Interest in the production of hard white spring wheat (HWSW) has increased dramatically in the United States both for domestic and export use.  The hard white spring wheat and specialty wheat breeding program at NDSU is committed to releasing quality, adapted HWSW cultivars to area producers.  The program was initiated in the spring of 1998 when Dr. Bill Berzonsky became project leader.  Currently, various advanced HWSW lines are being evaluated for yield, protein, disease resistance, agronomic characteristics, and bread baking quality.  The summer 2001 season will see the planting of drill strips of promising lines for seed increase and quality determination.  More information on HWSW can be found within this website.

Waxy Starch and End-Use Applications in Wheat

Starch, which is found in all plant tissues, is most abundant in the endosperm of cereal grains.  Starch is a carbohydrate composed of two types of glucose polymers, amylose and amylopectin.  Amylose is made of straight chains and behaves as a linear polymer.  Amylopectin contains the same straight chains but also branches, producing a larger molecule.  Low-amylose wheat is also referred to as waxy wheat.  The term ‘waxy’ was first applied to amylose-free mutants of maize, referring to the waxy appearance of the endosperm of dried kernels, compared with the flinty or translucent appearance of wild-type kernels.

Research has shown that a strong resistance to retrogradation exists for waxy starch.  This suggests that waxy starches may be superior for refrigerated and frozen bread dough products.  Waxy wheat properties may also extend the shelf-life of baked goods.  Studies suggest that reduced amylose content can retard staling because of the retrogradation behavior of amylose in starch gels or baked goods.  As heat is applied to starch, the unbranched amylose leaches out of the food.  When the food is cooled, the branched amylopectin does not set as tightly as if amylose were present.  Reducing or eliminating amylose therefore may reduce the onset of staling.

Starch is synthesized in specialized organelles known as amyloplasts, where amylose production is regulated by a granule-bound starch synthase (GBSS).   Waxy mutants of maize, barley and other plant species lack both GBSS and consequently amylose.  Therefore full, waxy mutants contain amylopectin but no amylose.

Three genes encode GBSS in hexaploid wheat.  Fully waxy wheat has null, or non-functioning alleles at each of these loci.  Wheat that is null at one or two of these alleles is termed a partial waxy wheat.  Breeders have been able to develop waxy wheats by hybridizing wheats carrying various null alleles.

Research is being conducted by the White Wheat and Specialty Wheat Breeding Project to develop partial waxy white wheat for use in frozen dough or Asian noodle markets.

Wheat Stem Saw Fly Resistant Wheat

The wheat stem sawfly (WSS), Cephus cinctus, has been causing yield loss in North Dakota since 1906.  In the 1940’s, the sawfly was responsible for up to 50% yield loss in western North Dakota wheat.  Although cultural control and solid stem wheat cultivars have held WSS damage to a minimum, yield loss is observed every year, primarily in western North Dakota.

The female WSS deposits an egg in the stem of a wheat plant during the stem elongation to boot stages.  The egg hatches and the larva feed inside the plant until late in the summer.  At this time, the larva move down the plant close to the ground surface, cuts a groove around the inside of the stem and plugs this stub with its body waste.  The cut stems fall over and are un-harvestable.    The larva over-winter here until it pupates the following May.

The best control of WSS is the use of solid-stem cultivars with solidness in the lower three internodes.  Shallow fall tillage has also shown up to 90% WSS control.  The Specialty Wheat Breeding project is developing quality, solid stem white wheat cultivars. (Source: Wheat Stem Insect Pests and Management Practices, NDSU Extension Service Bulletin, E-680).
 

Low Polyphenol Oxidase (PPO) Wheat

The influence of environment on these characteristics was examined on spring wheat lines from replicated field trials grown in 2000 at four North Dakota locations (Minot, Carrington, Casselton, and Prosper).

Graduate Research Assistant John Davies is making crosses with HWSW lines and un-adapted low PPO cultivars.  John is evaluating genetic and seed screening techniques for PPO that could be used in a breeding program and he is examining factors other than PPO that may influence noodle darkening.

Fusarium Head Blight (Scab) Resistant Wheat

The largest economic impact to small grains in the northern wheat growing regions of the U.S. has been fusarium head blight, commonly known as scab.  Caused by the fungus Fusarium graminearum, scab can be prevalent in susceptible cultivars of HRSW, durum and barley.  Yield losses are attributed to the sterility of florets, shriveled grain and low test weight kernels.  When scab symptoms are present, the entire wheat head or part of it will have a bleached appearance.  Affected kernels have a grayish or pinkish color and are referred to as “tombstones”.  Symptoms may be less severe if infection occurred later in the development of the wheat kernel.  Crops infected with high levels of scab have low value for end-use food processing, mycotoxins that are toxic to animals, or low seed vigor.

Different levels of scab resistance are recognized.  Type I resistance does not allow the infection to occur while Type II resistance prohibits the spread of infection with in the wheat head.  Alsen, a HRSW released by NDSU and the Agricultural Experiment Station (AES) in 2000, has Type II resistance.  The white wheat breeding program is screening advanced lines of HWSW for Type I and II resistance and promising lines are being selected for agronomic and end-use quality.  The  double haploid procedure is being used to shorten the cultivar development process, and the NDSU Wheat Germplasm Enhancement team is looking for molecular markers that can be used to screen for resistant cultivars.  Marker-assisted screening for scab resistance will allow us to screen for scab resistance even if the environment is not suitable for fusarium infection. (Source:  Fusarium Head Blight (Scab) of Small Grains, NDSU Extension Service Bulletin, PP-804.  Photos by Vernyl Pederson and Jim Miller).
 

High Grain Protein Content

Grain protein content (GPC) is a critical quality factor for hard wheat.  Protein content and quality are necessary for making good bread products and premiums are paid to growers for increased GPC.  An objective of the HWSW breeding project at NDSU is to release cultivars that have high GPC.

A single gene that has a major impact on increasing GPC was discovered in a wild wheat species.  Since then, the gene has been transferred to adapted durum (Langdon) and HRSW (Glupro) cultivars.  Crosses have been made with Glupro and advanced HWSW lines and adapted cultivars in order to transfer the increased GPC trait to HWSW cultivars for North Dakota production.  Graduate Research Assistant David Boehm is using molecular markers to screen for this gene and follow it to progeny after Glupro crosses and backcrosses to the white wheat parent.  In this way, the development of white wheat cultivars with increased GPC is faster and more efficient as only progeny with the gene are moved through the breeding program.  These progeny with the GPC gene will then be tested for agronomic and quality traits.
 

Nitrogen Fertilizer Effects on Frozen Dough End-Use Quality

In 2000, six HRSW cultivars were grown under three levels of N in replicated field trials at three North Dakota locations. Each plot was evaluated for yield, GPC, test weight, kernel brightness, falling number, kernel size, kernel hardness, and kernel weight.  Samples were  milled and will be tested for flour strength (farinograph), dough strength (extensigraph), and baking quality (loaf volume and proof time).  Samples will also be processed into dough and the same quality factors will be evaluated after three months of frozen storage.  This project is being conducted by Graduate Research Assistant David Boehm. For preliminary results on this project using MicroSoft PowerPoint, click here.
 

Double-Haploid Breeding Technique

The goal of any breeding program is to produce pure-bred cultivars that are high in quality and useful for area producers.  These cultivars should be true-breeding and homogeneous.  It would take seven years (F₇) for a self-pollinated plant to reach 98 % homozygosity and another two years for seed evaluation and increase.  A double-haploid (DH) breeding technique can develop homozygous lines in one generation.  Although evaluation and increase is still necessary, DH projects can reduce the time to develop new cultivars.

In one process, pollen (male gametes) from maize is used to fertilize the ovary (female reproductive organ) of the wheat plant.  Under normal circumstances where both parents are wheat a 2n embryo is produced with one set of chromosomes donated from each parent.  When a cross with maize is made, the maize chromosomes are eliminated due to the inability of maize chromosomes to move to the spindle poles during cell division, leaving the developing embryo with only a haploid, or 1n complement of wheat chromosomes.  Embryos rarely survive if left to develop in vivo, thus they are removed from the developing seed 14-28 days after the cross and placed on artificial nutrient medium.  When the plants reach a certain growth stage, they are treated with colchicine, which will promote doubling of the chromosome number.  If doubled, the 1n plant is now 2n.  The benefit is that the female chromosome set now doubled is homozygous at all loci.

We have a DH project to expedite haploid plant development.  This procedure is being implemented for wheat lines with increased grain protein content, scab resistance, sawfly resistance, low PPO enzyme activity, and waxy (low-amylose) starch.  Research specialist Sara Kleven is working on the development of DH materials for the white wheat breeding project.