Summary

This 3-year project will identify new genes and Quantitative Trait Loci (QTLs) for resistances to the most important foliar and root rot diseases of subterranean clover and deliver molecular markers closely linked to them for use in breeding programs. It addresses RIRDC’s Objective 3 aims of “increased profitability of seed production and decreased growing risk by providing new varieties and increased productivity” and the strategy of “plant breeding to target new varieties with improved seed and forage yield”.
The project leverages onto investments by Meat & Livestock Australia (MLA) and the Australian Research Council (ARC) and will exploit molecular biology technologies developed in these projects. The project consists of two integrated parts. The first part will phenotype the 97-member subterranean clover core collection, which represents ~ 80% of the genetic diversity within the species, and 28 diverse cultivars for reactions to the foliar diseases, clover scorch and rust, and to the root rot pathogens, Phytophthora clandestina and Pythium irregulare. The second part will identify molecular markers closely associated with genes and QTLs for resistance to each disease.
The outputs of this research will be: (i) a measure of subterranean clover diversity for resistance to the above diseases; (ii) an understanding of the number of different genes or QTLs that determine resistance to each disease; (iii) identification of potential parents to introduce new resistance genes into crossing programs; and (iv) discovery of molecular markers closely linked to genes or QTLs for disease resistance.
The Australian seed industry will benefit from this research through increased seed demand, by having new disease-resistant cultivars to market. Seed growers will benefit directly, as increased disease resistance will result in markedly higher seed yields, more reliable seedling establishment and a lower requirement to spray fungicides and herbicides.

Program

Pasture Seeds

Research Organisation

University of Western Australia

Objective Summary

This project will identify new genes and Quantitative Trait Loci (QTLs) for resistances to the most important foliar and root rot diseases of subterranean clover and deliver molecular markers closely linked to them. These diseases were identified by Nichols et al. (2014) as having a major impact on seed production. The project will utilise the 97-member core collection of subterranean clover, which represents around 80% of the total genetic diversity within the known 10,000 accessions of the species (Nichols et al. 2013), along with an additional 28 diverse cultivars. These 125 genotypes are currently undergoing detailed molecular characterisation in MLA project B.PBE.0037, which will enable the genetic control for resistance to each disease to be determined and molecular markers closely associated with resistance genes or QTLs to be produced.
The two most important foliar diseases of subterranean clover will be examined in this project; these are clover scorch (Kabatiella culivora) – both Race 1 and 2 (seedling and adult resistance) and rust (Uromyces trifolii-repentis). The two most important root rot diseases, Phytophthora clandestina and Pythium irregulare, will also be researched.
The specific objectives of the project are to:
1. Determine the level of diversity within subterranean clover for resistance to the four important major diseases above that currently have major adverse impacts both seed production and the saleability to producers of the seed produced;
2. Determine the genetic control for resistance to each major disease pathogen;
3. Identify potential the best parents for crossing to introduce new genes for resistance to these major important diseases into new cultivars of subterranean clover;
4. Identify molecular markers closely linked to genes or QTLs for resistance