Dynamic multiline population approach to resistance gene management.

ABSTRACT The dynamic multiline population breeding strategy integrates principles from the gene stacking and multiline approaches and allows application of the multiline strategy to cross-pollinated hybrid crops. 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 (1 from India and 1 from the United States). 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 A(4) 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 increased with each cycle, and frequencies averaged 18 to 38% in C1 to C4 hybrids, respectively, when inoculated with five single-uredinium isolates of Puccinia substriata var. indica. The hybrid populations and Tifleaf (TL)1 and TL2 were evaluated in three yield trials in 1998 to 1999. Disease-free forage dry matter yields did not differ among hybrids. Across trials, area under the disease progress curve (AUDPC) of TL1 and TL2 averaged 1,307, 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.