Identification of QTL affecting inorganic arsenic levels in rice grain

Authors: Barnaby, Jinyoung; FERNANDEZ-BACA, CRISTINA - US Department Of State; McClung, Anna; Edwards, Jeremy

Submitted to: ASA-CSSA-SSSA Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/27/2021
Publication Date: 11/7/2021
Citation: Barnaby, J.Y., Fernandez-Baca, C., McClung, A.M., Edwards, J. 2021. Identification of QTL affecting inorganic arsenic levels in rice grain. ASA-CSSA-SSSA Proceedings. Salt Lake City, Utah, November 7-10, 2021.

Interpretive Summary:

Technical Abstract: Consumption of rice containing arsenic (As) is linked to adverse health impacts including cancer. Limits have been placed on inorganic As (iAs) content, the highly toxic form, in milled rice. For example, FAO/CODEX limit for iAs is 200 ppb, and FDA limit is 100 ppb in rice-based infant food. Recent studies have shown that rice grain total arsenic (As) accumulation can be mitigated by water management practices such as alternate wetting and drying (AWD) during the growing season. However, a severe drying period not only reduced total As levels but also reduced grain yield, and when mild AWD cycles (a.k.a. safe-AWD) was applied to sustain yield, it failed to reduce grain total As. To protect against yield loss, rice farmers implement “safe”-AWD practices, which minimizes crop stress while maximizing irrigation savings; therefore, it is important to develop rice varieties that accumulate less grain As under “safe AWD” practices. A 2 year field study using a Lemont × TeQing chromosome segment substitution line (TIL) mapping population examined the impact of genotype and AWD severity on iAs grain concentrations. The TILs displayed a range in iAs concentrations, from less than 10 to up to 46 µg kg-1 under AWD30, 30% volumetric water content, (VWC) and from 28 to 104 µg kg-1 under safe-AWD. Additionally, seven quantitative trait loci (QTLs) were identified in the mapping population associated with grain iAs. A subset of eight TILs and their parents were grown in a controlled greenhouse environment and results confirmed the genotypic grain iAs patterns observed in the field, and further showed negative correlation between the number of days under AWD and grain iAs concentrations. Thus, longer drying periods to meet the same soil VWC resulted in lower grain iAs levels. Both the number and combinations of iAs-affecting QTLs significantly impacted grain iAs concentrations. Our study suggests that coupling AWD practices targeting a soil VWC of less than or equal to 30% coupled with the use of cultivars developed to possess multiple QTLs that negatively regulate grain iAs concentrations will be helpful in mitigating exposure of iAs from rice consumption.