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

Cistus species are widespread in the Mediterranean basin, especially in places characterized by high temperatures and arid soils. Despite a rich literature concerning the biological and pharmacological properties of Cistus species, to our knowledge, there are only few reports on pollen viability and little is known about microbial endophytes within pollen grains. Pollen viability and germination of Cistus creticus L. and C. monspeliensis L., from two sites of Sicily (Italy) over two years (2016-2017), were determined by 2,3,5 triphenyl-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 of 79.8-90.0% for C. monspeliensis and 86.6-91.6% for C. creticus, while germination was 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 microorganisms in all pollen samples and dominant species were identified.