INHERITANCE OF BULB COLOR IN THE ONION

Abstract

N THE onion the color of the bulb ranges from white to dark red and dark I yellow, a great assortment of shades of red and yellow being known. The attractiveness of a variety depends to a large degree upon the bulb color. Furthermore, colored bulbs are highly resistant to the onion smudge organism, Colletotrichum circinans (Berk.) Vogl., whereas white bulbs are susceptible. For these reasons it is important to understand the mode of inheritance of different colors. Genetic studies in this subject have been published, but in this paper data from additional crosses are presented which necessitate a modification of the conclusions drawn from this earlier work. REVIEW OF LITERATURE TSCHERMAK (1916) found that dark yellow and red bulb colors are dominant to white, with a complex segregation in the Fz. MEUNISSIER (1918) reported that sometimes yellow is dominant over red and over white, although a re-cessive yellow also occurs. RIEMAN(1931) has made a more detailed study of the inheritance of bulb color in the onion. He postulated a series of multiple alleles-namely, W a gene for red pigment, Wu a gene for yellow pigment, and w a gene for white. W is dominant over both Wu and w. In addition, there are the genes I and i,