Pollen fertility and seed viability of putative hybrid swarms of Pinus sylvestris and Pinus mugo in Slovakia

Abstract

Generally acknowledged reduction of the interspecific hybrid fertility was utilized in evaluation of the putative hybrid swarms of Scots pine (Pinus sylvestris L.) and mountain dwarf pine (P. mugo Turra) viability under field conditions. Pollen viability and seed quality of the trees from the four contact zones of P. syl­vestris and P. mugo in Slovakia were compared with the corres­ponding characteristics of the pure populations of these spe­cies from three reference localities. Pollen germination percentage was comparable in contact zones and control populations of the species. Statistically significant differences between the parent and hybrid groups were detected in pollen tube length only. In general, pollen tubes of the pure species populations were longer than those in contact zones. At the cone level, the individuals from contact zones possessed shor­ter cones than the trees of pure species populations P. mugo and P. sylvestris. This was paralleled by a lower number of seeds per cone in contact zones and higher amount of seeds per cone in the P. mugo population. Striking differences between individuals of the contact zones and reference populations were revealed also in germination potentials of their seeds. Significantly higher proportions of germinating seeds was found in the reference populations of P. mugo and P. sylvestris than in their contact zones. Contrary to seed quality parame­ters mentioned above, the fractions of filled but non-germina­ting seeds and amounts of empty seeds were higher in contact zones than in the parental species populations, indicating hig­her frequency occurrence of abortive embryogenesis in the former. The lower fertility characteristics of the individuals from contact zones indicate their hybrid nature.

Effect of storage on pollen viability in Pinus sylvestris L., Pinus mugo Turra and their hybrid swarms

“…This finding provides little support to our earlier studies which revealed profound differences between pollen viability of the parental species and hybrid swarm populations. The latter were shown to produce the pollen of reduced germinability and of shorter pollen tubes (Kormuťák et al, 2007) or with the retarded pollen tube growth only (Kormuťák et al, 2008(Kormuťák et al, , 2019. Evidently, the results presented in this study do not conform fully the concept which postulates the reduced fertility of the interspecific hybrids of plants including fertility of the hybrid swarm P. pumila × P. sibirica (Stebbins, 1950;Goroshkevich, 2004).…”

“…The collected and dried pollen is first soaked in liquid nitrogen for three min then freeze-dried at −65°C for 15 min and finally stored in a vacuum at −30°C (Mercier, 1995). Based on in vitro germination data, the pure species populations of P. sylvestris and P. mugo were repeatedly found to exhibit a higher viability of their pollen than hybrid swarms P. sylvestris × P. mugo whose pollen was characteristic by reduced germination percentage and shorter pollen tubes (Kormuťák et al, 2007(Kormuťák et al, , 2019. Nothing is known about the response of these taxa towards the long-term storage of their pollen.…”

Pollen viability and longevity in Juniperus taxa native to Slovakia

“…With its 30% water content 21 , the mature pollen of Cupresaceae is difficult to store for a longer period of time without using a more sophisticated container instead of polyethylene bags. Based on practical experiences with long-term storage of Abies and Pinus pollen at − 20 °C using desiccator with silica gel 22 – 24 , it seems that juniper pollen is much more sensitive to storage conditions compared to pollen of firs and pines. Therefrore, the use of a standardized container with liquid nitrogen as a storage medium is offerred as the only alternative for Juniperus pollen.…”