TORREYA 



Vol. 44 January 1945 No. 3 



Inactivation of Incompatibilities in Tetraploid Progenies of 

 Petunia axillaris 1 



A. B. Stout 



During the past five years the writer and his assistants 2 have carried on a 

 series of investigations to obtain direct experimental data from diploid and 

 derived autotetraploid progenies of Petunia axillaris on the effect which 

 autotetraploidy has on the heredity and expression of self- and cross-incom- 

 patibilities. 



Two (6, 9) preliminary reports of these studies were made in 1941 and 

 1942. Since then further cultures have been studied especially in regard to the 

 inter-group relations between the 2n and the 4n populations. The results ob- 

 tained to date on these matters may be summarized as follows : 



Intra-specific Reproduction of Diploid (2n = 14) Petunia axillaris 

 (Lam.) B. S. P. (P. nyctagini flora Juss.) 



Of this species 23 plants grown from seed obtained from Argentina and 

 also various further pedigreed seed progenies were remarkably uniform in 

 character and especially in the homomorphic differentiations of sexuality in 

 the hermaphrodite flowers. These features of fundamental specificity may be 

 represented as'AA. Were it not for the special factors of incompatibility this 

 fundamental specificity would give complete intra-specific reproduction. 



But fully adequate tests revealed that each individual of the entire popula- 

 tion which was studied, including successive generations, was self -incompatible 

 and that there were also cross-incompatibilities which operate in the simplest 

 type (the "personate" type) of intra-specific-incompatibilities known in her- 

 maphrodite flowering plants (4). The special incompatibility factors ("S" 

 factors) exist in addition to the constitutional sexuality of specificity (AA -f- 

 S x S y ). These factors are self-interacting in the physiological reactions of hap- 

 loid pollen tubes and diploid styles both in self-pollination and in cross-pollina- 

 tion. For a plant (AA -f ^ x S y ) there is incompatible reaction for both 



1 Presented in greater detail at the meeting of the Torrey Botanical Club on May 17, 

 1944 at The New York Botanical Garden. 



2 Before July 1943 Dr. Clyde Chandler was technical assistant to the writer in these 

 studies and since that date Miss Anita Appel has had this position. Most of the routine 

 pollinations and all of the technical laboratory studies of this research have been done by 

 them. 



Torreya for January (Vol. 44, 45-81) was issued January 31, 1945. 



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