Isolation of Pistillate Lines in Castor for Exploitation of Hybrid Vigour

A study of the spontaneous occurrence of female mutants indicated that it depends on the type of material. The pistillate plants in 13 pistillate progenies which segregated into 1: 1 ratio of pistillate and monoecious plants, reverted to monoecious nature during the season but the progeny of 625-4 ♀ X H.C₆ gave 62.9 per cent. strictly non-revertable pistillate plants; when such pistillate plants were crossed with U.S₃ 415-9 (E type; interspersed male flowers from base to top), the F₁ consisted of 55.8 per cent. strictly pistillate and 44.2 per cent. pistillate but with few interspersed staminate flowers which mature very much later than even the topmost female flower appearing on the spike. Thus, for all practical purposes the entire population could be treated as pistillate for purposes of using as a female parent for the production of hybrid seed.