Multivariate analysis compares and evaluates drought and flooding tolerances of maize germplasm

Multivariate analysis reveals the different physiological mechanisms and tolerances of maize germplasm in response to drought and flooding stresses. Drought and flooding are the two most important environmental factors limiting maize (Zea mays L.) production globally. This study aimed to investigate the physiological mechanisms and accurate evaluation indicators and methods of maize germplasm involved in drought and flooding stresses. The twice replicated pot experiments with 60 varieties, combined with the field validation experiment with 3 varieties, were conducted under well-watered, drought, and flooding conditions. Most varieties exhibited stronger tolerance to drought than flooding due to higher antioxidant enzyme activities, osmotic adjustment substances, and lower reactive oxygen species. In contrast, flooding stress resulted in higher levels of reactive oxygen species (particularly O-2(-)), ascorbate peroxidase, catalase, peroxidase, and soluble sugars but lower levels of superoxide dismutase, proline, and soluble protein compared with well-watered conditions. Superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, proline, soluble sugars, and protein contents, in addition to plant height, leaf area/plant, and stem diameter, were accurate and representative indicators for evaluating maize tolerance to drought and flooding stresses and could determine a relatively high mean forecast accuracy of 100.0% for the comprehensive evaluation value. A total of 4 principal components were extracted, in which different principal components played a vital role in resisting different water stresses. Finally, the accuracy of the 3 varieties screened by multivariate analysis was verified in the field. This study provides insights into the different physiological mechanisms and accurate evaluation methods of maize germplasm involved in drought and flooding stresses, which could be valuable for further research and breeding.

Automated summary

Multivariate analysis was used to uncover the physiological mechanisms and tolerances of maize germplasm in response to drought and flooding stresses. Drought and flooding are two major environmental factors limiting global maize production. This study aimed to investigate the physiological mechanisms and accurate evaluation indicators of maize germplasm under these stresses. Pot experiments and field validation experiments were conducted on 60 varieties under well-watered, drought, and flooding conditions. The results showed that most varieties exhibited stronger tolerance to drought due to higher antioxidant enzyme activities and osmotic adjustment substances, while flooding stress increased levels of reactive oxygen species and soluble sugars. Accurate indicators for evaluating maize tolerance to drought and flooding stresses were identified, and multivariate analysis successfully screened three varieties for further breeding. This study provides valuable insights into the physiological mechanisms and evaluation methods of maize germplasm under drought and flooding stresses.