Quantitative and molecular analyses of agronomic traits in cassava (Manihot esculenta Crantz)

[摘要] English: Diallel crosses were evaluated in three agro-ecologies in Colombia and parents and families selected for conventional and molecular breeding trials conducted during the study. At the same time an inter-specific cross was evaluated for the effective introduction of higher DMC from wild cassava relatives. High positive and negative GCA and SCA values were estimated for the agronomic yield traits. Harvest index and DMC were under the influence of additive gene action, while ComRt, FRY and DRY were more influenced by non-additive effects. Moderate to high heritability estimates were obtained for the different agronomic traits. High heritability values were estimated for DRY, FRY, DMC, HI, RtPlt and moderate for RtWt. AMMI analysis ranked FRY, DRY, HI and RtPlt as stable, DMC relatively stable and RtWt as unstable across environments. In the seedling stage DRY, FRY, RtWt, and ComRt ranked parents in the same direction. Dry matter content and HI ranked parents similar but in the opposite direction for other yield characteristics. Overall rating ranked MPER 183 and CM 4574-7 as best parents followed by SM 1565-15 and SM 1665-2. Seedling nursery and the diallel analysis identified SM 1741-1 and MPER 183 as good parents for a number of traits. Replication and blocking during clonal evaluation greatly reduced the non-genetic factors resulting in high correlation among traits evaluated. Fresh root yield, DMC, HI, RtWt and RtPlt were found to be important in determining DRY. Root weight was found to be the most important indicator of DRY. Crossing of the elite cultivar MTAI-8 to the wild relative M. tristis resulted in high DMC values ranging from 34.39% to 42.73%. Bulk segregant analysis showed that parent SM 1741-1 was associated with favourable QTLs for DMC. Markers SSRY 150 (R2=18.1%) and SSRY 160 (R2=28.9%) in the diallel cross, SSRY 99 (R2=22.68), SSRY 141 (R235.89) and NS 169 (R2=20.01) in the wild cross and SSRY 11 (R2=34.57), SSRY 62 (R2=50.21) and NS 644 (R2=29.09) in the mapping population showed association with DMC with values high enough for practical use in a MAS breeding programme.

[发布机构] University of the Free State