Location: Dale Bumpers National Rice Research Center
Project Number: 6028-21000-011-027-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Mar 1, 2017
End Date: Feb 28, 2022
Objective:
Identify genes associated with reduced accumulation of arsenic (As) in rice grains, and determine their association also with resistance to straighthead disease, and with concentration of As in flag leaves before and after grain fill.
Approach:
Rice accessions previously identified as producing grain high in As concentration (a.k.a. "Accumulators" of As) or low in grain-As ("Excluders") have been crossed, and F2 seed generated by USDA. The parents of these crosses were shown in 2015 to differ as well for resistance to As-induced straighthead disease, making these populations ideal for identifying genes affecting both traits, and for investigating if the two traits share common underlying genes or mechanisms, such as altered As-uptake, transport, or metabolism. The project will identify QTLs using next generation sequencing technology and a procedure known as QTL-seq, wherein gene sequencing in conducted on two pools of DNA per population per trait created by bulking tissues or DNA from subsets of progeny identified as having opposite extreme phenotypes (e.g., a high grain-As pool and a low grain-As pool). For grain-As, the phenotypic extremes will be identified using seeds from F2 plants, and then validated using seed from F2:3 progeny plants grown in flooded fields in Stuttgart, AR; grains analyzed by ICP-MS by collaborator. Phenotypic extremes for straighthead response will be identified using replicated F2:3 plots, verified using F3:4 progeny. Leaves collected from the F2 and F3 plants will be stored appropriately until the grain As and straighthead data are used to determine progeny for use in the bulked segregant DNA pools that will be sequenced (by commercial company). Once the progeny subsets with extreme grain-As are identified, they will be evaluated in Stuttgart, AR for straighthead response to determine if selection for grain-As caused also a change in straighthead response (as one would expect if the same genes affect both traits). Likewise, the progeny subsets selected for resistance versus susceptibility to straighthead will be evaluated for grain-As (seed produced in Stuttgart, AR; ICP-MS analyzed by collaborator or commercial labs).
