Self-Incompatibility and Outcrossing in Rape and White Mustard

N order to apply proper methods to the breeding of a specific crop, I a thorough knowledge of its niode of fertilization is necessary.When the breeding of oil plants was re-introduced, about twenty years ago, into the breeding programme at Svaliif, it was known that the seed setting of plants, selfed by isolating the inflorescences in bags, was much better in rape (Brctssica napus L. ssp.oleifera (METZG.)SINSK.)than in turnip rape (€3.cumpestris L. ssp.oleifera (METZG.)SINSK.) and white mustard (Sinapis alba L.).Since there was not very much information available regarding the degree of outcrossing or vicinism in these species, studies of this problem were undertaken.Part of this investigation has already been published.The present paper gives a brief summary of some of these results together with some more recent experiences concerning the niode of fertilization in rape. I. MODE OF FERTILIZATION RapeThe degree of spontaneous crossing between individual plants of rape under normal iield conditions has been studied by, among others, SYL-VEN (1920), OLSSON (1952) and PEHSSON (1956).In all these studies plants were used which were homozygous for some recessive gene giving a niorphological "marker" character.These plants were allowed to flower in large populations with nearly 100 per cent homozygosity for the corresponding dominant gene.The degree of cross-fertilization will show up directly in the progeny of the recessive plants.In the two last cited investigations dark or light yellow colour of the flower was used as marker character since these colour variants were shown to be recessive to normal lenion yellow colour ( S Y L V ~N , 1927).Besides these cha- -Hereditcis 46Sv.Matadorrape2 Summer rape