Yield impact of crown rot on winter cereal crop and variety selection (Nyngan 2015)

Take home message

• Barley and bread wheat varieties varied in their yield response to crown rot infection at Nyngan in 2015.
• Cereal crop and variety choice provided a significant 48-182% yield benefit over growing the susceptible bread wheat variety EGA Gregory under high levels of crown rot infection.
• Barley tends to have improved tolerance to crown rot but is very susceptible to infection and will not reduce inoculum levels.
• All winter cereal varieties are susceptible to crown rot infection and will not significantly reduce inoculum levels for subsequent crops. Cereal crop and/or variety choice is NOT the sole solution to crown rot.

Background

Crown rot, caused predominantly by the fungus Fusarium pseudograminearum is a significant disease of winter cereal crops in the northern NSW and southern Qld. All winter cereal crops host the crown rot fungus. Yield loss varies between crops and the approximate order of increasing loss is oats, barley, triticale, bread wheat and durum. Barley is very susceptible to crown rot infection and will build up inoculum but tends to suffer less yield loss through its earlier maturity relative to wheat. Late planted barley can still suffer significant yield loss especially when early stress occurs within the growing season.

Recent research highlights that some newer bread wheat varieties appear to vary significantly in their level of yield loss to crown rot with some northern region varieties (Sunguard, Suntop, LRPB Spitfire, LRPB Lancer and Mitch) appearing to suffer less yield impacts compared to the widely grown variety EGA Gregory. NSW DPI trials from a total of 23 sites conducted across the northern region in 2013 and 2014 indicate that this can represent a yield benefit of around 0.50 t/ha in the presence of high levels of crown rot infection.

Nyngan - 2015

A replicated crown rot yield loss trial was conducted at Nyngan as part of a series of 12 sites across northern NSW and southern Qld in 2015. Individual results from the Nyngan trial are presented here but should be interpreted in conjunction with the across site analysis of the full series of 12 trials conducted in 2015 (included elsewhere in these proceedings). There were two barley, 13 bread wheat and one durum entry evaluated across trials in 2015 (Figure 1). The trials used an inoculated versus uninoculated trial design, to evaluate the relative yield response of varieties to crown rot infection at each site. Each site was further soil cored at sowing (separate bulk samples across each range) to determine background pathogen levels using the DNA based soil test PreDicta B. Crown rot inoculum levels and populations of the root lesion nematodes (RLNs) Pratylenchus thornei and P. neglectus were below detection limit across the Nyngan trial site at sowing in 2015. A previous survey conducted by NSW DPI across the Nyngan region from 2010-2012 found this to be an area of NSW with inherently low RLN populations, which is a fortunate situation. RLNs feed inside the root systems of susceptible varieties and crops and can impact on grain yield potential. Furthermore, in winter cereals RLN can also exacerbate the expression of crown rot and hence increase the extent of yield loss.

Did cereal crop type and/or variety make a difference?

Figure 1. Impact of crown rot on the yield of two barley, 13 bread wheat and one durum entry - Nyngan 2015

At Nyngan, yield in the no added CR treatments (grey bars) ranged in the barley from 4.37 t/ha (La Trobe) to 3.45 t/ha (Commander), in the bread wheat from 3.28 t/ha (Beckom) to 2.48 t/ha (Sunguard) and was 2.37 t/ha with Jandaroi, the only durum variety included in the trial (Figure 1). The addition of crown rot inoculum at sowing (black bars) significantly reduced the yield of all but three of the entries (LRPB Spitfire, Viking and Sunguard) compared to the no added CR treatments (grey bars). In the remaining bread wheat entries, yield loss associated with high levels of crown rot infection ranged from 15% (0.44 t/ha) in LRPB Lancer up to 47% (1.22 t/ha) in EGA Gregory. In barley, yield loss was 12% (0.54 t/ha) in La Trobe and 13% (0.44 t/ha) in Commander (Figure 1). Yield loss associated with high crown rot infection was 41% (0.97 t/ha) in the durum variety Jandaroi at Nyngan in 2015.

Concentrating purely on the extent of yield loss associated with crown rot infection in the different varieties can potentially be misleading as entries can vary markedly in their actual yield potential in a particular environment and season. Amongst the bread wheat entries, Viking and Sunguard had the lowest yield loss from crown rot at Nyngan in 2015. However, in the absence of added CR (grey bars) Viking was significantly lower yielding than Beckom (0.62 t/ha), QT15064R (0.56 t/ha) and LRPB Gauntlet (0.47 t/ha) (Figure 1). Sunguard similarly in the no added CR treatment was between 0.80 t/ha to 0.44 t/ha lower yielding than the bread wheat entries Beckom, QT15064R, LRPB Gauntlet, LRPB Flanker, Sunmate, LRPB Spitfire and Suntop at Nyngan in 2015. Hence, selecting a variety on the basis of reduced yield loss to crown rot should not come at the expensive of yield potential.

Another option for evaluating the data is to concentrate on the absolute yield achieved under high disease pressure in the added CR treatments (black bars; Figure 1). Under high crown rot pressure yield ranged from 3.83 t/ha in the barley variety La Trobe down to 1.36 t/ha in the widely grown bread wheat variety EGA Gregory. Only the advanced bread wheat line V07176-69 and the durum variety Jandaroi were not significantly higher yielding than EGA Gregory in the presence of added CR. The average yield benefit over growing EGA Gregory under high crown rot infection ranged from 2.47 t/ha (182%) with the barley variety La Trobe down to 0.65 t/ha (48%) with the recently released bread wheat variety Mitch. However, the relative yield benefit compared to EGA Gregory was considerably greater with other bread wheat varieties such as LRPB Spitfire (1.35 t/ha; 99%), Beckom(1.33 t/ha), Viking (1.27 t/ha), LRPB Lancer (1.15 t/ha), Sunguard(1.11 t/ha) and Suntop (1.09 t/ha; 80%). Commander, the second barley variety in the trial, had a 1.64 t/ha (121%) yield benefit over EGA Gregory under high levels of crown rot infection in the added CR treatments at Nyngan in 2015 (Figure 1).

Implications

Barley is very susceptible to infection by the crown rot fungus. It does not have improved resistance to crown rot infection. Barley tends to yield better in the presence of crown rot infection due to its earlier maturity relative to bread wheat, providing an escape mechanism which reduces its exposure to evapotranspiration stress during the critical grain fill period. This is often referred to as tolerance. It is CRITICAL that growers do not continue to confuse tolerance with resistance when considering crown rot. Barley is likely to provide a yield advantage over wheat in the presence of high crown rot infection but it will not reduce inoculum levels for subsequent crops. This is similarly true with any bread wheat variety choice. Variety selection can improve yield in the presence of crown rot, though all varieties still suffer yield loss. Variety selection can help maximise profit in the current season but variety selection alone will not reduce inoculum levels for subsequent crops.

The barley variety La Trobe appeared quite promising for maximising yield in the presence of high crown rot infection at Nyngan in 2015 and was also considerably higher yielding than other entries in the no added treatment. La Trobe achieved a significant yield benefit over Commander barley (0.83 t/ha) and the best performing bread wheat variety LRPB Spitfire (1.22 t/ha) in the presence of high crown rot infection at Nyngan in 2015. La Trobe is malt accredited but relative grain price (malt vs feed barley; wheat vs barley), the increased susceptibility of La Trobe to BYDV, impact on Pt populations, segregation by grain accumulators and performance of other barley and bread wheat varieties not included in these trials (NVT Online) should be considered as part of potential variety choices for the Nyngan district. Unfortunately, grain quality data was not available at the time of writing this update paper and should be included in any variety selection considerations.

If forced into planting a cereal crop in a high crown rot risk situation then some barley varieties may provide a yield advantage over bread wheat in that season, provided early stress does not occur. Some of the newer bread wheat varieties do appear to be closing this gap to some extent. However, a key message is that this decision is only potentially maximising profit in the current season. Growing barley over bread wheat will not assist with the reduction of crown rot inoculum levels as barley is still very susceptible to infection. Significant yield loss can still occur in the best of the barley and bread wheat varieties in the presence of high crown rot infection (e.g. 12% in La Trobe at Nyngan in 2015). Crop and variety choice is therefore not the sole solution to crown rot but rather just one element of an integrated management strategy to limit losses from this disease.

Acknowledgments

The research undertaken as part of project DAN00175 is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the author would like to thank them for their continued support. The project is co-funded by the NSW state government through the NSW DPI who are also thanked for their support in fully funding our positions and laboratory and other infrastructure costs.  Technical assistance provided by Robyn Shapland, Patrick Mortell, Lizzie Smith, Sally Wright and Ray Platt (NSW DPI) is gratefully acknowledged. We finally thank Jack and Dione Carter for allowing us to conduct this trial on their property ‘Innaminna’ near Nyngan in 2015.    

Further reading

Simpfendorfer S (2016) Crown rot; does cereal crop or variety choice matter? GRDC Research Updates 2016.

Contact details

Dr Steven Simpfendorfer
NSW DPI, Tamworth
Mb: 0439 581 672
Email: steven.simpfendorfer@dpi.nsw.gov.au

Greg Brooke
NSW DPI, Trangie
Mb: 0437 140 577
Email: greg.brooke@dpi.nsw.gov.au

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