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- Author or Editor: D. F. Millikan x
Altered biochemical processes are pronounced and persistent in leaves of virus-sensitive cv., Spy 227, when grafted with buds of healthy or virus-infected ‘Golden Delicious’. Increases in total protein and decreases in RNA are associated with both grafting and virus infection but changes are also found in catalase, phosphatase, and RNAse. The nature of these effects suggest that virus infection may delay the protein and RNA catabolism normally associated with senescence.
Micrografting of apple (Malus domestica Borkh.) was achieved by placing a 0.1 to 0.2 mm scion explant derived either from field-grown or in vitro-grown shoot apices on the hypocotyl of a decapitated 15 day-old seedling. Under asceptic conditons, the scion and hypocotyl unite to form a complete plant which produces 4 to 6 leaves after 6 weeks. These plants were transplanted to sterile vermiculite and conditioned to ambient humidity for 1 week and then transplanted to soil. This technique was used to obtain virus-free plants from virus-infected plants.
Simazine at both 4 and 8 lb./A and amitrole at 2 lb./A, alone and in combination, altered the protein and RNA content of apple leaf tissue. Initially, simazine increased the protein content, but this effect progressively diminished until late June when it became nonexistent. Similarly, the use of amitrole caused an early season increase in protein content, later changing to a marked decrease. Greatest effects occurred in the total and globulin fractions while the soluble fraction was affected only slightly and this was limited to the first 6 weeks of growth.
Total RNA also was affected. This effect occurred in mid-May when simazine was stimulatory and amitrole acted as a depressant. These same effects persisted until late June when simazine at 4 lb./A and amitrole strongly decreased the RNA content. Enhanced action due to the simultaneous use of both chemicals did not occur, but there was evidence that the depressing effect due to amitrole was moderated when used with simazine, particularly in the period when shoot expansion ceased.
Pruning of spur blight (Didymella applanata (Niessl.) infected or cane blight (Botrytis cinerea Pers. ex Fr.) lightly infected red raspberry plants increased mortality. Pruning of plants heavily infected with Botrytis had no effect on plant mortality but were less productive than those heavily infected with Didymella, while unpruned lightly infected with Botrytis were more productive than those lightly infected with Didymella.