Hybridization, Introgression and Genetic Segregation among Cultivated and Feral Sorghum

Abstract

Aims: The East African region is a centre of diversity for sorghum, there is need for studies on the role of interspecific hybridization and introgression of domesticated sorghum genes in weedy backgrounds. Study Design: Interspecific hybridization between S. bicolor and the weedy accessions belonging to S. halepense, S. sudanense and S. bicolor ssp. verticilliflorum accessions was studied. Methodology: At anthesis panicles of the weedy accessions were emasculated and pollinated with pollen from S. bicolor. The F1, F2 and BC1 populations were evaluated for simple sequence repeat (SSR) loci and phenotypic polymorphisms. Results: A range of alleles were observed across the assayed loci (2-8) including unique and null alleles. Shannon information content ranged from 0.2 to 1.98 on the loci, showing high polymorphism and genetic differentiation of the accessions used in the study. Alleles of between 70 and 300bp were obtained from all loci except loci SB1764, SB5058, SB3420, SB2389 and loci SB3258. Phenotypic analysis of S. bicolor, S. sudanense, S. halepense and their F1 progenies showed significant variation on vegetative traits. S. sudanense had greater number of tillers (3.3), number of branches (0.3), total seed number (3010) and photosynthesis (110); S. bicolor had a higher 100 seed weight (3,1g) while S. halepense had the least flowering (65,1%) but more ratooning (3.8). In contrast to their parental species, the F1s had profuse tillering (2.3 - 3.4), were taller (121- 144 cm) and had more seed (2814 – 3243). The crosses had mid way clusters between respective parents in ssr loci dendogram analysis. A 3:1 and 1:1 segregation was observed in the F1 and BC1 populations respectively. Conclusion: F1 populations were obtained between S. halepense x S. bicolor and S. sudanense x S. bicolor. There is need for more studies on the role of crop to non-crop hybridization within the species.