Location: Crop Genetics Research
2021 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
Yield losses in upland cotton (Gossypium hirsutum) from reniform nematode (Rotylenchulus reniformis) infestation can exceed $100 million and the goal of this research program is the development of management strategies by evaluating resistant sources, transferring new sources of resistance to upland cotton, and identifying agronomic practices that would reduce nematode damage. Upland cotton germplasm accessions have not provided useful sources of reniform nematode resistance; however, resistance from related species can be transferred to upland cotton. Resistance from the Asiatic cotton species Gossypium arboreum has been identified by ARS researchers in Stoneville, Mississippi, on this project and the potential utilization of these resistant sources is the focus of further research. Agronomic practices may influence the deployment of resistant cultivars and university collaborators at Stoneville, Mississippi are evaluating management strategies to reduce cotton yield losses.
Two experiments are in progress in support of Objective 1, to determine the genetic inheritance of resistance from select Gossypium arboreum (A2) accessions. For the first test, a set of 20 F3 lines from the cross A2-711 (resistant) x A2-101 (susceptible) was challenged with reniform nematode under controlled conditions in a growth chamber. Also included in the test were the parents and known susceptible (A2-31, A2-40, Gossypium hirsutum ‘Deltapine 16’) and resistant (A2-404, Gossypium barbadense accession GB 713) checks. Counting the number of nematodes that successfully infected the plants is in progress. The results of this test are needed to confirm inheritance of the resistance from A2-711. For the second test, a set of 300 individual F2 seeds from the cross A2-354 (resistant) x A2-101, the parents, the F1 generation, and known susceptible and resistant checks noted above were planted in a growth chamber and inoculated with a Mississippi reniform nematode population. This test is still in progress in the growth chamber. The results will be used to determine whether the resistance from A2-354 is a dominant or recessive trait, and also will give us information about the number of genes controlling the resistance. Additionally, resistant accessions from the Gossypium arboreum germplasm collection have been planted in the field and crosses are being conducted for population development to evaluate the genetics of resistance for other accessions in order to identify additional genetic diversity for resistance. Seed production for F1 plants from crosses between three highly resistant accessions (A2-690, A2-737, and A2-849) with a susceptible accession were completed. These seeds were planted in the field during the 2021 growing season to develop segregating F2 populations for future nematode screening.
Plants from crosses between upland cotton cultivars and resistant Gossypium arboreum accessions have been maintained in the greenhouse in support of Objective 2 and seeds from the cross ‘DES119’ (Gossypium hirsutum) x A2-711 have been produced for nematode evaluation. Transferring resistance from Gossypium arboreum to upland cotton is a very time-consuming process. The two species are incompatible, and crosses fail to produce viable seeds; therefore, immature embryos are removed from developing fruit and grown on artificial media in the laboratory to generate plants, which can take up to six months and many plants with abnormal development are produced. As a result, progress in transferring additional sources of resistance has slowed over the past year. Upland cotton cultivars and resistant Gossypium arboreum accessions were planted in the field during the 2021 growing season in order to conduct additional crosses to transfer resistance genes. Furthermore, upland cotton plants with reniform nematode resistance transferred from Gossypium arboreum accession A2-190 were crossed back to several upland cotton cultivars to recover fertility and to select plants with traits more similar to the upland cotton cultivars.
Three growth chamber experiments measuring development and fecundity of reniform nematode on resistant cotton lines were established in support of Objective 3. The purpose of these experiments is to determine if the resistance prevents infection, slows nematode development, or limits the number of eggs produced by the adult female nematode. An experiment involving the resistant Gossypium arboreum accessions A2-394 and A2-690 was completed, and data analysis is underway. Briefly, plants were harvested every 2 days from 2 to 10 days after inoculation, then every 5 days from 15 to 30 days after inoculation and the numbers of vermiform, swelling, swollen, and gravid nematodes were recorded. At 20, 25, and 30 days after inoculation, the number of eggs in a single egg mass was determined for 50 individual nematodes per host line. We have just begun collecting the nematode data on the next experiment in this series involving the resistant Gossypium arboreum accessions A2-737 and A2-995, and its repeat has been planted and will soon be inoculated.
The characterization of plant growth, development, and productivity in response to reniform nematode infection for susceptible and resistant cotton cultivars in support of Objective 4, Sub-objective 4a was completed and a manuscript is in progress. This research demonstrated that growth patterns and maximum growth rates were similar among susceptible cotton cultivars (Deltapine 16 and PHY 490 W3FE) and resistant breeding lines (08SS110-NE06 and 08SS100); however, resistant lines had greater productivity with higher seed cotton yields and soil reniform nematode populations were reduced compared to susceptible cultivars. Resistant lines had greater transpiration, photosynthesis, stomatal conductance, and carbon dioxide assimilation efficiency that contributed to a 30% increase in seed cotton yields. The relationships between soil fertility and reniform nematode severity associated with plant damage and yield loss in susceptible and resistant cotton genotypes was completed in support of Objective 4, Sub-objective 4a and manuscripts are being prepared; one paper describing nitrogen effects was published. The effects of nitrogen, potassium, and phosphorus application on plant productivity and reniform nematode reproduction was evaluated in three greenhouse experiments. Reniform nematode reproduction was not affected by the increased application of nitrogen, potassium, or phosphorus, although resistant cotton lines reduced nematode reproduction compared to susceptible cultivars. Increasing soil fertility improved plant growth; however, no interactions with plant resistance were observed. These results indicate yield losses will still occur in susceptible cultivars even though fertility management improved plant growth.
The impacts of integrated reniform nematode management practices on cotton yield, quality and reniform nematode population densities were evaluated in support of Objective 5. The evaluation of new commercially-available nematicides on the management of the reniform nematode was completed for Sub-objective 5a and a manuscript is in progress. Reniform nematode resistant upland cotton breeding lines M123-1337, 08SS100, 08SS110-NE06 OP and the susceptible cultivar DP 1646 were included in field trails to evaluate the effect of nematicides on cotton productivity. Nematicide formulations were applied in-furrow, as seed treatments, or in combination. Seed-applied nematicides included BioST (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). The nematicides applied in-furrow were Velum Total (Bayer’s nematicide containing imidacloprid and fluopyram) and Temik 15G (aldicarb). Greater seed cotton yields were recorded for the nematicide applications. Seed cotton yields were also improved for the nematode resistant upland cotton lines following the application of nematicides. Additionally, nematicides reduced soil nematode populations with greater reductions observed when nematicides were used in combination with resistant lines. For Sub-objective 5b, the fourth year of a crop rotation study was completed to determine the effect of non-host/poor-host crops on management of the reniform nematode and crop yield. Data analysis is in progress. The non-host crops included corn, peanut, and reniform nematode resistant soybean, which were compared to continuous cotton as the control. Soil reniform nematode population densities were significantly reduced at the end of the growing season for the non-host crops with corn and soybean having lower nematode populations than peanut, whereas nematode population densities increased during the growing season for continuous cotton. Rotations with non-host crops can be an effective management strategy to reduce soil nematode populations early in the growing season. Crop rotation in combination with nematicide application and reniform nematode resistant cotton cultivars will benefit producers.
Accomplishments
Review Publications
Erpelding, J.E. 2020. Genetics of the fuzzless ovule phenotype of Gossypium arboreum accession PI 615733. Crop Breeding and Applied Biotechnology. 20(4):e32812044. https://doi.org/10.1590/1984-70332020v20n4a57.
Singh, B., Chastain, D.R., Reddy, K., Snider, J.L., Krutz, L.J., Stetina, S.R., Seghal, A. 2020. Earlyseason morphological and physiological responses of resistant and susceptible cotton genotypes to reniform nematode and soil nitrogen. Agronomy. 10(12):1974. https://doi.org/10.3390/agronomy10121974.
Erpelding, J.E. 2021. Genetic evaluation of the brown fiber phenotype for Gossypium arboreum accession PI 615733. Plant Breeding. 140:367-374. https://doi.org/10.1111/pbr.12890.
Erpelding, J.E. 2021. Genetic characterization of the red colored corolla phenotype for Gossypium arboreum accession PI 529731. Plant Breeding. 140:142-149. https://doi.org/10.1111/pbr.12884.
