Development of a model to predict the date of loquat fruit ripening

We developed models for predicting fruit ripening of loquat cultivars ( ʻ Mogi ʼ , ʻ BN21 gou ʼ and ʻ Biwa Nagasaki No.24 ʼ ) grown in orchards at four major loquat production regions of Japan (Chiba, Kagawa, Nagasaki and Kagoshima prefecture). The models were constructed based on temperature-dependent properties of fruit developmental rate (DVR), which were investigated by conducting temperature control experiments of potted loquat trees and by analyzing fruit growth records of loquats and daily temperature of the orchards collected over the past 12 years. Our experimental results suggested that there was a liner relationship between fruit growth rate and temperature in each cultivar regardless of growing stages. The most accurate predictions were made when we started DVR calculations with our models from the next day of the end of flowering date (about 22 to 27 days from full bloom). The models enable to estimate the period of fruit ripening for ʻ Mogi ʼ , ʻ BN21 gou ʼ and ʻ Biwa Nagasaki No.24 ʼ tree with mean errors of 3.9 days, 4.2 days and 2.9 days, respectively, although flowering time and fruit developing period varies at each region. For practical use of our models in agricultural field, precise information of flowering date and temperature in growing area is expected to be needed for minimizing the prediction errors.