| Analysis of plant height promotion by chromosome 6D
in common wheat D. SINGH, B.C. JOSHI and K. BATRA Division of Genetics, Indian Agricultural Research Institute New Delhi, India. Monosomic lines in the wheat variety Chinese Spring, developed by SEARS (1954), were used for producing aneuploid lines in an Indian wheat variety Pb. C591 (SWAMINATHAN et al. 1968). SINGH et al. (1970) reported the involvement of chromosome 6D of var. Pb. C591 for height character, where they observed that monosomic (2n=41) pants were about 30 cm shorter than disomic (2n=42) plants. Nullisomics in this line were still shorter (height of nullisomic 6D was observed to be about 70 cm). It was suggested that genes located on chromosome 6D promote height in variety Pb. C591. Effects were markedly noticeable even if one of the homologous chromosomes was missing. Height reduction in monosomic (2n=41) line 6D of var. Pb. C591 was further investigated to ascertain the mode of reducton in height. Data were taken on the internode number, internode length and plant height on monosomic (2n=41) and disomic (2n=42) plants separately. Mean values were calculated and the data were subjected to statistical analysis to test the differences between means of internodes, internode length and total length of the plants of monosomics and disomics. The internode distribution patterns of disomic (2n=42) and monosomic plants as seen from the Table 1, show that in disomic as well as in monosomic plants the basal internode is smallest in length and the successive internode have progressively increased lengths. The last internode that supports the spike is the longest and accounts for about 40% of the total culm length. Reduction in height in monosomic plants has been observed to be due to the shortening of all the internodes to a variable degree. The reduction in the absolute length of all the internodes was found in an order of 3.96 cm (16.90% of the total reduction) in Ist internode, 3.37 cm (14.38%) in IInd internode, 2.11 cm (9.00%) in IIIrd internode, 3.23 cm (13.78%) in IVth internode, 4.37 cm (18.65%) in Vth internode and 6.51 cm (27.78%) in the VIth internode. It is therefore, concluded that the gene(s) located on chromosome 6D of variety Pb. C591 which possesses genes for promoting the total plant height in this variety, promotes height by way of increasing the length of all the internodes with variable degree. It is likely that this gene product utilizs the GA like substances or the gene product itself functions like GA for promoting the plant height in this variety. Literature Cited SEARS, E.R. 1954. The aneuploids of common wheat. Research Bull. 572, Univ. of Missouri. pp. 1-59. SINGH, D., B.C. JOSHI & R.N. SAWHNEY 1970. Location of genes for height and root development on specific chromosomes of Pb. C591. EWAC Newsletter (Ed. C.N.Law), 3 : 63. SWAMINATHAN, M.S., V.L. CHOPRA, B.C. JOSHI & D. SINGH 1968. Development of monosomic series in an Indian wheat and isolation of nullisomic lines. Wheat Inf. Serv., 27 : 19-20. |