Rapid and non-destructive decay detection of Yali pears using hyperspectral imaging coupled with 2D correlation spectroscopy

The black spot disease caused by Alternaria alternata on Yali pears is a great concern as it compromises their edible quality and commercial value.To realize rapid and non-destructive classification of this disease,hyperspectral imaging(HSI)technology was combined with two-dimensional correlation spectroscopy(2DCOS)analysis.A total of 150 pear samples at different decay grades were prepared.After obtaining the HSI images,the whole sample was demarcated as the region of interest,and the spectral information was extracted.Seven preprocessing methods were applied and compared to build the classification models.Thereafter,using the inoculation day as an external perturbation,2DCOS was used to select the feature-related wavebands for black spot disease identification,and the result was compared to those obtained using competitive adaptive reweighting sampling and the successive projections algorithm.Results demonstrated that the simplified least squares support vector model based on 2DCOS-identified feature wavebands yielded the best performance with the identification accuracy,precision,sensitivity,and specificity of 97.30%,94.60%,96.16%,and 98.21%,respectively.Therefore,2DCOS can effectively interpret the feature-related wavebands,and its combination with HSI is an effective tool to predict black spot disease on Yali pears.

Gene Expression and Activity of Enzymes Involved in Sugar Metabolism and Accumulation During “Huangguan” and “Yali” Pear Fruit Development

Since the carbohydrate content affects pear flavor during the process of growth, it is necessary to determine the sugar components that accumulate in the fruit. We analyzed the fruit carbohydrate content, and the gene expression and activity ofacid invertase(AI), neutral invertase(NI), sucrose synthase(SS), and sucrose phosphate synthase(SPS) during the development of "Huangguan" and "Yali" pears. The results demonstrate that during development, the fruit sugar metabolism of the "Huangguan" pear follows a typical sorbitol–starch-soluble sugars middle model, whereas the "Yali" pear fruit follows a typical sorbitol–sucrose–starch-soluble sugars middle model. In the "Huangguan" pear, we found the AI and NI gene expressions, as well as AI( P < 0.05) and NI( P < 0.01) enzyme activities, to be positively correlated, whereas we found the NI gene expression and NI enzyme activity of "Yali" pear to be negatively correlated( P < 0.01). We observed the high levels oflate-stage AI and early-stage SS during development to roughly correspond with the gene expression found in the late and early stages, respectively, suggesting their potential regulatory roles in "Huangguan" pear fruit development. Our results indicate that the primary function of SPS during the early developmental stage is to accumulate sucrose, whereas the primary function of AI is to promote hexose accumulation during the late developmental stage ofmature "Yali" pear fruit.