| Results Monosomic populations 7A, 3B, 3D, 4D and 7D registered significant reduction in plant height indicating the presence of dwarfing genes on these chromosomes of UP 301. Three monosomic populations viz., 7A, 3D and 7D were earlier than disomic population while monosomic population 5A was significantly late (Table 1). Eight monosomic populations showed significant deviation from the disomic mean. Of these, populations monosomic for 2B and 4B had longer spike length whereas populations 1B, 3A, 3B, 3D, 5B and 7D had shorter spike length as compared to disomic mean. With regard to number of tillers per plant, monosomic populations 3D and 4D showed fewer tillers than disome, while populations 2B, 7B and 6D had more tillers (Table 2). Discussion Genetic investigations of plant height in wheat are numerous but not conclusive. Plant height has been reported to be under polygenic control with innumerable modifiers (ALLAN and VOGEL, 1963 and ALLAN et al., 1968). Cytogenetic investigations have led to the location of genes affecting plant height on almost all chromosomes in one or the other variety. SEARS (1954) identified homoeologous groups I, II, III, IV and 6A possessing genes for plant height determination in Chinese Spring. Chromosomes 2A and 4D of Sonora-64 and chromosome 6D of Lerma Rojo have been identified carrying genes for dwarfness (JHA and SWAMINATHAN, 1969). But BHOWAL (1970) using Cadet monosomic series found 15 chromosomes (i.e, 1A, 1B, 5A, 5D, 6A, 7A and homoeologus groups II, III and IV) affecting plant height in Sonora-64. SADANANDA (1976) associated a gene for dwarfness with chromosome 3D of Sharbati Sonora. Thus all the genes for dwarfness identified in the present study, except the one on 7D, were identified in Sonora-64 which very well agrees with the evolution of UP 301 from the cross between Lerma Rojo and Sonora-64. However, the major dwarfing genes identified in Lerma Rojo and Sonora-64 (JHA and SWAMINATHAN, 1969) except the one on chromosome 4D, were not identified in the present combinations. There is no report of a gene on chromosome 7D affecting plant height. But other two members of the homoeologous group VII (namely 7A and 7B) have been known to carry genes affecting plant height (BHOWAL, 1970 ; HALLORAN, 1974 and SADANANDA, 1976). Thus the identification of a dwarfing gene on chromosome 7D of UP 301 again demonstrates the functional relationship between the members of the homoeologous group. |
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