Objective To identify the gender of Bombyx mori chrysalis in the cocoon by rapid and non-destructive method based on near infrared transmission spectroscopy, improve breeding efficiency and reduce labor cost.
Method We used four silkworm varieties including Fu 9, 9 Fu, Xiang 7 and 7 Xiang, and compared their diffuse transmission spectra between 450-950 nm and 900-1700 nm. Partial least squares discrimination analysis (PLSDA), back propagation neural network (BPNN) and support vector machine (SVM) discrimination models were established and compared among different varieties. The robustness of the models was studied through the receiver operating characteristic(ROC) curve. Characteristic wavelengths were extracted by difference method and genetic algorithm.
Result The identification accuracy rates for Fu 9, 9 Fu, Xiang 7 and 7 Xiang varieties were 95.20%, 95.65%, 88.80% and 87.50% respectively using 450-950 nm spectra, and were 100%, 96.00%, 92.22% and 94.21% respectively using 900-1 700 nm spectra. Using PLSDA, BPNN and SVM models resulted in good identification of male and female silkworm pupae, the true female rates were 95.96%, 95.83% and 100%, the true male rates were 98.98%, 96.04% and 82.18%, and the accuracy rates were 97.46%, 95.94% and 90.86%, respectively. Based on the analysis of ROC curve, the PLSDA model was the optimal, followed by the BPNN model. Twenty bands were extracted manually as the equipment input, and the true female rate, true male rate and accuracy rate were 93.75%, 95.45% and 94.57% respectively based on the PLSDA model.
Conclusion Diffuse transmission spectra in the near infrared (900-1 700 nm) contains more classification information of male and female pupae compared with the visible-near infrared (450-950 nm). The PLSDA model is the optimal one among three models. After extracting the characristic bands, the accuracy rate can meet the requirements of actual production.
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