Selection of tolerant and susceptible wild soybean (Glycine soja siebold & zucc.) accessions under waterlogging condition using vegetation indices

The waterlogging tolerance and susceptibility of 164 wild soybean accessions were evaluated. All plants were exposed to waterlogging conditions for 14 days, and visual score evaluation and detection of vegetation indices were performed at 14 and 21 days after waterlogging (DAW). According to our results, approximately 90% of the wild soybean accessions showed a visual score of 1.0-3.5 in both measurements. Among the 26 vegetation indices, only 17 showed statistically high correlation with visual score; however, the maximum P-value was less than −0.58. Therefore, correlation tests were re-performed using the selected wild soybean accessions (waterlogging-tolerant and waterlogging-susceptible accessions). As a result, significantly high P-values were detected for anthocyanin reflectance index (ARI1) (P = 0.98069 at 14 DAW; P = 0.86734 at 21 DAW), ARI2 (P = 0.98434 at 14 DAW; P = 0.87934 at 21 DAW), photochemical reflectance index (P = −0.9801 at 14 DAW; P = −0.9268 at 21 DAW), and simple ratio pigment index (P = −0.8841 at 14 DAW; P = −0.81292 at 21 DAW). Root morphological traits also showed significant differences between waterlogging-tolerant and waterlogging-susceptible accessions. In waterlogging-tolerant accessions, root length was 3.7‒5.5-fold higher than that in waterlogging-susceptible accessions. Furthermore, waterlogging-tolerant accessions showed a 14.3%-56.3% increase in projected area compared with in waterlogging-susceptible accessions.