Introgression of high protein and pest resistance genes from inter-specific hybrids of Manihot esculenta ssp flabellifolia into cassava (Manihot esculenta Crantz)
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Date
2008-10
Authors
Akinbo, Olalekan Abiodun
Journal Title
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Publisher
University of the Free State
Abstract
Manihot esculenta ssp flabellifolia possesses valuable genetic variability for protein and disease resistance genes that were introgressed into cultivated cassava. FLA 444- 5 with a protein content of 10.5% (dry weight basis) was hybridised with cassava through controlled crosses and backcrossed to cassava to obtain the B1P2 family used in this study. The interspecific hybrids had protein values ranging from 0.77% - 11.25%, which indicated introgression of the trait. Application of in vitro seed germination, overcame the bottleneck of seed dormancy and insufficient planting materials for replicational trials at an early stage of evaluation. High positive and negative correlations were estimated in the B1P2 backcross family for yield traits, quality traits, and pests. Moderate to high heritability values were estimated for commercial roots, roots per plant, harvest index, root weight, fresh root yield, dry root yield, dry matter content, post harvest physiological deterioration, and protein content. Protein content and dry matter content were negatively correlated, but not significantly. Location and year did not show any significant difference in protein yield by genotype. Evaluation of whitefly in this study showed a high number of genotypes (86.70%) being resistant to infestation and infection in this Colombian high pressure pest region. SSR markers (817) were screened in the parental lines and four B1P2 progenies, 402 polymorphic markers were identified; of which 105 were used for map construction. The genetic map consisted of 29 linkage groups spanning 1249.55 cM with average marker interval of 16.16 cM. A total of three QTL (protg.7, protg.13 and protg.23) controlling protein were identified in the three different environments, with one QTL present across all three environments. The individual effects of alleles at these QTL ranged from 15% to 25% of the phenotypic variance explained.
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Keywords
Quantitative trait loci (QTL), Molecular map, Molecular markers (SSR), Pest, Yield, Protein, Introgression, Manihot esculenta ssp flabellifolia, Inter-specific cross, Cassava -- Disease and pest resistance -- Genetic aspects, Thesis (Ph.D. (Plant Sciences (Plant Breeding))--University of the Free State, 2008