Reproductive bud development of pears (Pyrus communis L.) with emphasis on the bourse shoot

Reynolds, L. P. ; Jacobs, G. ; Theron, K. I. (2005-04)

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For consistent yields in pear fruit production, knowledge of the development of the reproductive bud is required. The aim of this study was to gain more insight into the development of the primordial bourse shoot. The bourse shoot is important because of the ability of a bourse shoot to become reproductive, which can lead to bourse-over-bourse bearing. The progression of reproductive bud development in ‘Forelle’ and ‘Rosemarie’ was studied from primordial bourse shoot initiation until dormancy the following season. The primordial bourse shoot development in the reproductive bud before full bloom is poorly documented. The primordial bourse shoot was initiated in February 2003. The primordial bourse shoot development progressed during dormancy with a plastochron length of 60 to 80 days in June. The rate of preformed leaf formation increased rapidly until August, when the plastochron was 5 days. ‘Rosemarie’s’ primordial bourse shoot development was more advanced at full bloom. This is one of the possible reasons for the higher bourse-over-bourse bearing habit of the cultivar. The number of leaves of the bourse shoot of ‘Rosemarie’ was significantly greater than with ‘Forelle’, which has a low tendency for bourse-over-bourse bearing. Flower initiation of the terminal bud of the bourse shoot was 56 and 77 days after full bloom for ‘Forelle’ and ‘Rosemarie’, respectively. Initiation was well correlated with the cessation of bourse shoot growth. An increase in mitotic activity occurred during flower differentiation of the terminal bourse bud, with a peak of floral appendage formation during December and January. From February until dormancy enlargement of the floral parts took place.

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