Location: Crop Genetics Research
2020 Annual Report
Objectives
Objective 1. Characterize new sources of reniform nematode resistance in Gossypium (G.) arboreum and G. herbaceum germplasm accessions and identify DNA markers associated with resistance.
Objective 2. Introgress reniform nematode resistance from G. arboreum and G.
herbaceum accessions into G. hirsutum and develop breeding lines with resistance.
Objective 3. Determine effectiveness of unique sources of reniform resistance fromdiploid Gossypium germplasm accessions on nematode growth, reproduction, and
infection.
Objective 4. Characterize plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton lines and define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss.
Subobjective 4a. Characterize plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton lines.
Subobjective 4b. Define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss in susceptible and resistant cotton lines.
Objective 5. Evaluate impacts of integrated reniform nematode management practices on cotton yield, quality and reniform nematode population densities.
Subobjective 5a. Investigate the efficacy of new commercially-available nematicides on the management of the reniform nematode, cotton yield and cotton fiber quality.
Subobjective 5b. Investigate the effect of rotation with non-host/poor-host crops on management of the reniform nematode and crop yield.
Approach
Develop populations by crossing resistant accessions with one or more Gossypium (G.) arboreum accessions classified as susceptible or highly susceptible. Ovule culture will be used for the introgression of resistance from G. arboreum and G. herbaceum accessions to G. hirsutum varieties. Gossypium accessions with high levels of resistance to reniform nematode will be evaluated in growth chamber experiments to measure the effects of the resistance on number of infections, rate of development of females after infection, and production of eggs. Classical growth and agronomic analysis will be conducted over two years under field conditions at Mississippi State University’s Delta Research and Extension Center in Stoneville, Mississippi. A nutrient response experiment will be conducted under controlled environmental conditions. The relative efficacy of new seed-applied and in-furrow nematicides against the reniform nematode will be evaluated on one susceptible and two resistant cotton lines in a field trial to be established in two naturally-infested sites in Stoneville, Mississippi. A field trial will be established in a reniform nematode infested site in Stoneville, Mississippi.
Progress Report
The overall goal of this research program is to improve our understanding of the effects of reniform nematode (Rotylenchulus reniformis) on yield losses in upland cotton (Gossypium hirsutum) and to develop management strategies that will reduce those losses. The project falls under National Program 303, Component 3 (Plant Health Management), and Problem Statements 3A (Development and Deployment of Host Resistance) and 3B (Biologically-based Integrated Disease Management). In fiscal year 2020, research was conducted in Stoneville, Mississippi, by ARS researchers and university collaborators.
Resistance to reniform nematode does not exist naturally in upland cotton, so related species are the subject of studies to identify resistance to this nematode and move that resistance into upland cotton. Previous work by this research team has identified reniform nematode resistance in several accessions of the related Asiatic cotton species Gossypium arboreum, and this species remained the focus of our investigations related to Objective 1 this year. Highly resistant Gossypium arboreum accession PI 529740 was crossed with susceptible Gossypium arboreum accession PI 527929 to create a population that we used to determine how the resistance trait was inherited. Evaluation of the F2 generation last year showed that at least two recessive genes control resistance in PI 529740, and evaluation of the F2:3 generation in FY 2020 supported this two gene model. This confirms that plant breeders will have to develop and screen large breeding populations to identify resistant individuals that carry both genes. A second F2 population derived from resistant Gossypium arboreum accession PI 616205 crossed with PI 527929 was evaluated for nematode resistance and the data indicated that resistance was controlled by a single recessive gene.
Transferring resistance from Asiatic cotton to upland cotton is difficult. There are incompatibilities between the two species that do not allow them to cross-pollinate and set viable seeds, so specialized breeding approaches are needed. The transfer process requires a special technique called ovule culture for extracting the developing hybrid cotton embryos, growing them on artificial media, and regenerating plants. This process is very time consuming, as there is a long period where the plants are maintained growing on artificial media. During the 2019 field season, approximately 2,000 embryos were obtained from 111 crosses, although the growth of the embryos in culture was often poor due to unfavorable climate conditions. These crosses from 20 resistant Asiatic cotton accessions generated 30 seedlings and six hybrid plants were successfully recovered for six Asiatic cotton accessions.
Plants that are considered resistant to reniform nematode will reduce the population of the nematode over time. However, not all resistant cotton varieties will achieve this reduction in the same manner. Experiments to determine what mechanisms our most resistant plants use to suppress nematode populations continued in support of Objective 3. Possible mechanisms include limiting the number of nematodes that can infect the plant roots, stopping growth and development of the nematodes after they infect the roots, or limiting reproduction by the nematodes. Data analysis for experiments involving two resistant Gossypium arboreum lines (A2-190 and A2-100) are complete and results are being prepared for publication later this year. However, experiments evaluating the effects of resistance in two additional Gossypium arboreum lines (A2-354 and A2-690) are only partially complete. The first set of evaluations is finished, but work in the growth chamber and lab to conduct the second run of those experiments was not initiated this spring as planned due to the shift to maximized telework resulting from the COVID-19 pandemic. Further, under maximized telework, we were not able to initiate the experiments to assess nematode growth and development on additional resistant lines that had been identified.
Characterization of plant growth and development and yield responses to reniform nematode in susceptible and resistant cotton varieties has been completed in support of Objective 4, Subobjective 4.A. Results from this field study have been presented at scientific meetings, and a manuscript documenting responses of susceptible varieties (Deltapine 16 and PHY 490 W3FE) and resistant lines (08SS110-NE06 and 08SS100) to reniform nematode infection will be submitted in the coming weeks.
Cotton growth and development can be influenced by availability of plant nutrients, so the research under Objective 4 and Subobjective 4.B. seeks to define the relationships between soil fertility and reniform nematode severity with respect to plant damage and yield loss in susceptible and resistant cotton varieties. Three greenhouse studies evaluated the effects of nitrogen, potassium, and phosphorus application on plant growth and reproduction and pathogenicity of reniform nematode on the same varieties used in the field trial described above. The greenhouse nitrogen study is complete, and a manuscript is in preparation. Building on these results, a new field study was initiated to investigate the effect that nitrogen fertility has on nutrient partitioning and reniform nematode reproduction in cotton. Data analysis and interpretation are underway for the potassium study, which was successfully repeated. Results indicate that both susceptible and resistant genotypes exhibited similar growth responses to potassium, responding in the same quadratic manner to increasing potassium fertilization. Based on this, it appears that potassium applications ranging from 50% to 150% of the recommended rate do not alter the plant’s inherent response to reniform nematode in the cotton lines tested. Data collection is complete for the phosphorus study and analysis is pending.
The fifth project objective is to determine how to best manage the use of new cotton varieties with resistance to reniform nematode in a production environment. Resistant varieties are being evaluated in conjunction with commercial seed-treatment nematicides (Subobjective 5.A.) and crop rotation (Subobjective 5.B.).
Field trials using reniform nematode resistant lines M123-1337, 08SS100, 08SS110-NE06 OP and the susceptible variety DP 1646 in combination with nematicides that were applied either in-furrow or directly on the seed, were completed for the 2019 season. Commercially available seed-applied products with activity against nematodes also were applied including: BioST nematicide (Albaugh’s biological nematicide derived from heat-killed Burkholderia rinojenses), Nemastrike (Bayer/Monsanto’s new nematicidal seed treatment consisting of tioxazafen), and COPeO Prime (BASF’s new nematicidal seed treatment consisting of fluopyram, a fungicide with nematicidal properties). In addition to considering the activity of newer commercially available seed-applied nematicides, two in-furrow at-plant applications consisting of one liquid in-furrow (Velum Total, Bayer’s in-furrow nematicide containing imidacloprid and fluopyram) and one granular in-furrow (Temik 15G, consisting of aldicarb) also were included in the test. Overall, 08SS110, a reniform nematode resistant line combined with the base treatment and either BioSt or Nemastrike, provided greater seed cotton per acre than the commercial variety, DP1646, combined with seed applied or in-furrow treatment combinations. With regards to reniform nematodes per kilogram of soil, 08SS100, a reniform resistant line, combined with the base fungicide and Velum total applied as an in-furrow treatment provided a 64% reduction in the nematode population at the end of the season. These trials are being repeated during the 2020 field season, and plots were successfully established in May. Each trial was planted in a separate field, both of which have had a history of reniform nematode and should provide meaningful data on the integrated management of the reniform nematode.
The third year of a five-year rotational study (Subobjective 5.B.) was completed in late 2019. Reniform nematode populations at planting ranged from 0 to 9,625 per kilogram of soil in the trial. Corn, continuous cotton, peanut, and reniform nematode resistant soybean were the main rotational crops for the 2019 field season. Reniform nematode numbers in soil were reduced by 42% in corn plots, by 30% in reniform nematode resistant soybean plots, and by 13% in peanut plots during the cropping season, whereas nematode populations increased by as much as 24% on continuous cotton.
Plots for the fourth year of the rotation study were planted on time in 2020. The 2020 field season includes continuous cotton and four separate treatments consisting of three commercial cotton varieties (DeltaPine 1518 and Phytogen 444 and 490) compared to a USDA reniform nematode-resistant line (M-123-1337) to continue to consider the role of rotation on reniform nematode management. Soil samples will continue to be taken throughout the season to monitor the impact of the rotational hosts on reniform nematode populations.
Accomplishments
1. Plant growth and development and yield response in susceptible and resistant cotton lines was characterized. Cotton lines resistant to reniform nematode have been recently developed to reduce yield losses from the nematode, yet little is known of their agronomic responses in field environments infested with reniform nematode. In a two-year study, ARS researchers in Stoneville, Mississippi, conducted growth analysis at 1- or 2-week intervals for the first 12 weeks after planting for two resistant (08SS110-NE06.OP and 08SS100) and two susceptible (Deltapine 16 and PHY 490 W3FE) genotypes. Growth patterns and maximum growth rates for all four cotton lines were similar, despite resistant varieties having greater transpiration, photosynthesis, stomatal conductance, and carbon dioxide assimilation efficiency than the susceptible varieties early in the season. Resistant varieties had higher yields than susceptible ones and resulted in smaller reniform nematode populations at the end of the season. This work provides new information about physiological responses to reniform nematode in resistant lines of interest to the scientific community.
2. Combined effects of nitrogen fertility and host plant resistance on reniform nematode population development and cotton growth. Both soil fertility and reniform nematode infection affect early-season growth and development of cotton. To better define how these factors influence cotton, alone or in combination, ARS researchers in Stoneville, Mississippi, conducted a greenhouse study to examined nitrogen applications up to 150% of recommended rates on two resistant (08SS110-NE06.OP and 08SS100) and two susceptible (Deltapine 16 and PHY 490 W3FE) cotton lines grown in the presence and absence of reniform nematode. As nitrogen levels increased, so did plant height, mainstem node number, leaf area, dry weights, taproot length, and leaf temperature. Nitrogen level did not affect the reproduction of reniform nematode, and populations were significantly smaller on resistant lines than on susceptible lines at the conclusion of the test. No interaction between the level of nitrogen applied and inoculation with the nematode was found for morphological parameters on either resistant or susceptible cotton genotypes. The physiological parameters net photosynthesis, anthocyanin content, and chlorophyll content were higher in 08SS110-NE06.OP compared to other genotypes, but additional work is needed to determine what role these factors may have in resistance. Results from this work will serve as the foundation for future studies to better characterize the association between select physiological parameters and expression of host plant resistance and could be useful in improved management recommendations to optimize early season growth of cotton.
Review Publications
Erpelding, J.E. 2020. Genetic characterization of the petal spot phenotype for Gossypium arboreum accession PI 408798. Czech Journal of Genetics and Plant Breeding. 56:79-83. https://doi.org/10.17221/88/2019-CJGPB.
Kularathna, M.T., Overstreet, C., Mcgawley, E.C., Stetina, S.R., Khanal, C., Godoy, F.C., Mcinnes, B.K. 2019. Pathogenicity and reproduction of isolates of reniform nematode, Rotylenchulus reniformis, from Louisiana on soybean. Nematropica. 49:31-41.
Erpelding, J.E., Stetina, S.R. 2019. Genetic characterization of Gossypium arboreum accession PI 529740 for reniform nematode resistance. Plant Breeding. 138:871-879. https://doi.org/10.1111/pbr.12715.
Gaudin, A.G., Wallace, T.P., Scheffler, J.A., Stetina, S.R., Wubben, M. 2020. Effects of combining Renlon with Renbarb1 and Renbarb2 on resistance of cotton (Gossypium hirsutum L.) to reniform nematode (Rotylenchulus reniformis Linford and Oliveira). Euphytica. 216:67. https://doi.org/10.1007/s10681-020-02580-3.
