Addressing the threat of climate change to agriculture requires improving crop resilience to short-term abiotic stress

Climate change represents a serious threat to global agriculture, necessitating the development of more environmentally resilient crops to safeguard the future of food production. The effects of climate change are appearing to include a higher frequency of extreme weather events and increased day-to-day weather variability. As such, crops which are able to cope with short-term environmental stress, in addition to those that are tolerant to longer term stress conditions are required . It is becoming apparent that the hitherto relatively little studied process of post-stress plant recovery could be key to optimizing growth and production under fluctuating conditions with intermittent transient stress events. Developing more durable crops requires the provision of genetic resources to identify useful traits through the development of screening protocols. Such traits can then become the objective of crop breeding programmes. In this study, we discuss these issues and outline example research in leafy vegetables that is investigating resilience to short-term abiotic stress

Identification and QTL mapping of resistance to Turnip yellows virus (TuYV) in oilseed rape, Brassica napus

Key message Partially dominant resistance to Turnip yellows virus associated with one major QTL was identified in the natural allotetraploid oilseed rape cultivar Yudal. Abstract Turnip yellows virus (TuYV) is transmitted by the peach-potato aphid (Myzus persicae) and causes severe yield losses in commercial oilseed rape crops (Brassica napus). There is currently only one genetic resource for resistance to TuYV available in brassica, which was identified in the re-synthesised B. napus line ‘R54’. In our study, 27 mostly homozygous B. napus accessions, either doubled-haploid (DH) or inbred lines, representing a diverse subset of the B. napus genepool, were screened for TuYV resistance/susceptibility. Partial resistance to TuYV was identified in the Korean spring oilseed rape, B. napus variety Yudal, whilst the dwarf French winter oilseed rape line Darmor-bzh was susceptible. QTL mapping using the established Darmor-bzh × Yudal DH mapping population (DYDH) revealed one major QTL explaining 36% and 18% of the phenotypic variation in two independent experiments. A DYDH line was crossed to Yudal, and reciprocal backcross (BC1) populations from the F1 with either the susceptible or resistant parent revealed the dominant inheritance of the TuYV resistance. The QTL on ChrA04 was verified in the segregating BC1 population. A second minor QTL on ChrC05 was identified in one of the two DYDH experiments, and it was not observed in the BC1 population. The TuYV resistance QTL in ‘R54’ is within the QTL interval on Chr A04 of Yudal; however, the markers co-segregating with the ‘R54’ resistance are not conserved in Yudal, suggesting an independent origin of the TuYV resistances. This is the first report of the QTL mapping of TuYV resistance in natural B. napus

A review of sources of resistance to turnip yellows virus ( TuYV ) in Brassica species

Turnip yellows virus (TuYV; previously known as beet western yellows virus) causes major diseases of Brassica species worldwide resulting in severe yield‐losses in arable and vegetable crops. It has also been shown to reduce the quality of vegetables, particularly cabbage where it causes tip burn. Incidences of 100% have been recorded in commercial crops of winter oilseed rape (Brassica napus) and vegetable crops (particularly Brassica oleracea) in Europe. This review summarises the known sources of resistance to TuYV in B. napus (AACC genome), Brassica rapa (AA genome) and B. oleracea (CC genome). It also proposes names for the quantitative trait loci (QTLs) responsible for the resistances, Turnip Yellows virus Resistance (TuYR), that have been mapped to at least the chromosome level in the different Brassica species. There is currently only one known source of resistance deployed commercially (TuYR1). This resistance is said to have originated in B. rapa and was introgressed into the A genome of oilseed rape via hybridisation with B. oleracea to produce allotetraploid (AACC) plants that were then backcrossed into oilseed rape. It has been utilised in the majority of known TuYV‐resistant oilseed rape varieties. This has placed significant selection pressure for resistance‐breaking mutations arising in TuYV. Further QTLs for resistance to TuYV (TuYR2‐TuYR9) have been mapped in the genomes of B. napus, B. rapa and B. oleracea and are described here. QTLs from the latter two species have been introgressed into allotetraploid plants, providing for the first time, combined resistance from both the A and the C genomes for deployment in oilseed rape. Introgression of these new resistances into commercial oilseed rape and vegetable brassicas can be accelerated using the molecular markers that have been developed. The deployment of these resistances should lessen selection pressure for resistance‐breaking isolates of TuYV and thereby prolong the effectiveness of each other and extant resistance

Assembly and characterisation of a unique onion diversity set identifies resistance to Fusarium basal rot and improved seedling vigour

Conserving biodiversity is critical for safeguarding future crop production. Onion (Allium cepa L.) is a globally important crop with a very large (16 Gb per 1C) genome which has not been sequenced. While onions are self-fertile, they suffer from severe inbreeding depression and as such are highly heterozygous as a result of out-crossing. Bulb formation is driven by daylength, and accessions are adapted to the local photoperiod. Onion seed is often directly sown in the field, and hence seedling establishment is a critical trait for production. Furthermore, onion yield losses regularly occur worldwide due to Fusarium basal rot caused by Fusarium oxysporum f. sp. cepae. A globally relevant onion diversity set, consisting of 10 half-sib families for each of 95 accessions, was assembled and genotyping carried out using 892 SNP markers. A moderate level of heterozygosity (30–35%) was observed, reflecting the outbreeding nature of the crop. Using inferred phylogenies, population structure and principal component analyses, most accessions grouped according to local daylength. A high level of intra-accession diversity was observed, but this was less than inter-accession diversity. Accessions with strong basal rot resistance and increased seedling vigour were identified along with associated markers, confirming the utility of the diversity set for discovering beneficial traits. The onion diversity set and associated trait data therefore provide a valuable resource for future germplasm selection and onion breeding

The pangenome of an agronomically important crop plant Brassica oleracea

There is an increasing awareness that as a result of structural variation, a reference sequence representing a genome of a single individual is unable to capture all of the gene repertoire found in the species. A large number of genes affected by presence/absence and copy number variation suggest that it may contribute to phenotypic and agronomic trait diversity. Here we show by analysis of the Brassica oleracea pangenome that nearly 20% of genes are affected by presence/absence variation. Several genes displaying presence/absence variation are annotated with functions related to major agronomic traits, including disease resistance, flowering time, glucosinolate metabolism and vitamin biosynthesis

Crop Updates 2005 - Cereals

This session covers thirty six papers from different authors: WHEAT AGRONOMY 1. Optimum sowing time of new wheat varieties in Western Australia, Darshan Sharma, Brenda Shackley, Mohammad Amjad, Christine M. Zaicou-Kunesch and Wal Anderson, Department of Agriculture 2. Wheat varieties updated in ‘Flowering Calculator’: A model predicting flowering time, B. Shackley, D. Tennant, D. Sharma and C.M. Zaicou-Kunesch, Department of Agriculture 3. Plant populations for wheat varieties, Christine M. Zaicou-Kunesch, Wal Anderson, Darshan Sharma, Brenda Shackley and Mohammad Amjad, Department of Agriculture 4. New wheat cultivars response to fertiliser nitrogen in four major agricultural regions of Western Australia, Mohammad Amjad, Wal Anderson, Brenda Shackley, Darshan Sharma and Christine Zaicou-Kunesch, Department of Agriculture 5. Agronomic package for EGA Eagle Rock, Steve Penny, Department of Agriculture 6. Field evaluation of eastern and western wheats in large-scale farmer’s trials, Mohammad Amjad, Ben Curtis and Veronika Reck, Department of Agriculture 7. New wheat varieties for a changing environment, Richard Richards, CSIRO Plant Industry; Canberra 8. Farmers can profitably minimise exposure to frost! Garren Knell, Steve Curtin and David Sermon, ConsultAg 9. National Variety Trials, Alan Bedggood, Australian Crops Accreditation System; Horsham 10. Preharvest-sprouting tolerance of wheat in the field, T.B. Biddulph1, T.L. Setter2, J.A. Plummer1 and D.J. Mares3; 1Plant Biology; FNAS, University of Western Australia; 2Department of Agriculture, 3School of Agriculture and Wine, University of Adelaide 11. Waterlogging induces high concentration of Mn and Al in wheat genotypes in acidic soils, H. Khabaz-Saberi, T. Setter, I. Waters and G. McDonald, Department of Agriculture 12. Agronomic responses of new wheat varieties in the Northern Agricultural Region, Christine M. Zaicou-Kunesch and Wal Anderson, Department of Agriculture 13. Agronomic responses of new wheat varieties in the Central Agricultural Region of WA, Darshan Sharma, Steve Penny and Wal Anderson, Department of Agriculture 14. EGA Eagle Rock tolerance to metribuzin and its mixtures, Harmohinder Dhammu, David Nicholson and Chris Roberts, Department of Agriculture 15. Herbicide tolerance of new bread wheats, Harmohinder Dhammu1 and David Nicholson2, Department of Agriculture NUTRITION 16. The impact of fertiliser placement, timing and rates on nitrogen-use efficiency, Stephen Loss, CSBP Ltd 17. Cereals deficient in potassium are most susceptible to some leaf diseases, Ross Brennan and Kith Jayasena, Department of Agriculture 18. Responses of cereal yields to potassium fertiliser type, placement and timing, Eddy Pol, CSBP Limited 19. Sulphate of Potash, the potash of choice at seeding, Simon Teakle, United Farmers Co-operative 20. Essential disease management for successful barley production, K. Jayasena, R. Loughman, C. Beard, B. Paynter, K. Tanaka, G. Poulish and A. Smith, Department of Agriculture 21. Genotypic differences in potassium efficiency of wheat, Paul Damon and Zed Rengel, Faculty of Natural and Agricultural Sciences, University of Western Australia 22. Genotypic differences in potassium efficiency of barley, Paul Damon and Zed Rengel, Faculty of Natural and Agricultural Sciences, University of Western Australia 23. Investigating timing of nitrogen application in wheat, Darshan Sharma and Lionel Martin, Department of Agriculture, and Muresk Institute of Agriculture, Curtin University of Technology 24. Nutrient timing requirements for increased crop yields in the high rainfall cropping zone, Narelle Hill, Ron McTaggart, Dr Wal Anderson and Ray Tugwell, Department of Agriculture DISEASES 25. Integrate strategies to manage stripe rust risk, Geoff Thomas, Robert Loughman, Ciara Beard, Kith Jayasena and Manisha Shankar, Department of Agriculture 26. Effect of primary inoculum level of stripe rust on variety response in wheat, Manisha Shankar, John Majewski and Robert Loughman, Department of Agriculture 27. Disease resistance update for wheat varieties in WA, M. Shankar, J.M. Majewski, D. Foster, H. Golzar, J. Piotrowski and R. Loughman, Department of Agriculture 28. Big droplets for wheat fungicides, Rob Grima, Agronomist, Elders 29. On farm research to investigate fungicide applications to minimise leaf disease impacts in wheat, Jeff Russell and Angie Roe, Department of Agriculture, and Farm Focus Consultants PESTS 30. Rotations for nematode management, Vivien A. Vanstone, Sean J. Kelly, Helen F. Hunter and Mena C. Gilchrist, Department of Agriculture 31. Investigation into the adaqyacy of sealed farm silos in Western Australia to control phosphine-resistant Rhyzopertha dominica, C.R. Newman, Department of Agriculture 32.Insect contamination of cereal grain at harvest, Svetlana Micic and Phil Michael, Department of Agriculture 33. Phosure – Extending the life of phosphine, Gabrielle Coupland and Ern Kostas, Co-operative Bulk Handling SOIL 34. Optimum combinations of ripping depth and tine spacing for increasing wheat yield, Mohammed Hamza and Wal Anderson, Department of Agriculture 35. Hardpan penetration ability of wheat roots, Tina Botwright Acuña and Len Wade, School of Plant Biology, University of Western Australia MARKETS 36. Latin America: An emerging agricultural powerhouse, Ingrid Richardson, Food and Agribusiness Research, Rabobank; Sydne

Comparative Functional Genomics of Salt Stress in Related Model and Cultivated Plants Identifies and Overcomes Limitations to Translational Genomics

One of the objectives of plant translational genomics is to use knowledge and genes discovered in model species to improve crops. However, the value of translational genomics to plant breeding, especially for complex traits like abiotic stress tolerance, remains uncertain. Using comparative genomics (ionomics, transcriptomics and metabolomics) we analyzed the responses to salinity of three model and three cultivated species of the legume genus Lotus. At physiological and ionomic levels, models responded to salinity in a similar way to crop species, and changes in the concentration of shoot Cl− correlated well with tolerance. Metabolic changes were partially conserved, but divergence was observed amongst the genotypes. Transcriptome analysis showed that about 60% of expressed genes were responsive to salt treatment in one or more species, but less than 1% was responsive in all. Therefore, genotype-specific transcriptional and metabolic changes overshadowed conserved responses to salinity and represent an impediment to simple translational genomics. However, ‘triangulation’ from multiple genotypes enabled the identification of conserved and tolerant-specific responses that may provide durable tolerance across species

The evolutionary history of wild, domesticated, and feral Brassica oleracea (Brassicaceae)

Understanding the evolutionary history of crops, including identifying wild relatives, helps to provide insight for conservation and crop breeding efforts. Cultivated Brassica oleracea has intrigued researchers for centuries due to its wide diversity in forms, which include cabbage, broccoli, cauliflower, kale, kohlrabi, and Brussels sprouts. Yet, the evolutionary history of this species remains understudied. With such different vegetables produced from a single species, B. oleracea is a model organism for understanding the power of artificial selection. Persistent challenges in the study of B. oleracea include conflicting hypotheses regarding domestication and the identity of the closest living wild relative. Using newly generated RNA-seq data for a diversity panel of 224 accessions, which represents 14 different B. oleracea crop types and nine potential wild progenitor species, we integrate phylogenetic and population genetic techniques with ecological niche modeling, archaeological, and literary evidence to examine relationships among cultivars and wild relatives to clarify the origin of this horticulturally important species. Our analyses point to the Aegean endemic B. cretica as the closest living relative of cultivated B. oleracea, supporting an origin of cultivation in the Eastern Mediterranean region. Additionally, we identify several feral lineages, suggesting that cultivated plants of this species can revert to a wild-like state with relative ease. By expanding our understanding of the evolutionary history in B. oleracea, these results contribute to a growing body of knowledge on crop domestication that will facilitate continued breeding efforts including adaptation to changing environmental conditions