Evaluation of soybean related genetic resources in the Mekong Delta, and the identity of a new wild soybean related species Glycine mekongensis

Abstract

In order to evaluate genetic variation for conservation of cultivated landraces and wild Glycineae species samples collected in the Mekong Delta, 626 soybean cultivars, one perennial soybean-related species (wild, 'Dau Han The'), and another perennial wild species ('Dau Hoang') were analyzed to search for genetic variations of Kunitz trypsin inhibitor (KTI), 7S and 11S globulins. Interestingly, all 185 local cultivars had only one Ti^aTi^a genotype and the normal type of 7S conglycinin, whereas 441 cultivars introduced from foreign countries had 15 Ti^bTi^b and 1 Ti⁰Ti⁰ genotypes and several variations of 7S conglycinin. However, variation of 11S subunits was higher in soybean landraces than among introduced soybean cultivars. These data indicate that soybean landraces in Viet Nam have differentiated independently from a limited number of original soybean cultivars introduced to Viet Nam since 1975. Two wild Glycine relatives, 'Dau Han The' and 'Dau Hoang', contained subunit variations on 7S conglycinin and extremely reduced amounts of 11S glycinin. 'Dau Han The' had only oneα-type subunit corresponding with 7S α-subunit of soybean, but 'Dau Hoang' contained two α-type subunits smaller than α'-and α-subunits of soybean. In particular, this wild species had yellow flowers similar to some cultivars of Glycine wightii but its inflorescences were different, thus 'Dau Hoang' is being investigated to see if it really belongs within G. wightii or not. The 'Dau Han The' protein pattern was so different from other wild perennial species such as G. tomentella, and G. tabacina that we considered 'Dau Han The' to belong within G. mekongensis Thanh and Hirata. Moreover, 'Dau Han The' has many interesting characteristics such as the presence of creeping stolons, helping dry tolerant conditions, and an apparent resistance to pod borers (Etiella zinckenella), being a main serious insect to soybean seed production in tropical regions. The information will be necessary to improve essential amino acid composition and protein content in soybean cultivars.