Date of Award:
Master of Science (MS)
Agricultural Systems Technology and Education
For decades man has been interested in selection and hybridization of crop plants, but it has not been until in comparatively recent years that anything of importance has been done toward the improvement of perennial forage grasses.
Replies to questionnaries on grass breeding submitted to various agricultural institutions in 1936 revealed the fact that selection for improvement was then under way with a large number of grasses. Limited activities in this field have been in progress for 16 years or more, but organized and intensive grass breeding activities, for the most part, have been inaugurated only within the last ten years.
Many improved strains of grasses have been developed by selective breeding in foreign countries but very few of these have shown outstanding value in the United States. In fact, they are generally inferior.
There is a great deal of interest at the present time in this country in the field of grass breeding, but the smallness of the floral parts of some grasses makes the work of controlled hybridization tedious and slow. A simple, inexpensive, accurate method for bulk hybridization would be useful and would speed up the work. The study herein reported was designed to throw further light on the possibility of bulk hybridization. The technic involves immersion of inflorescences in water heated to specific temperatures to effect enactivation of pollen. As a necessary corollary, the desired pollen is then applied by any of several methods.
Several investigators, mentioned below, have shown that controlled heat treatments applied to inflorescences near the time of anthesis are effective in seriously reducing the viability of pollen without having a similar effect on the female gametophyte. However, none has demonstrated good female fertility following complete male sterilization. It has become apparent that influences of the plants' environment other than the heat of the emasculation treatment must be taken into consideration. In the present study, which was conducted on three important forage grasses, smooth bromegrass (Bromus intermis), crested wheatgrass (Agrpyron cristatum), and bluestem wheatgrass (Agropyron smithii), the general findings of earlier investigators are substantiated and in addition evidence is presented to show (1) the sterilizing effect of the isolation bag and (2) the existence of a daily cycle in the efficiency of emasculation of treatments at critical temperatures.
Clark, John W., "The Effect of Some Environmental Influences in Bulk Hybridization of Grass" (1942). All Graduate Theses and Dissertations. 3925.
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