Euphytica 29 (1980) 705-713 PRODUCTIVITY OF SINGLE-CULM AND MULTI-CULM PLANTS OF WINTER WHEAT CULTIVARS IN FIELD CONDITIONS S. BOROJEVIC and MARIJA KRALJEVIC-BALALIC Institute for Field and Vegetable Crops, Faculty of Agriculture, the University 2 1000 Novi Sad, Yugoslavia Received 3 January 1980 INDEX WORDS Triticum aesrivum ssp. vulgare, bread wheat, single- and multi-culm productivity, optimal density. SUMMARY The productivity of l-, 2-, and 3-culm plants of three winter wheat cultivars was studied under field conditions in three spatial arrangements. The treatments with 2- and 3-culm plants produced higher grain yield per unit area than the treatments with 1-culm plants. This was explained as the result of a higher interplant than intraplant competition. It seems that the interplant competition is lower with dwarf than with tall cultivars. The secondary culms may be as productive as the primary ones if there are only a few of them per plant and if they develop before the beginning of winter. If the tillering takes place mainly in spring, the differences in productivity between the primary and secondary culms are considerable. Under conditions of dry autumns and late planting not the tillering must be taken as the main factor which regulates the optimal number of spikes/m*, but the high planting rate. INTRODUCTION At the 3rd International Wheat Genetics Symposium in Australia in 1968 C. M. Donald reported on the design of a wheat ideotype and the laboratory studies which showed that the single-culm plants of the spring cultivar Pitic gave significantly higher grain yields per spike than the 2-culm and 3-culm plants of the same variety (DONALD, 1968a, 1968b). We decided to check his findings in the field with winter wheat cultivars. We also wished to confirm our earlier finding (BOROJEVIC et al., 1961) that high wheat yields are secured by the spikes on the main stem and that the tillering only com- pensates for unpredicted losses. MATERIALSANDMETHODS The method of DONALD (1968a) was followed as closely as possible in the field. The distance between rows in all treatments was 20 cm. The treatments were: High density : I. Distance within the row: 1 cm, leaving only one spike per plant, i.e. making 1-culm plants. II. Distance within the row: 2 cm, leaving two spikes per plant (2-culm plants). III. Distance within the row: 3 cm, leaving three spikes per plant (3-culm plants). Each spike thus had an area of 1 cm x 20 cm, which made theoretically 500 spikes/m’ (Fig. 1). 705