Results of nucleus substitution in Aegilops and Triticum species by means of successive backcrosses with common wheat

Ivan PANAYOTOV and Kosta GOTSOV

Institute for Wheat and Sunflower near Tolbuhin, Bulgaria

KIHARA (1951) and FUKASAWA (1953) were the first to make studies on nucleo-cyto-plasmic interactions in subtribe Triticinae. Substitution backcrosses were held among many species from Triticum, Aegilops and Secale later, connected with the new found sources of cytoplasmic male sterility and selection of hybrid wheat (WILSON and Ross 1962, NETTEVICH and FEDOROVA 1966, MAAN and LUCKEN 1972, PANAYOTOV and GOTSOV 1973a, 1973b, Popov, PANAYOTOV and GOTSOV 1974a). This was the base on which a voluminous amount of studies were made in the last years not only of theoretical, but of extreme practical significance too.

In 1970a special program was assumed in our country for investigation of nucleocytoplasmic interactions in subtribe Triticinae with the following main tasks:

1. Discovering a new genetic system of cytoplasmic male sterility for selection of hybrid wheat. Fertility restorers in this system should be of high stability under various condition and male sterile and restoring lines to be controlled by one gene for the easier selection of R lines.

2. Finding new sources for pollen fertility - restoring forms with T. timopheevi cytoplasm, which is basically used for selection of hybrid wheat. T. timopheevi cytoplasm is a fairly reliable source or male sterility, but fertility restoration is unstable and the selection of R lines is very difficult.

3. Studying the effect of foreign cytoplasms (sterile and fertile) on the phenotype reactions of wheat including the morphological characters, productivity, cold and disease resistance, vegetation period, grain quality etc.

Searching the solution of the problems we are making a number of substitution backcrosses using different Aegilops and Triticum species and common wheat (Table 1, 2). As a result of the hybridization 9 new sources of cytoplasmic male sterility for common wheat were found and these are: Ae. triaristata, Ae. recta, Ae. columnaris, Ae. biuncialis, Ae. machrochaeta, Ae. triuncialis, Ae. comosa, Ae. veldreichii and Ae. aucheri. Some new restoring sources of T. timopheevi cytoplasm were discovered (Popov, PANAYOTOV, GOTSOV, 1974b): The rest of the Aegilops and Triticum species and the amphidiploid T. Haynaltricum (H. villosa x T. dicoccum - ZHUKOVSKYI, 1964) do not influence the generative organs and pollen fertility. Some of them influence partialy on the fertility (Table 2).

One of the main idea in our investigations is finding a cytoplasm of favourable influence on the productivity of wheat as well as other characters which are subject of breeding work. For that reason we are making substitution backcrosses with 5 or 6 varieties of wheat in order to obtain several alloplasmic lines of the same cytoplasm. Comparative study of these lines with their analogues posessing their own cytoplasm under field and laboratory conditions will be held in the coming 1-2 years. Except yields, disease and cold resistance, protein content, baking qualities etc. will be studied.

Our aim is to gradually obtain lines of common wheat with cytoplasms of all Aegilops and Triticum species and later with Agropyron, Secale and other relatives to these species.

Preliminary studies show that wheat is highly influenced by foreign cytoplasms. Side by side with the negative effect in some cases a positive influence is to be observed as growth stimulation and a shorter vegetation period. According to us, the cytoplasms which do not influence on wheat fertility are of particular importance.

Studies in the vast field of interactions and nucleo-cytoplasmic combinations are required intensive scientific work. In order to include the whole subtribe Triticinae (enlisting more than 200 species) in the research works a close coordination between the Institutes from differenct internationally cooperated countries should be established.

(Received December 25, 1974)