Wheat Genetic and Genomic Resources Center and Its Contributions to the Kansas Wheat Industry

Introduction:
The WGGRC has a mandate to conserve the world's gene pool of wheat; evaluate useful genes and facilitate their transfer to wheat as improved germ plasm; conserve and develop cytogenetic stocks to facilitate genetic analysis and gene transfer; identify and catalogue wheat genes and facilitate their deployment for sustainable and profitable crop production; train undergraduate and graduate students, postdoctoral fellows and visiting scientists; and promote and enhance the awareness of genetic resource conservation and utilization needs and potentials to agricultural and academic administrators and professionals, producers, and consumers. The WGGRC has established a national and international network of scientists to undertake a collaborative research effort on collection, conservation, and utilization of the world's germ plasm of wheat. The Center's scientists publish the Annual Wheat Newsletter summarizing wheat improvement research from all the leading institutions of the world. Many Universities, public and private, and grower organizations in 33 states have endorsed the Center's mission. The WGGRC maintains a website (http://www.ksu.edu.wgrc/) that provides information on the germ plasm collection, publications, and many other educational and academic activities.

The current project is ongoing with continuous support (since 1981) from the Kansas Wheat Commission (KWC) and has provided solutions to long-term problems of the Kansas Wheat Industry. The project funds are used to collect, maintain, and evaluate wild wheat species for useful genes and transfer them into Great Plains adapted wheat varieties. Forty-seven germ plasm releases have been announced by the WGGRC. These germ plasm lines contain new genes for resistance to Hessian fly, greenbug, Russian wheat aphid, and wheat curl mite pests; leaf rust, powdery mildew, Septoria, and tan spot fungi; and the wheat streak, wheat spindle streak, and wheat soil borne mosaic viruses. These resistance genes are the focus of genetic, cytogenetic, and molecular analysis by WGGRC scientists and others. The overall goal of the project is broaden the genetic base of Kansas wheat, enhance its yield potential, reduce losses to wheat crop from pests, enhance the quality of the harvested crop, extend the productive life of wheat varieties, and protect the huge investment that goes into the development of a new variety. Center scientists work closely with wheat improvement team of K-State to release improved wheat cultivars that contribute immensely to the economy of the state.

Rationale and Significance:

Bread wheat has a narrow genetic base because of its recent origin. The wild relatives of wheat contain tremendous variation for broadening the genetic base of wheat. For this purpose, we must conserve the wild species, document genetic novelty, and introduce novel genes for wheat improvement. This is a continuous process as resistance genes breakdown and new traits are needed for new disease problems, new constraints that limit yield or novel end uses of wheat. The enriching of wheat gene pool is an integral part of wheat improvement program. There is no substitute for breeding through sexual hybridization and evaluation of the progenies in growth chambers, greenhouses, and field plots. This is because introduction of a targeted gene is often accompanied by other negative or positive traits that can be detected only by evaluations over several years. However, this process can be streamlined with new technologies and, thus, molecular and cytogenetic analysis of wild species and segregating materials is an integral part of germ plasm enhancement effort. New technologies also allow chemical isolation of genes for novel manipulations for improving the health of the wheat plant (durable disease control) and productivity.

Procedures and Methodology:

We have established standard procedures for germ plasm introduction, storage, regeneration, and distribution. Decisions for new germ plasm introductions are made based on long-term conservation goals, as an integral part of collaborative national and international projects and, in many instances, in response to a new threat to the Kansas wheat industry. Evaluation of germ plasm for pest resistance and other traits is done either in WGGRC laboratories or with collaborating scientists. We use genetic, cytogenetic, and molecular tools for transferring, characterizing, and establishing the novelty of newly introduced genes in Kansas-adapted breeding materials in close collaboration with our wheat breeders and other scientists. Research results are published in professional journals and improved germ plasm is registered with the Crop Science Society of America and maintained by the WGGRC for conservation and distribution.

Objective 1: Introduction of new germ plasm:
Approach: Under this objective, we import germ plasm to meet the new demands of the Kansas wheat industry. Proper channels for the acquisition of germ plasm have been established. Seed received under import restrictions must be grown in a quarantine greenhouse and inspected by the Kansas Department of Agriculture during vegetative growth, at flowering, and after harvest. Plants may be sprayed at heading with a fungicide to control seed-borne diseases. After the seed is inspected and deemed disease free, the quantity of seed harvested is reported to the KDA. The harvested seed must be treated with fungicide and then regrown to assure the absence of disease. Remnant seed then can be destroyed. Regeneration of both wild species and germ plasm lines will be accomplished in the greenhouse, for spring-types, and in a field plot at the Rocky Ford research area, where winter types can be evaluated for winter hardiness and resistance to local disease pressure.

Objective 2: Development of new germ plasm.
Approach: Newly introduced materials are evaluated for useful traits and bred into Kansas advanced wheat breeding lines through chromosome engineering and molecular-marker technologies.

In 2006, based on 2005 evaluation, 100 lines with potential adult plant resistance were selected and grown in the Rocky Ford Research Area, with two reps per line with same controls and experimental design as in 2005 Leaf rust ratings were taken on 5/8, 5/19, 5/25 and 6/1'. No symptoms were observed on checks on 5/8 but all Ae. tauschii lines gave a resistant reaction. Slow rusting resistance was documented in all lines and ranges of reactions were noted as in 2005.

For 2007, we have selected 50 lines with best potential for durable rust resistance for further field evaluation with same experimental disign and controls except four replicates will be plant ed per line. In addition, we will test the same lines for adult plant resistance with a range of rust isolates in the greenhouse experiments. Our goal is to identify ten best lines showing slow rusting and non-race specific resistance for transfer to wheat.

Progress Report

1. UPDATE on stripe rust and leaf rust resistance gene transfer from Aegilops geniculata.

Previously, leaf rust and stripe rust-resistant introgression lines were developed through induced homoeologous chromosome pairing between wheat chromosome 5D and 5Mg of Ae. geniculata. Genomic in situ hybridization (GISH) with Ae. comosa DNA as probe showed three different kinds of introgressions. All three types of introgression lines showed complete and similar resistance to the most prevalent races of leaf (PRTUS 25, PRTUS 35, PNMQ, MCDL, and PRTUS 6) and stripe rust (isolate KS2005 of PST-100) in Kansas. One resistant line (TA5602) with a cytologically undetectable introgressed segment and agronomically as good as the recipient parent (WL711) was used to transfer the leaf rust and stripe rust resistance to the Kansas winter wheat cultivars Jagger and Overley. The F1 between Jagger and rust-resistant introgression line (TA5602) was backcrossed further with Jagger and Overley to produce a BC3F1 plants. At present BC3F2 plants are being grown in the greenhouse to isolate homozygous, rust-resistant BC3F2 progenies in the Jagger and Overley background for further agronomic evaluations in the field and subsequent germ plasm release. Diagnostic polymorphisms between the rust-resistant introgression line and the recipient parents were identified using physically mapped RFLP and EST probes. CAPS (cleaved amplified polymorphic sequences) markers are being developed from the diagnostic ESTs, which will be useful for marker-assisted breeding for rust resistance in wheat. The introgressed alien segment in TA5602 was found to be a cryptic transfer that was less than 3.5 % of the chromosome arm 5DS. Mutagenesis using ethyl methanesulphonate identified an additional adult-plant, leaf rust-resistance gene (LrGen) in TA5602 suggesting this line could be a potential rust resistance gene pyramid for its deployment in agriculture.

2. UPDATE on leaf rust resistance gene transfers from Aegilops triuncialis.

We identified one cryptic leaf rust-resistant introgression line (TA5605) from progenies that were developed by directly crossing hexaploid wheat with rust resistant Ae. triuncialis. TA5605 was resistant to the most prevalent races of leaf rust PRTUS6, PRTUS25, and MCDL in Kansas. Bulk segregant analysis was used to identify the chromosome location of the rust resistant introgression using distally mapped molecular markers and an F2 population of a cross 'Jagger / TA5605'. Further genetic mapping using SSRs and RFLP markers showed that one SSR marker and three RFLP markers, mapped on chromosome arm 2BL, diagnostically identified the rust resistance of Ae. triuncialis in the introgression line TA5605 (T2BS•2BL-2tL(0.95)). Because the leaf rust resistance gene derived from unique source and its unique map location on the long arm of chromosome 2B the resistance gene was designated Lr58. The rust resistant line (TA5605), which is agronomically as good as the recipient parent (WL711), was used to transfer the leaf rust resistance to the Kansas winter wheat cultivars Jagger and Overley through a backcrossing breeding. Presently BC3F2 plants are being grown to isolate homozygous, rust-resistant BC3F2 progenies in the Jagger and Overley background for further agronomic evaluations in the field and subsequent germ plasm release. Diagnostically polymorphic SSR marker CFD50 also was found to be polymorphic in winter wheats Jagger and Overley, therefore, CFD50 was used for marker-assisted selection of Lr58 in the backcross-breeding program. This marker is being validated on a set of cultivars for its effectiveness in marker assisted selection of Lr58 in breeding programs.