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United States Department of Agriculture

Agricultural Research Service

Title: In Vitro Analysis of Cotton Pollen Germination

Authors
item Burke, John
item Velten, Jeffrey
item Oliver, Melvin

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 3, 2002
Publication Date: January 1, 2004
Citation: Burke, J.J., Velten, J.P., Oliver, M.J. 2004. In vitro analysis of cotton pollen germination. Agronomy Journal. 96:359-368

Interpretive Summary: Plant reproductive structures and the processes of pollination and fertilization are extremely stress sensitive developmental stages of most agronomic crops. Cotton is a crop whose economic value is intimately linked to its reproductive structures and successful fertilization. One factor contributing to differences in cotton yields is the sensitivity of cotton pollen to elevated temperatures which lowers fertilization success. The process of selecting pollen with improved heat tolerance could be accelerated with a rapid and reliable method of germinating cotton pollen in vitro. The present study describes the development of a cotton pollen germination media and technique that provides high pollen germination levels and improved pollen tube growth over existing methods. This procedure was used to evaluate the temperature sensitivity of pollen from greenhouse and field-grown cotton. The results show decreased pollen germination and tube elongation with temperatures above 28 deg C. Cotton flowers exposed to full sunlight were shown to experience internal temperatures 8 to 10 deg C above air temperatures, even under irrigated conditions. Pollen taken at 2 PM from flowers exposed to direct sunlight in the field showed reduced viability compared with pollen harvested at the same time from shaded flowers within the canopy.

Technical Abstract: Crop species grown throughout the United States experience environmental stresses that limit their growth, development, and full expression of their genetic potential for agronomic yield. Crops with economically valuable reproductive structures show the greatest negative discrepancy between average and record yields. Cotton is a crop whose economic value is intimately linked to its reproductive structures and successful fertilization. One factor contributing to differences in cotton yields is the sensitivity of cotton pollen to elevated temperatures which lowers fertilization success. The process of selecting pollen with improved heat tolerance could be accelerated with a rapid and reliable method of germinating cotton pollen in vitro. The present study describes the development of a cotton pollen germination media and technique that provides high pollen germination levels and improved pollen tube growth over existing methods. The medium comprises 10% (w/v) agarose (pH 7.6), 25 (w/v) sucrose, 0.52 mM KNO3, 3.06 mM MnSO4, 1.66 mM H3BO3, 0.42 mM MgS04.7H20 and 1.0 uM A3 gibberellic acid. The medium is overlayed with a thin layer of L-Broth Agar containing 10g/L tryptone, 5 g/L yeast extract, 0.5 g/L NaCl and 15 g/L agar immediately prior to use. Optimum pollen germination and rapid tube elongation occurred at 28 deg C under 80% relative humidity. This procedure showed decreased pollen germination and tube elongation with temperatures above 28 deg C. Cotton flowers exposed to full sunlight were shown to experience internal temperatures 8 to 10 deg C above air temperatures, even under irrigated conditions. Pollen from flowers exposed to direct sunlight at 2 PM showed reduced viability compared with pollen from shaded flowers within the canopy.

Last Modified: 7/25/2014