Examining genetic variation in maize inbreds and mapping oxidative stress response QTL in B73-Mo17 nearly isogenic lines

Authors: SORGINI, C - University Of Illinois; BARRIOS-PEREZ, I - University Of Illinois; BROWN, P - University Of Illinois; Ainsworth, Elizabeth - Lisa

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2019
Publication Date: 7/4/2019
Citation: Sorgini, C.A., Barrios-Perez, I., Brown, P.J., Ainsworth, E.A. 2019. Examining genetic variation in maize inbreds and mapping oxidative stress response QTL in B73-Mo17 nearly isogenic lines. Frontiers in Sustainable Food Systems. 3:51. https://doi.org/10.3389/fsufs.2019.00051.
DOI: https://doi.org/10.3389/fsufs.2019.00051

Interpretive Summary: Tropospheric ozone is a damaging air pollutant that accelerates senescence and causes visual damage to leaves of crop plants. Identifying genetic markers associated with ozone tolerance could accelerate breeding efforts. In this study nearly isogenic lines derives from B73 and Mo17 were screened in the field and in growth chambers at elevated ozone concentrations. Quantitative trait loci associated with ozone symptoms were identified, which could aid in future breeding. Additionally, experiments showed that the leaf damage identified in the field was also identified in growth chamber experiments, supporting the feasibility for rapid screening of ozone response in large populations in controlled environments.

Technical Abstract: Screening crop plants under elevated ozone concentrations ([O3]) is a pre-requisite for identification of tolerant lines, but few studies have mapped maize responses to elevated [O3]. B73-Mo17 nearly isogenic lines (NILs) were screened in the field under ambient (~40 ppb) and elevated (~100 ppb) [O3] at the Free Air gas Concentration Enrichment (FACE) research facility in Champaign, IL to identify maize leaf damage QTL associated with variation in O3-induced oxidative stress response. In Mo17 NILs, a significant leaf damage QTL was identified at 161Mb on chromosome 2. To assess the feasibility of high-throughput phenotyping and fine mapping of early season O3 leaf damage QTL, a subset of the nested association mapping founder lines were screened in a growth chamber experiment under ambient and elevated [O3]. Results showed that elevated [O3] decreased the number of green leaves while increasing the number of lesioned and dead leaves. Most lines showed the same general response to elevated [O3], but the degree of damage varied among lines. Next, tolerant and sensitive B73-Mo17 NILs identified from the FACE study, and hybrid crosses of the identified NILs with Mo17 (n= 20) were grown under elevated O3 (~150 ppb) in growth chambers (n=7). In the chambers, O3-sensitive lines could be distinguished from tolerant lines based on leaf lesions, but there was not a continuous degree of damage like that seen in the field. This research identified a repeatable O3-induced leaf damage QTL and developed populations and markers that can be used in future growth chamber fine mapping experiments. These results demonstrate the feasibility of high-throughput phenotyping and fine mapping of O3 leaf damage QTL in a controlled environment.