Location: Grain Legume Genetics Physiology Research
Project Number: 2090-21000-038-013-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: May 1, 2024
End Date: May 1, 2025
Objective:
Long-term expeditions of humans to Earth’s Moon for research and to develop infrastructure for more permanent space colonization will be safer and less dependent on re-supply if more food can be produced using lunar resources. Lunar “soil”, referred to technically as lunar “regolith”, is a poor substitute for earthly soil, lacking in structure, nutrients, organic matter, and soil microbes, while having poor water permeability and high concentrations of phytotoxic heavy metals. Recent studies demonstrated the model plant Arabidopsis thaliana could grow in different lunar regoliths although plants showed symptoms of stress associated with drought and heavy metal contamination (Paul et al. 2022. https://doi.org/10.1038/s42003-022-03334-8). However, actual lunar regolith that has been brought back from the moon is in very short supply, so researchers typically conduct experiments using lunar regolith simulants (LRS) that mimic the geochemical and physical properties of regolith samples collected at different lunar sites. Developing an effective and sustainable plant matrix requires amending LRS to contain plant growth nutrients, improve soil structure and water permeability, and reduce phytotoxicity associated with heavy metals. A simulated Martian regolith amended with green manure was used to grow lettuce (Caporale et al. 2020. https://doi.org/10.1016/jscitotenv.2020.137543).
Initial studies have been conducted using LRS amended with arbuscular mycorrhizal fungi (AMF) and vermicompost (VC) to grow desi-type chickpea. Chickpea was chosen because it is a nutritionally dense legume crop that is high in protein and dietary minerals and is colonized by beneficial rhizobacteria that fix atmospheric nitrogen. AMF sequester heavy metals, induce plant defense responses to heavy metals, and improve soil aggregation and structure. VC provides organic matter, phytonutrients, and a diverse soil microbiome. Chickpea produced seed when grown in three different ratios of LRS and VS (25%LSR/75%VS, 50%LRS/50%VS, 75%LRS/25%VS) amended with AMF. Additional studies are needed to determine if there is variation among chickpea genotypes for vigor when grown in LRS. Adult plant performance can be estimated by evaluating seedling and early growth stage vigor (Nguyen et al. 2022. https://doi.org/10.1007/s00122-021-03954-4).
The objectives of this research are: 1. Screen a collection of diverse chickpea accessions, cultivars, and USDA breeding lines for seedling vigor when grown in different ratios of LRS and VS, and 2. Determine how host genotype and different LRS/VC affect nodulation by M. ciceri. This study will identify chickpea genotypes that exhibit superior performance when grown in simulated lunar growth matrices. Improved understanding of how crop genotype and matrix ratios promote effective colonization by rhizobacteria will contribute to developing lunar cropping systems that are less reliant on exogenous sources of N fertilizer. Results may also suggest lines with exceptional seedling vigor that can be used to improve this trait of global importance to chickpea production.
Approach:
Objective 1. A set of 16 different chickpea genotypes will be selected from a USDA Chickpea Diversity Panel (Salaria et al.2023 Sci. Rep. https://doi.org/10.1038/s41598-023-41274-3). Seeds will be surface sterilized for 1 min in 5% NaOCl, rinsed twice in ddH2O, and blotted dry. Seeds will be treated with a mixture of commercial AMF (Mycoapply) and nitrogen-fixing rhizobacteria Mesorhizobium ciceri (Lalfix) before planting. Two different LRS/VC ratios will be tested, LRS50/VC50 and LRS75/VC25. LRS and VC will be mixed by weight (¿LRS = 1.3g /cm3, ¿VC = 0.39g /cm3). Control seedlings will be grown in 100% commercial potting soil. Conetainers will be filled with ~150 cm3 of potting soil or LRS/VC mix. Cheesecloth will be attached to the bottom of each conetainer to prevent loss of small particles. A single seed will be planted in each conetainer at a depth of approx. 4 cm. Five replicate conetainers will be planted for each genotype-treatment in a split plot design. Each conetainer will be watered after planting and on day 2, and then every other day for the duration of the experiment. Seedling germination and seedling vigor of an entry in both LRS/VC mixes will be evaluated 21 d after 50% of seedlings emerge in the potting soil control. Seedlings will be removed from conetainers and rinsed in tap water to remove soil or LRS/VC mix. Seedling length will be measured from 2nd node to highest leaf. The seedling will be excised immediately below the second node, and the tissue from 2nd node to highest leaf will be placed in an envelope, dried at 55o C overnight, and weighed to determine above ground dry biomass. Similarly, each seedling will be excised immediately below the root radicle, and the remaining root biomass will be dried overnight and weighed to determine dry root biomass. ANOVA will be conducted to detect significant genotype and treatment effects on seedling height and biomass dry weights. Means separations will be conducted for each treatment to detect genotypes exhibiting superior seedling vigor in LRS/VC growth mix.
Objective 2: After seedlings are rinsed in tap water as described above, three seedlings for each genotype-treatment will be visually rated for nodulation by M. ciceri based on a scale of 0-5. (Unkovich et al. 2008. ICIAR Monograph No. 136). ANOVA will be conducted to detect significant genotype and treatment effects on nodule development. Means separations will be conducted for each treatment to detect genotypes that can effectively form associations with nitrogen-fixing M. ciceri in LRS/VC growth mix.
