Inheritance of stem fasciation and twin/multi-embryonic seeds and genetic linkage between them in safflower

The derivatives of an interspecific cross between Carthamus palaestinus (wild species) X Carthamus tinctorius (cultivated species) showed exomorphic variations such as plants with flattened stems having a fasciated main capitulum forming a semi-circular structure of two to three capitula fused together. The other capitula of the fasciated plants were normal. Apart from the stem fasciation, these derivatives also produced twin/multi-embryo seeds. The objective of the present study was to find the mode of inheritance, the number of genes controlling stem fasciation and twin/multi-embryo seeds and linkage between the genes controlling the two traits. The results of the crosses made between fasciated derivatives and the normal genotypes revealed that F(1)s of all the crosses gave plants with normal stem and single embryo-seeds. The F-2 segregation gave a ratio of 13:3 for plants with normal and fasciated stems respectively as also for plants with single-embryo seeds and twin/multi-embryo seeds respectively. The F-3 generation segregations further support the role of inhibitory gene action in the control of stem fasciation and twin/multi-embryo seeds in safflower. The stem fasciation and twin/multi-embryo seeds are designated by the gene symbols FpFp and FsFs respectively. The genic analysis exhibited close linkage between FpFp and FsFs genes in coupling phase. Linkage between the genes for stem fasciation and twin/multi-embryo seeds is reported for the first time and its usefulness in identification of probable apomicts in safflower is discussed in the paper.