Dynamics of flowering of male and female inflorescence and pollen germination of hazel in the conditions of the Banja Luka region

Studying the hazel flowering was carried out in agro-ecological conditions of the Banja Luka in the period from December to March during 2010/2011 and 2011/2012. The study was conducted on 13 hazel cultivars in two orchards. In the first orchard, the following four cultivars were observed: ‘Tankoljuskasti’, ‘Multiflora’, ‘Merveille de Bollwiller’and ‘Tonda Gentile Romana’, whilst the second orchard included the following: ‘Hall’s Giant’, ‘Gustav’s Zellernuss’, ‘Istrian Round’, ‘Avellana’, ‘Romai’, ‘Apolda’, ‘Ludolph’s Zellernuss’, ‘Imperiale de Trebizonde’and ‘Jean’s’. Phenological observations of the development of flowering phenophase with the aforementioned cultivars were monitored every three days in both years. In 2010/2011 the blooming of male and female inflorescence of the observed hazel cultivars lasted from late December to mid-March in total. The presence and pollen germination was proven to be a limiting factor for a successful pollination and fruit set in 2011. Namely, the pollen of cultivars: ‘Hall’s Giant’, ‘Istrian Round’, ‘Ludolph’s Zellernuss’, ‘Avellana’, ‘Imperiale de Trebizonde’ and ‘Romai’ did not germinate, and with ‘Gustav’s Zellernuss’, pollen germination was very low (7,22%). In ‘Apolda’, ‘Jean’s’, ‘Merveille de Bollwiller’, ‘Tonda Gentile Romana’, ‘Multiflora’ and ‘Tankoljuskasti’ pollen germination ranged between 28,57-81,69%. In 2011/2012 the flowering of male and female inflorescence of the observed hazel cultivars started 30 to 45 days later than the previous year i.e., female inflorescence of all the observed cultivars bloomed in early and mid-March, except in ‘Tankoljuskasti’, in which female inflorescence bloomed in late January and early February. Male inflorescence of ‘Tankoljuskasti’, ‘Hall’s Giant’ and ‘Gustav’s Zellernuss’ bloomed in the second half of January and early February, and in all other cultivars in mid-March. Pollen germination in 2012 proved to be a limiting factor for ‘Apolda’ and ‘Romai’, as their pollen did not germinate, as well as for ‘Hall’s Giant’ and ‘Jean’s’ where pollen germination was below 5%. For other cultivars, pollen germination was very good and ranged from 37,24 (‘Merveille de Bollwiller’) to 73,97% (‘Multiflora’). Based on the analysis of dynamics of blooming and pollen germination of 13 hazel cultivars in two years, the monitoring of pollen germination and strategy of artificial pollination must be adopted as a basic approach to control hazel fertility in the conditions of the Banja Luka region.