A rather large number of papers on the genetics of sorghum (Sorghum vulgäre Pers.) has been published during the past 20 years. The sorghum plant is well adapted to genetic studies because of its growth habits, diversity of characters, and relatively small number of chromosomes. The number of seeds on a single head is usually not less than 500 and may reach a total of 6,000. Most varieties, under suitable conditions, produce tillers and nodal branches and thus continue to bloom intermittently until the plants are killed by frost. So far as known, all varieties of sorghum, including broomcom and Sudan grass, can be intercrossed freely, and the resulting hybrids are completely fertile. The inheritance of approximately 50 factor pairs in sorghum has been determined by the writers during the past 12 years. The characters were investigated to determine their linkage relations, and it has not seemed necessary to publish detailed data on simple independent genetic factors. Many of these genetic results were listed, however, in summary tables in an article on sorghum improvement (10). This paper reports a linkage group of three factors studied in the coupling phase and the independence of this group from several other factors that have been reported previously by the writers or by other workers. The linked factors are those for reddish and blackish plant color (Qq), presence and absence of brown nucellar layer (56), and normal green and a green-striped chlorophyll deficiency (Gsgs).

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