Improving ‘Piyarom’ date palm fruit quality with fruit thinning and bunch covering treatments

B. Madani, Horticultural Crops Research Department, Natural Resources Research and Education Center of Hormozgan, AREEO, Bandar Abbas, Iran

A.M. Dastjerdy, Department of Horticultural Science, Faculty of Agriculture and Natural Resources, University of Hormozgan, Bandar Abbas, Iran

A. Shahriyari, Horticultural Crops Research Department, Natural Resources Research and Education Center of Hormozgan, AREEO, Bandar Abbas, Iran

Date palms (Phoenix dactylifera L.) are an ancient horticultural crop cultivated for its sweet fruit which are also rich in nutrients, antioxidants and phenolic compounds (Hussain et al., 2016). Iran is one of the largest producing countries of dates growing 171,647 hectares of date palms with an annual production of 1,204,158 tons (FAO, 2018). Date fruit has five stages of growth and ripening; (1) Hababouk (cell division and elongation), (2) Kimri (firm full colored), (3) Khalal (physiolog­ically mature with a hard and crisp texture and a moisture content between 50­85%), (4) Rutab (partially browned, reduced moisture con­tent 30­45%, fibres softened, perishable), and (5) Tamar (fruit colour from amber to dark brown with a moisture content further reduced ­ below 25% down to 10% and less, and the texture is soft pliable to firm to hard) (Awad and Al­Qurashi, 2012). Date palm (Phoenix dactylifera L.) cv. Piyarom is one of the most impor­tant commercial semi­dry dates in Iran whichis con­sumed at tamar ripening stage and fruit reaches full maturity. It is widely grown in Hormozgan province of Iran with increasing export production. In com­mercial production, larger fruit with higher quality are more marketable and therefore fruit thinning is one of the main agronomic methods to improve fruit size and quality. Fruit thinning is widely used in horti­cultural production which increases fruit quality, reduces bi­annual bearing and ensures a physiologi­cal balance between vegetative and reproductive parts due to reduced competition for water and food absorption (Slatnar et al., 2020).

There are different times and methods for date palm thinning. For exam­ple, thinning 1/3 of the bunch at pollination period or 1/3 terminal tips of central strands in early kimri stage of fruit development, as has been described by El­Badawy et al. (2018) and Moustafa et al. (2019). However some date palm cultivars can react contrari­ly to the different treatments of thinning for exam­ple, Awad and Al­Qurashi (2015) reported that thin­ning 5­10 cm bunch four weeks after pollination in ‘Barhee’ date did not affect the qualitative characters of fruit. However, Ahmed et al. (2019) showed that thinning 1/3 terminal tips of central strands in early Kimri stage of fruit development of ‘Zaghlool’ decreased titrable acidity and increased soluble solid content. However there has been no research on the effects of different thinning options on the quality of ‘Piyarom’ date where most farmers in southern Iran currently use bunch thinning only at pollination peri­od. Pre­harvest covering of fruit is practiced in many crops and its usage is increasing in many countries to improve fruit quality. However, the effects of fruit covering on final fruit quality is variable and reflect differences in the covering type, fruit age at covering and cultivar response (Sharma et al., 2014). For example Kassem et al. (2010) stated that ‘Zaghlool’ dates covering with dark polyethylene at kimri stage did not affect total acidity (TA) and total soluble solid content (TSS). However, Awad and Al ­Qurashi (2012) concluded that bunch craft bagging after pollination increased bunch weight, TA and TSS, ascorbic acid and decreased total phenols and Rutab percentage of ‘Barhee’ date. Harhash and Al­Obeed (2010) showed that bunch bagging increased fruit and bunch weight and quality of ‘Succary’ and ‘Khalas’ dates. Harhash et al. (2020) further showed that bunch weight was greatly increased by covering bunches with white paper and white and brown cloth as compared to control. Fruit weight was increased remarkably by using white or kraft paper and white or brown cloth in covering bunches of ‘Barhee’ date palm while TSS was increased in the fruit which were produced from bunch covering with white or kraft paper and white or brown cloth over control. Due to its high consumer appeal, ‘Piyarom’ date is a promising cultivar for export but a more consistent high fruit quality is required. Therefore, this study assessed the effects of both date fruit thinning and the use of bunch covers on the bunch weight and quality of ‘Piyarom’ dates over two seasons.


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