| Cytology and fertility of hybrids between Mono V (5
B) Chinese Spring and Secale cereale L. and Aegilops columnaris
ZHUK. Juan-Ramon LACADENA Department of Cytogenetics and Plant Breeding Estacion Experimental de Aula Dei, Zaragoza, Spain In order to utilize the chromosome V (5 B) of T. aestivum as a mean to introduce into wheat the alien variation from its related species by meiotic recombination, crosses between a mono 5 B plant of Chinese Spring and rye (2n=14) and Ae. columnaris ZHUK. (2n=28) were made. Results are shown in Table 1. The chromosome numbers of the progenies indicate the different transmission rates of chromosome 5 B through the female gamete in both crosses: 17.6 % and 50 % in crosses involving Secale cereale and Ae. columnaris respectively. According to meiotic observations, the plant with 2n=29 chromosomes, found among the progeny of Mono 5 B Chinese Spring x rye, originated as a consequence of non-disjunction in a chromosome. Another cytological abnormality was found among the mono 5 B C. S. x Ae. columnaris progeny : a 35-chromosome hybrid had a very long chromosome in the somatic cells. Further meiotic observations showed the occurrence of inter-arm pairing, indicating that the long chromosome is an isochromosome. Hybrid fertility was studied in normal conditions and after being treated with an 0.15 % aqueous colchicine solution during 48 or 72 hours using Bell's technique. Results are shown in Table 2. Percentages of fertility were calculated by considering each spikelet to have two florets. On comparing the results obtained with and without colchicine treatment, clear differences in fertility of the hybrids become apparent, probably due to the production of chimaeras in the individuals treated with the drug. Different behaviour as to fertility of the hybrids deficient or not for chromosome 5 B has been also observed, the lowest percentages of fertility corresponding to the deficient ones. Likewise, results seem to indicate a greater affinity between T. aestivum and Ae. columnaris than between T. aestivum and Secale cereale. The external appearance of hybrid seeds is fairly good, specially that of Ae. columnaris hybrids. (Received June 29, 1966) |