Breeding

Our group is breeding for specific targets of interest to organic producers. These targets include:

Gametophytic incompatibility for exclusion of non-GMO pollen

This program will build on the Ga1-S germplasm being developed by the Mandaamin Institute, Cornell University and USDA-ARS. Donors for Ga1-S, Tcb1, and Ga2-S were crossed with inbred lines with agronomic traits desirable to organic producers. Backcross offspring containing the desired gametophytic incompatibility loci will be identified using a combination of crossing with known testers and molecular markers being developed by the USDA. Once the desired level of inbreeding is reached, the resulting lines will be fixed for the traits by sequential inbreeding coupled with testing using markers and crosses. The resulting set of lines will be crossed with a single tester in an opposite heterotic pattern to ascertain field performance for production, moisture and protein. The ability of different combinations of gametophyte factor alleles to exclude unwanted pollen will be assessed by de-tasseling the plants to be tested in isolation nurseries where the males are ga1/ga1 (the pollen to be excluded), and observing the extent of seed set. Each seed that develops would reflect a failure of the gametophyte factor to exclude the unwanted pollen. In addition, quantitative assessments of degree of pollen exclusion will be carried out using mixtures of pollen from plants that produce different colors of grain as shown in the figure. Pollen from a ga1/ga1 (non-excluding) plant with blue grain should be excluded by a plant with Ga1-S. If this pollen is mixed with pollen from a Ga1-S/Ga1- S (excluding) plant with yellow grain in a known ratio (determined by testing the mixture on a ga1/ga1 non-excluding plant), only yellow kernels should develop on the Ga1-S plant if exclusion is perfect. Comparison of the ratio of blue to yellow kernels on the plant to be tested to the ratio of the control plant indicates the degree of pollen exclusion of the test plant.

Native Insect Resistance

Corn Earworm

Maize is the preferred host for the corn earworm (Heliothis zea) in both tropical and temperate areas. Varieties originating in tropical and southern regions of the U.S. as well as the Caribbean have long been known to have protective husk qualities and have been a source for these qualities in corn breeding programs (Dicke and Guthrie, 1978). Recurrent and continued mass selection has been an effective method for improving plant populations for corn earworm resistance (Widstrom, Wiser, et. al. 1970; Zuber, Fairchild, et. al. 1971).

Fall Armyworm

The fall armyworm (Spodoptera frugiperda) is one of the most important pests of maize in tropical and subtropical areas of the Americas. It infests the corn plant from early seedling to grain maturity (Dicke and Guthrie, 1978). Ear injury through the husks is more prominent than with Heliothis and the succession of grain insects is perhaps more important. Lines originating from Antigua tested in other locations were considered to have a high level of resistance.
The use of Puerto Rico as a winter nursery and continuous conversion nursery site in the late 1990’s led to the awareness of the presence of both fall armyworm and corn earworm as endemic pests for which both the level of pressure and consistency of damage on susceptible material was severe and that without artificial infestation, screening and selection were possible. Based on this knowledge, Montgomery(2002, unpublished data) initiated a fall armyworm and corn earworm resistance screening, breeding and selection program in maize, with the intent of finding commercially useful levels of insect protection.

Blue corn

Grain samples have been obtained from replicated tests of the following maize accessions; Navajo Blue, Los Lunas Blue (Selected), Los Lunas Blue, Flor del Rio, Yoeme Blue, Ohio Blue, Hopi Blue, and Taos Blue. They have been evaluated in replicated trials across two seasons and several locations in New Mexico and Arizona. Total monomeric anthocyanin in samples will be determined spectrophotometrically by the methods of Kimura et al. (2007), Giusti and Wrolstad (2002) and Singleton and Rossi (1965), respectively. The pigments will also be extracted, partially-purified and analyzed for individual components by reverse-phase, HPLC-DAD using the methods of Jing and Giusti (2005) and Kurilich and Juvik (1999). In addition, infrared spectroscopy will be explored as a potential method to identify and/or quantify pigments in the germplasm (Brenna and Berardo, 2004; He et al., 2007). All analyses will be performed in triplicate. Following identification of the most promising germplasm for both good agronomic potential and expression of high blue kernel pigmentation, samples will be milled to determine the suitability of the flour for production of tortillas and tortilla chips, following nixtamalization. Color retention and food product quality will be determined using standard sensory evaluation procedures with guidance from NMSU and ISU food scientists.

QPM

Our approach to breeding QPM has been to cross elite adapted inbred lines to QPM varieties and recover inbreds by pedigree breeding. We monitor kernel opacity and screen for the presence of o2 with molecular markers. We spot check amino acid balance occasionally as well. Advanced lines are tested in multi-location yield trials on non-QPM testers to determine yield potential and on QPM testers to determine grain quality and yield of specific hybrid combinations. The NMSU and USDA-ARS groups have followed this approach in parallel. Last year, we exchanged germplasm and made crosses between the best performing inbred lines from NMSU and the best performing lines from USDA. We propose to initiate a new selection program in which selections are made from these crosses at each of our location, with selected lines being shared each year. By selection at test sites in both the southwest and the central corn belt, we anticipate development of broadly adapted germplasm with both heat and drought stress tolerance as well as resistance to a wide range of diseases and pests.

Methionine content

The biggest challenge in breeding for increased methionine content is measurement of the trait. We propose to use near-infrared spectroscopy (NIRS) for this purpose to determine the lysine, methionine, and cysteine composition of the grain. One of the products of our previous proposal is a calibration that enables this measurement to be made. This calibration is based on wet-chemistry data from lines being bred by Mandaamin (Jaradat and Goldstein, 2013; 2014) and high methionine breeding populations. Extreme methionine values will be verified by wet chemistry analysis using either the AOAC approved method or a less expensive microbial method that we have used to develop high methionine populations (Scott et al., 2008). USDA, Montgomery Consulting and Mandaamin Institute all have high methionine germplasm in the form of inbreds and breeding synthetics so we propose to follow our proposed general breeding plan and develop hybrids, breeding synthetics and OPVs with this trait. Because methionine content will be particularly well suited to corn used to make poultry feed, we will develop orange versions of this high-methionine corn. Chickens fed this orange corn produce eggs with a more desirable yolk color than chickens fed normal corn (see figure).