Testing retained sowing seed of hybrid canola over a range of rainfall zones (Adelaide)

Trent Potter¹, Sarah Noack² and Peter Hooper ²

¹ Yeruga Crop Research, ² Hart Field Site Group.

Take home messages

• Average yield loss of canola grown from retained hybrid seed varied from site to site, but ranged from 7 to 17 per cent when compared to the commercial hybrid sowing seed.
• Oil content of crops grown from retained hybrid seed was significantly lower than that from commercial hybrids.
• While some hybrids were less affected by using retained seed it is recommended that new seed is purchased each year.

Background

Canola hybrids are now available in Australia covering conventional, Clearfield®, triazine tolerant and Roundup Ready® herbicide systems. As farmers are used to sowing retained seed from open pollinated crops, they may wish to retain sowing seed harvested from the previous hybrid crop to reduce the up-front cost of sowing a canola crop. Little independent research has evaluated the effect on plant growth, blackleg resistance and grain yield. It is important that farmers have credible information as to the effect of retaining hybrid seed in all rainfall zones.

Recent on-farm research

On-farm research has previously been conducted as part of the Better Oilseeds project, but only based on one hybrid variety. This research showed a reduction in blackleg resistance in the retained hybrid seed but variable grain yield responses. Additional research conducted by Pacific Seeds showed significant yield reductions by retaining hybrid seed. This research, however, only tested Pacific Seeds hybrids and used seed harvested from yield plots and so would be expected to have some contamination from previously harvested plots.

This preliminary work highlights a need for further on-farm research to determine the effect of retaining hybrid sowing seed on plant growth, blackleg resistance and grain yield for the range of herbicide tolerance options over a range of rainfall zones in southern Australia.

Research objective

This research program aimed to conduct a series of trials in 2012 to measure the effect of retaining hybrid sowing seed on plant growth, blackleg resistance and grain yield compared to the original hybrid (ie. as purchased from seed supplier; referred to as ‘commercial’ here after) for a range of herbicide tolerance options in a range of rainfall zones in southern Australia.

Methodology

Replicated trials were conducted at four locations in different rainfall zones in the South Australia. Site locations were Minnipa and Lameroo for low rainfall, Bordertown for a medium rainfall and Bool Lagoon for high rainfall conditions. Plot size was 10 meters long by eight rows and three replicates were sown. Trials were conducted to compare the original hybrid seed with first generation farmer retained hybrid seed. Retained hybrid sowing seed was sourced from individual farmers commercial crops from 2011 to reduce the possibility of contamination in samples harvested from small plot yield trials.

Conventional (Hyola® 50 plus CB™Taurus at Bool Lagoon), Clearfield (Pioneer®45Y77, 45Y82, 46Y83 and Hyola® 575CL) and triazine tolerant (CB™ Tumby HT® and CB™ Jardee HT®) hybrids were assessed.  All seed was graded and assessed for germination to ensure good quality seed was used. Treatments under test were the retained hybrid seed plus and minus a fungicide treatment compared to the original hybrid seed also plus and minus a fungicide treatment. Varieties with the same herbicide tolerance were sown in groups to reduce the risk of damage by herbicides.

Plant vigour, internal blackleg infection, grain yield and oil content were measured.

Results

Flowering dates

Very little variation occurred for flowering date between the commercial hybrid and the retained sowing seed with only about one day difference in days to 50 per cent of plants having first flowers.

Early vigour

Some hybrids showed reduced early vigour when sown with retained seed but the response was variable.

Blackleg

Internal infection with blackleg was scored at three sites. A significant interaction between hybrid and seed type occurred at Lameroo and Bordertown with no significance at Bool Lagoon (Table 1). Several hybrids showed increased internal infection when sowing seed was retained.

Table 1. Internal blackleg infection (%) at three sites in 2012

Note: Within table, values followed by a different letter are significantly different.

When hybrid seed was retained Jockey® was needed to be applied to get a similar low level of blackleg as that produced by the commercial hybrid seed, except at Bordertown where very high levels of blackleg occurred (Table 2).

Table 2. Internal blackleg infection (%) affected by seed type and fungicide at three sites in 2012

Note: Within table for each site, values followed by a different letter are significantly different.

Grain yield

Grain yield was significantly higher for commercial over retained hybrid sowing seed at all sites except Bool Lagoon (Table 3), with the greatest percentage yield loss at the two lower rainfall sites of Minnipa and Lameroo. Overall, yield loss ranged from 7 to 17 per cent over all hybrids. A similar level of yield loss from three hybrids was shown at Hart in 2013 (Table 6).

Table 3. Mean grain yield (t/ha) for hybrid sowing seed in 2012

Note: Within table for each site, values followed by a different letter are significantly different.

Table 4. Grain yield of retained hybrid compared to commercial sowing seed for different varieties at all sites (%)

Table 5. Grain yield (t/ha) of retained and commercial hybrids as affected by fungicide at all sites 2012

Note: Within table for each site, values followed by a different letter are significantly different.

Can you use a mixture of commercial and retained hybrid seed?

One means of reducing the cost of sowing seed would be to use a mixture of commercial and retained hybrid sowing seed. A mixture of 33 per cent commercial seed and 66 per cent retained seed was tested at Hart, SA in 2013 (Table 6).  

Table 6. The grain yield (t/ha) of three canola varieties, from commercial, retained or mixed seed at Hart in 2013

Note: Within table, values followed by a different letter are significantly different.

While grain yield of CB™ Tumby HT® was not significantly affected by using retained seed or mixtures compared to the commercial sowing seed, the grain yield of the mixture was similar to that of the commercial hybrid for Pioneer® 45Y82, with and without Jockey®, and Hyola® 50 with Jockey® (Table 6).

Grain quality

Oil content of canola was significantly reduced when retained seed was used at all three sites tested (Table 7). However, protein content was not affected by retaining sowing seed compared to the commercial hybrids and glucosinolate content was only affected by retaining sowing seed at Bool Lagoon and in this case the variation was very minor compared to the acceptable limits for canola quality.

Table 7. Oil content of commercial and retained hybids in 2012

Note: Within table for each site, values followed by a different letter are significantly different.

Financial returns from using retained hybrid sowing seed compared to commercial hybrid seed

Relative financial returns were calculated based on a price per tonne of $600. Oil content calculated at the normal contract basis resulted in the grain from the commercial hybrid producing a premium of about $6 per tonne over the retained grain. Likewise the cost of preparing retained sowing seed ready for sowing was calculated at $6 per hectare, graded, treated with fungicide and bagged.

As can be seen from Table 8, the use of commercial hybrid sowing seed gave a good financial return over the use of retained hybrid seed for most hybrids at most sites. Using a price of $26 per kg for hybrid seed and a sowing rate of 2.5 kg/ha the difference in returns of over $65 per hectare produces a benefit to using commercial seed. Oil content premium and grading and fungicide cost reduced this threshold by $12 per hectare and $18 per hectare when grain yield could be expected to be 1 and 2 t/ha respectively.

Table 8. Difference in $ return from commercial and retained hybrid sowing seed for each variety at all four sites in 2012

Summary

In many cases higher grain yields and reduced impact of blackleg occurred when commercial hybrid sowing seed was used rather than retained hybrid sowing seed. Benefits of commercial hybrid sowing seed outweighed the cost of buying that seed. Differences between hybrids are likely to be caused by the hybrid breeding system being used by the different companies and the degree of heterosis between parental lines that are used to produce each hybrid.

Similar results have been shown in recent studies in Canada where a yield reduction of up to 13 per cent has been shown for retained hybrid canola seed.

Perhaps mixtures of commercial and retained sowing seed may be used to reduce the cost of sowing seed while still obtaining reasonable grain yields. However, this needs to be further investigated with more hybrid varieties and sites before good conclusions can be drawn.

Acknowledgements

The majority of this work was funded by GRDC as a Fast Track project administered by the Southern Regional Panel, with some also undertaken by the Hart Field Site Group. The field work was conducted by the SARDI New variety Agronomy (NVA) group at Struan and Clare research centres, SA.

Contact details

Trent Potter

PO Box 819, Naracoorte SA 5271

0427 608 306

trent@yeruga.com.au