Section 8 — Cytato.xonomy and Experimental Taxonomy 



normal chromosome number as a result of une- 

 qual distribution of the chromosomes at anaphase 

 I. The loose bivalents observed in a number of 

 cells at metaphase I signify some lack of specific- 

 ity in pairing of the homologous chromosomes 

 which may represent the visible remnants of the 

 effects of earlier translocations through which 

 species differentiation has occurred. The high 

 percentage of pollen sterility and the low seed set 

 in the hybrids may partly be caused by extensive 

 intrachromosomal rearrangements, since it is 

 difficult to reconcile the very low fertility with the 

 relatively low frequencies of visible cytological 

 anomalies only. The precocious division of the 

 bivalents is considered, therefore, to be the 

 result of segmental and genetic differences 

 between the parental species. The hybrids exhib- 

 iting this desynaptic behavior were found in 

 crosses between L. japonicus x L. schoelleri, L. 

 krylovii X L. filicaulis, L. japonicus X L. a I pin us, 

 and L. schoelleri x L. krylovii. 



8.6. The Phylogenetic Riddle of Astragalus (Legumi- 

 nosae). G. F. Ledingham (Regina, Canada). 



Chromosome counts of 252 species of Astra- 

 galus have been made. The species counted fall 

 into two distinct groups; the 163 Old World 

 species are based on an 8-chromosome series with 

 23 per cent polyploidy while the 89 New World 

 species counted form an "aneuploid" series with 

 n = 11 (39 species), n = 12 (34), n = 13 (12), or 

 « = 14 (3) and n = 22 (1), the last species being 

 the only polyploid. Ten Old World species 

 (6 with In = 16 and 4 with 2n = 32) have 

 spread recently, probably during the Pleistocene, 

 from N.E. Asia into N.W. America, but these 

 are still easily recognized by their morphological 

 similarity to other Old World species. There is 

 no indication of an aneuploid series among Old 

 World species of Astragalus and no deviation 

 from the 8-chromosome number series except 

 for A. boeticus (In = 30), A. pentaglottis {In = 

 28) and A. somalensis (In = 20) and these occur 

 in the Mediterranean area or in Africa. Thirty 

 species of Oxytropis have been counted and these 

 all have n = 8 or some multiple of 8, 36 per cent 

 polyploidy. Oxytropis seems to be an integral 

 part of Old World Astragalus. The origin and 

 significance of the consistent differences between 

 New and Old World phylogenetic lines of 

 Astragalus is discussed. 



8.7. Cytogenetics of Vicia cracca and V. tenuifolia. 



Arne Rousi (Piikkio, Finland). 



Vicia cracca L. consists of three chromosome 



races (In = 12, In = 14 and In = 28). The two 

 latter ones are morphologically close to each 

 other and have basically similar karyotypes. The 

 karyotype of the 12-chromosome race suggests an 

 origin from the 14-chromosome race as a result 

 of one or probably two interchanges and the 

 subsequent loss of one chromosome. Systemati- 

 cally it seems to tally with the taxon V. cracca 

 subsp. Geraldi (All.) Gaudin. Spontaneously 

 arisen albinotic and inviable seedlings with 13 

 chromosomes were interpreted as hybrids 

 between the 12- and 14-chromosome races on 

 the basis of their karyotypes and hemagglutin- 

 ating properties. This suggests that these races 

 are effectively isolated by means of hybrid in- 

 viability. Hybridization between the self-in- 

 compatible 14- and 28-chromosome races was 

 attempted by placing solitary potted individuals 

 of the former among populations of the latter. 

 The seed set of the diploids was very low, but one 

 viable triploid and one tetraploid arose, the 

 latter being apparently a result of an unreduced 

 egg cell. Although there is a selection against 

 triploids the isolation between the 14- and 28- 

 chromosome races is therefore not complete. 

 V. tenuifolia Roth occurs as a diploid (2n = 12) 

 and a tetraploid (In = 24) race, the diploid 

 being rare and somewhat distinct. The karyo- 

 types of both are basically similar to the 12 

 chromosome race of V. cracca. Certain morpho- 

 logical resemblance between this race and 

 tetraploid V. tenuifolia suggests a close evolu- 

 tionary relationship. 



8.8. Cytological Studies in Melilotus Polyploids. 



J. Jaranowski (Poznari, Poland). 



Inducement of artificial polyploids in the genus 

 Melilotus was mainly intended to utilize them 

 in the attempts to overcome the barriers of re- 

 productive isolation in species hybridization. 

 Owing to their peculiar properties these poly- 

 ploids were closely examined and cytologically 

 analysed to obtain some information on the 

 relationship of species. 



The basic number of chromosomes for the 

 genus Melilotus is n = 8. Fourteen species, 7 

 varieties 3 species hybrids (M. alba x M. offi- 

 cinalis), and 33 [different forms of backcrosses of 

 the species hybrids were treated with colchicine 

 (0-2-0-7 percentage cone.) to induce polyploidy. 



The number of polyploids obtained in the 

 different species varies greatly. Biennials (be- 

 longing to the section Eumelilotus) and annuals 

 (belonging to the section Micromelilotus) re- 

 sponded quite differently to colchicine treatment 



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