Cytogenetic work has shown that the tetraploid wheats, Triticum turgidum and T. timopheevii, and the hexaploid wheat T. aestivum have one pair of A genomes, whereas hexaploid T. zhukovskyi has two. Variation in 16 repeated nucleotide sequences was used to identify sources of the A genomes. The A genomes of T. turgidum, T. timopheevii, and T. aestivum were shown to be contributed by T. urartu. Little divergence in the repeated nucleotide sequences was detected in the A genomes of these species from the genome of T. urartu. In T. zhukovskyi one A genome was contributed by T. urartu and the other was contributed by T. monococcum. It is concluded that T. zhukovskyi originated from hybridization of T. timopheevii with T. monococcum. The repeated nucleotide sequence profiles in the A genomes of T. zhukovskyi showed reduced correspondence with those in the genomes of both ancestral species, T. urartu and T. monococcum. This differentiation is attributed to heterogenetic chromosome pairing and segregation among chromosomes of the two A genomes in T. zhukovskyi.

The origin and genomic constitution of the tetraploid perennial species Dasypyrum hordeaceum (2n = 4x = 28) and its phylogenetic relationships with the annual diploid Dasypyrum villosum (2n = 2x = 14) have been investigated by comparing the two genomes using different methods. There is no apparent homology between the conventional or Giemsa C-banded karyotypes of the two Dasypyrum species, nor can the karyotype of D. hordeaceum be split up into two similar sets. Polymorphism within several chromosome pairs was observed in both karyotypes. Cytophotometric determinations of the Feulgen-DNA absorptions showed that the genome size of D. hordeaceum was twice as large as that of D. villosum. Both the cross D. villosum x D. hordeaceum (crossability rate 12.1%) and the reciprocal cross (crossability rate 50.7%) produced plump seeds. Only those from the former cross germinated, producing sterile plants with a phenotype that was intermediate between those of the parents. In these hybrids (2n = 21), an average of 13.77 chromosomes per cell paired at meiotic metaphase I. Trivalents were only rarely observed. Through dot-blot hybridizations, a highly repeated DNA sequence of D. villosum was found not to be represented in the genome of D. hordeaceum. By contrast, very similar restriction patterns were observed when a low-repeated DNA sequence or different single-copy sequences of D. villosum or two sequences in the plastidial DNA of rice were hybridized to Southern blots of the genomic DNAs of the two Dasypyrum species digested with different restriction endonucleases. By analyzing glutamic-oxaloacetic-transaminase, superoxide dismutase, alcohol dehydrogenase, and esterase isozyme systems, it was shown that both Dasypyrum species shared the same phenotypes, which differed from those found in hexaploid wheat. In situ hybridizations using DNA sequences encoding gliadins showed that these genes were located close to the centromere of three pairs of D. villosum chromosomes and that they had the same locations in six pairs of D. hordeaceum chromosomes. We conclude that the autoploid origin of D. hordeaceum from D. villosum, which cannot be defended on the basis of chromosomal traits, is suggested by the other findings obtained by comparing the two genomes. Key words : Dasypyrum hordeaceum, Dasypyrum villosum, phylogenetic relationships.

Genes coding for glutenin-like subunits and for several prolamin subunits with electrophoretic mobilities (lactate-PAGE) corresponding to those of omega- and gamma-gliadins of wheat were located inDasypyrum villosum chromosome1V. Genes controlling four gliadinlike subunits with electrophoretic mobilities corresponding to those of alpha- and gamma-gliadins were located on the short arm of chromosome6V and on the long arm of chromosome4V. N-terminal amino acid sequences of these four components were also determined and homology with alpha-type gliadins was demonstrated. The presence of genes coding for glutenin- and gliadin-like subunits on chromosomes1V and6V demonstrates homoeology between theD. villosum chromosomes1V and6V and the chromosomes of homoeologous groups 1 and 6 in wheat. It is likely that the additional locusGli-V3 on chromosome4V originated by translocation from theGli-V2 locus.

Six monosomic addition lines were produced in which different Dasypyrum villosum (L.) Candargy chromosomes were added to the chromosome complement of Triticum durum Desf. cv. 'Creso'. Each added alien chromosome was found to have a specific effect on plant morphology and fertility. Transmission rate varied widely (from 7.5 to 27.7%) among the six univalent chromosomes. Different monotelosomic addition plants derived by a relatively high frequency of chromosome misdivision were isolated. The addition lines should be useful for studying Dasypyrum chromosome homoeology and the introduction of alien variation into durum and common wheats.

A large collection of melon (Cucumis melo L.) germplasm has been established at the Section of Genetics and Plant Breeding, Bari University (Italy). In the present work, data regarding the variation of 20 bio-agronomical traits recorded on entries and landraces collected in Albania and Apulia region (Southern Italy) are reported. The main objective of the study was to assess and describe, by means of univariate and multivariate analyses, the genetic diversity in the collection composed by genotypes classified in the Inodorus and Cantalupensis groups. The results obtained showed a large variation for all the traits examined. Furthermore, it was possible to identify valuable genotypes for future breeding programmes aimed at improving melon traits, particularly for the Inodorus group, which is an important crop in many Southern Italian sites. Genotypes of interest were especially selected for earliness and lateness, fruit shape, soluble solids content, storage time and fruit firmness.