Male Sterility in the Carrot

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Abstract
A d-sterile carrot plant was found in 1945-46 at the U.S. Regional Vegetable Breeding Laboratory, Charleston, S. Car. This plant was grown from a root selected in a commercial stock of the var. Tendersweet in 1945. Caging of certain umbels occurred a day or so before the first flowers normally would open, and these umbels were observed daily for exserted stamens, the stage at which blowflies are introduced into the cages as pollinating agents. A few days after flies were placed in the cage, although no stamens were evident, the anthers of this plant were shriveled and brown before any petals unfolded. No exserted stamens appeared. An umbel of the var. Nantes Strong Top was placed in water and introduced into the cage with the d -sterile plant. This method was continued with fresh umbels from the Nantes plant. Later the 2 entire plants were isolated in one cage. The seed on the selectivity caged umbels was harvested separately from the others because seed had set on the [male] -sterile plant by open pollination. The pollen parents of these seeds were unknown. Female fertility of the [male] -sterile plant appeared normal. A part of the hybrid seed was planted and the 67 roots produced were harvested and planted in the field later in different locations. The flower types of these F1 plants showed 39 c?-sterile and 15 normal. The remainder of the plants were not classified. The abnormal specimens appeared like the parental cf-sterile plant found in the winter 1945-46 greenhouse planting. The mode of inheritance of the d-sterile character is unknown. To determine whether d-sterile plants produce self-fertile pollen, umbels of 4 segregates were caged with blowflies. Three plants set a few seeds. Exami-nation of plants in other carrot breeding lines disclosed 4 plants which showed varying degrees of apparent d sterility. Each plant produced a very small number of exserted stamens. Two specimens shed pollen. All 4 set an abundance of open-pollinated seed. This partial d sterility was not seen in classifying the F1 population which was segregated for the d -sterile character.