| Material and method The work was carried out with substitution lines Chinese Spring (Hope), Chinese Spring (Timstein), both made by Dr. E. R. SEARS (SEARS et al. 1957) and received from Dr. C. N. LAW. The controls were Chinese Spring-S (ex Dr. SEARS), Chinese Spring-R (ex. Prof. R. RILEY), Hope, Timstein and three standard varieties Cama, Manella and Orca. Furthermore T. dicoccum No. 42, T. durum Nos. 73, 74 and 75,. Bobin, Gabo and Marquis have been studied. Their origin is given in Table 2. About 50 seeds of each variety or line were placed in petri dishes and were soaked in tap water for 24 hours at room temperature. After this period the water was removed and 3 cm3 1 % aqueous solution of phenol was added. Sufiicient light was supplied together with room temperature. After four hours the intensity of the pigmentation of the grains was scored against that of the standard varieties: Cama=9 (blackish), Manella=6 (brownish) and Orca= 3 (pale brownish). Difference of one point may be caused by differences in genetic background. Identification The result of the work is presented in Table 1. Within both substitution lines the substitutions C.S. (2A-Hope), C.S. (2A-Timstein) and C.S. (2D-Timstein) are conspicuously different from the others and from Chinese Spring lines. These three substitutions have the same score as Hope and Timstein. From these observations it might be concluded that 2A and 2D carry a locus for Tc and that the allele of Tc on 2A of Hope and Timstein and 2D of Timstein has a stronger effect than the alleles of Tc of Chinese Spring. It is interesting to observe that these loci of Tc are on chromosomes of homeologous group 2. This may point to a possible locus on 2B. BHOWAL et al. (1969) reported that the locus of Tc is confined to the A-genome. Its presence on 2D of Timstein also points to the D-genome. A second conclusion is that apparently there is no dosis effect, because the pigmentation of Timstein (two strong alleles) is similar to C.S. (2A-Timstein) and C.S. (2D-Timstein). These substitutions have only one strong allele. Furthermore the strength of the allele on 2D (Hope) is similar to that of 2D (Chinese Spring). If there is a Tc-locus on 2B, the strength of this allele is equal for Hope, Timstein and Chinese Spring. Parentage of Hope and Timstein: It is interesting to check the pigmentation of the parents of Hope and Timstein because both varieties derive from a 6x x 4x cross. Gabo has been included because this variety is a sister variety of Timstein (KNOTT and ANDERSON 1956, WATSON and STEWART 1916, ZEVEN 1969). The parents are: Hope - Marquis x T. dicoccum Yaroslav Timstein - Bobin2 x T. durum Gaza. It is not known whether the tetraploid accessions mentioned in Table 2 are genotypically identical to the plant(s) used as the actual parents. The pigmentation scores of Yaroslav emmer is 7 and of Marquis 8. Hope may have derived its Tc-allele of 2A from either Marquis or Yaroslav. Timstein and Gabo score 8 and 9 respectively, while Bobin has 8 and Gaza-durums 3 or 4. The Tc-allele of 2A of Timstein probably comes from Bobin, while that of 2D must have come from this variety. It is very remarkable that Timstein has the same greyish veil as was observed for T. durum accessions (see also BLANCHARD, 1953 in Introduction). Although my Gazadurums have no such veil Timstein very probably derives this character from its durum parent. No such veil was observed in Gabo. |
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