| Inheritance of dwarfness in Olesen's Dwarf ( T.
aestivum L.) S. C. ANAND and H. S. AULAKH Punjab Agricultural University, Ludhiana, India Introduction Dwarf wheat varieties are responsible for a major break through in wheat production in many parts of the world. This was because of their response to heavy doses of fertilization without lodging. The dwarfness in these varieties was derived from the Japanese Norin-10 source. It is controlled by two major independent recessive genes and several modifying factors (BRIGGLE and VOGEL 1968). Since the dwarfness in Norin-10 source is recessive, a large population is required to be grown to select plants with several dwarfing genes. Recently the authors came across another short variety Olesen's Dwarf. This variety was picked from the wheat material grown in Rhodesia and is of unknown genetic origin1). The inheritance of dwarfness in this strain has not yet been reported. The present paper deals with the mode of inheritance of dwarfness in Olesen's Dwarf as it is different from other sources of dwarfness in wheat. Material and method Olesen's Dwarf wheat strain was crossed with the tall indigenous variety C 306. The F1 was back crossed with both the parents. The two parents, the F1, the two back crosses and the F2 plants were grown in a compact block in 1969-70 at the Punjab Agricultural University, Ludhiana. The plants were spaced 15 cm apart with 42 cm distance between rows. Any gap which occurred between the plants was filled. The height of the plants was measured from the ground level to the tip of the spike (excluding awns) at maturity. Results and discussion The means and variances of parents and other generations are given in Table 1 and their frequency distribution is represented in Table 2 and Fig. 1. The tall parent C 306 had a mean height of 132.2 cm and the Olesen's Dwarf was only 50.6 cm high. The height of F1 plants was 81.8 cm which was lower than the mean of the parents, indicating partial dominance for dwarfness. The average height of the F2 plants was 86.9 cm which further confirmed that the dominance for dwarfness was incomplete and some other gene action was also involved. The frequency distribution of the F2 plants (Table 2 and Fig.1) showed bimodal distribution with a larger number of plants at 76 cm and fewer plant in between. This indicates the operation of two different genes controlling the expression of plant height in this cross. In the back cross generation, the plants segregated into dwarf or tall ones with approximately 5% overlapping only. This suggests that only few genes are involved. The frequency distribution in the F2 and back cross generations further indicates that there are two major genes controlling height in Olesen's Dwarf. One of the genes has greater effect on plant height than the other. The plant height in the F2 and back cross generations varied according to the following assumptions given in Table 3. Dwarfness is partially dominant over tallness. The two genes have cumulative effect. If only one of them is present, the plant is semi-tall. The heterozygotes of both the genes are medium in height. The homozygotes are shorter than the heterozygotes. It is very likely that there are so me modifying factors in addition to the two major factors controlling height. The authors have not come across in the literature such inheritance in wheat. Summary Olesen's Dwarf wheat variety was crossed with the tall variety C 306. The segregation of height in the F2 and back cross generations indicated the existence of two major genes controlling this chaiacter. The dwarfness is partially dominant and the two genes have cumulative effect. This variety has a different source of dwarfness and has not been reported so far. Literature cited BRIGGLE, L. W. and O. A. VOGEL 1968. Breeding short stature, disease resistant wheats in the United States. Euphytica 17 (1968 Suppl. 1): 107-130. (Received November 16, 1970) |
| 1) Personal communication, Dr. R.G. ANDERSON, The Rockefeller Foundation, New Delhi., India. |