Wednesday, November 15, 2006

Identification of Aegilops tauschii Coss. Accessions Resistant to Rusts, Karnal Bunt and Cereal Cyst Nematode and their Utilization for Development of Synthetic Hexaploids.

Sunish Sehgal1, I. Sharma2, Damanjeet Kaur2, K. Singh2, and Navtej S. Bains2. (1) Punjab Agricultural University, Ludhiana, 141004, India, (2) Punjab Agricultural University, Lab No 22, Wheat Section, Department of Plant Breeding Genetics and Biotechnology, Ludhiana, 141004, India

Aegilops tauschii, a diploid progenitor (D-genome) of hexaploid wheat is important source of resistance to diseases and pests. A collection of 250 accessions of Ae. tauschii was screened for resistance to stripe rust, leaf rust, Karnal bunt and cereal cyst nematode under artificially inoculated conditions for 3 consecutive years. Screening against rust involved recording of disease intensity against a mixture of races prevalent in North India Eleven accessions were resistant to both stripe rust and leaf rust, three of them being completely free of disease symptoms. Against stripe rust, 16 accessions were resistant and 102 accessions were moderately resistant. A larger proportion of  Ae. tauschii accessions(117) was resistant to leaf rust with another 73 accessions showing moderate resistance.  A subset of Ae. tauschii collection (132 accessions) was screened for resistance to Karnal bunt using a mixture of 12 isolates endemic to North India. Nine accessions were free from KB when screened for 2 years. One hundred ninety eight accessions were screened for resistance to cereal cyst nematode. Four accessions were highly resistant, 7 accessions were resistant and 14 others were moderately resistant to cereal cyst nematode. To mobilize these valuable genes to wheat, 100 synthetic hexaploid wheats were developed by crossing Triticum durum with Ae. tauschii. One synthetic wheat was free from both rusts and Karnal bunt and 4 others were resistant to leaf rust and Karnal bunt. Most of the synthetic wheats were moderately resistant to stripe rust and highly resistant to leaf rust.