Alternate branch fruit cluster in satsuma mandarin [Citrus unshiu]: New fruit control method for biennial bearing prevention and quality improvement.
1995
Kihara T. | Iwagaki I. | Okuda H. | Kawase K.
Satsuma mandarin "Aoshima" is known for its tendency to display biennial bearing as well as for its good quality with a high sugar content. It is difficult to achieve stable production and fruit grows too large off-year when conventional fruit thinning is applied. Improved method for fruit control is required for "Aoshima". Alternate branch fruit thinning and other fruit control methods were investigated for the prevention of biennial bearing and improvement of quality. In alternate branch fruit thinning, young fruits are completely removed from some branches and allowed to cluster on other branches. The fruit control system mentioned above was designated as alternate branch fruit cluster method. 1) The application of the alternate branch fruit cluster method enabled to prevent biennial bearing and to stabilize the production of "Aoshima". The method also enabled to secure fruits with a medium size and higher Brix value. 2) The application of the alternate branch fruit cluster method resulted in reduced variation in fruit quality in a tree canopy. 3) Fruit of "Shilverhill" and old satsuma line, became frequently too small when the alternate branch fruit cluster method was applied because "Shilverhill" does not show a strong tendency to biennial bearing. Quality improvement by the alternate branch fruit cluster method was not as distinct as in the case of "Aoshima". 4) Practically, the alternate branch fruit cluster method consists of selected 20 to 25 lateral branches of 2 to 2.5cm in diameter (500-600 leaves) in the case of fully mature 20-year-old "Aoshima" and pairs of cluster-fruit branch and defruited branches are distributed in a tree canopy. An amount of about 1.5 to 2 times as much fruit as in the case of conventional thinning should be left on cluster-fruit branches.
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