Effect of Pollination Methods on Fruit Set, Yield, Physical and Chemical Properties of Hayani Date Palm Cultivar

Date palm trees are classified as a evergreen dioecious fruit tree, where the male and female flowers exist on separated trees. In fruits with seeds, successful fruit set are dependent on the efficacy of pollination. Successful pollination is critical for kernal formation and fruit growth and development, especially in nuts and in drupe fruits with one seed like dates and stone fruits. Pollination in date palm is defined as a transfer of pollen grain from male to female tree either naturally or by hand or mechanical methods. Pollination of 60-80% of the female flowers is considered satisfactory and will usually lead to a good fruit set (Al–Ekidy, 2000).

The date palm naturally is wind pollinated, but this method was inefficient and economically unfeasible (AL-Bakr, 1972). The traditional pollination method in date palm that commonly used in Middle East region is hand pollination. However the mechanical pollination requires mixing the pollen grains with a filler material to minimize the amount needed from pollen grains. Different filler materials were tried such as wheat flour, wheat bran, starch and crushed dry male flowers after the pollen grains extraction. (El-Refaey and El-Dengaw, 2017 and Samouni, et al, 2016)

The pollination methods could affect physical and chemical properties on date fruits. There are many opinions to determine which pollination method is better in date palms. Most of the research results showed that the hand pollination in date palm is very effective to obtain a high fruit set. For example, in ‘Samani’ date, wind pollination method gave significantly higher in fruit length, diameter, weight, flesh weight, flesh/seed weight ratio and TSS than hand pollination, but gave lower fruit set percentage than in hand pollination (Bakr, et al, 1988).

Previous studies focused on studying the effect of different pollination methods on physical characteristics of the date fruits (Hamood and Mawlood, 1986; Shabana et al, 1986 and Ibrahim, 1988). In general, these studies suggested that mechanical pollination increased labor efficiency, produced comparable yield with lower fruit set, required more pollen and offered greater returns compared to hand pollination. Many previous studies showed that fruit set, yield and fruit quality in mechanical pollination were close to those of hand pollination (Brown et al. 1969; Brown et al, 1970; Hamood and Shalash, 1987 and Shabana et al, 1998). El-Mardi et al, (2002), pointed out that many factors could influence the efficiency of mechanical pollination, including weather, physiological conditions of the palms and their arrangement and spacing in the orchard.

In ‘Kustawi’ date palm, Al-Khafaji, (1993), did not obtain any significant differences between hand and mechanical pollination with regard to fruit set, bunch weight, water content, TSS and total sugar using different pollen grain dilutions 1:6 or 1:9 or 1:12 (pollen: filler ratio). These results indicated that the economic advantages of using the mechanical pollination compared to the difficult and the cost of hand pollination method. Othman et al. (1990) explained that the hand pollination on ‘Sayer’ flower date gave higher fruit weight and mesocarp during Khalal stage, where mechanical pollination gave higher fruit diameter, larger fruit size and higher moisture content, during Khalal and Rutab stage. However, there were no significant differences between both methods in regard to total soluble solid during Khalal and Rutab stages. EL-Makhtoun et al. (1995) found that the dust pollination treatment significantly increased fruit and flesh weight, seed weight, flesh/seed ratio, fruit dimensions, TSS, total sugar and reducing sugar, than those of normal hand pollination in ‘Zaghloly’ date.

El-Mardi et al, (2002) used different pollination methods (hand pollination, hand duster and motorized duster in various ratios with filler). The motorized duster produced lower fruit set than hand duster, and that was probably due to the large amount of pollen being blown away from the target, and the lowest fruit set was obtained in hand pollination. But they found that, there was no significant effect of pollination method on yield and physical or chemical properties during the same stage of fruit development.

Soilman et al, (2017) examined the impact of water suspension spray at different concentrations on some physical and chemical fruit properties on Segae date palm cultivar, they found the highest bunch weight and yield was produced from spray pollination at 2 gmpollen with 3 gmsugar per liter followed by hand pollination.

The aim of this study is to make a comparison between the hand and dusting pollination methods in relation to fruit set, yield, physical and chemical characteristics of date palm fruits under Ghour Al-safi / Jordan environmental conditions for Hayani dates palm cultivar.