Growth patterns analysis of pomegranate fruits of 'Mollar de Elche' during the final phase of development and maturation

Abstract

Physical properties of fruit such as weight, volume and aril size are important from a marketing viewpoint in pomegranate (Punica granatum L.). The fruit growth measurement and analysis is important for yield prediction and development of optimal maturity indices in fruit crops. In this sense, studies on fruit growth are generally based on the measurements of fruit diameter and fresh weight in deciduous fruit crops destined for the fresh market. The objective of this work was to analyze the growth of 'Mollar de Elche' pomegranate fruit as a function of growing degree days. The present study was carried out under the agro-ecological conditions of Elche (Alicante, Spain) Determinations were carried out during the late stages of fruit development and maturation (i.e., August 10th (at 92 days after full bloom (DAFB)) to October 26th (169 DAFB)). Twenty fruits samples were taken weekly for morphological characterization; including diameter, height (excluding calyx), fresh and dry weight (drying at 60°C to a constant weight) and weight fresh of arils were measured. A regression analysis was done to obtain the growth models. During this period of growing, fruit diameter increased from 78 to 95 mm and fruit length from 67 to 82 mm. High correlations in fruit diameter (r2=0.94), height (r2=0.90) and fresh weight (r2=0.94) was obtained in linear regression analysis. Moisture content of fruit varied significantly from 74 to 78% at last fruit maturity stage. The fruit continued to grow even after the optimum harvesting stage, between 146 and 160 DAFB, following the characteristic sigmoid shape in transversal and polar diameter and weight. Therefore, these curves could facilitate the prediction of fruit size and determine the optimum time of harvesting, the temporal identification of critical stages, and may aid in the optimization of crop management. In addition, relative growth rates could be useful to correlate the diameter percentage obtained with the phenological code in BBCH scale.