Fig 1.
HRM curve profiles from maize and cowpea DNA titration.
(A) Normalised High Resolution Melting (HRM) curve profiles of rbcL amplicons generated from mixtures of maize DNA and cowpea DNA according to the titration series: 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% maize DNA (in cowpea DNA). Melt curve shapes reflect differences in the sample composition. (B) Relationship between HRM fluorescence and maize DNA concentration. Mean fluorescence values recovered from normalised High Resolution Melting (HRM) profiles of maize DNA in maize + cowpea DNA mixtures at 83.5°C. The graph shows a strong linear relationship between mean fluorescence and the species composition in the DNA admixture. Error bars represent standard error of the mean.
Fig 2.
HRM curve profiles from a titration of maize + cowpea flour mixtures.
Normalised High Resolution Melting (HRM) analysis of rbcL amplicons generated from template DNA extractions from ground flour of maize and cowpea grain according to the titration series: 0, 5, 10, 30, 50, 70, 90, 95 and 100% maize grains (in cowpea grains). (A) Normalised HRM curves of DNA from each of the ground seed mixtures. (B) Linear regression for HRM profile of cowpea and maize seed flour mixes at a melt temperature of 84.1°C. Error bars represent the standard error of the mean. Linear regression of samples containing >50% maize can be described by the relationship y = 0.2984x + 17.964 and has an R2 value of 0.9716.
Fig 3.
Relationship between aerosol particle profile and sampling position as well as DNA isolated from pure maize and cowpea.
(A) Decay of airborne tissue (non-starch) and starch particles at various heights above bins containing maize and cowpea grains. Error bars represent 2x standard deviation. (B) Concentration of maize and cowpea DNA recovered from aerosol samples collected at different sampling heights (H) in cm from grain bins containing maize or cowpea grains. Error bars indicate 2x standard deviation and account for 95% of variation. (C) Concentration of maize and cowpea DNA recovered from aerosol samples collected at different sampling distances (in cm) from grain bins containing maize or cowpea grains. Error bars indicate 2x standard deviation and account for 95% of variation.
Fig 4.
HRM profiles from aerosol samples above a titration of maize + cowpea seed mixtures.
High Resolution Melting (HRM) analysis of rbcL amplicons generated from template DNA extractions recovered from aerosol samples collected 10cm above 10kg grain bins containing 0%, 5%, 10%, 30%, 50%, 70%, 90%, 95% and 100% of maize grains with cowpea grains. (A)Normalised HRM curves of aerosol samples collected above each part of the grain mixture titration series. (B) Linear regression for normalised HRM profile of all aerosol samples collected 10cm height above grain bins at a melt temperature of 83.5°C. Error bars represent standard error of the mean.
Fig 5.
Species-specific minibarcode frequencies from aerosol samples collected above a titration of maize + cowpea seed mixtures.
Frequency of maize and cowpea-specific mini-barcode sequences recovered from aerosol samples collected above individual grain bins in a titration series containing 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% (Coriolis samples) and 0%, 5%, 10%, 30%, 50%, 70%, 90%, 95% and 100% (vacuum samples) of maize grains in cowpea grains. (A) Histogram of the relative percentage of maize and cowpea mini-barcode sequences recovered from aerosol samples collected using a Coriolis aerosol sampler 60cm above bins representing the titration series of grain mixes. (B) Histogram of the relative percentage of maize and cowpea mini-barcode sequences recovered from aerosol samples collected using a hand-held, high power vacuum sampler 10cm above bins representing the titration series of grain mixes.