KEY FINDINGS:

• Cereal variety choice can have a large impact on Pratylenchus thornei (Pt) population build-up within paddocks, which can then affect how following crops and/or varieties perform in the rotation.
• Significant differences were evident between varieties with an 8.9-fold difference in final Pt populations between the best (Commander) and worst (Mitch) entries.
• Very susceptible varieties should be avoided in paddocks with known root lesion nematode (RLN) populations as they can increase the population to high risk levels in one season (e.g. 19.1-fold increase with Mitch).
• There was no significant difference between varieties in crown rot inoculum level that developed during the season based on postharvest PreDicta B assessment.

Conclusions

Cereal variety choice can have a significant impact on the build-up of Pt populations within paddocks with an 8.9  fold difference in final populations between the best and worst variety at this site in 2015. Starting Pt populations of below 2.0 Pt/ g soil are considered low risk, populations between 2.0 and 15.0 Pt/g soil are considered medium risk and above 15.0 Pt/g soil are considered high risk for yield loss in intolerant crops or varieties in the northern region. This could have serious consequences for the production of following Pt intolerant crops and/or varieties within the rotation with all but two entries (Commander and Suntop) increasing the Pt population from a medium to a high risk level in one season or with one variety (Mitch) increasing the Pt population as high as 105.0 Pt/g soil at this site in 2015. Recent NSW DPI research has also demonstrated that significant yield loss still occurred in the moderately tolerant wheat variety EGA Gregory with high risk (>15.0 Pt/g)  populations in the top 30 cm of soil at sowing. Very susceptible varieties should be avoided in paddocks with known RLN populations as they can blowout the population to high risk levels in one season.

Although varieties appear to significantly differ in their yield in the presence of crown rot infection, differences in the levels of partial resistance, which limits the rate of spread of the crown rot fungus through the plant during the season, do not appear to result in significant variation in inoculum levels at harvest. Partial resistance does not actually prevent the plant from being infected but rather slows the rate of fungal growth in the plant arguably delaying expression of the disease which can translate into a yield and grain quality (reduced screenings) benefit. However, the crown rot fungus, while being a pathogen when the winter cereal plant is alive, is also an effective saprophyte once the plant matures and dies. This saprophytic colonisation of infected tillers late in the season as the crop matures is the likely reason why limited practical differences in residual inoculum levels are created between varieties and winter cereal crop types.

 

Further research across sites is required to confirm differences in resistance of barley and wheat varieties to Pt as this can have significant implications for the build-up of Pt populations within a paddock and hence following rotational choices. For instance, while it appears that Mitch has a useful level of tolerance to crown rot (average 0.54 t/ha higher yielding than EGA Gregory in 2015), its increased susceptibility to Pt resulted in it taking nematode populations from a medium risk level at sowing to an extremely high risk level by harvest at Macalister in 2015 (Figure 1). Hence, Mitch should only be considered for production in paddocks known to be free of Pt as its increased susceptibility to Pt is likely to override the yield gain in the presence of crown rot when considering the whole rotational sequence.

 

• Cereal variety choice can have a large impact on the build-up of Pratylenchus thornei (Pt) populations within paddocks which can then impact on the performance of following crops and/or varieties in the rotation.
• Significant differences were evident between varieties with a 22-fold difference in final Pt populations between the best (SuntopA) and worst (MitchA) variety.
• Very susceptible varieties should be avoided in paddocks with known Root Lesion Nematode (RLN) populations as they can increase the population to high risk levels in one season.
• There was no significant difference between varieties in the level of crown rot inoculum they developed during the season based on post-harvest PreDicta B assessment.

• Zymoseptoria tritici and Pyrenophra tritici-repentis, the disease-causing pathogens of septoria tritici blotch (STB) and yellow leaf spot (YLS), can produce ascospores on wheat stubble regardless of their resistance status.
• Any infected wheat stubble has the ability to initiate an epidemic for up to 2 years.
• Reduce harvest cut height to limit Z. tritici colonising stubble.
• Excess harvest material must be removed from the paddock to produce a net reduction of Z. tritici inoculum.
• Minimise disease impacts by using an integrated approach to management.

• Faba beans produced more dry matter than vetch (7.64 v 6.32 t/ha), however nutrition treatment did not influence peak biomass levels.
• Highest grain yield for faba beans (PBA NasmaA) was just over 3.5 t/ha compared with 1.2 t/ha for vetch (Popany).
• Faba bean yield increased by 0.85 t/ha when inoculated with rhizobia compared to no inoculation, where no extra nutrition was supplied.
• The addition of nitrogen reduced nodulation but did not affect yield.
• The addition of experimental FAR PGR21-1 to vetch increased crop height, while PGR21-2 had a shortening effect on faba beans.
• Inoculation was more important than crop nutrition, suggesting inoculated crops were capable of supplying sufficient nitrogen for growth at this site.

• In the high yielding 2020 season, flowering earlier than the optimal flowering period resulted in significant yield penalties.
• Grain yield responses varied in response to sowing date, and the highest yields occurred when varietal phenology was matched with the recommended sowing windows.
• A key recommendation for growers is to remain disciplined with sowing dates.

• Phenology and grain yield responses were significantly influenced by seasonal conditions in 2019.
• Severe heat stress and terminal drought conditions favoured faster developing spring genotypes, which achieved the highest grain yields in 2019.
• Grain yield responses varied in response to sowing date, and highest yields occurred when phenology was matched with recommended sowing windows.

• The most intense of three heat events avegarged 35.5 degrees celcius and reduced grain numbers per spikelet by 21%.
• Significant genetic variation was observed for floret sterility induced by natural heat events. The variety Halberd was identified as most heat tolerant and Westonia as most heat sensitive.
• The results indicate a genetic variation that could be exploited to improve wheat crop resilience under heat stress. 

• Sowing date, particularly for mid–late maturing varieties, was found to be a significant determinant of grain yield potential, with yield reductions of >25% observed due to a delayed sowing date (8 May vs. 7 June).
• Variety and sowing date in particular affected grain quality parameters, with a significant increase in the level of screenings for all varieties when the sowing date was delayed.
• Higher plant populations had a greater influence on grain yield when the sowing date was delayed. Yield potential was optimised at 200 plants/m2 for a 7 June sowing date vs. 100 plants/m2 for the earlier 8 May sowing date, supporting the principal of increasing targeted plant populations when sowing is delayed.
• Altering variety and maturity type, and increasing targeted plant population in response to a delayed sowing date did not fully compensate for yield losses associated with a delayed vs. timely sowing date.

Conclusions:

Results from this experiment highlight the importance of timely sowing, particularly for mid–late maturing varieties. Yield reductions of approximately 1.3 t/ha averaged across plant population treatments were recorded for the mid–late maturing varieties LRPB LancerA and EGA GregoryA with delayed sowing, which equates to a 25% and 26% yield decline, respectively. Similarly, the late maturing variety EGA EaglehawkA suffered a yield penalty of around 22% (0.98 t/ha) whilst the mid maturing variety SuntopA suffered a 14% (0.70 t/ha) yield reduction due to delayed sowing. In comparison, the earlier maturing varieties LRPB DartA and LRPB SpitfireA suffered only minimal yield reductions when SD was delayed. Importantly however, the earlier maturing varieties did not exhibit any yield advantage over the later maturing varieties in SD 2 and were significantly lower yielding than these varieties at SD 1. Temperature and plant available water during anthesis/grain fill would also have affected both yield potential and grain quality parameters, with limited effective in-crop rainfall in September/October, and temperatures exceeding 35 °C for an extended period from 4 October. The longer season variety EGA EaglehawkA in particular had high screenings for both SDs, and also produced a low yield in SD 2, reinforcing the need to sow this variety early due to its lack of adaptability under unfavourable conditions. Increasing plant population had a greater influence on GY when SD was delayed, with yield potential optimised at 200 plants/m2 in SD 2 vs. 100 plants/m2 in the earlier SD 1, supporting the principal of increasing targeted plant populations with delayed sowing. These findings further emphasise the advantage of planting early in the sowing window compared to delayed sowing just simply in terms of input seed requirements. Variety selection and sowing date particularly affected grain quality parameters and screenings. There was a significant increase in the level of screenings for all varieties when sowing was delayed. LRPB LancerA was the only variety in this experiment that achieved screenings of <5%, but only at SD 1. All other varieties, including LRPB LancerA in SD 2, exceeded the critical 5% screenings receival standards level. LRPB LancerA appears to have excellent grain stability with significantly lower screenings than either EGA GregoryA or SuntopA. Findings from this experiment indicate that there were differences between varieties in terms of grain stability, due possibly to variations in kernel shape/plumpness and or kernel weight stability. These results also highlight the adaptability of some of the mid–late season 16 | NSW Department of Primary Industries varieties, and the yield and quality advantages of sowing these varieties early, compared with sowing earlier maturing varieties later

• Fungicide reduced disease levels in all varieties, but failed to eliminate disease completely.
• Observed differences in disease levels agreed with published variety resistance ratings.
• Early infection of yellow leaf spot (YLS) caused high yield losses in the more susceptible varieties.
• Variety selection will always play an important role in high risk areas.
• Crop rotation and best practice methods are required to maximise the benefits of correct variety selection.

• Fungicide reduced disease levels in all varieties, but failed to eliminate the disease completely.
• Observed differences in disease levels were broadly in agreement with published variety resistance ratings.
• Yield losses were observed in the more susceptible varieties due to early disease development.
• Low disease levels from an early stage can cause yield losses.
• Variety selection will always play an important role in managing disease in high risk areas.

• Sowing date and variety maturity choice is a balance between the risk of frost versus terminal heat stress.
• Earlier sowing can increase frost risk, but also generally maximises yield potential and reduces the extent of yield loss from crown rot.
• Cereal crop and variety selection can have a significant impact on yield where there are high levels of crown rot infection.
• Durum wheat, barley or bread wheat varieties with increased susceptibility to crown rot, should only be grown in paddocks known to have lowrisk inoculum levels based on testing (e.g. PreDicta B).
• 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.

• The quicker maturing varieties LRPB DartA, HatchetA LivingstonA, MaceA, SceptreA, MitchA and SuntopA were generally lower yielding than other entries at SD1, but were more yield competitive with other entries at SD2 and SD3.
• The longer season varieties EGA WedgetailA (6.08 t/ha) and EGA EaglehawkA (5.88 t/ha) were the highest yielding varieties at SD1, followed by CutlassA (5.51 t/ha) and LRPB FlankerA (5.36 t/ha).
• The mean yield at SD1 (4.89 t/ha) was not significantly different from SD2 (4.63 t/ha), but SD3 (3.56 t/ha) was significantly lower yielding than either SD1 or SD2.
• All varieties yielded their lowest from SD3.
• Protein percentages were low to moderate (mean of 9.8% for SD2 and 10.3% for SD1) with no significant difference from SD for any of the entries