| Consequntly, these observations raise certain problems concerning the
genomic constitution of Ae. ventricosa. Firstly, if it is assumed that the bivalents observed are D associations, it may be concluded that no close homology exists between the D and MV genomes. However, considering that in the (T. aestivum x Ae. ventricosa) hybrid, the genetic system from chromosomes 5B and 3D must be effective and restrict pairing to homologous chromosomes, our observations do not weaken the KIHARA hypothesis. The D and MV genomes might be homeologous to the same degree as the A and B genomes. Only the cross of Ae. ventricosa with the mono 5B of T. aestivum, unsuccessfull until now, might confirm this. Secondly, the relationships between the D genomes of T. aestivum and Ae. ventricosa do not seem as close as in the case of T. aestivum and Aegilops squarrosa (RILEY and CHAPMAN 1960), or Aegilops cylindrica (ASPIAZU and LACADENA 1970). In fact, in the hybrid (T. aestivum x Ae. squarrosa) with A B D D genomes, RILEY and CHAPMAN observed usually 7II, mostly closed, while in the present investigation only 5II, mostly open, were formed. Likewise, in the F1 hybrids between T. aestivum and Ae. cylindrica with A B D D C genomes, studied by ASPIAZU and LACADENA, the meiotic pairing is rather complicated but the mean number of bivalents is 7.17 and there are some multivalents. It is of interest to note that SIDDIQUI and JONES (1967), in a study of (Aegilops ventricosa x Triticum dicoccum) x T. aestivum hybrids demonstrated also that the D genome of Ae. ventricosa is not completely homologous with the D genome of Ae. squarrosa or T. aestvum. However, the pairing observed by these authors is more incomplete than ours. In the present status, the transfer of genes from the MV genome of Ae. ventricosa to common wheat remains difficult by the normal processes of recombination, and the differenciation of the D genome of this species, as illustrated by some lack of pairing with the D genome of wheat, could make introgression into wheat more difficult than from Ae. squarrosa. Literature cited ASPIAZU A. and J. R. LACADENA 1970. Introduction of alien variation into wheat by gene recombination. Gen. Iberica 22: 121-127. KIHARA, H. 1949. Genomaualyse bei Triticum und Aegilops. IX systematischer Aufbau der Gattung Aegilops auf Genomanalytischer Grundlage. Cytologia 14: 135-144. KNOBLOCH, I. W. 1968. A check list of crosses in the Gramineae Michigan state University, E. LANSING, 170 pp. RILEY, R. and V. CHAPMAN 1960. The D genome of hexaploid wheat. W.I.S. 11: 18-19. SIDDIQUl, K. A. and J. K. JONES 1967. Cytogenetic studies of intergeneric hybrids involving Ae. ventricosa and species of Triticum. Can. Journ. of Gen. and Cyt. 9: 776-784. SIMONET, M. 1952. Sur l'etude meiotique des hybrides Ae. ventricosa avec des Triticum tetraploides et de leurs hybrides (Ae. ventricosa x T. durum) et (Ae. ventricosa x T. dicoccum) avec Triticum vulgare. Ann. Amel. Plantes 2: 175-188. (Received February 10, 1972) |
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