Context. Broadening the genetic base of canola (Brassica napus) is needed to develop improved hybrid cultivars. Wide genetic diversity is present in its parental species B. rapa and B. oleracea. In the case of B. rapa, the yellow sarson type from Asia is genetically distinct from all other types.

Aims. The objective of this research was to investigate the prospect of using yellow sarson to improve the performance of hybrid canola cultivars.

Methods. Inbred B. napus canola lines derived from an B. napus × B. rapa interspecific cross, and their F₁ hybrids with the B. napus parent, as a tester, were compared on agronomic and seed quality traits; the inbreds were also evaluated for genetic diversity by using molecular markers.

Key results. Seed yield of the hybrids was significantly greater than the inbreds and the B. napus parent and exhibited more than 15% mid-parent heterosis (MPH). Genetic diversity did not show significant correlation with seed yield in the inbred population; however, it showed a positive correlation with MPH. Inbred yield as well as MPH showed a positive correlation with hybrid yield. For other traits, the performance of the inbreds showed a significant positive correlation with the performance of the hybrids; the average MPH for these traits was low or close to zero.

Conclusions. The yellow sarson gene pool showed great potential for use in the breeding of hybrid canola.

Implications. The knowledge gained and germplasm developed from this research can be used by breeders and researchers to develop improved canola cultivars.

Context. Water is widely assumed to be the factor most limiting the growth of annual crops in rainfed environments, but this is rarely tested at sub-continental scale.

Aims. Our study aimed to determine the key environmental and management variables influencing the yield of wheat and barley in the grain-production regions of southern Australia, using data from National Variety Trials.

Methods. We used generalised additive models to determine the importance of climatic and management variables on wheat and barley grain yield. We determined the effects of the best one, two or three variables and their interactions.

Key results. The aridity index, defined as the ratio of cumulative rainfall to potential evapotranspiration, was the single strongest determinant of grain yield for both crops. Model performance was further improved by separating the aridity index into pre-seasonal and seasonal components. Interestingly, other variables that might be expected to influence yield, such as nitrogen fertilisation and extreme temperatures, had relatively minor effects. A comparison between data collected over two 6-year periods showed that there had been yield gains and increased water-use efficiency with time, especially in wetter environments.

Conclusions. Our findings illustrate the importance of water availability for grain production in this region and suggest opportunities for benchmarking and yield prediction through use of readily available climate data.

Implications. Our study reinforces the importance of factors such as water-use efficiency and drought tolerance as goals for cultivar development and agronomic research in wheat and barley. It also highlights the potential of National Variety Trial data as a resource for understanding grain production systems and climate resilience. Further work could explore the value of additional variables and improved weather data.

Context. The goal of increasing sequestration of carbon (C) in soil assumes that management factors can be as influential as intrinsic factors such as climate and parent material.

Aim. The hypotheses tested in this study were (i) that soil C would increase more in limed than in unlimed pasture treatments, and (ii) that well-managed perennial pasture treatments would accumulate soil C to a greater depth than annual pasture treatments.

Method. An 18-year field experiment was conducted on a duplex soil in the mixed farming zone of south-eastern Australia. The experiment contained four treatment contrasts: limed and unlimed perennial and annual pasture systems. Soils samples to 120 cm were taken annually and analysed for C and nitrogen (N) concentrations. Soil C and N stocks were calculated.

Key results. The four treatments produced a similar annual rate of increase in soil C concentration and C stocks. The increase in C stock was confined to the surface 30 cm of soil in all four treatments, leading to the rejection of both hypotheses. Nitrogen concentration and N stocks to 30 cm depth increased significantly over the 18 years, with no difference among treatments.

Conclusion. Pasture land use increased soil C storage by ~700 kg ha⁻¹ year⁻¹; however, the increase was confined to the surface soil.

Implication. The soil C sequestered in this duplex soil is vulnerable to erosion. The co-retained N might have more value from both production and environmental perspectives.

Context. Ratoon stunting disease (RSD), caused by Leifsonia xyli subsp. xyli (Lxx), poses a significant economic threat to sugarcane (Saccharum hybrid) worldwide. RSD is hard to manage due to its elusive visible symptomology and disease rating of cultivars is subjective.

Aims. We aimed to develop a sensitive, rapid, and quantitative Lxx diagnostic method able to correlate Lxx titre and disease resistance rating of sugarcane cultivars.

Methods. A Lxx diagnostic method was developed using heat lysis-based reagent-free DNA isolation from xylem sap followed by loop-mediated isothermal amplification (LAMP)-based colorimetric and fluorescence quantification within a single microcentrifuge tube. Bacterial titre was then statistically correlated with industry-agreed disease resistance ratings for key sugarcane cultivars.

Key results. The diagnostic was highly sensitive (1 cell/μL) and reproducible (%s.d. = <5%, for n = 3), and showed excellent linear dynamic range (i.e. 10 pM−1 aM or 10⁷−10⁰ copies/μL, r = 0.99) for quantitative Lxx detection. LAMP quantifications were completely concordant with quantitative polymerase chain reaction quantification from the same samples. Additionally, a strong correlation was determined between the detected quantitative bacterial titres and known cultivar disease resistance ratings (r = 0.82, n = 10, P < 0.001).

Conclusion. The novel LAMP-based Lxx diagnostic was validated as a fast, simple, and relatively cost-effective means of RSD resistance rating, making it a reliable contribution towards RSD management.

Implications. The development of this diagnostic tool provides a practical solution for accurately measuring Lxx titre and assessing disease resistance in sugarcane plants, aiding in effective risk management of RSD spread, and mitigating its economic impact on sugarcane crops worldwide.