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AGT Narrabri wheat breeder Meiqin Lu checking Sunvex at Narrabri during mid September 2008. While many surrounding crops were badly infested with stripe rust Sunvex was showing excellent resistance.

Source: Australian Grain Technologies (AGT)

Seed available for 2009 planting

Combining APH quality (for northern New South Wales and Queensland) with good levels of resistance to stripe (including Yr17 virulent strain) stem and leaf rust as well as moderate tolerance to yellow leaf spot, as has been achieved with Sunvex, is a relatively rare but highly desirable feature in Australian wheats. Most of Sunvale’s other desirable traits have also been maintained or improved on in Sunvex.

Sunvale has proven a popular variety in northern NSW and Qld but its intolerance to yellow leaf spot has been a major concern. AGT’s Narrabri based breeding team, led by Dr Meiqin Lu, in collaboration with Qld Department of Primary Industries and Fisheries researchers have developed Sunvex from a breeding strategy specifically targeted at improving the yellow leaf spot tolerance of Sunvale. 

Yellow leaf spot is a disease that can devastate potentially high yielding crops in wetter years like 1998. It was responsible for more than 50 percent yield loss in many susceptible (S or VS) varieties in northern cropping areas from Dubbo to central Qld. Varieties with MR ratings (Sunvex has a MR rating) generally suffered minor to significantly less yield loss in that epidemic.

Sunvex, like Sunvale, has main season maturity, good yield and useful crown rot tolerance. Root lesion nematode (P. thornei) tolerance is also believed to be useful but yet to be confirmed (MT-MS).

Sunvex is a little shorter than Sunvale and is likely to exhibit improved standability in high yielding conditions. It has also inherited Sunvale’s grain black point tolerance (R-MR), an important feature in wet spring conditions when black point susceptible varieties have been regularly downgraded.   

Septoria tritici is an important leaf disease in central and southern NSW and can at times cause damage in northern NSW and southern Qld. Sunvex has improved tolerance compared to Sunvale (MR-MS compared to MS) and much better tolerance than many other commonly grown varieties. 

Rust Resistance

Especially important is the inclusion of new combinations of genes for resistance to rust which improves the diversity of genetic resistance among Australian wheats to these potentially devastating diseases. Multiple gene rust resistance in Sunvex also adds to its ability to combat possible new rust disease mutations or new strains from overseas, a constant threat to the nation’s wheat varieties.

Sunvex has maintained Sunvale’s high level of stripe rust resistance which is based on Yr17 and multiple Yr APR genes.   Sunvex’s stem rust gene combination gives more resistance to stem rust than Sunvale. While Sunvale has adequate stem rust resistance to the current pathotypes in Australia, an extra gene in Sunvex is useful against UG99 (the African pathotype). It has a different combination of leaf rust genes and slightly better leaf rust resistance. Sunvex has Lr24Lr37Lr34, Sr24Sr38Sr36, Yr17YrAPRs. Sunvale has Lr3Lr37Lr34, Sr38Sr36, and Yr17Yr APRs.

Table 1. Disease ratings for Sunvex and control varieties for QLD and NSW.

Notes: Disease ratings of check varieties were from “Winter Crop Variety Sowing Guide”—NSW DPI.

Sowing window

Sunvex’s ideal sowing window varies according to region and paddock proneness to frost risk but it is mainly in line with main season varieties like Sunvale. For example in many northern NSW areas it’s preferred sowing time is from around mid May to mid June. Preferred sowing time recommendations in Qld vary widely because of environment differences with again the guide for Sunvex being varieties like Sunvale.

Grain Quality

Sunvex has similar grain quality to Sunvale but better Yellow Alkaline Noodle colour and colour stability. It is eligible for APH grade in North NSW and Queensland, subject to meeting receival standards.

Sunvex like most varieties is susceptible to pre-harvest sprouting (Ellison and Sunlin are standout pre-harvest sprouting tolerant bread wheats).

Adaptation and yield

Overall Sunvex has yielded similar to slightly higher than Sunvale. Based on NVT long term analyses, it has yielded similar to Sunvale in north west NSW and slightly higher in south west NSW and central Queensland. It has yielded slightly lower than Sunvale in north east and south east NSW and southern Queensland (Table1).

Table 2. Yield Performance of SUN434H and control varieties (% of Janz) in NSW and Queensland
(2000-2007 NVT MET data)

Breeding

Sunvex is the result of a complex cross (CNT3/4*3765//2*Cunningham/3/2*Sunvale) with Sunvale a major parent and a CIMMYT line a yellow leaf spot resistant donor.

The cross was made by the Qld DPI & F Leslie Research Centre Toowoomba Yellow Spot Backcrossing Program. Screening for yellow spot resistance was conducted at the Leslie Research Centre. Subsequent selections (BCF3 – BCF7) for rust resistance, agronomic type, grain quality and grain yield were undertaken in both PBI Cobbitty and by AGT wheat breeder Meiqin Lu and her team at Narrabri.  Further testing in northern NSW and Queensland for grain yield, end-use quality and disease resistance was conducted up to 2005, followed by AGT national and NVT trials.

Assessment code

Sunvex was tested as SUN434H. It is a bearded spring type variety.

Availability

Commercial quantise of Sunvex seed will be available to northern NSW and Queensland growers for sowing in autumn 2009 through an AGT Seeds affiliate or your local retailer.

Plant Breeders Rights

Sunvex is protected by PBR and all production (except seed saved for planting) is liable to an End Point Royalty (EPR) which funds future wheat breeding and evaluation. Sunvex growers will be subject to a Growers license that acknowledges an EPR of $2.75/t plus GST has to be paid on all production other than seed retained for their own planting.

Disclaimer

The information contained in this release is based on knowledge and understanding at the time of writing. Growers should be aware of the need to regularly consult with their advisors on local conditions and currency of information.

For further information: www.ausgraintech.com; phone 02 6881 6210.

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