The Development of an Improved Medium for the In Vitro Germination of Corylus avellana L. Pollen

Abstract

The European hazelnut (Corylus avellana L.) is a self-incompatible wind-pollinated species 15 of significant economic-productive interest, cultivated mainly between the Mediterranean basin 16 and the Black Sea. Hazelnut breeding programs and high cropping in commercial orchards are 17 necessarily linked to the availability of fertile pollen with wide germinability and high viability. 18 Our objective was to develop an improved method to determine the germinability of pollen, com-19 paring the results obtained with those applying protocols taken from the literature. Pollen germi-20 nability was firstly evaluated on a wild type accession using boric acid (H3BO3), calcium nitrate 21 (Ca(NO3)2), magnesium sulfate (MgSO4), potassium nitrate (KNO3), casein hydrolysate and dif-22 ferent concentrations of sugars, including sucrose (10, 15 and 25%) and two monosaccharides, 23 glucose and fructose. The optimal composition included 15% sucrose in a semisolid medium 24 composed of 1% of animal gelatin, containing collagen. This formulation was then tested on three 25 cultivars of commercial interest, evaluating the effect of different concentrations of sucrose. The 26 comparison between different in vitro germination methods showed that the hanging drop tech-27 nique in a semi-solid medium provides a statistically higher germination index compared to the 28 liquid and solid/agarized techniques. This study proposes an easy and rapid use medium for in 29 vitro determination of the germination index of Corylus avellana L. pollen.