Breeding success has created a novel problem for the National Mungbean Improvement Program (NMIP): it can no longer visually select ‘winners’ from its elite breeding lines.
Program leader Dr Merrill Ryan, a principal research scientist at the Queensland Department of Agriculture and Fisheries (DAF), says the breeding program has relied on subjective quality testing to date, in line with standard industry practices. “We look for evenness of seed colour, size and shape – parameters that drive acceptance in export markets,” she says.
“However, the breeding program has done such a great job in selecting the best-quality varieties in the world, that now we can’t visually detect the minute gains in advanced material. We really want to select winners, but it is beyond our scoring capabilities.”
Now in its fifth phase, the program is addressing this by moving to high-throughput, objective grain quality assessments to interpret evenness of colour, shape and size. This will allow for more effective and efficient breeding for grain size and uniformity and give a clearer understanding of how the environment affects these traits. Ultimately, it would stabilise grower profitability through consistent grain quality.
Dr Ryan says new screening methods will allow quality screening to be introduced much earlier in the breeding cycle. “We won’t wait until advanced generations to select for quality.”
This is just one of the NMIP’s new objectives. Funded by DAF and GRDC and based at the Hermitage Research Facility in Warwick, Queensland, the NMIP is the ‘hub’ that links mungbean research, ensuring it is delivered to Australian growers. It was previously led by DAF’s Col Douglas, who is now a National Tree Crop Intensification program principal horticulturalist.
Heat tolerance
Dr Ryan says new efforts in heat tolerance screening will assist in making new varieties climate change ready. The aim is to identify heat-tolerant parent material, particularly suited to the hot and dry conditions faced around central Queensland and the Western Downs.
The planting window for mungbeans in that region has shifted over the past decade – from a pre-Christmas sowing to a January or February one – with the increasingly hotter and drier summer conditions to blame.
“This new focus allows NMIP to partner with physiologists to identify lines that will be able to better handle hot conditions – temperatures higher than 35°C – and widen the sowing window options.”
Department of Agriculture and Fisheries principal research scientist Dr Merrill Ryan. Photo: Courtesy Dr Merrill Ryan
A key component of this task will be screening 140 lines annually, with access to more internationally sourced genetic diversity thanks to DAF’s project links with the Australian Centre for International Agricultural Research (ACIAR) and the addition of wild Australian mungbean germplasm.
In Kingaroy glasshouses, DAF physiologist Dr Yash Chauhan will screen and compare heat-stressed plants with a control set of plants to look for genotypic differences. Traits to be studied include leaf senescence (ageing), pod number per plant, seed size, seed number per pod and yield differences.
“Mungbeans will push further into northern Queensland, and where the heat couples with humidity, this subtropical crop will handle conditions well. Issues arise where heat and low humidity exist. This includes areas like Emerald, Roma and the Western Downs. We don’t understand the relationship between heat and humidity and are not attempting to study that in this project, but we wish to identify better material for dry heat conditions,” Dr Ryan says.
This also fits in with the NMIP’s ethos to challenge the broadly adapted, one-variety-fits-all paradigm.
GRDC Northern Panel member and former Emerald-based agronomist Graham Spackman says research to assess potential heat-tolerant material is welcome. “Most growers in the Emerald region have been sowing mungbeans later in the summer for about 10 to 15 years in an effort to minimise heat stress,” he says.
“However, if we had more heat and drought-tolerant options that could be sown earlier, we could bring the planting window forward, which would improve the chances of receiving summer rain and potentially double-crop into wheat.”
Emerald agronomist Joshua Bell from JB Ag Services concurs. “Heat-tolerance work is needed. Yield potential is greatly reduced by lack of follow-up rain early in the crop; improved heat tolerance would extend this window. If reliability of mungbeans can be improved, the area grown will increase.”
Disease resistance
For the first time, the program will have a full-time dedicated mungbean pathologist, helping improve disease resistance research.
Dr Ryan says this is important to tackle bacterial diseases, such as tan and halo spot, which are unique to Australia, as well as powdery mildew and increasing issues around Fusarium wilt infection.
The work will see a refinement to screening methodologies, challenging plant material with consistent quantities of aggressive pathotypes and moving some field-based testing to glasshouse/bubble house methods. This will eliminate field and seasonal variation that has caused inconsistent results in recent years, she says.
For example, tan spot work will move to a pot-based screening technique. “Tan spot is more of an issue in drier environments. In the field at Warwick, we experience too much rainfall to induce one specific disease. Other diseases such as halo blight, conducive to the wetter climate, often confound the tan spot disease screening data.”
Genetic tools
Underpinning the work will be the use of new genetic selection tools and models. They concurrently measure the potential of broadly adapted release lines, those lines best suited to regional adaptation and lines with potential to be superior parent candidates.
Dr Ryan says the program’s genomic selection for yield is groundbreaking. “We are one of the few pulse breeding programs in the world attempting to do this. Using genomic selection for yield is a complex task and will allow us to predict the yield potential of material not yet in field trials using previous pedigree performance coupled with the presence of chromosomal regions across the genome.”
The genetic work includes the use of single-nucleotide polymorphism (SNP) markers, which mark a genetic location and help to transition to genome-wide association mapping. This approach will identify gene associations and enable stacking of different genes conferring disease resistance, improving the durability of resistance deployed in new varieties.
The end goal is to release high-value, high-yielding lines. “The industry is worth $120 million annually and mungbeans are the highest-value broadacre grain crop option in the northern region. We have quite a task ahead: to increase yield stability while maintaining world-standard grain quality in a crop that is presently 98 per cent exported.”
Dr Ryan is embracing the challenge, having come full circle with this crop. “I first bred this crop in the early 2000s alongside breeding chickpeas for Queensland. In recent times I have been researching the genetics of pigeon pea, another summer pulse alternative. It is great to be back and looking at the mungbean germplasm with fresh eyes.”
End point royalties
Last year, mungbeans moved to an end point royalty (EPR) system to better support continued varietal improvement and share production risks with growers.
EPRs are a fee charged to growers and paid to both breeders and commercialisation partners. They provide vital financial support and feedback to breeders to help ensure the development of new varieties that meet the needs of growers and their end-user customers.
The co-owners of varieties bred by the NMIP – GRDC and DAF – in conjunction with commercial partner the Australian Mungbean Association, made the decision to move to an EPR system.
All current NMIP varieties are affected by the change. GRDC commercialisation manager (north) Chris Murphy says the EPR system is a contractual relationship based on variety performance and yield. “In the past with a seed point royalty, growers paid regardless of how their mungbean crop performed. Under the EPR system, they pay based on yield, which is far fairer and effectively shares the production risk between growers, breeders and commercial partners.”
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More information: Merrill Ryan, 07 4542 6710, merrill.ryan@daf.qld.gov.au