Pollen viability and endophytic yeast species of Cistus creticus L. and Cistus monspeliensis L.

Cistus species are widespread in the Mediterranean basin, even in places characterized by high temperatures and arid soils. Despite a rich literature concerning the biological and pharmacological properties of Cistus genus, to our knowledge, there are only a few reports on pollen viability and little is known about microbial endophytes within pollen grains. Pollen viability and germination of Cistus creticus L. and Cistus monspeliensis L., from two sites of Sicily (Italy) over two years (2016-2017), were determined by 2,3,5 tryphenil-tetrazolium chloride (TTC) staining and an in vitro germination test. Dominant microorganisms, flowing from pollen openings (colpora), were identified by molecular methods. Furthermore, for comparison, in 2017 microbial endophytes of C. eriocephalus Viv. from Serra S. Bruno (Calabria, Italy) were studied. The optimal medium composition for rapid in vitro germination was determined. Pollen viability was in the range 79.8-90.0% for C. monspeliensis and 86.6-91.6% for C. creticus, while germination was in the range 56.5-62.4% for C. monspeliensis and 50.1-58.8 for C. creticus. Statistical analysis by correlation coefficient showed a significant relationship between viability and germination, whereas significant differences (P<0.05) were observed between (TTC) staining and the in vitro germination test. Yeasts were the dominant microrganisms in all pollen samples and dominant species were identified.