Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2000
Publication Date: 3/1/2001
Citation: Wilson, J.P., Gates, R.N., Panwar, M.S. 2001. Dynamic multiline population approach to resistance gene management. Phytopathology 91:255-260.
Interpretive Summary: Irresponsible use of resistance genes will result in an erosion of available, effective resistance. Pest populations often possess remarkable genetic plasticity which allows the pests to overcome new resistances in time. Whether new genes for resistance to diseases or pests are derived from germplasm collections or developed by novel genetic engineering techniques, it is imperative that new strategies for maintaining the effectiveness of the genes are developed. The gene stacking or the multiline approaches are improvements to using single resistance genes however, those approaches have weaknesses inherent in their application. A new strategy called the dynamic multiline population approach combines the strengths of the gene stacking and multiline strategies. The approach confronts a variable and dynamic pathogen population with a variable and dynamic host population. Theoretical evidence indicates that the resulting genetic complexity resulting from the method is unmatched by other breedin strategies. Experimental evidence indicates that it is a viable approach to breeding for disease resistance in hybrid crops. The method is more likely to maintain the effectiveness of resistance genes, and should be explored as a potential method of maintaining the effectiveness of Bt-toxin genes.
Technical Abstract: The dynamic multiline population breeding strategy integrates principles from the gene-stacking and multiline approaches. Experiments were conducted to evaluate the effectiveness of the breeding approach. Backcross derivatives of pearl millet Tift 23DB were developed with rust resistance from 18 Burkina Faso landraces, 3 Pennisetum glaucum subsp. monodii accessions, and 2 elite inbreds (one from India and one from the U.S.). Four cycles of open pollination were made, the last two in the field in rust epidemics. Cytoplasmic male-sterile (CMS) counterparts of the populations in the A4 cytoplasm were included and advanced simultaneously with the B population. Hybrids with Tift 383 were produced on CMS cycles 1 (C1) through C4. Frequency of hybrid seedlings with resistance to single-ur um isolates of Puccinia substriata var. indica averaged 18 to 38% in C1 and C4 hybrids, respectively. The hybrid populations and Tifleaf 1 and Tifleaf 2 were evaluated in 3 yield trials in 1998-99. Disease-free forage dry matter yields did not differ. Across trials, area under the disease progress curve (AUDPC) of TL1 and TL2 averaged 1307, C1 and C2 averaged 914, and C3 and C4 averaged 604. Final severities of TL1 and TL2 averaged 67%, C1 and C2 averaged 47%, and C3 and C4 averaged 30%. When analyzed by regression analysis, AUDPC was reduced 12.2%, final rust severity was reduced 13.3%, and digestible biomass was increased 4.1% per cycle.