Qi Zhang, NDSU Department of Plant Sciences

Waterlogging (i.e. flooding) is a major constrain in agricultural production, affecting about 10% of land worldwide. Farmers in North Dakota have experienced severe waterlogging damage in the last two decades. One of the most economically effective methods to reduce stress damage is use of tolerant plants. Furthermore, waterlogging-tolerant plants are less likely to be affected by other stresses such as disease and insect infections and weed invasion, thus reducing other inputs (e.g., chemical applications). Consequently, economic revenue is increased.

We are conducting this project to develop a screening method to evaluate corn waterlogging tolerance and subsequently using this method to determine relative tolerance of 16 corn populations maintained in the NDSU corn germplasm collection.

Development of a waterlogging tolerance screening method: Corn seeds were germinated in plastic tubes amended with a soil:sand (1:1, v:v) mixture which mimicked the field condition, held in cone-containers. The containers were soaked in ½ strength Hoagland solution after seedling to ensure sufficient nutrients for germination and seedling growth. Corn plants were grown to 2-3 leaf stage (~ 10 days after sowing) and then subjected to the control (i.e. non-waterlogging) or waterlogging (containers held in plastic tubs with water level 2 cm above the soil surface) for 3, 6, or 9 days.

Waterlogging caused limited growth reduction above the ground and at 0-5 cm depth below the ground (data not shown). Three-day waterlogging caused approximately 50% root reduction at all rooting depths between 10 cm and 25 cm (Table 1). Root growth of the plants under 6-day waterlogging decreased with increasing rooting depth, ranging from 21.0 mg at 5-10 cm depth to 1.2 mg at 20-25 cm depth. The extended waterlogging, 9-day, caused severe root damage (~ 80% growth reduction compared to the control) from 10 cm below the soil surface. Six-day waterlogging duration was selected to screen waterlogging tolerance in corn.

Table 1. Corn tissue dry weight (mg) at 5-25 cm depth below the soil surface after 3-, 6-, and 9-day (D) of the control (i.e. non-waterlogging) and waterlogging condition. Numbers in the parenthesis indicated the ratio between waterlogging to the control within the same waterlogging duration.Means followed by the same letter were not significant different (P≤0.05) within the same duration of the control and waterlogging treatments.

Relative waterlogging tolerance of 16 corn populations: Relative waterlogging tolerance of ‘NDEarlyGEM21a’, ‘NDEarlyGEM3’, ‘NDEarlyGEM10’, ‘NDSSR’, ‘NDSM(M-FS)C10Syn2’, ‘NDEarlyGEM4’, ‘NDEarlyGEM5’, ‘NDEarlyGEM26’, ‘Leaming(S-FS)C6’, ‘NDSMo17’, ‘NDSMB73’, ‘NDBS39’, ‘NDBS29’, ‘NDSHLC(FS-M-FS)C6’, ‘NDBS16’, and ‘NDBS28’, was determined following the method described previously. These 16 populations vary in maturity. The plants were cross pollinated within each population in the field and harvested in fall 2016. Due to the potential of genetic differences of waterlogging tolerance both among and with corn populations, more than one-hundred seeds of each population need to be included for each growing condition. By Aug. 2017, the experiment had been repeated six times (Run) (60 seeds/population/growing condition). The results below are concluded based on the data from Run 1 to Run 6.

Tissue biomass was higher under the non-waterlogging condition than the waterlogging condition, except the 0-5 cm depth in which a reversed trend was observed (59.9 mg under non-waterlogging vs. 64.9 mg under waterlogging, data not shown). It suggested that waterlogging might increase tissue growth at 0-5 cm depth where relative more oxygen presents compared to lower soil depths. A growing condition x population interaction was observed in the above and below ground biomass, except the 0-5 cm depth (data not shown). Each corn population performed similarly under the non-stressed and stressed conditions. Therefore, the growing condition x population interaction was most likely due the close ranking of waterlogging tolerance in the corn populations tested in the present study. For example, ‘NDEarlyGEM4’ and ‘NDBS39’ had high shoot and root biomass both under the non-waterlogging and waterlogging condition; while, ‘NDSSR’ was the worst performer under both condition. No genetic differences were observed in root growth at 15-25 cm depth under the waterlogging treatment. Overall, ‘NDSM(M-FS)1C0Syn2’, ‘NDEarlyGEM4’, ‘Leaming(S-FS)C6’, ‘NDSMo17’, ‘NDBS39’, ‘NDSHL(FS-M-FS)C6’, and ‘NDBS16’ had higher shoot and root growth under the waterlogging condition, which may be contributed by their higher tissue biomass under the non-waterlogging condition.

Table 2. Above and below ground biomass of 16 corn populations under non-waterlogging (i.e. control, C) and waterlogging (W) condition at the seedling stage.

No growing condition (non-waterlogging and waterlogging) x population interaction was observed in the below ground biomass at the 0 – 5 cm depth. Biomass at the 0 – 5 cm soil depth included the below ground stem and root. Data were pooled across the control (i.e. non-waterlogging) and waterlogging conditions.