Data_Sheet_1_Examining Genetic Variation in Maize Inbreds and Mapping Oxidative Stress Response QTL in B73-Mo17 Nearly Isogenic Lines.docx

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 (NAM) 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.