MATURITY INDEXES FOR PEARS

In our search for a reliable maturity index several methods like heat sum computation, elapsed time from full bloom to harvest, fruit firmness and starch degradation pattern have been investigated.

Among the maturity criteria tested, starch content and its degradation pattern appeared to be the most reliable one.
Over four years of investigation a close relationship between starch content and physiological maturity of the fruit was found.
At the onset of the climacteric rise in respiration starch contents of ‘Moltke’, ‘Amanlis’, ‘Herzogin Elsa’ and ‘Philip’ were 3, 35, 6 and 18 percent respectively.
Starch content is given as percentage area of the cut curface of the fruit stained blue by iodine.

Fruit firmness varied over the years.
At the stage of full maturity firmness differed as much as 2 kilograms.
The year to year variation render fruit firmness a less reliable maturity index for pears grown in Norway.

Under normal climatic conditions number of days as well as accumulated heat units gave a fairly good estimate of optimum harvest date.
However, under atypical climatic conditions large deviations from normal was recorded.

Susceptibility to friction discolouration decreased with maturity but increased with duration of storage.
Discolouration increased with diminishing firmness.

Symposium on Integrated Fruit Production

A. Kvåle

https://doi.org/10.17660/ActaHortic.1990.285.14