Biotech Approaches to FHB Resistant Wheat and Barley

This project seeks to utilize molecular genetics to enhance resistance to scab in wheat and barley. There are two major areas of research:
1) gene discovery; and
2) wheat and barley genetic engineering for enhanced scab resistance.

 Specific objectives related to FHB:
1) identify mechanisms and essential genes for scab resistance; and
2) develop scab resistant wheat and barley germplasm through genetic engineering. This progress report reviews advancements for the period of July 2001 – July 2003.

1. Identify mechanisms and essential genes for scab resistance

We generated a large set of genes expressed in wheat and barley during F. graminearum infection and examined these genes. We developed cDNA libraries from Sumai 3 wheat spikes and Morex barley spikes spray-inoculated with F. graminearum.  We funded Dr. Olin Anderson (USDA-ARS, Albany, CA) to sequence 10,000 expressed sequence tags (ESTs) from the wheat library.  We funded Dr. Rod Wing (Clemson University) to sequence 5,000 ESTs from the barley library. To date, 10,000 wheat and 5,000 barley ESTs have been generated and deposited in Genbank.  The wheat and barley ESTs are providing the tools and information for understanding the interaction between small grains and F. graminearum.

To initiate an understanding of genes that may provide increased FHB resistance, we conducted an analysis of genes and categorized ways in which they convey resistance.  To further our understanding of genes involved in resistance, we conducted a computerized comparison of the genes expressed in common between the wheat and barley libraries prepared from F. graminearum-infected spikes.  Our intent is to identify genes expressed in common in two different plants infected with the same pathogen. 

In addition, we compared our barley ESTs to 15,000 ESTs from three barley cDNA libraries prepared from barley leaves inoculated with Blumeria graminis (causal agent of powdery mildew). In this case, we are studying the genes that are expressed in common in the same plant infected by two different pathogens.

We have identified a set of rarely-expressed genes involved in plant-pathogen interactions that may play a role in resistance. Currently, we are examining the expression of this select group of genes during F. graminearum infection.

In many respects, we are essentially gathering genetic clues into the interaction between wheat and barley and F. graminearum, identifying genes involved in resistance and susceptibility.

2. Develop scab resistant wheat and barley germplasm through genetic engineering

We have a large set of antifungal protein genes that are available for wheat and barley transformation, and have developed transgenic wheat with examples of all antifungal protein genes and with combinations of these genes.

We have conducted multiple FHB screens on some of the transgenic (genetically-engineered) lines, and identified lines expressing significant reduction in FHB severity compared to non-transgenic controls. In general, the transgenic lines that exhibit enhanced resistance ranged from 25-45% FHB severity, compared to the non-transgenic controls (Bobwhite and nontransformed siblings of the transgenic events) that exhibited between 60-90% FHB severity.

Our data shows that we have developed transgenic wheat that exhibits enhanced resistance to FHB.  We will screen these lines for FHB resistance in the field in the summer of 2004.  Further, we continue to develop and advance various combinations of transgenes and their expression in wheat and barley.

We are developing, in collaboration with Dr. David Garvin (USDA-ARS, St. Paul, MN), a model system for studying wheat FHB. The wheat cultivar Apogee is susceptible to FHB and flowers within 30 days.  Therefore, approximately 5-6 consecutive FHB screens can be conducted in a single year on this genotype.  As a proof of concept, we developed a transformation system in this genotype and have generated transgenic wheat.

   – Dr Gary J. Muehlbauer, Department of Agronomy and Plant Genetics