Recipient Organization
NEW MEXICO STATE UNIVERSITY
1620 STANDLEY DR ACADEMIC RESH A RM 110
LAS CRUCES,NM 88003-1239
Performing Department
Plant and Environmental Sciences
Non Technical Summary
The tepary bean (Phaseolus acutifolius), a relative of common bean (e.g. pinto beans) has been grown in the semi-arid Southwest and northern Mexico for centuries and it is well known for its drought resistance (Nabhan and Felger, 1978; Pratt and Nabhan, 1988; Miklas et al., 1994). It has a short life-cycle and can be planted as late as July in low to mid-elevations in New Mexico. Tepary beans are also known to form symbiotic associations with Rhizobia bacteria, thus enabling them to fix atmospheric nitrogen and return it to the soil for subsequent crops (Mapp, 2008). Anecdotal observations in Botswana (Molosiwa et al., 2014) and research in Virginia (Bhardwaj, 2013) suggest that tepary vegetation can provide good quality forage for ruminant animals. Teparies could also rapidly produce vegetative biomass for "plow-down" as a cover crop with little or no irrigation during the monsoon season. One cutting, or grazing, followed by "plow-down" is entirely feasible. It is important to determine if these promising attributes of tepary bean will enable it to become a future non-thirsty, dual-purpose, forage and cover crop. If so, it will help mitigate the risks associated with drought and ensure continued profitability in future cropping systems.
Animal Health Component
25%
Research Effort Categories
Basic
25%
Applied
25%
Developmental
50%
Goals / Objectives
Identify tepary bean varieties adapted to New Mexico conditionsIdentify those tepary varieties with the greatest potential for grain production, forage production, or green manure utilizationDetermine microbial species associated with nodulation of tepary rootsDetermine tepary varieties with the highest soil N contribution through nodulationIncrease virus-free seed stocks of the most promising varieties for additional cooperative research and farmer trials
Project Methods
We will evaluate the grain yield, vegetative biomass, percent (ground) cover, nodulation activity, forage quality, and maturity of previously selected tepary varieties in replicated field studies. Recently released varieties from Colorado State University/USDA-ARS Tropical Agriculture Research Station (Porch et al., 2013) cooperative breeding program (CSU Tep 148, TARS Tep22, TARS Tep32), several varieties improved through mass selection by Mike Sheedy at the University of Arizona Maricopa Agriculture Center (Maricopa black, Maricopa yellow, Maricopa brown, Maricopa white), and a mottled variety from Chiapas, Mexico (Native Seeds SEARCH accession) that we have mass-selected for two cycles, will be evaluated at two locations during two years. In addition, larger numbers of landrace accessions (uncharacterized germplasm) will be evaluated through observations at one location to identify promising accessions for further testing. We received 25 accessions from the Native Seeds/SEARCH collection and we have also received 25 accessions from Dr. Harbans Bardwaj (Virginia State University) who previously screened the entire USDA tepary germplasm collection for drought resistance using a rain-out shelter. Canopy ground cover will be estimated as described by Contreras-Govea et al (2009) at flowering and two weeks post-flowering. Grain yield will be determined by hand-harvesting 3 meter sub-plots within each short-row plot. Leaf samples will be obtained at flowering and forage quality will be determined at Ward Laboratories, Kearney, NE.Additional two-row plots will be planted of the best (four-five) performing varieties at the low fertility site at Fabian Garcia Science Center in Las Cruces and at one Agricultural Science Center (ASC) in late June/early July in replicated split-plot field experiments (main plots-inoculated vs. non-inoculated; sub-plots-tepary accessions). Irrigation will be provided as needed to ensure stand establishment. "Rescue" irrigation will be applied only if there is a long duration (10 days) between subsequent rainfall events of 1.3 cm or more. Canopy ground cover will be estimated as described by Contreras-Govea et al. (2009) at flowering and two weeks post-flowering. Entire plants at the plot-ends will be uprooted at the initiation of flowering to determine nodulation effectiveness (number of nodules per plant). Destructive sampling of sub-plots will be performed again two weeks after flowering to determine total biomass and forage quality. At the 60-day mark, soil samples will then be obtained from the center of each two-row plot, and the plots will be plowed under. Additional soil samples will be obtained again at three subsequent three-week intervals to determine the amount of N that was made available for fall planted grain crops (wheat or barley).As part of an AES funded M.S. student project, we will then characterize native tepary-Bradyrhizobium symbiosis by obtaining five nodules from each of the four end-plants within each replicate. The rhizobia-host specificity will be determined by isolating bacteria on YEM plates and verifying that they stain as Gram-negative. The student will then use molecular DNA based techniques to answer questions about the identity and colonization ability of nitrogen fixing root nodule forming bacteria. The identity of native root nodule forming bacteria will be compared exploring two genetic markers (nifH and 16S rDNA) within tepary populations as well across tepary varieties. Differences in colonization ability will be investigated by determining the degree of nodulation (determined by nodule dry weight/root dry weight) as well as numbers of nodule forming bacteria using quantitative PCR. DNA will be extracted from the putative rhizobia species and the rDNA regions will be PCR amplified using primers conserved among most/all bacterial species (27F and 519R as forward and reverse primers, respectively). Obtained and purified PCR products will be sent to Genewiz (www.genewiz.com) for sequencing.We will conduct seed increases of superior tepary varieties and perform BCMV (potyvirus) testing using Agdia testing services (www.agdia.com/testing-services/). Strip-plot research will be initiated to demonstrate efficacy of "plow down" and cattle grazing feasibility in cooperation with the Tucumcari ACS. We will also perform water budget, ecosystems services, and economic analysis in comparison with e.g. an alfalfa based cropping system. The strip plots will be conducted a second year. A cooperator in Agricultural Economics will be sought at this later time. "Starter" seed lots (approx.one kg) will be provided to farmer cooperators for on-farm trials during the final year of the project.