1. In the present report, the external characteristics, the number of somatic chromosomes and meiosis in PMC's of trigeneric triple F₁ hybrids raised from Triticum vulgare × Haynaldia villosa F₁×Secale cereale (TvCHRF₁) were described.
2. The trigeneric hybridization was more successful when T. vulgare × H. villosa F₁ was crossed as the female to S. cereale than when the cross was made in the other direction. This situation is the same as that found in Emmer wheat-Haynaldia-Secale hybridization.
3. 55 grains of trigeneric triple F₁ were sown, of which 15 grains germinated and 4 mature plants were obtained. The percentage of the number of mature triple F₁ plants to the number of pollinated florets was 0.137.
4. The number of somatic chromosomes varied from 31 to 36 among 10 plants of TvCHRF₁ (Table 1). The somatic chromosome number of eu-trigeneric triple F₁ hybrids was 35. This number is the same as the sum of the gametic chromosome numbers of the three parents, T. vulgare (21), H. villosa (7) and S. cereale (7). In these trigeneric triple F₁'s, 7 out of the 31_??_36 somatic chromosomes were introduced from S. cereale (_??_) and the remaining 24-29 from TvCHF₁ (_??_, 2n=28).
5. The triple F₁ hybrids, whose meiosis in PMC's was studied, were classified into the following 3 groups according to their somatic chromosome numbers:
(a) A group having 2n=35 chromosomes; 6 individuals were included in this group, of which only one matured. At the MI of meiosis 1_??_7 bivalents were observed (Figs. 6_??_13). The frequency of the bivalents in PMC's is shown in Table 3. Almost all the bivalents consisted of 2 elements of equal size, but in a few cases heteromorphic pairs were observed. 4_II appeared to be the mode (Table 3). Most of the bivalents were stick-shaped, but some of them were ring-shaped. Trivalents of V-shape were observed in addition to bivalents at MI (75 trivalents in 1, 000 PMC's) and tetravalents of N-shape were observed only in 2 cases among 1, 000 PMC's.
(b) A group having 2n=31 chromosomes; 2 individuals were included in this group. At the MI of meiosis of PMC's 0_??_5 and 0_??_6 bivalents were observed with the mode of 0_II (Figs. 14_??_19). The frequency of bivalents is shown in Table 3. Stick-shaped bivalents were commonly observed in both individuals, while ring-shaped ones were only rarely found in No. 1 individual (9 ring-shaped among 621 bivalents). Heteromorphic bivalents were also observed only in a few cases. Trivalents of V-shape were observed in rare occasions, but no tetravalents were found.
(c) A group having 2n=32 chromosomes; only 1 individual was included in this group. At the MI of meiosis of PMC's 0_??_5 bivalents were observed (Figs. 20_??_24). Frequency of the bivalents is shown in Table 3, in which 0_II was the mode. Almost all the bivalents were stick-shaped. Trivalents of V-shape were rarely observed, but no tetravalents were found.
6. Although a few bivalents might have been consisting of chromosomes of R or V genomes, most of the bivalents observed in the triple F₁'s seem to have been formed by autosyndesis between the chromosomes of AB or ABD genomes of T. vulgare used as the grandparent, according to the results of cytological investigations in F₁'s between Triticum and Haynaldia by Kostoff (1937), between Haynaldia and Secale by Nakajima (1951, '59), between Triticum and Secale by Nakajima (1952, '54, '56, '57, '58, '60) and between Aegilops squarrosa and Haynaldia villosa by Zennyozi (1961).