## 3 Results and Discussion  
### NIRS Calibration and Validation of PLS Models  
#### 3.1.1 Taro  
The actual or reference values of taro flour samples from the first trial for control and drought conditions were obtained by chemical quality analysis (and are presented in Table S1, as the variation in primary constituents within each acc.). Overall, an average increase in the N, Pt, Pb, and M content was recorded in both shoot and corn organs under stress. The M-corn increase under drought conditions was significantly different from the control (\(p\leq 0.05\)). An average slight decrease in St, \(\Delta^{13}\)C, and \(\delta^{15}\)N content was also registered in both organs under such conditions. In this particular case, drought significantly decreases (\(p\leq 0.05\)) the \(\delta^{15}\)N-shoot content when compared with control conditions. Still, from these primary chemical constituents, St is the most abundant constituent produced in corms, followed by Pt, M, and Pb. On the contrary, the shoots have Pt as the main abundant constituent, followed by St, M, and Pb. Therefore, the St-corn and Pt-shoot are chemotypes for representing the most abundant constituents produced by taro organs in both control and drought conditions, ranging from 48.44 to 45.18 g/100g DW, and from 11.48 to 12.44 g/100g DW, respectively [34]. The Pearson correlation coefficient (r) from the reference values is shown in 35 significant correlations overall among these quality constituents, of which 12 were strongly correlated with \(|\)r\(|\)\(\geq\) 0.50 (Table S2). These correlations observed between primary chemical constituents allow the quality identification between acc. under drought, which could be important for selecting the best ones for breeding purposes [17]. The strongest significant correlations were observed between St-corm and Fb-corm (\(-0.87\)), followed by Pt-corm and N-corm (\(0.85\)). The St-corm also showed a moderate correlation with Pt-corm (\(-0.46\)) and M-corm (\(-0.48\)), whose relationship between constituents agrees with previous studies on 315 taro acc. from various geographical origins [17]. On the other hand, the CaOx-shoot had a positive significant correlation with St-shoot (\(0.52\)), which in turn was negatively correlated with Pt-shoot content (\(-0.39\)), also confirming previous studies on taro's oxalate quantitation [47]. The \(\Delta^{13}\)C-corm showed a moderate correlation with CaOx-corm (\(0.40\)) and \(\Delta^{13}\)C-shoot (\(0.41\)). Meanwhile, \(\delta^{15}\)N-corm showed a weak correlation with N-corm (\(0.31\)). This set of correlation coefficients indicates that increased chemotype St-corm contents under drought will reduce fiber, protein, and minerals. Therefore, the higher chemotype Pt-shoot content will consequently present higher CaOx-shoot and lower St-shoot content with drought conditions. This could assist taro breeders in their choice and selection of the best ones for taro breeding programs [39]. However, the chemotypes St-corm and Pt-shoot presented distinct correlations (r) according to their origin (Table S2). The St-corm from the Canary Islands acc. showed negative correlation with Pt-shoot (\(-0.78\)) and Fb-corm (\(-0.76\)), while the St-corm from Madeira Island acc. had a negative correlation with Fb-corm (\(-0.93\)). The Pt-shoot only showed correlation with CaOx-shoot (\(0.64\)) for the SPC accessions. This is a strong indication that we might observe a distinct genetic variation to stress response, as no differences between control and drought conditions could be identified. The chemical reference values for each plant organ from the first trial were used to implement the calibration set. Another set of flour samples from the first trial were held and used as an independent validation set. NIRS spectra were obtained for corms (Figure 2A) and shoots (Figure 2B) calibration sets, and for the independent validation test sets for corms (Figure 2C) and shoots (Figure 2D).