New gene combinations conferring resistance to the bacterial blight disease of cotton
2004
Abdalla, K.M.,University of Bakht er Ruda, Ed Duiem (Sudan). Faculty of Agriculture and Natural Resources | Mustafa, A.M.,Agricultural Research Corporation, Wad Medani (Sudan). Cotton Breeding Program | Ibrahim, A.S.,University of Gezira, Wad Medani (Sudan). Faculty of Agricultural Sciences
F2 plants comprising different gene combinations were evaluated for cotton bacterial blight resistance in the field of the Gezira Research Station and the greenhouse of the Plant Pathology Centre of the University of Gezira, Neshashiba, Wad Medani, during the autumn of 2002. Results generally showed significant differences between different gene combinations in resistance to the new race of the bacterium Xanthomonas campestris pv. malvacearum. Leaf disease grades ranged from 4 to 6. Most of the plants fell into grade 5. Genotype 12, with expected gene combination of (B2B3B6B7B9B12), expressed the hight level of resistance with a mean disease grade of 4, while genotypes 7, 11 and 15 showed the lowest level of resistance with a mean disease grade of 6. The results indicated the importance of genetic background B2B3B7 in improving resistance to both the old and the new races when one of the following major genes B4, B6, B8, and B12 is incorporated. In such background, resistance level improves as the number of genes increases. Therefore, the commerical resistant cultivars having B2B6 genetic backgound to the old race of the bacterium can be replaced by the genetic background involving B2B3B7 in addition to one of the four major genes mentioned above in order to protect the cotton crop. Genotypes 5, 6, 12, and 19 were recommended for further improvement as they expressed relatively high level of resistance to the pathogen
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