Investigation of flower phenology , xenia, and metaxenia in some of commercial hazelnut cultivars

Pollination is one of the most critical stages for kernel formation in nut fruits, and without pollination, most fruit will be blanks, so that, to commercial production of hazelnut orchards, should be used two or more cultivars as pollinizer. The aim of this study was to investigate the phenology of flowers, xenia and metaxenia in four commercial hazelnut cultivars and select a suitable and compatible pollinizer for four commercial hazelnut cultivars.

This study was conducted as a two-factor factorial in a completely randomized design. The first factor is pollen, and the second factor is four cultivars having three replications in the period of 2019-2020 in Astara Horticultural Research Station. Gerde Eshkvarat, Riasnet, Daviana and Negret were used as pollinizer cultivars and Ronde, Nemsa, Ganjeh and Atrak cultivars were selected as maternal cultivars. In addition to open pollination (control), self-pollination of maternal cultivars was performed. At the time of fruit ripening, 100 nuts were harvested from each treatment, the variables related to the quantitative characteristics of the fruit, and the nut kernel were determined.

The results of phenology showed that the cultivars were protanderious and the opening time of male flowers (catkins) and shedding of pollen grains were from mid-January to March 24. The opening time of female flower clusters and stigma ready to accept pollen grains varied from January 19 to March 31. The study of xenia and metaxenia in this study showed that the quantitative traits of nut and kernel were strongly influenced by the sources of pollen grains. Increased fruit set and kernel percentage by 87% and 49.84% and the percentage of fruit drop decreased to 31.65% and blank nut by 10.86%. However, when pollen grains of Gerde Eshkorat cultivar were used, the percentage of fruit set, nut and kernel weight and percentage of kernel decreased to 75.86%, 2.48 g and 46.64%, respectively, and the percentage of blank nut with 15.60% and dropping fruit increased by 41.6. In the case of self-pollination, the percentage of fruit drop and the amount of blank nut increased, and the percentage of fruit set, nut, kernel weight, and kernel percentage decreased.

Based on the results, the source of pollen grains affected nut and kernel characteristics of hazelnuts through xenia and metaxenia effects. The effects of treatments on important components of hazelnut yield (nut and kernel weight, kernel and fruit set percentage, fruit drop and blank percentage) were remarkable and it was statistically significant at the 5% probability level. Therefore, for the economic production of hazelnut orchards, pollinizer cultivars should be used that overlap with the main cultivars in terms of pollination period and genetic compatibility.