Water deficit effects on peanut genotypes with large root systems

Temporal and spatial root distribution in peanut genotypes with large root systems under water deficit conditions were studied. Peanut plants were grown and periodic root observations were done using minirhizotrons. Methodologies for fast root image acquisition and analysis were developed. These methodologies were found to be accurate, fast, and easy to use.; Of all plant shoot traits observed, water stress significantly reduced leaf area, leaf number, stem length and plant biomass compared to well-watered plants. Significant root distribution differences between drought tolerant and susceptible genotypes were found. Tolerant genotypes have distinct primary root capable of plastic responses and fast development at deep soil layers during periods of water deficit.; Effects of light intensity and water deficit under high temperature were also studied. There were no significant effects of light intensity on peanut growth under high temperature conditions. Level of high light intensity used may not have been high enough or have not included enough UV to cause reduction in plant shoot traits.; Water stress effects were aggravated by high temperatures. Plant shoot reductions ranged from 33% to 98% in water stressed plants compared with well watered plants. Drought tolerant genotypes were able to maintain its root system, whereas susceptible genotypes had large reduction of roots.; Water deficit increase susceptibility to preharvest aflatoxin contamination. Aflatoxin is caused by the fungi Aspergillus parasiticus and Aspergillus flavus. Growth and survival of A. flavus were monitored using minirhizotrons. Results showed greater A. flavus growth under water deficit conditions. However, minimal seed infection was observed after harvest. Further studies on pod invasion and seed infection under natural soil conditions are needed and the minirhizotron system can provide the technique to make observations.; In general, a large root system is not enough for thorough water extraction during periods of low water availability. The ability to exhibit plastic root responses with root growth at lower depths with available moisture is important during drought. Genotypes which exhibit these responses can be used to accelerate development of and increase chances of developing drought tolerant cultivars.