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Strawberry and cranberry response to growth regulators and fertilizers McArthur, David Albert James


The growth and yield response of strawberry (Fragaria X annassa Duch.) and cranberry (Vaccinium macrocarpon Ait) to various growth inhibitors, but especially to paclobutrazol (PP333), and fertilizers were investigated in glasshouse and field studies. PP333 decreased vegetative growth in a rate-dependent manner in both strawberry and cranberry. PP333 delayed fruit ripening in strawberry and decreased fruit set and fruit size in cranberry. PP333 decreased pollen germination of strawberry. Soil residues of PP333 were biologically active when measured 11 weeks after application in the strawberry study and when measured after 50 weeks in a cranberry study. In a field study with cranberry, PP333 caused a decrease in vegetative growth and an increase in flowering in the next season after treatment. Two-dimensional partitioning was used to account for yield variation from treatment effects on adjusted yield variates. The truss number was the most important contributor to yield variation in the strawberry, but was not affected by treatments. PP333 made a substantial contribution to yield variation in strawberry through its effect on fruit development and ripening. In the cranberry, fruit set was the major contributor to yield variation and PP333 influenced yield substantially through its effect on fruit set. In glasshouse studies, PP333 decreased shoot elongation in cranberry within 3 weeks of application, and increased the number of branches on primary shoots. Buds were formed within 7 weeks of treatment and some of the buds contained flowers. Shoot growth was greater with a high rate of NPK fertilizer than with the low fertilizer rate and was greater in peaty soil than in sandy soil. While bud set was not modified by soil type or fertilizer rate, high NPK fertilizer decreased floral induction. Some effects of PP333 treatment were decreased by gibberellic acid, but generally these effects here not reversed. In a field study with the cranberry, PP333 increased flower bud set for flowering and non-flowering uprights but slightly decreased floral induction for non-flowering uprights.

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