Linkage studies in Tribolium castaneum Herbst. VII. The map position of four sex-linked lethals.

Abstract

Investigators worlting with Triboliz~n7 C ~ S ~ ~ I Z ~ Z L I I Z and T. c o ~ z f u s z ~ n ~ have generally observed that in the presence of a fairly high ill ovo mortality (amounting to as much as 30-40 per cent) the number of male and female progeny produced b y wild type females is about equal. As in many other organisms, the female sex in flour beetles is homogametic (for cytological studies of these two species of beetles see Smith, 1952). Hence, the presence of sexlinked recessive lethals in cultures o r populations would be expected to lead to departures from the expected one to one sex ratio. A number of deviations fro111 equality of sexes are also 011 record: Park (1937) observed a shortage of Inales in F,, F1 and bacltcross matings involving the autosomal recessive mutation pearl in T. cnstnfrezan. Park et nl. (1945) reported shortages of inales in the progeny of F,, F, and b'lcl<crosses involving the autosomal recessive ebony in T. C O ~ Z ~ ~ L S Z L ~ H , favoring the view that the greater mortality of males was the result of selection operating within the culnlres. Sokoloff, Slatis and Stanlev (1960) found significant deviations froin equality in sex ratio in c o n n e c t i o n ~ ~ ~ i t l ~ genetic crosses involving the semidominant autosonla1 mutation black, the deviations in some replicates approaching the 2: 1 ratio characteristic for sex-linked lethals; but further crosses failed to establish the presence of such a lethal, and thus the aberrant ratios could not be explained in this manner. T w o sex-linked genes with lethal effects have been described in Tribolizan: 1) striped ( S t ) , a dominant mutation producing broad, whitish longitudinal stripes on the elytra, and a lowering of viability of St/+ females with the few surviving males being sterile and having white elytra in T. co~z fusz~m (RilcDonald, 1959), and 2) a recessive sex-linked lethal in T. cnstm2ezLm (Sokoloff et nl., 1960) which had to be discarded before it could be mapped because of disease in the stock. T h e purpose of this coinnlunication is to report the discovery of four additional sex-linked lethals in T. castnneunz and their positions on the map of the X chromosome.