus (TmRSV) was detected by ELISA indexing in leaf tissue from 23 of 59 clones of Malus domestica Borkh., 1 to 6 years after inoculation with TmRSV-infected buds. However, TmRSV was repeatedly detected from only 10 of the 23 clones: Mailing (M) 26, MM 106, MAC-30, MAC-39, and P-2 and the fruiting cultivars ‘Northern Spy’, ‘Spigold’, ‘Spijon’, ‘Stayman’, and ‘Wayne’. ‘Northern Spy’ and most of its derivatives appeared to be highly susceptible to TmRSV infection, in that the virus was consistently recovered from inoculated plants.
Leaf samples collected during the 1988-90 seasons were analyzed to evaluate influence of selected rootstock clones on the composition of Northern Spy apple leaves. Rootstocks included 17 elite selections from the Geneva breeding program plus M.9, M.26, M.7, MM.106 and MM.111 as references. Rootstock selections were grouped according to relative vigor and compared with appropriate references. Significant rootstock effects were more frequent in the two smaller tree-size groups. Each of the 10 elements analyzed exhibited significant rootstock effects in two or more vigor groups. No rootstock selection consistently resulted in higher or lower concentrations of all elements when compared with the reference rootstock of similar vigor.