BIOLOGICAL NITROGEN FIXATION OF LEGUMINOUS CROPS GROWN ON DEGRADED SOILS IN UGANDA, RWANDA, AND TANZANIA
Sugarbeet and Bean Research
2012 Annual Report
1a.Objectives (from AD-416):
To identify, study, and develop common bean germplasm with improved nitrogen fixation potential for use in Rwanda, Uganda, and Tanzania. To examine the relationship between nitrogen fixation and seed quality, including seed sugars and antioxidant levels.
1b.Approach (from AD-416):
Germplasm Screen: Common bean germplasm will be screened in 2 field sites in Rwanda under high and soil N levels and+/- Rhizobium inoculums. Superior N fixers will be identified via measurement of seed N levels in combination with nodule number and nitrogenase activity (acetylene reduction). Germplasm will be locally adapted and will be of the two important growth habit types for the region, determinate bush and climbing bean. Germplasm will also be screened in US using same methods, but adapted to U.S. and with type II and type III growth habits. Seed antioxidant activity and total flavonoids for all lines will be measured.
Molecular mapping: A preexisting common bean RIL populations will be identified to use to map traits related to BNF. The population will be planted in MI for 2 years in two environments: low soil N and high soil N. Traits to be measured include seed total N, plant N, nodule number, nodule nitrogenase activity, seed antioxidant and total flavonoids. SSR markers will be added to the RIL population if necessary. QTL analysis will be conducted with phenotypic and molecular data.
A panel of over 300 diverse Andean bean genotypes was assembled. This panel includes materials from North and South America, and Africa. The genetic diversity of these materials was evaluated with 534 molecular markers (SNPs). These lines were planted in a replicated field trial in Entrican, MI in June 2012. The lines are being evaluated for biological nitrogen fixation capacity in the field trial. Crosses have been made between high nitrogen fixing lines and lines with superior agronomic and commercial characteristics. They are currently at the F2 generation.