Section 13 — Plant Genetics and Breeding 



which on subsequent hybridization with F. mos- 



chata gave allo-octoploid hybrids. The sequence 



of colchicine treatments and hybridizations 



being: 



F. vesca (2x) -> F. vesca (4x) x F. moschata 



(6x) -> 5x hybrid -> lOx hybrid F. moschata 



(6x) x lOx hybrid -> 8x hybrid. 



The allo-octoploid hybrids closely resembled 

 the hexaploid parent in vegetative characters 

 and in being dioecious. In view of this morpho- 

 logical similarity, it is conceivable that the 

 controversial mid-nineteenth-century variety 

 "Belle Bordelaise", could have been a sim- 

 ilar allo-octoploid hybrid, having originated 

 through chance non-reduction in both parents. 

 In such circumstances this octoploid derivative 

 could have provided an opportunity for F. mos- 

 chata to enter into the evolutionary history of 

 some present-day varieties of F. grandiflora. 



13.4. Natural and Experimental Festulolium Hybrids 

 and Their Derivatives. F. Wit (Wageningen, 

 The Netherlands). 



Lolium perenne, L. multiflorum and Festuca 

 pratensis are important forage grasses. In 

 addition to their valuable qualities, they show, 

 however, some imperfections which are difficult 

 to eliminate by conventional breeding methods. 

 Intergeneric hybridization might be useful, 

 either through the transfer of single desirable 

 characteristics or through the production of 

 stable and fertile alloploids. 



A study of some natural hybrid swarms from 

 L. perenne (2/2 = 14) F. pratensis (2/7 = 14) 



showed that the predominating plants were 

 triploids (73-94 per cent, and belonged to two 

 distinct groups). Both are supposed to have 

 partly originated by fertilization of unreduced 

 egg cells of the male sterile diploid hybrid. They 

 may be represented by the genome formulae 

 LLF and LFF respectively. 



As unreduced gametes are rare, these triploids 

 must exhibit high competitive abilities. They 

 are, however, unstable and partly sterile. 

 Corresponding hexaploids might represent stable 

 and fertile plants. 



The development of successful alloploids 

 requires efficient methods to provide for the 

 widest possible range of genomic and genetic 

 recombinations. Results of breeding experiments 

 suggest a method starting with the production of 

 hexaploids LLFFFF. Such plants can easily be 

 obtained either by colchicining seeds from the 

 cross Lolium 2x x F. prat ent sis 4x, or by cros- 

 sing Lolium 4x and Festuca 8x. By backcrossing 

 to diploid Lolium large numbers of tetraploids 



LLFF are obtained, which by a second backcross 

 produce triploid seeds LLF. By colchicine treat- 

 ment these give rise to hexaploids LLLLFF. 

 The triploids LLF are reasonably fertile, they 

 may be the proper plants for starting introgression 

 breeding. 



13.5. Breeding Spineless Gooseberries using Ribes 

 nigrum as Donor Parent. R. L. Knight and 

 Elizabeth Keep (Maidstone, Great Britain). 



Seedlings and mature plants of black currant 

 (Ribes nigrum) are entirely devoid of spines. 

 Sterile diploid hybrids (BG) between black 

 cuirant (BB) and gooseberry (R. grossularia, 

 GG) and the fertile colchiploids (BBGG) derived 

 from them bear weak nodal and internodal 

 spines when juvenile but are free from both 

 types of spine on their mature growth. 



Crosses between diploid gooseberry, as female, 

 and these alloploids failed, except for one cross 

 from which sterile diploids were produced. The 

 reciprocal crosses set few seeds most of which 

 failed to germinate, but three triploid (BGG) 

 and one approximately triploid plant were 

 obtained. The spine development of these 

 four plants was similar to that of self-bred 

 progenies from BBGG allotetraploids. 



Crosses of the triploid (BGG), as female, with 

 diploid gooseberries (GG) failed, or in one case 

 gave a single very weak distorted seedling. 

 Crosses between diploid gooseberries, as females, 

 and the triploid (BGG) set poorly. From over 

 2000 flowers pollinated, 62 plants were raised, 

 all of which closely resembled gooseberries in 

 their vegetative growth and all appeared to be 

 diploid. Root tip counts of eight of these 

 confirmed them to be 2/7 = 16. Some plants with 

 much reduced juvenile spines, and no mature 

 spines were present. These have not yet flowered 

 but they should show adequate fertility for 

 crossing with a range of gooseberry varieties 

 for the immediate selection of commercial 

 spineless types. 



13.6. Amphihaploids and Amphidiploids obtained 

 by Hybridization between Aurea Forms of 

 Nicotiana rustica L. and N. tabacum L. 

 Igor Bolsunov (Fiirstenfeld, Austria). 



Interspecific hybridization of N. rustica var. 

 aurea x N. Tabacum var. aurea is extremely 

 difficult. By operating crossings of different 

 cultivars and strains belonging to the aurea 



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