R. C. MCGINNIS and J. H. MELNYK
Cereal Breeding Laboratory, Winnipeg, Manitoba, Canada.
Genome studies in the genus Aegilops have now progressed to the point where most species have been given a genome formula. One of the few species for which the formula is incomplete is Ae. juvenalis (Thell.) Eig =(Ae. turcomanica Rosh.). In a recent chart prepared by Tanaka and Kihara (W.I.S. No. 1), Ae. juvenalis was given the genome formula D (M?)+?, although no published cytological evidence to support this proposal was presented. Recently, McGinnis (C.J.A.S. 1956) studied a number of interspecific and intergeneric F1 hybrids involving Ae. juvenalis and found that the D and Cu genomes probably constitute two of the three chromosome sets. In an attempt to determine the third genome the authors have crossed Ae. juvenalis with four members of the Sitopsis group and cytologically analysed the F1 hybrids. The pairing data from these hybrids are presented in the following table.
It can be seen from the table that the hybrids involving Ae. speltoides and Ae. Aucheri (S genome) gave a much higher pairing frequency than the hybrids involving Ae. sharnensis and Ae. longissima (Sl genome) indicating that the chromosomes of Ae. juvenalis are more homologous to the chromosomes of the S genome than of the Sl. The amount of pairing is indicative of the presence of the S genome in Ae.juvenalis. From the evidence available thus far, it seems probable that the genome formula for Ae. juvenalis is CuDS.