SHOOT GROWTH OF GREEN GAGE PLUM IN RELATION WITH PHASES OF BIENNIAL BEARING

For the last forty years, many studies have been made in various countries, on the shoot growth of fruit trees having biennial bearing habit, specially on apple trees.
Generally, the tendency of greater length of shoots takes place during the natural large production year ("on" year) i.e. of low or no floral induction.
In fact, during this phase, spurs are shorter (MACK, 1924; MECARTNEY, 1925), and the long shoots are longer than in "off" year (MACK, 1924; TUCKER and POTTER, 1929; WILCOX, 1937). Besides, according to MACK, in "on" phase, the number of spurs is smaller, whereas larger shoots are in great number.

On the contrary, complete blossom or fruitlet removal generally brings a very important increase of shoot length (CHANDLER, 1925; BOWMAN, 1941; MAGGS, 1963; BARLOW, 1966) whereas increases floral induction when this considerable treatment is made in "on" year on alternate bearing trees (GOURLEY, 1915; AUCHTER, 1919; ROBERTS, 1920; BAILEY, 1928; READ, 1931; ALDRICH and FLECHTER, 1932; McCORMICK, 1933; ALDRICH and WORK, 1934; HOBLYN et.al,1936; BOBB and BLAKE, 1939; FISHER and BRITTON, 1940; HARLEY et al. 1942; BROWN, 1942 – on apple trees; BOWMAN, 1941 – on plum-trees; HODGSON and AGGERS, 1941 – on orange-trees; FISHER, 1951 – on apricottrees).

Therefore, a contradiction exists:

• tendency for strong growth associated with low initiation ("normal on year");

• strong growth associated with important initiation ("artificial off year" by blossom or fruitlet removal).

We have tried to give accurate details of these facts,

Symposium of Working Group on Plum Genetics and Plum Breeding

J. COURANJOU

https://doi.org/10.17660/ActaHortic.1968.10.20