| I. Research Notes Use of Ae. speltoides and nulli 5B tetra 5D "Chinese Spring" for inducing homoeologous recombinations in a wheat-Aegilops addition line Francoise DOSBA1) I.N.R.A., station d'Amelioration des Plantes Centre de Recherches de Rennes, Bp no23-35650, LeRheu, France. Since KIMBER (1974) described a range of variation in Ae. speltoides and divided it into low, intermediate, high and super high pairing groups, it appears very important to select high or super high pairing Aegilops for inducing homoeologous recombinations. Thus, if the absence of recombination allows the obtention and the study of addition lines, such as wheat-Aegilops ventricosa lines (DOSBA et al, 1978), the induction of homoeologous recombination is necessary to transfer the alien genetic information into wheat. The study reported in this paper was designed to evaluate the pairing group of different accessions of Ae. speltoides and to compare the efficiency of Ae. speltoides or "Chinese Spring" nulli 5B tetra 5D in inducing homoeologous recombinations into a wheat Aegilops addition line. Four accessions of Ae. speltoides (included Ae. speltoides no 25 supplied by Dr G. KIMBER and considered as super high pairing) were crossed with T. aestivum cv Moisson. In these hybrids, the mean meiotic pairing reveals significant differences between Aegilops speltoides no 25 and the three others (Table 1 and 2). Particularly, the univalent mean, is lower in the hybrids with Ae. speltoides no 25 than with the other ones; and it appears that the decrease in univalent number is compensated by the formation of multivalents. So, in the purpose of inducing homoeologous recombinations between the Mv chromosome of the addition line wheat Ae. ventricosa no 255 and the wheat chromosomes, we tried to cross this line with Ae. speltoides no 5 and no 25, or with "Chinese Spring" nulli 5B tetra 5D. Concerning Ae. speltoides, only the crosses with Ae. speltoides no 5 succeeded. The analysis of the F1's meiotic pairing shows more associations than expected (19"+1"'+2') for the crosses 255 x nulli 5B tetra 5D and less for the cross 255 x Ae. speltoides no 5 (Table 3). In the first case, the numerous multivalents observed are probably due to the presence of two reciprocal translocations (5B-7B,1B-6B) which differenciate "Chinese Spring" from the recipient parent of the addition line, the french variety "Moisson" (BOURGEOIS et al, 1978). One trivalent may be originated from trisomy 5D, the other from 7B/5B-5B/7B-7B and one quadrivalent from 1B-1B/6B-6B-6B/1B. However, it should be noticed 14.65% of cells do not present any univalent. So recombinations could occur between the added chromosome and those of wheat. Meiotic behaviour of the F1 hybrid 255 x Ae. speltoides no 5 compared to "Moisson" x Ae. speltoides no 5 one's shows a decrease in the number of chiasmata per cell. The lack of pairing may be due to the fact that the accession no 5 was not fixed for inducing homeologous pairing. The progeny of these hybrids died before maturity except for the self-pollinated generation issued from 255 x "Chinese Spring" nulli 5B tetra 5D. The analysis of some plants at the F3 generation reveals an heterogeneity in the meiotic behaviour as well for univalents as for multivalents. The line v 255 possesses no specific marker on its added chromosome. So it is difficult to assess the level of recombination between this chromosome and the wheat chromosomes. But occurrence of recombination can be assumed from the F1 analysis. Literature Cited KIMBER G., 1974. The relationships of the S genome diploids to polyploid wheats. Wheat Inf. Serv., 38, 1-5. DOSBA F., DOUSSINAULT G., and RIVOAL R., 1978. Extraction identification and utilization of the addition lines T. aestivum x Ae. ventricosa. Proc. 5th Int. Wheat Genetics Symposium New Delhi 332-337. BOURGEOIS F., DOSBA F., and DOUAIRE G., 1978. Analyse et identification des translocations reciproques presentes chez le geniteur VPM et les varietes "Marne", "Moisson" et "Roazon" Ann. Amelior. Plantes, 28, 4, 411-429. KRAMER C.Y., 1956. Extension of multiple range tests to group means with unequal numbers of replications. Biometrics 307-310. |
| 1) With the technical assistance of Anne-Marie TANGUY. |