Soybean Mutations Mapping: Applications in Functional gene analysis and Soybean Improvement

Soybean [Glycine max (L.) Merr.] is the most widely consumed legume crop in the world, providing about 68% of world protein supply as well as food oil and renewable fuels. We developed several EMS mutagenesis soybean populations (Cooper et al., 2008; Meksem et al., 2008; Liu et al., 2012), and did a forward screening of these populations to identify genes of economical importance. We identified several lines with altered phenotype in specific traits, mainly oil, protein, high nodulating lines, high yielding and soybean cyst nematode resistance. A subset of the mutagenized population containing about 1000 families (M3 and M4 lines), was screened using reverse genetic approach: TILLING, the following mutants were identified within the omega-6 fatty acid desaturase gene FAD2, one silent mutation: F1274 (L249=), two missense mutation: F1284 (P284L) and F1796 (Q22R) in the FAD2-1A isoform. Another missense mutation: F812 (P163S) was identified in the other FAD2-1B isoform, all the four mutations resulted in an increase in oleic acid content up to 2.5 times compared to the wild type parent Forrest.

Using a forward screening approach, we were able to identify four mutants: F605, F620, F714, and F813, all of which contain high level of seed stearic acid with an increased level of up to 2.4 times compared to the wild type parent Forrest used to develop the mutagenized population. Each of these four mutants was identified to carry one missense or nonsense mutation of SACPD-C: Q83* (F605), L79F (F620), D77N (F714), and P102L (F813), among them, Q83*, L79F, and P102L are the new SACPD-C alleles identified in soybean.

The identified mutants can be used as new SCN resistant soybean sources with high seed stearic and oleic acid contents for further breeding purposes.

Keywords: Soybean, EMS mutagenesis, mutants population, mutation breeding, fatty acids, stearic acid, SACP-D, SACPD-C, SACP-B, soybean cyst nematode.