372 Colchicine 



tion of interspecific segregations. Some lack of uniformity showed up 

 in the fifth and hiter generations, where the early stages were uni- 

 form and did not segregate for fruit color, shape, and size. Some inter- 

 genomal pairing may have occurred. A homology between certain 

 chromosomes was demonstrated with some pairing in the diploid 

 hybrid. Such amphiploids shoidd make excellent material to test the 

 principles basic to amphiploidy and their practical possibilities. ^^^ 



The interspecific hybrid Trifoliinn repens X T. nigrescens was 

 made by crossing two colchicine-induted polyj^loids of the respective 

 species involved.!^ By special culturing methods the hybrid was saved 

 in the seedling stages. The explanation for incompatibility at the 

 tetraploid level can be adapted from the case in diploids. i'* Par- 

 ticularly interesting in the amphiploid TrijoUum is the fact that the 

 incompatibility apjilied to diploids and to autoploids holds for the 

 polyploid that brings the two species together. 1 he loci of genes which 

 determine incompatibility must be at the same place in both species; 

 furthermore, intergenomal pairing must occur in order to explain 

 the genetic mechanism of incompatibility through oppositional alleles. 



A new species, Ribes nigrolaria, was created by the use of colchi- 

 cine and hybridization. Two Linnean species, Ribes nigrum, the 

 black currant, and R. grossiilaria, the gooseberry, were the diploid 

 parents. 1 hus genomes from two important horticultural species 

 were combined. These were developed and are under observation 

 at the Alnarp Horticultural Station, Sweden, under the direction of 

 Professor Fredrik Nilsson. 



Among these and other cases there should come into prominent 

 use new plant breeding materials that combine the genie composi- 

 tion from two or more natural and artificial species. In some in- 

 stances only a specific trait such as disease resistance may be desired. 

 The key to a new jjlateau for plant breeders can be found among 

 artificial amphiploids. 



REFERENCES 



1. Alcaraz, M. The transmission of resistance to mosaic in tobacco hvhrids. 9th 

 Internat. Cong. Genet. Bellagio, Italy. No. 269. 1953. 



2. , AND Tamayo, a. Tire production of tetraploid plants of Xicaliaim 



nistira and A', tabacuni l)v nse of colchicine. Bol. Inst. Nac. Invest. Agron. 

 Madrid. 11:46-87. 1944. 



3. Amin, K. Application of colchicine to cotton. Indian Farming. 4:237-58. 1943. 



4. ANni.RSON, E. (see Ref. Xo. 2, Chap. 11). 



5. Armstronc, J., AND McLf.man, H. Aniphi|)loidv in Triticinn-Agropvroii luhrids. 

 Sci. Agr. 24:285. 1944. 



6. Bartoi.ucci, a. II fenomeno della poliploidia ed il tabacco. I. L'uso della 

 colchicina e della centrifiigazione dei semie per trasformare gl'ibridi sterili in 

 ibridi fertili. Roll. Tech. R. Inst. Sper. Tabacchi Schiafati. 36:141-18. 19.39. 



7. Beaslev, }. The ])roilnction of polyploids in G()ss\j>iinii . Join. Hcred. 31: 

 39-48. I94o. Meioiic chromosome behavior in species, species hybrids, haploids, 

 and indnced polyploids of Gossxiuinn. Genetics. 27:25-54. 1942. 



