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Natural Breeding Structure in the Bromus carinatus Complex as Determined by Population Analyses

Jack R. Harlan
American Journal of Botany
Vol. 32, No. 3 (Mar., 1945), pp. 142-148
Stable URL: http://www.jstor.org/stable/2437533
Page Count: 7
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Natural Breeding Structure in the Bromus carinatus Complex as Determined by Population Analyses
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Abstract

A total of 232 families taken from as many individual wild plants were analyzed for evidence of variation within a local race and for interbreeding between races. Plants within a family were generally extremely uniform, indicating a high degree of homozygosity for individual wild plants. Differences exhibited between families of the same local race indicate that a given race is not genotypically uniform. Some families clearly showed segregation indicative of interracial hybridization. An hypothesis for the natural breeding structure in Bromus carinatus is presented involving the habit of facultative cleistogamy and explaining the existence of swarms of local races. Self-pollination is the rule, but highly heterozygous interracial hybrids occur occasionally in chasmogamous panicles. Through selfing, this heterozygosity is rapidly reduced, and in a few generations one to several new recombinations of the original characters become established as new, uniform races restricted in genetic variability.

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