Increasing fruit size in Abate Fetel and Forelle pears

Fruit size is an important marketing and quality parameter and has a significant effect on the economic value of fruit.  The application of synthetic cytokinins are believed to enhance fruit size by stimulating and extending the cell division period in fruit when applied at the correct stage of fruit growth.  In addition, combination of prohexadione-calcium (P-Ca) with gibberellins₄₊₇ (GA₄₊₇) was used successfully on Japanese pear (Pyrus pyrifolia Nakai) and ‘Bing’ sweet cherry to improve fruit size.  This combination of GA₄₊₇ and P-Ca was evaluated and combined with 6-benzyladenine (6-BA) treatments on European pear (Pyrus communis L.) cultivars, Forelle and Abate Fetel to see if a similar effect on fruit size can be achieved under South African growing conditions.  On both ‘Forelle’ and ‘Abate Fetel’ the combination of GA₄₊₇ and P-Ca increased fruit size but this was more pronounced in ‘Abate Fetel’.  6-BA did not improve fruit size in these two cultivars over two consecutive seasons.

The PGRs N-phenyl-N’ -1,2,3-thiadiazol-5-ylurea (TDZ), N (2-chloro-4-pyridyl)-N’ -phenylurea (CPPU), 6-benzyladenine (6-BA) and 2,4-dichlorophenoxyacetic acid (2,4-D) successfully increased fruit size in the pear cultivars Coscia and Spadona in Israel.  These PGRs were applied to ‘Forelle’ and ‘Abate Fetel’ to determine if a similar effect could be achieved.  None of the growth regulators applied had a significant effect on fruit size.  The stage when the cell division period in ‘Forelle’ and ‘Abate Fetel’ ends was also determined as being 34 and 45 days after full bloom, respectively which can be used in the future to better schedule the time of fruit size enhancement treatments.