In vitro pollen germination and pollen grain morphology in some sweet cherry (Prunus avium L.) cultivars

Abstract

In vitro pollen germination on agarose-sucrose medium, and pollen grain morphology by scanning electron microscopy, were investigated in four sweet cherry (Prunus avium L.) cultivars ('Karina', 'Kordia', 'Regina' and 'Summit'). The highest percentage of in vitro pollen germination over a three-year period was observed in 'Regina' (46.60 +/- 3.58%), and the lowest in 'Kordia' (26.68 +/- 1.59%). The results suggested a major influence of cultivars specificities which induced the different response to experimental conditions among years. The differences in morphological characters of pollen grains - size and shape (length, width and length/width - L/W ratio), germinal furrows (number and shape, length, width, distance between furrows) and exine ornamentation (the number of ridges in 100 mu m(2) of exine, ridges and stria width) were significant enough to separate and identify the investigated cultivars. When all parameters were considered together, the pollen of each cultivar exhibited a unique pattern. The results also suggested a relationship between pollen grains properties and origin of the studied sweet cherry cultivars. The most significant differences were observed among 'Summit' (North American cultivar) and the other three European cultivars investigated. The highest similarity in pollen grain characteristics was observed between 'Karina' and 'Regina', originating from the same parental combination.