High crown rot risk and should growers plant barley or wheat in northern NSW and southern Queensland

Take home messages

• In 62% of trial comparisons the barley variety Commander provided a significant yield benefit (av. 1.04 t/ha) over the bread wheat variety EGA Gregory when grow in the presence of crown rot infection.
• In 30% of trial comparisons the effect of choosing Commander or EGA Gregory was neutral in the presence of crown rot infection.
• In 8% of trial comparisons Commander resulted in a significant yield penalty (av. 0.48 t/ha) compared to growing EGA Gregory, likely due to stress occurring earlier in the season.
• Barley and bread wheat varieties do vary in yield response in the presence of crown rot infection.
• Barley is very susceptible to crown rot infection and will not reduce inoculum levels for subsequent cereal crops.

Background

Crown rot caused predominantly by the fungus Fusarium pseudograminearum (Fp), is a major disease of wheat and barley crops in the northern grains region (NGR) of Australia, and is estimated to cost growers around $97m annually (1, 2). The NSW Department of Primary Industries has pioneered the evaluation of relative yield responses of bread wheat, durum and barley varieties to crown rot in the NGR since 2004, using an inoculated versus uninoculated trial design. In a preliminary study conducted in the NGR (3), it was found that the average yield loss from crown rot was 20% in barley (4 varieties), 25% in bread wheat (5 varieties) and 58% in durum (EGA Bellaroi). The aim of this research was to compare the relative benefit of growing barley or wheat in the presence of crown rot infection, based on data collected from 32 replicated field experiments conducted between 2009 and 2015.

What did we do?

Between 2009 and 2015, 32 replicated small plot field experiments, that included the bread wheat variety EGA Gregory, a widely grown cultivar across the NGR, and the dominant malting barley variety Commander, were conducted by NSW DPI. All field experiments were replicated, and had uninoculated vs. inoculated (2 g inoculum/m row) treatments at sowing using sterilised durum grain colonised by five isolates of Fp as described by (4), with six trial sets including a sowing date component. If the interaction of sowing date was significant (P< 0.05) data from both dates was presented, if the effect of sowing time was not significant (ns) the average yield result across both planting times is presented. In total this provided 37 comparisons between EGA Gregory and Commander across seasons.

As the focus is in the relative performance of barley vs. wheat in the presence of Fp infection, only yield results from treatments inoculated with Fp are presented. Consequently, this is a comparison across sites and years under high crown rot pressure. The emphasis being on the actual yield achieved under high Fp infection levels, rather than percentage yield loss from crown rot, given that yield is a main determinant of profitability for growers.

What did we find?

In 23 of 37 comparisons (62%) Commander provided a yield benefit over growing EGA Gregory (range +0.28 to +2.20 t/ha; av. +1.04 t/ha) in the presence of crown rot (Table 1). In 11 of 37 comparisons (30%) the difference in yield between Commander and EGA Gregory was not significant (ns). In three comparisons (8%) Commander was actually significantly lower yielding than EGA Gregory (range -0.33 to -0.77 t/ha, av. -0.48 t/ha). In 2011, at both sites, mild conditions in terms of temperature and adequate soil water limited the expression of crown rot with no significant yield difference between inoculated and uninoculated treatments. In all other trials seasonal conditions favoured varying but significant levels of crown rot expression.

Table 1. Yield of barley cv. Commander compared to wheat cv. EGA Gregory in NSW DPI trials inoculated with Fusarium pseudograminearum from 2009-2015

Barley is generally considered more tolerant of crown rot (reduced yield impact) than bread wheat (5) as it tends to escape severe evaporative stress, which exacerbates expression, by maturing earlier. However, as the two sowing times at Garah in 2013 highlighted, this escape mechanism is dependent on sowing time with all four barley varieties in the trial (including Commander) suffering a much higher percentage yield loss from crown rot on the later sowing time (20-30%) relative to the earlier timing (6-11%) (data not shown). Barley is very susceptible to infection by the crown rot fungus and if sown later in its planting window is more likely to filling grain under increased evapotranspiration stress which may lead to significant yield loss from crown rot. Despite this, Commander is still likely to be higher yielding than EGA Gregory, as can be seen from the trial results for Coonamble 2009, Tamworth 2009 and 2014, and Bithramere in 2014 (Table 1).

What about newer wheat and barley varieties?

Recent research conducted across 11 sites in 2013, 12 sites in 2014 and 12 sites in 2015 has highlighted that some of the more recently released bread wheat varieties produced higher yield in the presence of crown rot infection than the widely grown, but more susceptible variety, EGA Gregory. Data on the relative yield of barley varieties in the presence of crown rot is however, limited.

Replicated trials were conducted at Tamworth and Garah in 2014 where a range of barley and wheat varieties were evaluated for their relative yield in the presence of high levels of crown rot infection. The impact of crown rot on yield was determined through the comparison of yield between plots either inoculated or uninoculated with Fp at sowing.

Trial results from Tamworth in 2014, found that Fp infection caused yield losses in the barley varieties ranging from 10% in La Trobe up to 29% in Oxford. In the bread wheat varieties yield loss ranged from 14% in Spitfire up to 23% in EGA Gregory. There were however, low to moderate background levels of crown rot across the site which potentially reduced the differences in yield loss. Hence, only the actual yields of each variety measured in the inoculated Fp treatment (high infection level) are presented (Figure 1).

Figure 1. Yield of seven barley and seven bread wheat varieties in the presence of high crown rot infection – Tamworth 2014
(​varieties in the graph above are protected under the Plant Breeders Rights Act 1994)

(Values are the average of 20^th May and 10^th June sowing dates; bars followed by the same letter are not significantly different at the 95% confidence level)

With the exception of Oxford, all barley varieties were higher yielding than EGA Gregory in the presence of high levels of crown rot infection (Figure 1). The reduced biomass barley plant types, Hindmarsh and La Trobe produced higher yield than the other barley varieties being 0.71 t/ha and 0.72 t/ha higher yielding than Commander, respectively. All of the newer wheat varieties were higher yielding than EGA Gregory in the presence of high levels of Fp infection. Suntop (0.73 t/ha), Sunguard (0.74 t/ha) and LRPB Spitfire (0.85 t/ha) provided the greatest yield advantage over EGA Gregory (Figure 1). However, even the best bread wheat variety LRPB Spitfire was between 0.51 to 1.32 t/ha lower yielding than all of the barley varieties, with the exception of Oxford.

Although Garah was a considerably lower yielding site than Tamworth, encouragingly, the trends in varietal yield performance in the presence of crown rot were consistent with Tamworth. Fp infection caused yield loss in the barley varieties ranging from 17% in Hindmarsh up to 31% in GrangeR. In the bread wheat varieties yield loss ranged from nil in LRPB Lancer up to 40% in EGA Gregory. Actual yield of each variety measured in the inoculated Fp treatment (high infection level) is presented below (Figure 2).

Figure 2. Yield of seven barley and seven bread wheat varieties in the presence of high crown rot infection – Garah 2014
(​varieties in the graph above are protected under the Plant Breeders Rights Act 1994)

(Values are the average of 2^nd May and 12^th June sowing dates; bars followed by the same letter are not significantly different at the 95% confidence level)

With the exception of Oxford and GrangeR, all barley varieties were higher yielding than EGA Gregory in the presence of high levels of crown rot infection with Compass (0.29 t/ha), La Trobe (0.38 t/ha), Fathom (0.38 t/ha) and Hindmarsh (0.54 t/ha) all providing significant yield benefits (Figure 2).The best barley variety Hindmarsh was 0.30 t/ha higher yielding than the best bread wheat variety LRPB Lancer (Figure 2).

Implications for growers

Barley in most seasons yields 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 evaporative stress during the critical grain filling stage. To some extent this may also be why the barley variety Oxford, which has a longer maturity, does not yield as well as other barley varieties in the presence of crown rot infection. The escape mechanism is lost through the delayed maturity. It is critical that growers do not continue to confuse improved yield performance in the presence of infection with resistance when considering crown rot. Barley is likely to provide a yield advantage over wheat in the presence of high crown rot infection due to its earlier maturity relative to wheat. Importantly however, barley will not reduce inoculum levels for subsequent crops as it does not have improved resistance to crown rot infection compared to bread wheat (5).

The crown rot fungus is believed to be triggered by moisture/temperature stress to proliferate in the base of infected tillers which results in constriction of the xylem (water transport structure in stems) and results in the production of whiteheads. However, the crown rot fungus does not care what time of year it is when the stress occurs. If there is limited stored soil moisture and relatively high temperatures at earlier growth stages then the crown rot fungus will still proliferate which can reduce biomass production and even kill plants. This has been particularly noticeable in commercial durum and barley crops in the northern region in previous seasons and was evident in inoculated plots of Commander at Terry Hie Hie and Macalister in 2014. This is the likely reason for the negative yield response of Commander compared to EGA Gregory in the presence of crown rot infection at these sites in 2014.

If forced into planting a cereal crop in a high crown rot risk situation some barley varieties may provide a yield advantage over bread wheat in a given season. Importantly, some of the newer bread wheat varieties do appear to be closing this gap to some extent. Nevertheless, 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 very susceptible to infection. Significant yield loss is still occurring in the best of the barley and bread wheat varieties in the presence of high crown rot infection. 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.

Acknowledgements

This project was co-funded by NSW DPI and GRDC under projects DAN00175 and DAN00167, which was made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. Technical assistance provided by Robyn Shapland, Finn Fensbo, Patrick Mortell, Kay Warren, Karen Cassin, Paul Nash, Stephen Morphett, Jim Perfrement, Patrick Mortell, Peter Formann and Rod Bambach (all NSW DPI) for sowing, maintaining and harvesting trials is greatly appreciated. We also thank NVT operators for conducting some trials and co-operating growers for use of their paddocks.

References

Murray GM, Brennan JP (2009). Australasian Plant Pathology 38, 558–570.

Murray GM, Brennan JP (2010). Australasian Plant Pathology 39, 85-96.

Daniel R, Simpfendorfer S. (2008) The impact of crown rot on winter cereal yields. GRDC Grains Research Update paper, February/March 2008

Dodman RL, Wildermuth GB (1987). Australian Journal of Agricultural Research 38, 473- 486.

Liu Y, Ma J, Yan W, Yan G, Zhou M, Wei Y, Zheng Y, Liu, C (2012). Journal of Phytopathology 160: 412-417.

Contact details

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

​Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994