| I. Research Notes Aegilops speltoides promotion of homoeologous pairing in one Triticum aestivum x Agropyron intermedium derivative Yvonne CAUDERON and G. RYAN Station de Genetique et d'Amelioration des Plantes I.N.R.A.-78000-Versailles, France It will be reported here some preliminary data from a wider program designed to exploit the disease resistance of A. intermedium by transferring it into common wheat. In this part of the work, one ditelosomic addition line, TAF 2d (21II ABD +tII 7 Agi Alpha) previously obtained (GAUDERON et al. 1969), was used as female in crosses with a strain of Ae. speltoides (collected near ASHQUELON, Israel, and kindly provided by M. FELDMAN), with the aim of inducing homoeologous pairing between the Agropyron telosome, carrying a gene (s) for resistance to stem rust (Puccinia graminis tritici ERICKS. and HENN.) and its wheat homoeologous (7D). In successive backcrosses, several common wheat cvs (Vilmorin 27, Champlein, Capitole) ahd another ditelosomic addition line, TAF1 d, were used as male parents. Different features for successive generations are summarized in Table 1. Both the F1 and BC1 plants showed almost complete self sterility but gave some seeds when backcrossed to wheat. Seed setting was better on BC1 (4.28%) than in F1 (2.36%). The pollen sterility decreased from 95 to about 50%. However anthers were indehiscent in both cases. Germination time showed a considerable decrease, and viability was increased in BC1 seeds; chromosome numbers of the 8 BC1 plants were respectively: 2n=35 (4 plants), 36 (2 plants), 37 (1 plant), 37t (1 plant from a backcross to TAF1 d). These results are in agreement with those obtained by RILEY and KIMBER (1966) in one "standard" cross, T. aestivum cv Holdfast mono 5B x Aegilops bicornis (FORSK.) JAUB. So if pattern is the same for the next generations of this cross it may be assumed that the chances to recover, many meiotically regular 42-chromosome derivatives would be high. Chromosome pairing at M1 was studied for both the F1 and TAF2 d, and compared to other relevant data, (Table 2): a mean number of 24.23 associated chromosomes per cell was found. The level of pairing is high: 83.5% of the chromosomes are involved in associations against 99.8% in TAF2 d. More than 50% of the bivalents are closed and the mean number of xta/cell is 18.49 (0.64/chromosome). In Table 3 frequencies of different chromosome configurations per cell are recorded. An unique feature of this hybrid is the presence of the Agropyron telosome acting as a cytological marker and thus allowing to measure accurately specific pairing between Agropyron and Triticum homoeologous chromosomes. In this case, heteromorphic configurations were clearly identified in 15 cells and Agropyron telosome was included in 12II, 2III, and 1IV (CAUDERON et al. 1973) |
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