Cytogenetics of new Guizotia Cass. (Compositae) interspecific hybrids pertaining to genomic and phylogenetic affinities

 The following crosses were made using four recognized species/subspecies and a new population of Guizotia, referred to as Chelelu after the name of the locality in Ethiopia from which it was collected: G. scabra subsp. schimperi × Chelelu, Chelelu × G. scabra subsp. scabra, G. zavattarii × G. arborescens and Chelelu × G. zavattarii (all accessions with 2n=30). Plant morphology as well as mitotic and meiotic chromosome analysis confirmed the hybrid nature of the obtained progeny. At metaphase I of meiosis, the F₁ hybrid plants (2n=30) showed a mean of about 95%, 31%, 63% and 0.50% of the pollen mother cells with 15 bivalents, and a mean of about 14.95, 13.75, 14.40 and 7.86 bivalents per cell, respectively. The respective mean pollen stainability was about 67%, 19%, 31% and 2%. From the results it was concluded that Chelelu is more closely related to G. scabra subsp. schimperi than to G. scabra subsp. scabra but more to the latter than to G. zavattarii. Guizotia zavattarii and G. arborescens are closely related to each other. Based on the cytological observations made, the probable basic chromosome number for the genus is discussed. Received November 5, 1999 Accepted August 21, 2001