Fatemeh Shakeri f.shakeri@ag.iut.ac.ir February 15, 2009 Department of Horticultural Sciences Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc Language: farsi Bahram Baninasab; bbanin@cc.iut.ac.ir Cyrus Ghobadi; cyrus@cc.iut.ac.ir Excessive growth of some strawberry cultivars grown under control conditions for a one-year cycle or in high-density planting systems may often cause irregular pollination, reduced fruit set, a greater incidence of misshapen fruits and fungal disease and a delay in ripening. To avoid these problems, partial defoliation before flower emergence or during bloom is a common practice. A different approach to control vegetative growth, operations currently done by hand or mechanical means, is represented by the use of growth retardants which, to be suitable, should reduce the vegetative growth without adversely affecting yield, fruit quality and reduce hand labor. Out-of-season production is another problem in cultivation of strawberry. In June bearing strawberries, short days is necessary for flower initiation and flowering to produce one crop per growing season. On the other hand, growth regulators with similar effects of short-days on flower initiation may promote out of season production and increase yield in strawberries. Paclobutrazol is one of the most applicable triazole compounds and is widely used in inhibiting extension growth and promoting plant flowering in different methods. Therefore, this research was conducted in two separate experiments. In the first experiment the effects of applying different rate of Paclobutrazol on vegetative and reproductive growth of strawberry cv. Selva were studied with different application methods (drench and foliar spray). A factorial experiment in a completely randomized design with three replications was used. Paclobutrazol was applied at 0, 0.5, 1, 1.5 and 2 mg active ingredient per plant at 3 to 4 leaves stage. Results of first experiment indicated that appling of Paclobutrazol reduced leaf area, petiole length, shoot fresh and dray weight, while petiole diameter, leaf chlorophyll content and harvest index increased. Using paclobutrazol at rate of 1 mg active ingredient per plant lead to maximum increase in yield (17.27%). High rate of Paclobutrazol reduced root growth and diameter. Applications of PBZ as foliar spray was more effective than soil drench in reducing leaf area, shoot fresh weight and increasing harvest index .Also foliar spray of PBZ decreased shoot dry
