| Results and discussion The inheritance of resistance in Kalyansona to race 21 was studied in crosses of PbC 591 monosomic lines with Kalyansona. Kalyansona produced 'O;' type of reaction to race 21, whereas PbC591 produced a highly susceptible reaction of '4' type to this race. The F2 data for race 21 showing the mode of segregation in different monosomic F2 families, including PbC591 (disome) x Kalyansona are presented in Table 1. A good fit to a ratio of 3R:1S was obtained in the F2 of the disomic cross (control) as well as in the 18 families of the monosomic F2's (F2 of monosomic 5B and 7D x Kalyansona could not be studied) . In the cross involving chromosome 5A, expected monogenic segregation was not obtained. 29 plants out of 30, from the progeny of monosomic 5A showed resistant type of reaction (Table 1) thereby suggesting that the dominant resistance gene, which governs resistance against race 21, is located on this chromosome of Kalyansona. A perusal of literature has revealed that so far no stem rust resistance gene has been located on chromosome 5A in any variety. It is thus proposed that the major dominant gene in variety Kalyansona, which governs resistance against race 21 of stem rust is an undescribed gene, or a possible translocation of a small segment into chromosome 5A from some other chromosome. Acknowledgement The work reported here forms a part of the PL480 project "Identification of genes conferring resistance to different rusts in wheat and the synthesis of hexaploids with new resistance genes." References SEARS, E.R. 1954. The aneuploids of common wheat. Univ. Missouri Res. Bull. 572, pp 58. STAKMAN, E.C., M.N., LEVINE and W.Q. LOEGERING 1944. Identification of physiologic races of Puccinia graminis tritici. U.S.D.A. Bur. Ent. Pl. Quar. E 617, pp. 22. STAKMAN, E.C., D.M. STEWART and W.Q. LOEGERING 1962. Identification of physiologic races of Puccinia graminis var. tritici. U.S.D.A. Agric. Res. Serv. No. E 617 (Rev), pp 53. SWAMINATHAN, M.S., V.L., CHOPRA B.C. JOSHI and D. SINGH 1968. Development of monosomic series in an Indian wheat and identification of nullisomic lines. Wheat Inf. Serv., 27: 19-20. |
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