Omics technologies, namely genomics, transcriptomics, proteomics, metabolomics, and phenomics, are becoming an integral part of virtually every commercial cereal crop breeding program, as they provide substantial dividends per unit time in both pre-breeding and breeding phases. Continuous advances in omics assure time efficiency and cost benefits to improve cereal crops. This review provides a comprehensive overview of the established omics methods in five major cereals, namely rice, sorghum, maize, barley, and bread wheat. We cover the evolution of technologies in each omics section independently and concentrate on their use to improve economically important agronomic as well as biotic and abiotic stress-related traits. Advancements in the (1) identification, mapping, and sequencing of molecular/structural variants; (2) high-density transcriptomics data to study gene expression patterns; (3) global and targeted proteome profiling to study protein structure and interaction; (4) metabolomic profiling to quantify organ-level, small-density metabolites, and their composition; and (5) high-resolution, high-throughput, image-based phenomics approaches are surveyed in this review.

Clubroot disease resistance has been introgressed from Brassica rapa into canola following different approaches including a B. napus × B. rapa interspecific cross; however, the details of this cross are not available. To extend our knowledge of this cross for the introgression of resistance to multiple pathotypes, we crossed a clubroot-resistant turnip with a susceptible canola and backcrossed the F₁′s to canola. The backcross population was subjected to pedigree breeding with selection for clubroot resistance and canola-quality traits; selection for resistance to pathotype 3H and 3A was performed in the early and advanced generations, respectively. The advanced generation lines were also evaluated for resistance to 3H, 3A, 2B, and 5x, and for field resistance to clubroot, and agronomic and seed quality traits. Following this, we developed canola lines carrying resistance to multiple pathotypes and nuclear DNA content similar to B. napus. Resistance to 3H showed a weak correlation with other pathotypes whereas resistance to 3A showed a strong positive correlation with 5x indicating that resistance to these pathotypes was under a similar genetic control. Thus, the results demonstrate that resistance to multiple pathotypes can be introgressed from a turnip into a canola even when selection for resistance to single pathotype is performed in early generations.

Clubroot disease, caused by Plasmodiophora brassicae, is a threat to Brassica crops; therefore, understanding of host-resistance is important for developing clubroot-resistant cultivars. Using multi-omics analysis of clubroot-resistant (CR) and -susceptible (CS) near-isogenic lines (NILs) of B. napus, carrying the resistance of turnip (B. rapa var. rapifera), we characterized the host resistance mechanisms. Through proteome analysis, we identified 6626 differentially abundant proteins (DAPs) (2353 in CR-NILs, 4273 in CS-NILs) (q < 0.05), of which 50 in CR- and 62 in CS-NILs were detected across the disease developmental stages. Notable proteins included those involved in reactive oxygen species scavenging (BnaA09T0647200WE)], cell-wall modifications (BnaA04T0244300WE) and glucosinolate biosynthesis (BnaA01T0266700WE) in the CR-NILs. Additionally, disease-resistance proteins like ENHANCED DISEASE RESISTANCE 2-like (BnaA03T0055600WE) and hairpin-induced family protein YLS9 (BnaA08T0237900WE) showed increased abundance in CR-NILs. In contrast, CS-NILs exhibited decreased abundance of defense-related proteins, including proteins containing CUPIN domain (BnaA09T0578800WE) and LACCASE (BnaA02T0019200WE). Integration of proteome data with transcriptome data revealed 33 genes in CR- and 32 in CS-NILs showing a consistent pattern, including the genes related to PLANT INVERTASE/PECTIN METHYLESTERASE INHIBITOR (BnaC04T0003100WE), KELCH MOTIF (BnaC02T0374800WE), LACCASE (BnaA02T0019200WE), and antioxidant-related transcripts [GLUTATHIONE S-TRANSFERASES (BnaA03T0280900WE) and 4-HYDROXYPHENYLPYRUVATE DIOXYGENASE (BnaA09T0641500WE)]. Our findings offer valuable new targets for breeding clubroot-resistant B. napus.

Understanding the intricate molecular interplay between Brassica hosts and the pathogen Plasmodiophora brassicae, causative agent of clubroot disease, is pivotal for devising effective resistance to this disease in Brassica crops. While existing transcriptomic studies have elucidated the host responses to pathogen infection, a comprehensive analysis employing near-isogenic lines (NILs) remains imperative for better understanding of the resistance mechanisms. In this study, we conducted a comparative transcriptome profiling utilizing clubroot-susceptible (CS-NILs) and clubroot-resistant (CR-NILs) near-isogenic Brassica napus lines, carrying the clubroot resistance of turnip (B. rapa var. rapifera), at 7 and 14 days after inoculation. We observed the upregulation of the genes governing phytohormone signaling, receptor kinases, transcription factors, calcium fluxes, and glucosinolate metabolism in the CR-NILs. In addition, the novel differentially expressed genes (DEGs) pertaining to jasmonic acid, calcium signaling, receptor kinases, and glucosinolate biosynthesis were also observed to be differentially expressed. Based on our results, we propose a comprehensive model delineating the molecular events potentially contributing to clubroot resistance in B. napus CR-NILs. Our findings have contributed to an enhanced understanding of the potential mechanisms involved in clubroot resistance which may have utility in targeted breeding initiatives to mitigate the threat of clubroot disease in Brassica crops including canola.