Location: Crop Genetics and Breeding Research
2023 Annual Report
Objectives
1. Deployment of root-knot nematode resistance in cotton and peanut.
1.A. Determine the economic value of growing nematode-resistant vs. a susceptible cultivar in continuous and rotated peanut.
1.B. Evaluate the economic effect of growing M. incognita-resistant cotton in fields with damaging levels of the nematode.
2. Identify and screen nematode resistant crops that can be grown in rotation with cotton and peanut.
2.A. Identify sources of resistance to Meloidogyne incognita in sorghum that differ from known sources of resistance.
2.B. Identify sorghum cultivars that are poor hosts for Pratylenchus brachyurus and Meloidogyne arenaria.
3. Increased understanding of the interactions between plant-parasitic nematodes and the soil microbiology community and how that contributes to disease.
3.A. Evaluate the interactions of nematode parasitism, the salicylic acid (SA) and jasmonic acid (JA) plant defense pathways, and Fusarium oxysporum f.sp. vasinfectum in the Fusarium wilt disease complex in cotton.
3.B. Investigate the contribution of predatory nematodes in suppressing root-knot nematodes.
3.C. Identify the host and environmental factors that influence the attachment of Pasteuria penetrans spores to Meloidogyne arenaria.
Approach
The long-term goal of our research is to develop integrated approaches for managing plant-parasitic nematodes in cotton and peanut. Host-plant resistance is the most consistent means of reducing yield losses from nematodes. Our research will investigate the most effective deployment of resistance in cotton and peanut for improving yield and economic returns. For sustainable long-term production, farmers cannot rely solely on host-plant resistance for managing plant-parasitic nematodes. Therefore, we will investigate other management options. We will identify crops that can be grown in rotation with cotton and peanut that will reduce population densities of damaging nematodes. Biological control organisms are being marketed for use in cotton and peanut, and they also occur naturally in fields. We will investigate the contribution of predatory nematodes to suppression of root-knot nematodes and the environmental factors that influence the susceptibility of these nematodes to their host-specific bacterial pathogen, Pasteuria penetrans. Nematodes commonly interact synergistically with other plant pathogens to cause greater crop losses. We will investigate how nematodes interact with cotton’s innate defense systems and whether that plays a role in the Fusarium wilt disease complex.
Progress Report
Both technician positions on this project were vacant from January 2022 until June 2023, and one of the two scientist positions has been vacant since September 2022. We anticipate filling the scientist position before the end of FY2023.
We planted peanut to keep the root-knot nematode populations up in the field we plan to use to determine the economic value of planting peanut in a crop rotation system. We were unable to initiate the experiment in FY23 due to the loss of a scientist and a critical technician. (Subobjective 1A)
We initiated the experiment to evaluate the economic benefit of growing nematode-resistant cotton (Objective 1) in FY23, one year behind schedule due to the loss of a critical technician. We are conducting independent tests in two fields to try to make up for lost time. (Subobjective 1B)
Greenhouse evaluation of sorghum genotypes commonly used for hybrid development to identify potential sources of resistance to Meloidogyne incognita (Subobjective 2Aa) was delayed by the loss of a technician. However, the screening is largely complete now. Evaluation of the sorghum association panel (SAP) has not yet been started due to the lack of a technician, but that screening should begin in the coming months (Subobjective 2Ab). We discovered that the mutant lines we plan to use to evaluate potential resistance genes in sorghum (Subobjective 2Ac) were not genetically pure, so we are trying to fix that problem so that we can proceed with the evaluations.
Evaluation of sorghum for resistance to Meloidogyne arenaria and the lesion nematode has not begun due to the loss of a scientist and a technician. (Subobjective 2B)
Investigation of the interactions of nematode parasitism, the salicylic acid (SA) and jasmonic acid (JA) defense pathways, and Fusarium oxysporum f.sp. vasinfectum in the Fusarium wilt disease complex in cotton (Subobjective 3A) was delayed by the lack of technical support. However, we are now evaluating the methods and will begin greenhouse testing before the end of the calendar year.
The study of the effect of predatory nematodes on M. incognita (Subobjective 3B) has been delayed due to the loss of a scientist and a technician. Similarly, the studies on environmental factors that affect the nematode parasite Pasteuria penetrans (Subobjective 3Ca) and the effect of soil and host plant on attachment of P. penetrans (Subobjective 3Cb) have been delayed for the same reason.
Accomplishments
1. Nematode resistance in cotton involves the jasmonic acid (JA) defense pathway. The physiological mechanisms of resistance to the root-knot nematode (RKN) in cotton are not well understood. ARS and University of Georgia researchers in Tifton, Georgia, documented that RKN infection in resistant cotton plants caused significant overexpression of multiple genes in the jasmonic acid (JA) plant defense pathway compared to the reaction in susceptible plants, which suggests a massive JA response following RKN infection in resistant plants but not in susceptible ones. These results help explain the physiological mechanisms that resistant cotton plants use to defend themselves against RKN parasitism.
Review Publications
Ballen-Taborda, C., Chu, Y., Ozias-Akins, P., Holbrook Jr, C.C., Timper, P., Jackson, S.A., Bertioli, D.J., Leal-Bertioli, S. 2022. Development and genetic characterization of peanut advanced backcross lines that incorporate root-knot nematode resistance from Arachis stenosperma. Frontiers in Plant Science. 12:785358. https://doi.org/https://doi.org/10.3389/fpls.2021.785358.
Marquez, J., Hajihassani, A., Davis, R.F. 2022. Evaluation of summer and winter cover crops for variations in host suitability for M. incognita, M. arenaria, and M. javanica. Nematology. 24:841-854. https://doi.org/10.1163/15685411-bja10172.
Timper, P., Davis, R.F. 2022. Evaluation of host-plant resistance and high residue rye for management of Meloidogyne incognita in cotton. Crop Protection. 161:106060. https://doi.org/10.1016/j.cropro.2022.106060.
