Agronomic evaluation and molecular genotyping of selected soybean (glycine max (l) merril) varieties grown in different environmental regions of East Africa
Okwany, Zedekiah W. Agina
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Soybean (Glycine max. (L)Merril) is one of the most popular pulses in the world. It has been known to man for a long time since its first record goes as far as 2500 BC in China and Manchuria. Glycine max belongs to the subgenus soja, which also contains G. soja and G. gracilis. Soybean is grown primarily for the production of seed, has a multitude of uses in the food and industrial sectors, and represents one of the major sources of edible vegetable oil and of proteins for livestock feed use. Genes greatly determine morphological characteristics of living organisms. Environmental conditions may also determine these characteristics, some of which are important in agronomy. This study aimed at investigating the relationship that exists between agronomic and molecular characteristics of selected soybean cultivars grown in different regions of East Africa. The results will be used to advice both the farmers and researchers on the cultivar they cultivate/study and their relationship to agronomic value respectively. This information will also be used in breeding programmes. In this research, different soybean cultivars from different regions of East Africa (Kenya, Uganda and Tanzania) were grown in different blocks within one region (Mbita point in Kenya). Agronomic characteristics were observed and recorded from germination to post harvest time. For molecular analysis, genomic DNA was extracted according to Phenol Chloroform method. This was followed with PCR process using custom ordered pair of primers that corresponded to the flanking ends of the targeted gene fragment (5S ribosomal genes). Restriction Fragment Length Polymorphism (RFLP) was then performed on the isolated PCR fragments by digesting DNA using various restriction enzymes determined by computer based simulation of already sequenced genes of known Glycine species. Gene clean was performed on PCR materials. The elute was confirmed on agarose gel then sent for automated sequencing ABI prism (AppliedBiosystems) at (ILRI). The resulting gene sequences were compared with gene sequences of known Glycine species using various enzymes in computer based simulations. This enabled get a marker (Sac II) for the 5S ribosomal genes in Glycine max. The gene sequences were then subjected to gene blast using MEGA 4 and resulted with a phylogenetic tree for the East African soybean. The studied cultivars were found to be closely related to Glycine max. RFLP results were compared with agronomic performance. There was significant difference in plant height (F= 106.131, df = 12, p<0.05); number of branches (F=25.227, df =12, p<0.05); weight of the whole plant (F = 6.634, df = 12, p<0.05); total number of seeds per plant from the various cultivars (F = 13.330, df = 12, p<0.05); weights of total seeds per plant from various cultivars (F = 5.124, df =12, p<0.05). Significance differences observed in various parameters analysed in this study were not reflected in the cultivars’ genetic characteristics. The marker (sac II) identified in this research will be useful in further research in soybeans. The best performing cultivars (TGX-1876-2E, Namsoy 4M, Nam II and Nyala) will also be recommended for soybean farmers around Lake Victoria region. These results will also assist plant breeders to produce hybrids from the best performing cultivars.