Agronomic tweaks for new and not so new wheat varieties

Rohan Brill¹, Matt Gardner² and Steven Simpendorfer²

¹ NSW DPI, Coonamble
² NSW DPI, Tamworth

Introduction

There are several new and relatively new varieties of wheat available for 2013, including Suntop, LongReach Dart, LongReach Spitfire, Sunguard, LongReach Gauntlet and LongReach Impala. These varieties will complement older varieties that are still widely planted and recommended, especially EGA Gregory.

Specific differences in varietal performance include the relatively high grain protein of LongReach Spitfire and the consistently high yield across a range of sowing dates of EGA Gregory and more recently Suntop. Other varieties have been shown to have specific advantages such as being quick to flower, improved resistant/tolerance to specific diseases or with a niche grain quality.

Interpretation of recent trials (within the past five years) needs to be done with some caution as most have been planted into situations of very high soil moisture content. While conditions can quickly change, currently soil moisture levels are very low in most of the major cropping regions west of the Newell Highway. Limited trial data from such situations indicates that quicker flowering varieties may have an advantage if soil moisture levels are low at planting and spring rainfall is below average.

Newer varieties

Maximum receival quality, time to flower, stripe rust resistance and yellow leaf spot resistance of the major newer varieties is summarised in Table 1, using EGA Gregory as a comparative benchmark. The ‘time to flower’ column has been determined by collecting anthesis data from several northern NVT and VSAP trials. Time to flower is used instead of maturity as maturity can vary depending on soil moisture and dry down conditions, however anthesis is a clearer crop development stage and is a crucial component in selecting a new variety.

Table 1: Maximum receival quality, quickness to flower, stripe rust resistance and yellow leaf spot resistance of seven wheat varieties.

Suntop has been given an APH classification in the north, giving three main options for APH wheat in the northern region; EGA Gregory, Suntop and LongReach Spitfire. Of the three APH varieties, LongReach Spitfire is more likely to meet the 13 % protein threshold, as trial results over two seasons indicates that it has a grain protein advantage over the other two varieties, even at similar yield levels.

All varieties are rated MR to stripe rust, which is a recommended trait. Although fungicides are not expensive, the loss of income as a result of missing a preventative spray due to reasons such as wet paddocks can be quite expensive. Further, each of these newer varieties has been shown to perform at least as well as varieties with lesser resistance to stripe rust.

LongReach Dart is very quick to flower and combined with it being MR-MS to yellow leaf spot, appears best suited to wheat on wheat situations.

Time of sowing trials

Two wheat time of sowing trials have been conducted in the northern grains region over recent seasons with the support of GRDC under the VSAP project. The trials have incorporated new and near release varieties with more widely grown varieties. The trials target sowing at early (TOS 1), mid (TOS 2) and late (TOS 3) timings in the sowing window.

In 2011 and 2012 at Trangie, EGA Gregory and Suntop have been the highest yielding varieties across a range of sowing times (Table 2). The yield of Suntop has been very similar between TOS 1 and TOS 2 in both seasons. In 2012 EGA Gregory had slightly higher yield from TOS 1 compared with TOS 2; however in 2011 EGA Gregory yielded 1 t/ha more from TOS 2 than TOS 1. The lower yield of EGA Gregory from TOS 1 in 2011 was not related to frost. Rather, TOS 2 had a harvest index of 0.46 compared with 0.36 from TOS 1 but total dry matter production for TOS 1 and TOS 2 were similar. However the proportions of total dry matter accumulation pre and post anthesis were 65 % and 35 % for TOS 1 and 55 % and 45 % for TOS 2. This indicates that less water was used for pre-anthesis growth in TOS 2 compared with TOS 1, leaving more water for grain-fill.

Table 2: Grain yield of 12 wheat varieties at three sowing dates in 2011 and 2012 at Trangie Agricultural Research Centre.

At Tamworth in 2012, there was no statistical difference between the yields of EGA Gregory when it was sown on the 26th April compared with the 20th May (Table 3); however two varieties that were much quicker to flower than EGA Gregory, Livingston and LongReach Spitfire, did have higher yield from the early sowing date. When sown on 26th April, Livingston and LongReach Spitfire flowered 12 days earlier than EGA Gregory.

Table 3: Grain yield of eight wheat varieties sown at three sowing dates at Tamworth in 2012

Tip 2. Where soil moisture profiles are good at sowing but planting is forced late (June), the mid-season varieties EGA Gregory and Suntop have been higher yielding than most varieties that are much quicker to flower.

Varietal maturity is a major component for selecting a variety and deciding when to sow. At Trangie, recent VSAP trials have indicated an optimum flowering date of around mid-September. This has generally been achieved with the early or mid-season sowing dates, with significant yield loss across the trials as a result of late planting. Despite this, when planting is delayed due to environmental circumstances, EGA Gregory has still achieved higher yields than many quicker varieties such as LongReach Crusader and Livingston, even though it has flowered up to one week later (Table 4). This was the case in 2011 and 2012, where EGA Gregory was the highest or close to highest yielding variety from the late planting dates at both Trangie and Tamworth. Suntop has also yielded relatively well with later sowing dates over both seasons.  

In contrast to the varieties that achieve relatively high yield across a range of sowing dates, grain yield in 2012 of the unreleased line LPB07-0548 and Sunvale was relatively high at the early sowing date, but had significant yield loss where sowing was delayed to the middle sowing date and further yield loss from the late sowing date (Tables 2 and 3).

Table 4: Anthesis date of twelve wheat varieties sown at three dates at Trangie Agricultural Research Centre in 2012, as well as eight varieties sown on 20^th May at Tamworth in 2012

In 2012, the middle planting date at Trangie was only one day after the middle planting date at Tamworth; however all varieties reached anthesis quicker at Trangie than at Tamworth, which is due to warmer conditions received at Trangie in 2012. On average the difference in flowering between Trangie and Tamworth from the middle sowing date was approximately 7-9 days. Sunvale was the main exception being 12 days later flowering at Tamworth than at Trangie from the middle sowing date.

The trials reported above were all planted into good profiles of moisture, which may have skewed results to favour high yielding mid-season lines such as EGA Gregory and Suntop. The 2009 VSAP time of sowing trial at Trangie planted into a moderate soil profile combined with a dry spring produced contrasting results to 2011 and 2012. Varieties that were quick to flower (early maturing) out yielded the mid and late maturity lines across all sowing dates (Figure 1). The early maturing lines included (among others) Livingston and LongReach Crusader, the mid maturity lines included EGA Gregory and Sunvale and the late maturity lines included Sunzell, EGA Eaglehawk and Sunbri.

Tip 3. Where soil moisture profiles are below average at sowing, there is a greater risk in planting varieties that are slower to flower. In such situations it is recommended to increase the proportion of quicker maturity varieties relative to mid or late maturity varieties.

Figure 1: Grain yield of early, mid and late maturity groups sown at three sowing dates in a trial at Trangie Agricultural Research Centre in 2009

The harvest index (averaged across three sowing dates) in 2009 of the quick maturity lines was significantly higher (0.38) than the mid-maturity lines (0.32) and especially the late maturity lines (0.23). Harvest index was negatively correlated with the number of days taken from sowing to anthesis.

When selecting a sowing date, producers aim to balance the risks of frost, heat and moisture. Where moisture levels are low at sowing, the frost risk of sowing a quick flowering line relatively early may be worth accepting. With low starting soil water, later plantings are more likely to suffer from moisture deficiency in spring compared with where soil moisture profiles are good at sowing. In such seasons where enough rain is received in April to commence planting wheat, trials have shown that if sowing a late maturity variety such as EGA Eaglehawk, plant population should be reduced to 30-40 plants/m²  (Hunt and Brill 2012).

Suntop or EGA Gregory?

Trials over the past two seasons have consistently produced good yield with both Suntop and EGA Gregory, where they are either the highest or near highest yielding varieties across a range of trials. Both varieties have an APH classification for northern NSW, are high yielding and should be sown around the same time.  The question then is which variety to sow? A summary of VSAP trial results in 2012 suggest that EGA Gregory (3.2 t/ha) had higher yields than Suntop (2.8 t/ha) where the trial was sown on red soil, but the yield of Suntop (4.3 t/ha) was higher than EGA Gregory (4.1 t/ha) where sown on heavy (vertosol) soil. The reason for this is unclear at the time of writing; however EGA Gregory has slightly improved acid soil tolerance compared to Suntop but is more susceptible to crown rot. Several of the trials are being assessed for the effect of crown rot to determine if this disease was involved in yield differences.

In the 2011 Trangie VSAP time of sowing trial, lodging scores were taken at harvest to determine varietal differences. Lodging was not observed at all in Suntop, but was moderate in EGA Gregory. The greatest amount of lodging in this trial was in the varieties LongReach Gauntlet, Sunguard and Sunvale.

Grain quality

With good moisture profiles at sowing, there has not been the opportunity to assess how varieties maintain grain quality in response to stress. The data that is available comes from VSAP nitrogen trials at Coonamble and Spring Ridge in 2012, where high N rates induced water stress. The data reported here is screenings (% of sample passing through a 2 mm sieve), which is affected by grain size as well as grain shape, so might not fully reflect the effect of stress on actual grain size.

LongReach Spitfire had relatively low screenings in both trials, with screenings not rising significantly with increasing N application rates (Figures 2a and 2b). Suntop had the highest screenings at Spring Ridge, but was similar to LongReach Spitfire at Coonamble except at the highest N application rate. 

Figure 2: Screenings of four varieties with four rates of nitrogen applied at sowing in VSAP trials at Spring Ridge (a) and Coonamble (b) in 2012.

l.s.d. (p = 0.05) Spring Ridge = 0.56 %, Coonamble = 0.61 %.

Root lesion nematode Pratylenchus thornei resistance and tolerance

Tip 4. Where Pratylenchus thornei numbers are high or unknown, it is best to plant a variety with a good level of tolerance and resistance to Pt. Further work is required on evaluating new varieties as not all data generated is consistent.

Good levels of resistance and tolerance to the RLN Pratylenchus thornei (Pt) are highly desirable for the northern grains region, as these nematodes can cause significant yield loss to a range of crops. The Winter Crop Variety Sowing Guide (WCVSG) publication reports national based ratings for both tolerance and resistance to Pt and another species Pratylenchus neglectus (Pn) to assist growers to make decisions to reduce yield loss from RLN and also limit the build-up of nematodes under wheat crops (Table 5).

Table 5: Resistance and tolerance of eleven wheat varieties to the root lesion nematode
Pratylenchus thornei

Some of the national resistance ratings do not appear to closely reflect what has been seen in field trials at Trangie and other locations. Every plot was cored (0-30 cm) on TOS 2 from the 2011 time of sowing trial at Trangie in March 2012 to determine Pt build-up under the different varieties. In effect this is a way to measure the resistance of a variety to Pt under field conditions. The starting level of Pt prior to sowing the 2011 trial was 10,200 Pt/kg soil. Plots where the varieties Lincoln, Axe, and LongReach Crusader had been planted had a significant build-up of Pt numbers over the season in line with their S or S-VS ratings. Plots that were planted to LongReach Gauntlet in 2011 had a significant reduction in Pt numbers consistent with its MR-MS rating. The greatest discrepancies were with the varieties Sunguard and LongReach Spitfire. Both these varieties are currently rated VS to Pt, so it would be expected that Pt populations would build-up similar to other susceptible varieties such as Axe, LongReach Crusader and Lincoln. This was not the case though, with Sunguard and LongReach Spitfire plots having significantly fewer or similar Pt populations as Sunvale and EGA Gregory which are both rated MS-S. Further work is required to evaluate the resistance of these recently released varieties under field conditions as current ratings, based predominantly on glasshouse evaluations, appear inconsistent with field performance across trials and regions.

Figure 2: Resistance of 18 wheat varieties to Pratylenchus thornei – Trangie 2011

Starting Pt population at sowing 2011 of 10,200 Pt/kg soil (0-30cm). Bars followed by the same letter are not significant (p = 0.05).

Conclusion

EGA Gregory and Suntop have been consistently high yielding in trials across a range of sowing times and agronomy trials over the past two seasons. Along with Sunguard, these varieties have high levels of tolerance to the RLN Pratylenchus thornei and should form a good portion of wheat production in northern NSW.

LongReach Spitfire has several advantages over other varieties including a high relative grain protein concentration and low screenings; however the yield of LongReach Spitfire has been quite variable across trials.

LongReach Gauntlet and LongReach Dart appear better suited to situations where wheat is a dominant crop in the rotation, as LongReach Gauntlet has good resistance to the RLN Pratylenchus thornei, while LongReach Dart is quick to flower and has useful resistance to yellow leaf spot.

LongReach Impala was a relatively high yielding variety in 2012 with a good level of stripe rust resistance; however it’s a soft wheat classification may limit marketing opportunities.

The unreleased line LPB07-0548 appears to offer some potential for growers looking to plant a variety in April without risking significant frost damage, as it was much slower to flower from an early sowing than most other varieties investigated in these trials, while not producing large canopy biomass.

Reference

Hunt J and Brill R (2012) Strategies for improving water use efficiency in western regions through increasing harvest index. Proceedings of GRDC Updates for Advisors, Nyngan 2012.

Contact details

Rohan Brill
NSW DPI
Ph: 02 68221000
Email: rohan.brill@dpi.nsw.gov.au

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