Estimation of Pollen Viability, Shedding Pattern, and Longevity of Creeping Bentgrass on Artificial Media

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Abstract
An estimation of pollen viability is needed to determine pollen daily shedding pattern and longevity. Both parameters provide valuable information for plant breeding and contribute to the risk assessment of pollen‐producing transgenic crops. Pollen viability of ‘Crenshaw’ creeping bentgrass (Agrostis stolonifera L.) was estimated through pollen germination on media containing sucrose (1‐alpha‐D‐glucopyranosyl‐2‐beta‐D‐fructofranoside, at 0.25, 0.5, 1.0 M), H3BO3 (1.0, 2.0, or 4.0 mM), and CaCl2 (1.0, 2.0, or 4.0 mM). The highest pollen germination percentage was obtained on a medium containing 1.0 M sucrose, 1.0 mM H3BO3, and 2.0 mM CaCl2 Concentrations of all three medium components had significant effects on pollen germination. No two‐way or three‐way interactions among sucrose, H3BO3, and CaCl2 were observed. A high sucrose concentration of 1.0 M severely inhibited pollen tube growth, causing shorter and thicker pollen tubes. Pollen‐tube length of pollen germinated on medium containing 1.0 M sucrose averaged 137 μm, while those germinated on medium containing 0.5 M sucrose averaged 248 μm. The daily shedding pattern of pollen of Crenshaw creeping bentgrass was determined by collecting and germinating pollen from 0800 through 1700 h at 1‐h intervals. The results indicated there were two peaks of pollen viability, with the first one occurring at 0900 h and the second peak at 1400 h. The longevity of Crenshaw and ‘Penncross’ pollen was assessed by storing the pollen in a desiccator at 21°C and a relative humidity of 64 to 66%. Our results showed that creeping bentgrass pollen lost viability dramatically within the first 1.5 h of storage and lost viability completely after 3 h of storage.