Transfer of rye chromosomes carrying Karnal bunt resistance to Triticum aestivum cv. WL711.
Renu Datta, H.S. Dhaliwal, Sanjeev Gupta and D.S.
Biotechnology Centre, Punjab Agricultural University, Ludhiana- 141 004, Punjab, India.
The disomic addition lines of chromosomes 4R and 6R of Secale cereale cv. Imperial rye in Triticum aestivum cv. Chinese Spring were completely free from Karnal bunt disease of wheat under artificial inoculation. The rye chromosomes 4R and 6R were transferred into a high yielding but Karnal bunt susceptible bread wheat variety WL711 through backcrossing. The monosomic and disomic addition lines of 4R and 6R in WL711 also maintained resistance against a particular isolate of Karnal bunt during backcrossing whereas their euploid segregants were as susceptible as the recurrent parent. The 4R and 6R addition lines, however, were susceptible to a new isolate of Neovossia indica virulent on triticale. The work to substitute the rye chromosomes for their B and D wheat genome homoeologues is in progress.
Karnal bunt caused by Neovossia indica (Mitra) Mundkar (Syn. Tilletia indica ) is a very serious disease of wheat. It was first reported in Karnal, a district in northern India, in 1930 (Mitra, 1931). It appears in epidemic proportion in the north-western states of India, Pakistan and Mexico (Munjal 1975; Goel et al. 1977). Karnal bunt not only causes appreciable losses in yield but also renders grains unfit for human consumption (Sekhon et al. 1981). Aujla et al. (1982) developed a technique for artificial epiphytotic of Karnal bunt which has been used for screening wheat and related species for resistance to the disease. Only a very small proportion of durum and bread wheat lines has been found to be resistant to Karnal bunt under artificial inoculations (Gill 1987).
However, the search for genetic sources of resistance to Karnal bunt in related species of wild wheat, Aegilops and cultivars of rye under artificial inoculation have met with some success. Dhaliwal et al. 1986; Warham et al. 1986; Pannu et al. 1994). Chromosomes 6 and 7 of Secale cereale cv. Imperial rye as wheat~rye addition lines in Chinese Spring were found to carry resistance to Karnal bunt under artificial inoculations (Dhaliwal et al. 1987).
The Chinese Spring being slightly late often escapes Kamal bunt incidence even under artificial conditions. The maintenance of resistance of the rye chromosomes in a high yielding but Karnal bunt susceptible commercial wheat variety needs to be investigated before efforts could be made to transfer the resistance from the rye chromosomes.
The present investigation was undertaken to transfer the rye chromosomes carrying gene(s) for resistance to Karnal bunt in WL711, a high yielding Karnal bunt susceptible variety through backcrossing.