Location: Crop Genetics Research
Project Number: 6066-22000-094-001-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2021
End Date: May 31, 2026
Objective:
1. Determine the efficacy of commercially available reniform nematode resistant cotton cultivars compared with USDA-developed cotton breeding lines.
2. Determine the influence of different cotton production stresses on reniform nematode populations when different cotton breeding lines are exposed to abiotic and biotic stressors.
2a. Influence of different irrigation practices
2b. Influence of two different insect pressures
2c. Influence of weed pressure
3. Characterize plant growth and development responses to reniform nematode in susceptible and resistant cotton lines and define the relationships between soil moisture and reniform nematode severity with respect to plant damage and yield loss.
Approach:
Objective 1: To assess efficacy of different reniform nematode breeding lineages by comparing commercially available reniform nematode resistant cultivars and USDA breeding lines, trials will be conducted at Mississippi State University’s Delta Research and Extension Center in fields with established reniform nematode populations. Treatments will be two commercially available resistant cotton cultivars, three resistant breeding lines, and one commercially available susceptible cultivar. Soil samples will be collected at planting, midseason, and harvest and nematode populations counted. Plant agronomic characteristics will be assessed. Plots will be harvested and cotton plot samples ginned for lint turnout.
Objective 2: To evaluate stressors on nematode populations, reniform nematode susceptible cultivars and resistant breeding lines will be subjected to conditions with different, important biotic and abiotic stressors. In all trials soil samples will be collected at planting, midseason, and harvest and reniform nematode populations will be determined. Agronomic characteristics and yield will be assessed.
2a. Treatments will be two commercially available resistant cotton cultivars and three breeding lines. One trial will be in a non-irrigated field setting and an identical trial in an irrigated setting.
2b. Treatments will be two commercially available resistant cotton cultivars and three resistant breeding lines. One trial will be in a location with aggressive insect management and an identical trial in a field with minimal insect management.
2c. Trials will be conducted in growth chambers in pots infested with reniform nematodes. Treatments will be two commercially available resistant cotton cultivars and three breeding lines. One trial will have aggressive weed management while an identical trial will have minimal weed management.
Objective 3. The relationship between soil moisture and reniform nematode severity on plant damage will be studied in the growth chamber. Untreated seeds of two resistant cotton lines and two commercially available varieties will be planted in each pot filled with a steam-sterilized growth media fertilized to current recommended nutrient levels. Upon stand establishment plants will be inoculated with 1,000 reniform nematodes. Beginning at emergence, plant growth parameters will be recorded weekly. Varieties will be exposed to drought and flooding at 40 days post inoculation for 5-7 days. Water regimes will then be returned to optimal conditions and plants will recover for 2 weeks. Then, midday, single-leaf gas exchange and chlorophyll fluorescence will be measured. At the end of the test, leaf area, main stem length, and main stem node number will be recorded before placing all plant material in a forced-air dryer to determine dry mass for leaf, stem, and root material. Nematodes extracted from all of the soil in each container will be counted. Data collected during drought/flood will include pigments, leaf gas-exchange, and chlorophyll fluorescence. After recovery measurements will include these same parameters plus aboveground biomass, leaf area, shoot length, node number, and root growth metrics.
