Breeding maize under biodynamic-organic conditions for nutritional value and N efficiency/N2 fixation

Authors: GOLDSTEIN, WALTER - Mandaamin Institute; Jaradat, Abdullah; HURBURGH, CHARLES - Iowa State University; POLLAK, LINDA - Retired ARS Employee; GOODMAN, MAJOR - North Carolina State University

Submitted to: Open Agriculture Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2019
Publication Date: 6/27/2019
Publication URL: https://handle.nal.usda.gov/10113/6497006
Citation: Goldstein, W., Jaradat, A.A., Hurburgh, C., Pollak, L., Goodman, M. 2019. Breeding maize under biodynamic-organic conditions for nutritional value and N efficiency/N2 fixation. Open Agriculture Journal. 4:322-345. https://doi.org/10.1515/opag-2019-0030.
DOI: https://doi.org/10.1515/opag-2019-0030

Interpretive Summary: Modern maize cultivars and hybrids have been developed to respond to mineral nitrogen inputs in order to meet yield targets of 150 to 200 bushels per acre. However, high rates of nitrogen input may diminish water and air quality as well as endanger human and animal health. Moreover, increasing grain yield can favor starch production at the expense of protein, minerals and other beneficial constituents of the maize kernel. This program developed high-quality maize as a potential alternative for organic farmers. The grain produced by this program is more nutritionally balanced, less expensive and more sustainable as a feed source for farm animals. This is because the selection process in the breeding program focused on shifting protein composition in favor of the protein portions that are rich in essential amino acids. Better proteins enable animals to more efficiently produce body weight and high-quality products such as eggs. Another objective of the breeding program was to increase maize’s ability to efficiently obtain nitrogen with less applied fertilizer. This includes increasing the ability of the maize plant to partner with soil microbes so that it can fix its own nitrogen and produce high levels of quality protein in the grain. A major outcome of the program was the appearance of soft kernels, rich in high-quality proteins packed with more essential amino acids, as well as higher quantities of trace elements, especially iron and zinc. The quality of the grain was documented in joint publications of USDA-ARS in Morris, MN, and Mandaamin Institute, Elkhorn, WI. Yield results for 2016 and 2017 indicated that the nitrogen efficient/putative N2 fixing hybrids can yield higher amounts of grain and protein per hectare than conventional hybrids under nitrogen-limiting conditions, but not as well under conditions with high rates of manure application. These results validated a breeding approach that simultaneously combined breeding for nutritional quality and for nutrient efficiency under organic conditions. The basis for nitrogen efficiency and protein quality in our cultivars could be attributed to shifts in root efficiency, microbial relationships, and protein metabolism. Higher yield and better protein quality of the breeding program, most likely, can be attributed to a better adaptation of the maize plant to reduced fertilizer inputs, thus fostering beneficial plant-microbial partnerships. In addition, maize breeding under organic conditions also benefitted from keen breeder insights and adherence to breeding and selection principles under low external inputs of organic farming. The extent to which the results can be explained by factors beyond the classical principles of genetics deserves further research and clarification. The new germplasm will be of value to maize producers by reducing nitrogen inputs and to animal husbandry by providing an environmentally-friendly and less expensive source of an essential amino acid and high-quality protein. We encourage other researchers and farmers to test our approach to increase nutritional value, profitability and agricultural sustainability for maize and other small grain crops.

Technical Abstract: An overview is given for an ongoing maize breeding program that improved maize populations, inbreds, and hybrids in the Midwestern USA. Breeding and selection of maize for nitrogen efficiency and grain quality occurred under biodynamic conditions in Wisconsin, on an organic winter nursery in Puerto Rico, a biodynamic winter nursery in Hawaii, and a conventional winter nursery in Chile. Emphasis was on improving protein quality, carotenoid content, competitiveness with weeds, nitrogen (N) efficiency/N2 fixation, and cross incompatibility to genetically engineered (GE) maize. Adaptation and selection emphasized early vigor and optimized yield under N-limited conditions. The basis for N efficiency and protein quality in maize cultivars developed by the program may be attributed to shifts in root uptake efficiency, microbial relationships, and protein metabolism. Germplasm sources of two alleles (i.e., Ga1 and Tcb1) in maize were utilized to induce cross incompatibility. The program produced inbreds and hybrids with increased N efficiency and protein quality coupled with softer grain texture, darker foliage due to high nitrogen content, and greater activity of roots relative to conventionally-bred cultivars. Grain protein quality was improved by utilizing opaque kernels that emerged in populations during the course of the program in surprisingly high frequencies. Nitrogen efficiency was emphasized by breeding with landraces that may fix N2 in association with microbes coupled with selection for response traits under N-limited conditions. When compared with conventional maize hybrids under same conditions, the best hybrids developed by the program exhibited 30% more of the essential amino acid methionine and 16% more protein in the grain than conventional hybrids; thus, producing more protein yield per hectare. Results illustrate the potential and importance of breeding under biodynamic-organic conditions.