MICROSPOROGENESIS IN NINE HAZELNUT GENOTYPES

Microsporogenesis is an important process in male flower development whose timing may be correlated with the time of pollen shed in hazelnut (Corylus avellana L.). Early to very late blooming cultivars were identified and the relationship between microsporogenesis and time of pollen shed were studied. The cultivars included in the study, listed in order from early to very late bloom time, were ‘Tonda Gentile delle Langhe’, ‘Tonda di Giffoni’, ‘Barcelona’, ‘Hall’s Giant’, ‘Creswell’, ‘Brixnut’, ‘Gem’, ‘Gasaway’, and ‘Contorta’. Three catkins from a single tree of each variety were randomly selected once per week from the beginning of August to the end of November 2002. The catkins were fixed in formalin alcohol acetic acid (FAA) solution, embedded using the Technovit 7100 kit, stained with toluidine blue, and examined by light microscopy. On 4 August, different varieties were at varying stages of microsporogenesis. Later blooming varieties contained archesporial cells, whereas early blooming cultivars had pollen mother cells present. Pollen mother cells were present in anthers of all cultivars by 22 August. Microspores were seen at the end of September, when hazelnut catkin dormancy is purported to begin. Stage of microspore development was correlated with bloom time and chilling requirement.