| Methods to improve the gene flow from rye and wheat
to Triticale1) R. DE V. PIENAAR Department of Genetics, University of Stellenbosch, Republic of South Africa Introduction The superior potential of the Triticale introductions from the Canadian-Mexican improvement program and from Salinas, Cal., was immediately apparent in the Eastern Orange Free State (JORDAAN et al. 1970) and also at Stellenbosch. They, however, lacked general adaptation and failed under adverse conditions. In 1970 it was therefore decided to start a Triticale improvement program at Stellenbosch. The history and potentials of Triticale have been adequartely reviewed by JENKINS(196). Crossability with rye Eighty-two of the better durum introductions and other tetraploid wheats were screened for crossability with the seven best local and introduced rye cultivars. The results summarized in Table 1 were similar to those of KROWLOW (1970). Only 0.6% of the cross-pollinated durum florets yielded viable kernels, but by means of ROMMEL'S (1958) embryo-culture technique the yield of seedlings was improved to 1.2% (Table 2). KNOBLOCH (1968) cited various successful crosses between Triticum turgidum ssp. carthlicum and rye. Seventeen different crosses between this subspecies and rye were therefore made. Two introductions of ssp. carthlicum v. stramineum2) hybridized readily with the rye cultivars and yielded more than 23 viable kernels per 100 cross-pollinated florets (Table 1). It can, therefore, serve as a very effective bridge for transferring rye genes to the secondary Triticale. The other varieties of carthlicum, notably rubiginosum, were incompatible with rye. A carthlium hexaploid strain from Sweden hybridized readily with rye to yield very fertile octaploids after colchicine treatment, and were tetraploid. Ten high-quality T. aestivum ssp. vulgare cultivars were crossed with 7 rye cultivars in order to transfer genes for better adaptation and quality via new primary Triticales to the introduced secondary Triticales. An average of 2.4% of the cross-pollinated florets yielded viable kernels (Table 1). Embryo culture did not significantly improve the yield of seedlings (Table 2). According to RILEY and CHAPMAN (1967) the wheat cultivars from the East tend to hybridized more readily with rye. Since KNOBLOCH (1968) also cited various successful T. aestivum ssp.sphaerococcum x S.cereale crosses, it was decided to cross 4 sphaerococcum introductions with 6 rye cultivars. All sphaerococcum varieties, including echinatum, rotundatum and rubiginosum, hybridized with readily rye-on the average 20.7% of florets yielded viable kernels (Table 1). The sphaerococcum x vulgare F1 hybrids when crossed with rye likewise gave a good set of viable kernels (Table 1). T. aestivum ssp. sphaerococcum must, therefore, be considered an efficient bridge for transferring rye genes via new primary octaploid Triticales to the secondary Triticales. SISODIA and MCGINNIS (1970b) recommended that pentaploid wheat hybrids, resulting from Dinkel x Emmer crosses, be hybridized with rye. Our sphaerococcum x durum F1 hybrids, when crossed with 4 rye cultivars, did not set any kernels (Table 1). |
| 1) Copied from the Proceedings of the 4th Wheat Genetics Symposium by
the kind permission of the Editors and Organizing Committee. 2) These strains were found to be hexaploid. |
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