The primary objective of this research was to reveal the effect of cryotreatment on pollen reproductive ability in vivo by monitoring pollen tube growth in sweet cherry (Prunus avium L.) pistils. The influence of cryotreatment was considered from the context of its interaction with pollinizer genotype, and the possibility for usage of in vivo parameters for assessment of pollen fertility. Pistils of sweet cherry cultivar ‘Regina’ were pollinated with both cryotreated and fresh pollen of ‘Kordia’ and ‘Summit’. Quantitative parameters of pollen tube growth in vivo (pollen tube number in certain pistil parts, pollen tube dynamics, and fertilization percentage) were determined using the fluorescence microscopy method, and the obtained data were analyzed together with those obtained for in vitro pollen performance and fruit set. The research indicated that: (i) Reproductive ability of cryotreated sweet cherry pollen can be estimated by analyzing parameters of its performance in vivo, which should be combined with in vitro test; (ii) Semi- or fully-compatible female recipients, whose sporophytes are supportive for male gametophytes should be used for the assessment; and (iii) The key parameters for in vivo testing are pollen tube number in the upper part of the style and in the ovary, as well as fertilization percentage, i.e. the percentage of pistils with penetration of the longest pollen tube in the nucellus of the ovary on the 10th day after pollination. Therefore, in vivo testing of the pollen reproductive ability after cryotreatment can give answers about pollen quality with valuable credibility, in a maximum of two weeks after thawing and rehydration.
Radičević et al. (Wed,) studied this question.