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Salinity affects the photochemical activity of photosystems (PSs) in plants. However, it is not clear which components in the photosynthetic processes are sensitive to salt stress. In this study, simultaneous measurements of prompt chlorophyll a fluorescence (PF), delayed chlorophyll a fluorescence (DF) and modulated 820 nm reflection (MR) were employed to investigate the effect of salt stress on the entire photosynthetic electron chain in maize leaf tissues, including the PSII donor side, electron transfer between PSII and PSI, and the PSI acceptor side. For the PF transients, salt stress induced a pronounced K-band; a positive L-band; a significant reduction in PI ABS , RC/CS O , TR O /ABS, and ET O /TR O ; and a significant increase in ABS/RC and RE O /ET O . Analysis of the normalized MR kinetics showed that the re-reduction kinetics of P700 + and PC + became slower and occurred at later times under salt treatment. For the DF signals, a decrease in the amplitude of the DF induction curve and a change in the shape of both the induction curve and the decay curve were observed under salt stress. These results suggest that salt stress decreased the number of active PSII reaction centers, impaired the connectivity between independent PSII units, destroyed the oxygen-evolving complex, and limited electron transport beyond the primary quinone acceptor Q A − . In contrast, the photochemical activity of PSI was largely unscathed. The results obtained from measuring three simultaneous signals were in good agreement.

Maize grain contamination with aflatoxin from Aspergillus flavus (A. flavus) is a serious health hazard to animals and humans. To map the quantitative trait loci (QTLs) associated with resistance to A. flavus, we employed a powerful approach that differs from previous methods in one important way: it combines the advantages of the genome-wide association analysis (GWAS) and traditional linkage mapping analysis. Linkage mapping was performed using 228 recombinant inbred lines (RILs), and a highly significant QTL that affected aflatoxin accumulation, qAA8, was mapped. This QTL spanned approximately 7 centi-Morgan (cM) on chromosome 8. The confidence interval was too large for positional cloning of the causal gene. To refine this QTL, GWAS was performed with 558,629 single nucleotide polymorphisms (SNPs) in an association population comprising 437 maize inbred lines. Twenty-five significantly associated SNPs were identified, most of which co-localised with qAA8 and explained 6.7% to 26.8% of the phenotypic variation observed. Based on the rapid linkage disequilibrium (LD) and the high density of SNPs in the association population, qAA8 was further localised to a smaller genomic region of approximately 1500 bp. A high-resolution map of the qAA8 region will be useful towards a marker-assisted selection (MAS) of A. flavus resistance and a characterisation of the causal gene.