The project outcome will be adopted by Australian wheat breeding companies to fast track the development of new wheat cultivars with enhanced resistance so growers remain profitable under SNB epidemics.
Stagonospora nodorum blotch (SNB) caused by the pathogen Stagonospora nodorum is rated as the second most significant necrotrophic fungal disease of wheat in Western Australia with an average 9% yield loss at an estimated annual cost of $108 million to wheat growers across the wheatbelt.
Although cultural and fungicide management practices have contributed to decreasing severity of the disease in wheat production, increasing on-farm production costs has prompted the need to develop wheat varieties with effective resistance to SNB.
Previous GRDC investments through projects DAW00089 and DAW00126 made significant advances in identifying novel sources of resistance to SNB in flag leaf and glumes. Knowledge and resources to manipulate the genetic control of adult plant resistance can be used to develop appropriate SNB resistance in wheat varieties. Therefore, this project (DAW00248 commenced July 2015, completing June 2020) will deploy and validate effectiveness of combining different genes from existing and new genetic sources that will enhance SNB resistance in Australian wheat varieties.
Resistance genes to SNB have been identified in global wheat germplasm and new genes are also being sought. There is a need, therefore, to combine genes from unadapted wheat lines into Australian varieties and apply DNA marker technologies to track and select lines with different gene combinations. Selected lines need to be evaluated in field trials for proof-of-concept that specific gene combinations express enhanced resistance in Australian wheat production environments. Proof-of-concept will increase the probability of breeding companies adopting and utilising genes and associated DNA markers for commercial variety development.
- Identify existing and new sources of SNB resistance that can be used in germplasm development and commercial breeding.
- Deploy existing and new resistance genes from global wheat accessions into Australian cultivars and identify single or gene combinations that will make significant improvements in flag leaf and glume resistance.
- Evaluate and identify wheat germplasm with single or combined genes that express improved SNB resistance in Australian wheat production environments.
- SNB resistance rankings for Australian commercial cultivars, international accessions, landraces, synthetic derived material and newly developed germplasm made available to Australian wheat breeding companies (see SNB Database Entries in Documents section).
- New wheat germplasm with gene combinations validated for improved SNB resistance in Australian production environments and delivered to Australian breeding companies for commercial variety development.
- DNA markers used to track and select gene combinations for enhanced SNB resistance delivered to Australian breeding companies for use in marker assisted breeding.
Activities in 2018 validated expression of resistance in global germplasm accessions in multi-environment trials and identified alternative sources of SNB resistance, generated new data and delivered necessary resources for commercial breeding of new wheat varieties with enhanced SNB resistance for Western Australia. These include:
- New germplasm selected using DNA markers with single and combined flag leaf resistance from chromosomes 1B, 2D, 2A and 5B evaluated in irrigated spore-inoculated trials at Northam and Manjimup in 2018. Proof-of-concept concluded that combining genes from 2 or 3 different chromosomes consistently expressed enhanced flag-leaf resistance in multi-location trials in 2017-2018 (see attached Database Entries SNB file) than genes from a single chromosome. Germplasm and DNA markers were delivered to Australian wheat breeding companies for deploying SNB resistance in commercial variety development.
- Evaluation of 239 global wheat lines from CIMMYT, ICARDA and landraces for flag leaf and glume SNB resistance benchmarked against historical and recently released Australian commercial wheat varieties at Northam and Manjimup in 2018 (see attached Database Entries SNB file). Moderate to high correlation for flag leaf response between multi-location trials in 2016-2018. Wheat accessions Ajana, ZJN12 Qno25 and ZWW10 Qno127 consistently expressed flag leaf SNB resistance in multi-location trials in 2016-2018
- Significant disease pressure at Manjimup in 2018 produced reliable evaluation for glume resistance in global wheat accessions and inbred lines selected for single and combined genes. A selection of wheat lines from CIMMYT showed significant glume resistance and inbred lines selected for combined genes trended to have lower glume disease scores at Manjimup in 2018 than those selected for single genes (see attached Database Entries SNB file).
- Resistant lines with consistently low flag leaf SNB response in multi-location trials (2016-2018) were used as donor parents for population development where inbred lines were selected for new gene combinations on chromosomes 1A, 6A and 7A using SNP markers identified from genome-wide association studies (see attached SNP Marker Protocol)
- Annotated genes identified within regions controlling flag leaf and glume SNB resistance by aligning whole wheat genome sequence on chromosomes 1B, 2A, 2D, 5D and 4B. Candidate genes advancing as diagnostic markers for screening and selection for flag leaf and glume SNB resistance in germplasm development and breeding.
Project activities in 2019 will focus on:
- Consistency of SNB expression, particularly for glumes, in Australian and global wheat lines and evaluation of inbred lines selected with new gene combinations for flag leaf SNB response in using irrigated spore inoculated managed environments at Katanning and Manjimup in 2019.
- Evaluation of lines with new gene combinations for glume resistance selected using SNP technologies
- Diagnostic DNA marker development from candidate genes identified by aligning the wheat genome sequence with chromosome regions controlling flag leaf and glume SNB resistance.