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Sclerotinia sclerotiorum is a necrotrophic fungus causing devastating stem rot and associated yield losses of canola/rapeseed (Brassica napus) worldwide, including in Australia. Developing host resistance against Sclerotinia stem rot is critical if this disease in canola/rapeseed is to be successfully managed, as cultural or chemical control options provide only partial or sporadic control. Three B. napus breeding populations, C2, C5 and C6, including the parents, F1, F2, BC1P1, and BC2P2, were used in a field study with an objective of exploring the inheritance pattern of disease resistance (based on stem lesion length [SLL]) and the genetic relationships of disease with stem diameter (SD) or days to first flowering (DTF), and to compare these new adult plant stem resistances against S. sclerotiorum with those of seedling (cotyledon and leaf) resistances in earlier studies. Heritability (broad sense) of SLL was 0.57 and 0.73 for population C2 at 3 and 5 weeks postinoculation and 0.21 for population C5 at 5 weeks postinoculation. Additive genetic variance was evident within all 3 populations for DTF but not for SD. Narrow-sense heritability for DTF was 0.48 (C2), 0.42 (C5), and 0.32 (C6). SD, DTF, and SLL were all inherited independently, with no significant genetic covariance between traits in bivariate analysis. Genetic variance for SLL in populations C2 and C5 was entirely nonadditive, and there was significant nonadditive genetic covariance of SLL at 3 and 5 weeks postinoculation. Generation means analysis in population C2 supported the conclusion that complex epistatic interactions controlled SLL. Several C2 and C5 progeny showed high adult plant stem resistance, which may be critical in developing enhanced stem resistance in canola/rapeseed. Although population C6 showed no genetic variation for SLL resistance in this study, it showed significant nonadditive genetic variance at the cotyledon and leaf stages in earlier studies. We conclude that host resistance varies across different plant growth stages, and breeding must be targeted for resistance at each growth stage. In populations C2, C5, and C6, resistance to S. sclerotiorum in stem, leaf, and cotyledon was always controlled by nonadditive effects such as complex epistasis or dominance. Overall, our findings in relation to the quantitative inheritance of Sclerotinia stem rot resistance, together with the new high-level resistances identified, will enable breeders to select/develop genotypes with enhanced resistances to S. sclerotiorum.

Sclerotinia sclerotiorum infects host plant tissues by inducing necrosis to source nutrients needed for its establishment. Tissue necrosis results from an enhanced generation of reactive oxygen species (ROS) at the site of infection and apoptosis. Pathogens have evolved ROS scavenging mechanisms to withstand host‐induced oxidative damage. However, the genes associated with ROS scavenging pathways are yet to be fully investigated in S. sclerotiorum. We selected the S. sclerotiorum Thioredoxin1 gene (SsTrx1) for our investigations as its expression is significantly induced during S. sclerotiorum infection. RNA interference‐induced silencing of SsTrx1 in S. sclerotiorum affected the hyphal growth rate, mycelial morphology, and sclerotial development under in vitro conditions. These outcomes confirmed the involvement of SsTrx1 in promoting pathogenicity and oxidative stress tolerance of S. sclerotiorum. We next constructed an SsTrx1‐based host‐induced gene silencing (HIGS) vector and mobilized it into Arabidopsis thaliana (HIGS‐A) and Nicotiana benthamiana (HIGS‐N). The disease resistance analysis revealed significantly reduced pathogenicity and disease progression in the transformed genotypes as compared to the nontransformed and empty vector controls. The relative gene expression of SsTrx1 increased under oxidative stress. Taken together, our results show that normal expression of SsTrx1 is crucial for pathogenicity and oxidative stress tolerance of S. sclerotiorum., Normal expression of SsTrx1 is crucial for pathogenicity, sclerotial development, and oxidative stress tolerance of Sclerotinia sclerotiorum.

Lipaphis erysimi is a key pest of rapeseed-mustard in Indian subcontinent. Although chemical control is the basis of its management, the unsustainability of this approach has accelerated global research efforts to find alternate solutions. Host plant resistance is one among these. A set of introgression lines were developed using Brassica fruticulosa previously found to be resistant to L. erysimi. Rigorous screening over the years led to the identification of 3 introgression lines (I8, I79, and I82) for field resistance to aphids. We evaluated these introgression lines under field and laboratory conditions along with B. fruticulosa (resistant parent), B. juncea var. PBR-210 (susceptible parent) to elucidate the mechanism of resistance. Significantly a smaller number of aphids settled on circular leaf discs of B. fruticulosa, I8 and I82 compared to that on PBR-210 after 24 and 48 h of release. A similar trend was observed in free choice field experiment with significantly less aphid colonization on B. fruticulosa, I8, I79 and I82 compared to PBR-210 indicating lower aphid preference for these genotypes. Further, no choice experiments revealed significant negative effects of these genotypes on aphid demographic parameters (nymphal survival, development period, fecundity and longevity). Tolerance may not be a mechanism of resistance as aphid population failed to develop on these genotypes. Thus, resistance in these introgression lines may be attributed to a synergistic combination of antixenosis and antibiosis mechanisms.

Heavy doses of gamma irradiation can reduce linkage drag by disrupting large sized alien translocations and promoting exchanges between crop and wild genomes. Resistance to mustard aphid (Lipaphis erysimi) infestation was significantly improved in Brassica juncea through B. juncea-B. fruticulosa introgression. However, linkage drag caused by introgressed chromatin fragments has so far prevented the deployment of this resistance source in commercial cultivars. We investigated the patterns of donor chromatin segment substitutions in the introgression lines (ILs) through genomic in situ hybridization (GISH) coupled with B. juncea chromosome-specific oligonucleotide probes. These allowed identification of large chromosome translocations from B. fruticulosa in the terminal regions of chromosomes A05, B02, B03 and B04 in three founder ILs (AD-64, 101 and 104). Only AD-101 carried an additional translocation at the sub-terminal to intercalary position in both homologues of chromosome A01. We validated these translocations with a reciprocal blast hit analysis using shotgun sequencing of three ILs and species-specific contigs/scaffolds (kb sized) from a de novo assembly of B. fruticulosa. Alien segment substitution on chromosome A05 could not be validated. Current studies also endeavoured to break linkage drag by exposing seeds to a heavy dose (200kR) of gamma radiation. Reduction in the size of introgressed chromatin fragments was observed in many M3 plants. There was a complete loss of the alien chromosome fragment in one instance. A few M3 plants with novel patterns of chromosome segment substitutions displayed improved agronomic performance coupled with resistance to mustard aphid. SNPs in such genomic spaces should aid the development of markers to track introgressed DNA and allow application in plant breeding.

The cultivated Brassica species include numerous vegetable and oil crops of global importance. Three genomes (designated A, B and C) share mesohexapolyploid ancestry and occur both singly and in each pairwise combination to define the Brassica species. With organizational errors (such as misplaced genome segments) corrected, we showed that the fundamental structure of each of the genomes is the same, irrespective of the species in which it occurs. This enabled us to clarify genome evolutionary pathways, including updating the Ancestral Crucifer Karyotype (ACK) block organization and providing support for the Brassica mesohexaploidy having occurred via a two-step process. We then constructed genus-wide pan-genomes, drawing from genes present in any species in which the respective genome occurs, which enabled us to provide a global gene nomenclature system for the cultivated Brassica species and develop a methodology to cost-effectively elucidate the genomic impacts of alien introgressions. Our advances not only underpin knowledge-based approaches to the more efficient breeding of Brassica crops but also provide an exemplar for the study of other polyploids. Correcting organizational errors of the Brassica A, B and C genomes reveals the conserved structure of each genome across species and genome evolutionary pathways. Genus-wide pan-genomes were constructed, helping to elucidate the genomic impacts of alien introgressions.

Alternaria leaf spot (Alternaria brassicae) can be a devastating disease in canola (Brassica napus) and mustard (B. juncea), but there are no highly effective host resistances available. Screening of 150 diverse Brassicaceae varieties under glasshouse conditions highlighted important novel resistances. In particular, Camelina sativa ‘4076’ and Diplotaxis erucoides ‘Wasabi Rocket’ had complete resistance across disease assessment parameters (leaf incidence [%LDI]; severity [%LAD]; consequent defoliation [%LCI]). The next most resistant varieties were C. sativa ‘CSA’ (%LDI 0.6; %LAD 0.4), ‘4144’ (%LDI 1.2; %LAD 0.5), ‘405’ (%LDI 1.7; %LAD 0.7), C. sativa ‘3274’ (%LDI 2.5; %LAD 0.8), Carrichtera annua ‘CAN3’ (%LDI 7.7; %LAD 4.0), and Sisymbrium irio ‘London Rocket’ (%LDI 2.1; %LAD 0.8), all with %LCI values of 0. Other genotypes showing high-level resistance included S. erysimoides ‘SER 4’ (%LDI 11.8; %LAD 5.6; %LCI 0) and D. cardaminoides ‘Wild Rocket’ (%LDI 15.5; %LAD 7.2; %LCI 0), and those showing moderate resistance were Brassica carinata ‘ML-EM-1’ (Rungwe), B. insularis ‘Moris’, B. napus ‘ZY006’, B. oxyrrhina ‘BOX1’, B. oleracea var. capitata ‘Sugarloaf’, B. tournefortii ‘CN01-104-2’, and Sinapis alba ‘Concerta’ with %LDI 21.6 to 29.8, %LAD 12.8 to 21.0, and %LCI 0 to 5.7. In particular, B. napus ‘ZY006’ for canola and B. oleracea var. capitata ‘Sugarloaf’ can now be directly utilized (i.e., without crossing impairment) for Brassica species and vegetable breeding programs, respectively. While all B. juncea genotypes were susceptible, there were some less susceptible varieties from India in comparison with genotypes from Australia or China. The most susceptible test genotype was Rapistrum sativus (%LDI 89.4; %LAD 83.9; %LCI 71.0), highlighting the value of the resistances identified. These findings not only highlight a range of novel resistances against A. brassicae for canola, mustard, and other diverse Brassicaceae breeding programs to develop resistant commercial varieties, but also emphasize highly susceptible varieties to avoid in both breeding programs and commercial situations conducive to Alternaria leaf spot.

Genome wide association studies enabled prediction of many candidate genes for flowering, maturity and plant height under differing day-length conditions. Some genes were envisaged only from derived B. rapa. Flowering and plant height are the key life history traits. These are crucial for adaptation and productivity. Current investigations aimed to examine genotypic differences governing days to flowering, maturity and plant height under contrasting day-length conditions; and identify genomic regions governing the observed phenotypic variations. An association panel comprising 195 inbred lines, representing natural (NR) and derived (DR) forms of Brassica rapa (AA; 2n = 20), was evaluated at two sowing dates and two locations, representing different day-length regimes. Derived B. rapa is a unique pre-breeding material extracted from B. juncea (AABB; 2n = 36). Population structure analysis, using DArT genotypes established derived B. rapa as a genetic resource distinct from natural B. rapa. Genome wide association studies facilitated detection of many trait associated SNPs. Chromosomes A03, A05 and A09 harboured majority of these. Functional annotation of the associated SNPs and surrounding genome space(s) helped to predict 43 candidate genes. Many of these were predicted under specific day-length conditions. Important among these were the genes encoding floral meristem identity (SPL3, SPL15, AP3, BAM2), photoperiodic responses (COL2, AGL18, SPT, NF-YC4), gibberellic acid biosynthesis (GA1) and regulation of flowering (EBS). Some of the predicted genes were detected for DR subpanel alone. Genes controlling hormones, auxins and gibberellins appeared important for the regulation of plant height. Many of the significant SNPs were located on chromosomes harbouring previously reported QTLs and candidate genes. The identified loci may be used for marker-assisted selection after due validation.

Genome wide association studies allowed prediction of 17 candidate genes for association with nitrogen use efficiency. Novel information obtained may provide better understanding of genomic controls underlying germplasm variations for this trait in Indian mustard. Nitrogen use efficiency (NUE) of Indian mustard (Brassica juncea (L.) Czern & Coss.) is low and most breeding efforts to combine NUE with crop performance have not succeeded. Underlying genetics also remain unexplored. We tested 92 SNP-genotyped inbred lines for yield component traits, N uptake efficiency (NUPEFF), nitrogen utilization efficiency (NUTEFF), nitrogen harvest index (NHI) and NUE for two years at two nitrogen doses (No without added N and N100 added @100 kg/ha). Genotypes IC-2489-88, M-633, MCP-632, HUJM 1080, GR-325 and DJ-65 recorded high NUE at low N. These also showed improved crop performance under high N. One determinate mustard genotype DJ-113 DT-3 revealed maximum NUTEFF. Genome wide association studies (GWAS) facilitated recognition of 17 quantitative trait loci (QTLs). Environment specificity was high. B-genome chromosomes (B02, B03, B05, B07 and B08) harbored many useful loci. We also used regional association mapping (RAM) to supplement results from GWAS. Annotation of the genomic regions around peak SNPs helped to predict several gene candidates for root architecture, N uptake, assimilation and remobilization. CAT9 (At1g05940) was consistently envisaged for both NUE and NUPEFF. Major N transporter genes, NRT1.8 and NRT3.1 were predicted for explaining variation for NUTEFF and NUPEFF, respectively. Most significant amino acid transporter gene, AAP1 appeared associated with NUE under limited N conditions. All these candidates were predicted in the regions of high linkage disequilibrium. Sequence information of the predicted candidate genes will permit development of molecular markers to aid breeding for high NUE.

Rfo is located on a radish chromosome fragment (~ 108 Kb), which is seated in the middle of a pretty large C genome translocation at the distal region of chromosome A09 of B. juncea. Ogura cytoplasmic male sterility (CMS) is used to produce hybrids in Indian mustard (Brassica juncea L.). Fertility restorers for this CMS were developed by cross-hybridizing B. juncea (AABB; 2n = 36) with B. napus (AACC; 2n = 38) carrying radish Rfo gene. This hybrid production system is normally stable, but many commercial mustard hybrids show male sterile contaminants. We aimed to identify linkage drag associated with Rfo by comparing hybridity levels of 295 handmade CMS x Rfo crosses. Although Rfo was stably inherited, hybridity was

Hyaloperonospora brassicae causes downy mildew, a major disease of Brassicaceae species. We sequenced the genomes of two H. brassicae isolates of high (Sample B) and low (Sample C) virulence. Sequencing reads were first assembled de novo with software's SOAPdenovo2, ABySS V2.1 and Velvet V1.1 and later combined to create meta-assemblies with genome sizes of 72.762 and 76.950Mb and predicted gene densities of 1628 and 1644 /Mb, respectively. We could annotate 12.255 and 13,030 genes with high proportions (91-92%) of complete BUSCOs for Sample B and C, respectively. Comparative analysis revealed conserved and varied molecular machinery underlying the physiological specialisation and infection capabilities. BLAST analysis against PHI gene database suggested a relatively higher loss of genes for virulence and pathogenicity in Sample C compared to Sample B, reflecting pathogen evolution through differential rates of mutation and selection. These studies will enable identification and monitoring of H. brassicae virulence factors prevailing in-field.

Timely transition to flowering, maturity and plant height are important for agronomic adaptation and productivity of Indian mustard (B. juncea), which is a major edible oilseed crop of low input ecologies in Indian subcontinent. Breeding manipulation for these traits is difficult because of the involvement of multiple interacting genetic and environmental factors. Here, we report a genetic analysis of these traits using a population comprising 92 diverse genotypes of mustard. These genotypes were evaluated under deficient (N75), normal (N100) or excess (N125) conditions of nitrogen (N) application. Lower N availability induced early flowering and maturity in most genotypes, while high N conditions delayed both. A genotyping-by-sequencing approach helped to identify 406,888 SNP markers and undertake genome wide association studies (GWAS). 282 significant marker-trait associations (MTA's) were identified. We detected strong interactions between GWAS loci and nitrogen levels. Though some trait associated SNPs were detected repeatedly across fertility gradients, majority were identified under deficient or normal levels of N applications. Annotation of the genomic region (s) within ± 50 kb of the peak SNPs facilitated prediction of 30 candidate genes belonging to light perception, circadian, floral meristem identity, flowering regulation, gibberellic acid pathways and plant development. These included over one copy each of AGL24, AP1, FVE, FRI, GID1A and GNC. FLC and CO were predicted on chromosomes A02 and B08 respectively. CDF1, CO, FLC, AGL24, GNC and FAF2 appeared to influence the variation for plant height. Our findings may help in improving phenotypic plasticity of mustard across fertility gradients through marker-assisted breeding strategies.

Research to control yield losses from Sclerotinia (Sclerotinia sclerotiorum) in oilseed rape (Brassica napus) has focused on stem resistance. However, resistance to leaf infection against this pathogen would also be beneficial, both in limiting additional plant leaf damage and in reducing inoculum build up within-crop and resultant spread onto stems. Three B. napus breeding populations, C2 (NC-8 × RQ-001-NCA-8 NC2-7), C5 (cv. Charlton × RQ-001-NCA-8 NC2-7) and C6 (cv. Charlton × NC4-5), were screened for leaf resistance (based on mean lesion diameter) under controlled environment conditions. Each population consisted of parents (P1 and P2), F1, F2, BC1P1 and BC2P2, except for C5 that lacked BC1P1. Moderate broad sense heritability for leaf resistance (0.45) to S. sclerotiorum was only found in population C6, where genetic variance was mostly non-additive. Analyses of generation means and variances indicated that both dominance and complex epistatic interactions were present in C6. Bivariate analysis revealed a positive genetic covariance between the non-additive effects for mean leaf lesion and cotyledon lesion diameters, and significant negative covariance of residuals, which supports a common genetic control of cotyledon and leaf resistance to S. sclerotiorum. These results will guide breeders in selection and development of genotypes with both cotyledon and leaf resistance against this important pathogen worldwide.

The cultivated Brassica species include numerous vegetable and oil crops of global importance. Three genomes (designated A, B and C) share mesohexapolyploid ancestry and occur both singly and in each pairwise combination to define the Brassica species. With organizational errors (such as misplaced genome segments) corrected, we showed that the fundamental structure of each of the genomes is the same, irrespective of the species in which it occurs. This enabled us to clarify genome evolutionary pathways, including updating the Ancestral Crucifer Karyotype (ACK) block organization and providing support for the Brassica mesohexaploidy having occurred via a two-step process. We then constructed genus-wide pan-genomes, drawing from genes present in any species in which the respective genome occurs, which enabled us to provide a global gene nomenclature system for the cultivated Brassica species and develop a methodology to cost-effectively elucidate the genomic impacts of alien introgressions. Our advances not only underpin knowledge-based approaches to the more efficient breeding of Brassica crops but also provide an exemplar for the study of other polyploids.

Sclerotinia rot, caused by the fungal pathogen Sclerotinia sclerotiorum, is a devastating disease on oilseed rape and mustard worldwide. While the focus to effectively control yield losses from Sclerotinia has been on locating stem resistance, resistance to leaf and to early (cotyledon) stage resistance to this pathogen are also important, both not only limiting additional plant damage, but also inoculum build up and spread onto stems. Three Brassica napus breeding populations developed in India, C2 (NC-8 × RQ-001-NCA-8 NC2-7), C5 (cv. Charlton × RQ-001-NCA-8 NC2-7) and C6 (cv. Charlton × NC4-5), were screened for cotyledon resistance (based on lesion diameter) under controlled environmental conditions to investigate the inheritance of disease resistance. Each population consisted of parents (P1 and P2), F1, F2, BC1P1 and BC2P2, except for population C5 which lacked BC1P1. Moderate broad sense heritability of 0.42, 0.31 and 0.49 for cotyledon resistance was found in populations C2, C5 and C6, respectively, and there was mostly non-additive genetic control of resistance. Analyses of generation means and variances indicated that the additive-dominance model was adequate to explain genetics of cotyledon resistance in population C2. There was heterosis for susceptibility (i.e., larger lesion diameter). The dominance × dominance digenic epistasis explained genetic control in population C6, with heterosis towards resistance (i.e., smaller lesion diameter). This information is critical for breeding for resistance to this important pathogen in Australia, India and elsewhere.

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot, is a devastating necrotrophic pathogen which causes severe yield losses to oilseed production worldwide. Most of efforts at the genetic mitigation of the disease have not been successful. Present investigation was conducted to functionally characterize the effect of down-regulating Ssoah1 during host infection and explore the possibility of boosting host resistance by silencing this gene. We utilized host-induced gene silencing (HIGS) to silence Ssoah1 gene in the S. sclerotiorum fungus. A HIGS based vector was constructed and transformed into Arabidopsis thaliana. The pathogenicity assays in the transgenic A. thaliana lines revealed three T

Some 154 Brassicaceae genotypes (78 Brassica napus, 38 B. carinata, 25 B. juncea, three Raphanus sativus, two each of Rapistrum rugosum and B. incana and one each of Crambe abyssinica, B. fruticulosa, Hirschfeldia incana, B. insularis, B. oleracea and Sinapis arvensis), were inoculated with a mixture of seven isolates of Hyaloperonospora brassicae to identify effective host resistances. Many highly resistant genotypes were identified, particularly R. sativus Krasnodar Market B (%Disease index 6.6) and Pegletta (%DI 9.0); B. carinata Tamn Rex-sel Green (%DI 7.6), BRA926/18 (%DI 9.7) and PI360884 (%DI 9.7); and B. juncea, Ringot1 (%DI 9.7). A further 13 B. carinata, seven B. juncea and single R. sativus (Boss) and B. incana (UPM6563) genotypes were also highly resistant (%DI 11.1), as were B. oleracea CPI106844 (%DI 14.6) and Crambe abyssinica (%DI 17.4). Almost all B. carinata and B. juncea genotypes showed high resistance (%DI 7.6–22.2). In contrast, B. napus genotypes showed wide ranging responses, from high resistance in SN-8 (%DI 22.2%) to extreme susceptibility in Hyola 450TT and Thunder TT (%DI 83.7, 95.5, respectively). R. rugosum, B. fruticulosa, H. incana and B. insularis genotypes ranged from moderately to highly susceptible (%DI 55.2–78.8). This study highlights the ready availability of very high levels of pathotype-independent resistance across diverse Brassicaceae to H. brassicae, particularly R. sativus, B. carinata, B. juncea, B. oleracea and C. abyssinica. Resistances identified can be utilized as sources of resistance in oilseed and vegetable Brassicaceae breeding programs and/or directly deployed as new varieties where downy mildew is prevalent.

Very few near-infrared reflectance spectroscopy (NIRS) calibration models are available for non-destructive estimation of seed quality traits in Brassica juncea. Those that are available also fail to adequately discern variation for oleic acid (C18:1 ), linolenic (C18:3 ) fatty acids, meal glucosinolates and phenols. We report the development of a new NIRS calibration equation that is expected to fill the gaps in the existing NIRS equations.; Results: Calibrations were based on the reference values of important quality traits estimated from a purposely selected germplasm set comprising 240 genotypes of B. juncea and 193 of B. napus. We were able to develop optimal NIRS-based calibration models for oil, phenols, glucosinolates, oleic acid, linoleic acid and erucic acid for B. juncea and B. napus. Correlation coefficients (RSQ) of the external validations appeared greater than 0.7 for the majority of traits, such as oil (0.766, 0.865), phenols (0.821, 0.915), glucosinolates (0.951, 0.986), oleic acid (0.814. 0.810), linoleic acid (0.974, 0.781) and erucic acid (0.963, 0.943) for B. juncea and B. napus, respectively.; Conclusion: The results demonstrate the robust predictive power of the developed calibration models for rapid estimation of many quality traits in intact rapeseed-mustard seeds which will assist plant breeders in effective screening and selection of lines in quality improvement breeding programmes. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

Rfo is located on a radish chromosome fragment (~ 108 Kb), which is seated in the middle of a pretty large C genome translocation at the distal region of chromosome A09 of B. juncea. Ogura cytoplasmic male sterility (CMS) is used to produce hybrids in Indian mustard (Brassica juncea L.). Fertility restorers for this CMS were developed by cross-hybridizing B. juncea (AABB; 2n = 36) with B. napus (AACC; 2n = 38) carrying radish Rfo gene. This hybrid production system is normally stable, but many commercial mustard hybrids show male sterile contaminants. We aimed to identify linkage drag associated with Rfo by comparing hybridity levels of 295 handmade CMS x Rfo crosses. Although Rfo was stably inherited, hybridity was 85 percent in several combinations. Genome re-sequencing of five fertility restorers, mapping sequencing reads to B. juncea reference and synteny analysis with Raphanus sativus D81Rfo genomic region (AJ550021.2) helped to detect ~ 108 Kb of radish chromosome (R) fragment substitution in all fertility restorers. This radish segment substitution was itself located amidst a large C genome translocation on the terminal region of chromosome A09 of B. juncea. The size of alien segment substitution varied from 11.3 (NTCN-R9) to 22.0 Mb (NAJR-102B-R). We also developed an in silico SSR map for chromosome A09 and identified many homoeologous A to the C genome exchanges in the introgressed region. A to the R genome exchanges were rare. Annotation of the substituted fragment showed the gain of many novel genes from R and C genomes and the loss of B. juncea genes from the corresponding region. We have developed a KASPar marker for marker-aided transfer of Rfo and testing hybridity levels in seed production lots.

We investigated phenotypic variations for pod shattering, pod length and number of seeds per pod in large germplasm collections of Brassica juncea (2n = 36; AABB) and its progenitor species, B. rapa (2n = 20; AA) and B. nigra (2n = 16; BB). Pod shatter resistance was measured as energy required for rupturing a mature dry pod, with a specially fabricated pendulum machine. Rupture energy (RE) ranged from 3.3 to 11.0 mJ in B. juncea. MCP 633, NR 3350 and Albeli required maximum energy to shatter a pod. It ranged from 2.5 to 7.8 mJ for B. rapa with an average of 5.5 mJ. B. nigra possessed easy to rupture pods. Correlation analysis showed strong associations among these traits in B. juncea and B. rapa. Genome wide association studies were conducted with select sets of B. juncea and B. rapa germplasm lines. Significant and annotated associations predict the role of FRUITFULL, MANNASE7, and NAC secondary wall thickening promoting factor (NST2) in the genetic regulation of shatter resistance in B. juncea. NST2 and SHP1 appeared important for pod length and seeds per pod in B. rapa. Candidate gene based association mapping also confirmed the role of SHP1 and NST2 in regulating pod shattering and related pod traits in B. rapa and B. juncea. Footprints of selection were detected in SHP1, SHP2 (B. rapa, B. nigra and B. juncea), RPL (B. rapa) and NAC (B. juncea). Our results provide insights into the genetic architecture of three pod traits. The identified genes are relevant to improving and securing crop productivity of mustard crop.

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is a major disease of crop brassicas, with inadequate variation for resistance in primary gene pools. We utilized a wild Brassicaceae species with excellent resistance against stem rot to develop a set of B. juncea - B. fruticulosa introgression lines (ILs). These were assessed for resistance using a highly reproducible stem inoculation technique against a virulent pathogen isolate. Over 40% of ILs showed higher levels of resistance. IL-43, IL-175, IL-215, IL-223 and IL-277 were most resistant ILs over three crop seasons. Sequence reads (21x) from the three most diverse ILs were then used to create B. juncea pseudomolecules, by replacing SNPs of reference B. juncea with those of re-sequenced ILs. Genotyping by sequencing (GBS) was also carried out for 88 ILs. Resultant sequence tags were then mapped on to the B. juncea pseudomolecules, and SNP genotypes prepared for each IL. Genome wide association studies helped to map resistance responses to stem rot. A total of 13 significant loci were identified on seven B. juncea chromosomes (A01, A03, A04, A05, A08, A09 and B05). Annotation of the genomic region around identified SNPs allowed identification of 20 candidate genes belonging to major disease resistance protein families, including TIR-NBS-LRR class, Chitinase, Malectin/receptor-like protein kinase, defensin-like (DEFL), desulfoglucosinolate sulfotransferase protein and lipoxygenase. A majority of the significant SNPs could be validated using whole genome sequences (21x) from five advanced generation lines being bred for Sclerotinia resistance as compared to three susceptible B. juncea germplasm lines. Our findings not only provide critical new understanding of the defensive pathway of B. fruticulosa resistance, but will also enable development of marker candidates for assisted transfer of introgressed resistant loci in to agronomically superior cultivars of crop Brassica.

Field host resistance against the white leaf spot pathogen Pseudocercosporella capsellae was determined across one hundred and seventeen Brassica napus, eleven B. juncea, four B. rapa, five B. oleracea, eight B. fruticulosa and one B. carinata genotypes. Of the one hundred and seventeen B. napus, there were seven lines of B. napus containing weedy crucifer introgression, sixteen lines with B. carinata introgression, fifty six lines of synthetic B. napus from B. juncea into B. carinata and B. rapa into B. oleracea, while remaining B. napus were commercial varieties from Australia. There was wide and significant (P < 0.001) variation across the test genotypes in terms of relative disease development assessed either as % leaves diseased index (%LDI), values ranging from 0 to 68, or % leaves collapsed index (%LCI), with values ranging from 0 to 38. B. rapa subsp. oleifera ATC 95966 Bo was the most resistant genotype to white leaf spot disease (%LDI = 0, %LCI = 0). Very high resistance was observed in all five B. oleracea genotypes (%LDI < 13, %LCI ≤ 10) and of these B. oleracea var. gongylodes Tronchuda with %LDI = 1.0 and %LCI = 2.5 and B. oleracea var. sabellica Kailan with %LDI = 2.4 and %LCI = 2.0 were the most resistant. Eight B. fruticulosa genotypes showed high resistance with %LDI < 15 and ≤ 10 %LCI. While eight out of twelve B. juncea varieties were highly susceptible, there was a range in %LDI of 5–58 and %LCI of 10–30 and with both Montara and VT 535 G showing best resistance of this species. Amongst B. napus genotypes, more than ten of the Australian commercial cultivars demonstrated comparatively higher resistance to white leaf spot disease than the most resistant genotypes with weedy introgression or synthetic B. napus, with commercial cultivars Oscar and Stubby considered to be highly resistant. These resistances offer unique opportunities both for direct deployment where white leaf spot is severe and for oilseed and vegetable Brassica spp. breeding programs to develop commercial cultivars with effective resistance.

Allohexaploid Brassica populations reveal ongoing segregation for fertility, while genotype influences fertility and meiotic stability. Creation of a new Brassica allohexaploid species is of interest for the development of a crop type with increased heterosis and adaptability. At present, no naturally occurring, meiotically stable Brassica allohexaploid exists, with little data available on chromosome behaviour and meiotic control in allohexaploid germplasm. In this study, 100 plants from the cross B. carinata × B. rapa (A2 allohexaploid population) and 69 plants from the cross (B. napus × B. carinata) × B. juncea (H2 allohexaploid population) were assessed for fertility and meiotic behaviour. Estimated pollen viability, self-pollinated seed set, number of seeds on the main shoot, number of pods on the main shoot, seeds per ten pods and plant height were measured for both the A2 and H2 populations and for a set of reference control cultivars. The H2 population had high segregation for pollen viability and meiotic stability, while the A2 population was characterised by low pollen fertility and a high level of chromosome loss. Both populations were taller, but had lower average fertility trait values than the control cultivar samples. The study also characterises fertility and meiotic chromosome behaviour in genotypes and progeny sets in heterozygous allotetraploid Brassica derived lines, and indicates that genotypes of the parents and H1 hybrids are affecting chromosome pairing and fertility phenotypes in the H2 population. The identification and characterisation of factors influencing stability in novel allohexaploid Brassica populations will assist in the development of this as a new crop species for food and agricultural benefit.

Brassica napus introgression lines (ILs), having B-genome segments from B. carinata, were assessed genetically for extent of introgression and phenotypically for siliqua shatter resistance. Introgression lines had 7–9% higher DNA content, were meiotically stable, and had almost normal pollen fertility/seed set. Segment introgressions were confirmed by fluorescent genomic in situ hybridization (fl-GISH), SSR analyses, and SNP studies. Genotyping with 48 B-genome specific SSRs detected substitutions from B3, B4, B6, and B7 chromosomes on 39 of the 69 ILs whereas SNP genotyping detected a total of 23 B-segments (≥3 Mb) from B4, B6, and B7 introgressed into 10 of the 19 (C1, C2, C3, C5, C6, C8, C9, A3, A9, A10) chromosomes in 17 ILs. The size of substitutions varied from 3.0 Mb on chromosome A9 (IL59) to 42.44 Mb on chromosome C2 (IL54), ranging from 7 to 83% of the recipient chromosome. Average siliqua strength in ILs was observed to be higher than that of B. napus parents (2.2–6.0 vs. 1.9–4.0 mJ) while siliqua strength in some of the lines was almost equal to that of the donor parent B. carinata (6.0 vs.7.2 mJ). These ILs, with large chunks of substituted B-genome, can prove to be a useful prebreeding resource for germplasm enhancement in B. napus, especially for siliqua shatter resistance.

Effective host resistance is the most cost-effective long term prospect for successful management of white leaf spot disease (Pseudocercosporella capsellae) in Brassicaceae. In two separate field trials, 168 genotypes were screened. In the first trial, lines of Brassica oleracea var. capitata (59), Brassica napus (34), Brassica juncea (6) and B. juncea containing wild weedy Brassicaceae introgression(s) (14) were arranged; and in the second, Australian historic and current B. napus (45) and B. juncea (10) varieties were screened. There was wide variation in expression of resistance, from complete resistance to highly susceptible as assessed by two disease parameters, viz. (i), Area Under Disease Progress Curve (AUDPC) for percent leaves diseased (values 0–221.2) and (ii) Percent Leaf Collapse Index (%LCI) values for leaf collapse due to disease (0–38.7). Brassica oleracea var. capitata was overall the most resistant species, while B. juncea the most susceptible with the majority having AUDPC values >75 and B. napus was intermediate. Five B. oleracea var. capitata genotypes were completely resistant, with 0 AUDPC and %LCI values. Pioneer® 45Y22 (RR) ‘Mystic’ and ‘Wahoo’ were also highly resistant, with the least %LCI (

Brassica rapa L. (AA; 2n = 20) store considerable amounts of oil and protein reserves in the seeds. Genetic enhancement of these seed storage products is sought to meet specific requirements of the producers and consumers of edible oils, biofuels, animal feed and other industrial products. This necessitates the introduction of new genetic variation and a greater understanding of the trait genetics. We tested 195 germplasm lines of B. rapa for oil, protein and glucosinolates under the environment conditions differing for day length and ambient temperatures during development and maturation of the seeds. This helped to document phenotypic variations for these traits and also identify accessions with extreme phenotypes. DArT genotyping and genome wide association studies enabled detection of SNP markers within or near the genes that are associated directly or indirectly with the biosynthesis of oil (LTPG5, FRK7, SSE1, LACS8, LTPG33), protein (VTI1B, TSB2, SESA4, bZIP1, PPI1, K18J17.13) and glucosinolates (IMD1, MYB119, ILR3, IQD1, ADS2, SOT18). We also envisaged a gene, PLAT2. It is a member of PLAT-plant-stress subgroup of proteins. PLAT2 can be a target for breeding efforts aimed at improving abiotic stress tolerance. Introduction of novel allelic diversity may be more desirable for the development of designer genotypes rather than the simple repackaging of the genetic variation extant in the crop gene pools. It is for the first time that an attempt has been made to characterize allelic diversity extant in the ‘A’ sub genome of B. juncea for its deployment in B. rapa genepool.

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a serious disease of many cruciferous crops and frequently poses a threat to the sustainable and profitable production of these crops worldwide. Differences in seedling resistance to S. sclerotiorum across 46 diverse cruciferous genotypes from 12 different species were assessed by comparing the extent of pathogenesis on inoculated cotyledons under controlled conditions. Selections of Brassica carinata, B. incana, B. juncea, B. napus, and B. napus introgressed with B. carinata, B. nigra, B. oleracea, B. rapa var. rosularis, B. rapa var. chinensis, B. tournefortii, Raphanus raphanistrum, R. sativus, and Sinapis arvensis were tested. The average size of lesions on cotyledons 48 h post inoculation varied from 0.8 to 7.3 mm. The three most resistant genotypes with the smallest lesions were all from B. oleracea (viz., B. oleracea var. italica ‘Prophet’ and B. oleracea var. capitata ‘Burton’ and ‘Beverly Hills’). Representatives of R. raphanistrum, S. arvensis, B. juncea, and B. carinata were the most susceptible to S. sclerotiorum, with the largest lesions. To our knowledge, this is the first report of high levels of resistance to S. sclerotiorum in B. oleracea at the cotyledon stage and also the first report of the host cotyledon reactions against S. sclerotiorum for all tested species except B. napus and B. juncea. The mean lesion size for B. napus introgressed with B. carinata was 5.6 mm, which is midway between the lesion size for the two parent species B. napus (5.1 mm) and B. carinata (5.8 mm). Separate genetic control for cotyledon versus mature plant resistance was demonstrated by the lack of correlation between lesion size from S. sclerotiorum on the cotyledon with the severity of disease initiated by stem inoculation or natural processes in a previous field test. On the most resistant genotypes, B. oleracea var. italica Prophet and var. capitata Burton, growth of S. sclerotiorum on the cotyledon surface prior to penetration was severely impeded, production of appressoria inhibited, and both cytoplasm shrinkage and protoplast extrusion in S. sclerotiorum hyphae prevalent. This is the first report of such resistant mechanisms in B. oleracea. Genotypes with cotyledon resistance identified in this study will be of great value not only in furthering our understanding of resistance mechanisms across different cruciferous species but also could be exploited for developing commercial crucifer cultivars with high-level resistance against S. sclerotiorum.

Nitrogen (N) is a critical input for plant growth and development. A better understanding of N uptake and utilization is important to develop plant breeding strategies for improving nitrogen use efficiency (NUE). With that objective in mind, we assayed a SNP-genotyped association panel comprising 92 inbred lines for the activities of nitrate reductase (NR), nitrite reductase (NIR), glutamine synthetase (GS) and glutamate synthase (GOGAT). All these enzymes are associated with N assimilation. The experiments were carried out at two levels of N application: no added N (N0) and agrnomically recommened dose (100 kg/ha) of N application (N100). Genome wide association studies (GWAS) helped to identify several marker-trait associations (MTAs), involving chromosomes A01, A06, A08, B02, B04, B05 and B08. These explained high phenotypic variation (up to 32%). Annotation of the genomic region(s) in or around significant SNPs allowed prediction of genes encoding high affinity nitrate transporters, glutamine synthetase 1.3, myb-like transcription factor family protein, bidirectional amino acid transporter 1, auxin signaling F-box 3 and oxidoreductases. This is the first attempt to use GWAS for identification of enzyme QTLs to explain variation for nitrogen assimilation enzymes in Brassica juncea.

A set of 96 Brassica juncea–Erucastrum cardaminoides introgression lines (ILs) were developed with genomic regions associated with Sclerotinia stem rot (Sclerotinia sclerotiorum) resistance from a wild Brassicaceous species E. cardaminoides. ILs were assessed for their resistance responses to stem inoculation with S. sclerotiorum, over three crop seasons (season I, 2011/2012; II, 2014/2015; III, 2016–2017). Initially, ILs were genotyped with transferable SSR markers and subsequently through genotyping by sequencing. SSR based association mapping identified six marker loci associated to resistance in both A and B genomes. Subsequent genome-wide association analysis (GWAS) of 84 ILs recognized a large number of SNPs associated to resistance, in chromosomes A03, A06, and B03. Chromosomes A03 and A06 harbored the maximum number of resistance related SNPs. Annotation of linked genomic regions highlighted an array of resistance mechanisms in terms of signal transduction pathways, hypersensitive responses and production of anti-fungal proteins and metabolites. Of major importance was the clustering of SNPs, encoding multiple resistance genes on small regions spanning approximately 885 kb region on chromosome A03 and 74 kb on B03. Five SNPs on chromosome A03 (6,390,210-381) were associated with LRR-RLK (receptor like kinases) genes that encode LRR-protein kinase family proteins. Genetic factors associated with pathogen-associated molecular patterns (PAMPs) and effector-triggered immunity (ETI) were predicted on chromosome A03, exhibiting 11 SNPs (6,274,763-994). These belonged to three R-Genes encoding TIR-NBS-LRR proteins. Marker trait associations (MTAs) identified will facilitate marker assisted introgression of these critical resistances, into new cultivars of B. juncea initially and, subsequently, into other crop Brassica species.

Seed size and seed metabolites have been the targets of direct or indirect selection during domestication and subsequent crop breeding. Understanding these traits and associated genetics can prove very useful for plant translational research. Large germplasm assemblage (235) of Brassica juncea and its progenitor species (B. rapa and B. nigra) was evaluated to establish seed trait variations for seed size and seed metabolites. Seeds were smallest in B. nigra and largest in B. juncea. Australian B. juncea and Indian B. rapa var brown sarson types averaged more seed oil content. Seed size and oil content were generally higher in modern cultivars in comparison to the land races. Allelic diversity for known associated genes for seed-size and oil-content (AP2, ARF2, TTG2, GRF2, GL2, CYP78A5, CYP78A6, MINI3, IKU2, IKU1, BRI1, DGAT, GPDH, LPAAT, GPAT and DA1) was studied so as to infer the effect of domestication on seed traits. Three genes (IKU1, IKU2, AP2) in B. rapa, two (TTG2 and GL2) in B. nigra and two (IKU1 and GRF2) in natural B. juncea were identified as targets of selection on the basis of Fst outlier and/or sequence diversity tests. We report parallel divergence for seed traits between B. juncea and B. rapa. Directional selection appeared stronger for seed-size as compared to correlated seed metabolites. Positive selection on seed-size is likely to have played a significant role in structuring regional variation in the germplasm.

Backcross substitution of Brassica juncea (2n = 36; AABB) nucleus into the cytoplasm of a wild crucifer, Brassica fruticulosa helped in development of a new cytoplasmic male sterility (CMS) system. Male sterility was complete, stable, and expressed as rudimentary anthers containing sterile pollen grains. There was no impact on other floral as well as vegetative characters. All the natural B. juncea genotypes evaluated maintained the sterility. Gene for fertility restoration could be successfully introgressed from cytoplasm donor species. Genomic in situ hybridization studies revealed B. fruticulosa intogression in at least three chromosomes of the recipient species. Genetic studies carried out on F1, F2 and test cross progenies derived from hybridizing cytoplasmic male sterile and fertility restoring genotypes revealed a monogenic dominant control for the fertility restoration. Bulked segregant analysis with 588 SSR and 30 ISSR primers allowed identification of putative primers associated with fertility restoration. Co-segregation analysis of ten such primers with Rff gene revealed that Rf was flanked by two markers, namely cnu_m316 and nia_ m22, which were located 27.1 (LOD = 3.0) and 19.7 cM (LOD = 3.0) respectively around the gene in question. Distinctness of new CMS system from the ogura CMS was also demonstrated. This newly developed CMS-fertility-restorer system has a significant potential for hybrid seed production programs in mustard as an alternative to currently popular ogura CMS system.

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is a serious problem in oilseed rape and mustard worldwide. Locating effective sources of host resistance to this disease offers the best long term prospects for its improved management. For this reason, 19 Brassica napus genotypes from Australia (6), China (7) and India (6) and 34 Brassica juncea genotypes from Australia (6), China (3) and India (25), were screened for resistance to SSR under field conditions using a stem inoculation test. There were significant differences ( P B. napus and B. juncea test genotypes in relation to the stem lesion length. The most resistant B. napus genotypes were Oscar from Australia, Zhongyou-za No. 8, Fan 168 and Ding 110 from China, all with stem lesion lengths ≤4.1 cm. The most susceptible B. napus were GSL2 from India, and 03-p74-11 from China, with stem lesion lengths ≥12 cm. The most resistant B. juncea genotypes were Aravali and Bio-902 from India with stem lesion lengths ≤5.7 cm; while the most susceptible were JM018 from Australia, Xinyou 8 and Xinyou 9 from China, Sanjucta Ascsh and Basanti from India, all with stem lesion lengths >10 cm. In particular, this high level resistance in B. napus Oscar from Australia, Zhongyou-za No. 8, Fan 168 and Ding 110 from China provides sources of resistance for oilseed Brassica breeding programs in Australia; particularly resistance to pathotype 76, the dominant prevailing S. sclerotiorum pathotype. It is noteworthy that progenies from B. napus crosses of Oscar with Ding 110 express isolate-independent host resistance, making Oscar and Ding 110, and potentially their progenies, an ideal target to exploit in developing new commercial rapeseed cultivars that not only have more effective resistance to SSR, but resistance that is effective across multiple pathotypes of this pathogen. These findings ensure successful management of SSR based on host resistance rather than fungicides is now possible providing breeders take the opportunities now presented.

Field resistances against Sclerotinia rot (SR) (Sclerotinia sclerotiorum) were determined in 52 Chinese genotypes of Brassica oleracea var. capitata, 14 Indian Brassica juncea genotypes carrying wild weedy Brassicaceae introgression(s) and four carrying B-genome introgression, 22 Australian commercial Brassica napus varieties, and 12 B. napus and B. juncea genotypes of known resistance. All plants were individually inoculated by securing an agar disc from a culture of S. sclerotiorum growing on a glucose-rich medium to the stem above the second internode with Parafilm tape. Mean stem lesion length across tested genotypes ranged from 68 mm. While there was considerable diversity within the germplasm sets from each country, overall, 65% of the B. oleracea var. capitata genotypes from China showed the highest levels of stem resistance, a level comparable with the highest resistance ever recorded for oilseed B. napus or B. juncea from China or Australia. One Indian B. juncea line carrying weedy introgression displayed a significant level of both stem and leaf resistance. However, the vast majority of commercial Australian oilseed B. napus varieties fell within the most susceptible 40% of genotypes tested for stem disease. There was no correlation between expressions of stem versus leaf resistance, suggesting their independent inheritance. A few Chinese B. oleracea var. capitata genotypes that expressed combined extremely high-level stem (≤1 mm length) and leaf (≤0.5 mean number of infections/plant) resistance will be particularly significant for developing new SR-resistant horticultural and oilseed Brassica varieties.

Field resistances/susceptibilities against Albugo candida race 2V were determined for 29 Indian Brassica juncea varieties and compared with resistant varieties from China (6) and Australia (7). ‘Basanti’ (AUDPC incidence 46.7; AUDPC severity 29.2) represents the first high-level resistance to race 2V in Indian varieties. Several others showed lower but still useful levels of resistance, including Narendra Ageti Rai-4 (AUDPC incidence 150.6; AUDPC severity 66.8) and JM1 (AUDPC incidence 167.1; AUDPC severity 83.7). Highly susceptible Indian varieties had AUDPC incidence values >200 and severity >100. ‘Basanti’ had least stagheads/plant (0.32), while Narendra Ageti Rai-4 had lowest % plants with stagheads (2.48). In contrast, almost half of Indian varieties had stagheads/plant >1 and % plants with stagheads >4, and >26 for ‘Kranti’. The resistance in ‘Basanti’ paves the way forward towards significantly improved white rust management in mustard in India. JM06011, JM06021, JR049 from Australia and CJB-003 from China had zero leaf incidence. There were significant (P

A core subset of genetically fixed lines was selected through stratified sampling to represent the allelic variations within Brassica juncea gene pools. It included germplasm accessions from India, China, and Australia, as well as B. Juncea introgression lines carrying alien genetic variation and/or cytoplasm from wild crucifers, namely Diplotaxis cardaminoides, Diplotaxis tenuisiliqua, and Erucastrum abyssinicum. The aim of the study was to infer the influence of underlying cytoplasm on population structure and trait variation. Molecular characterization using nuclear SSR markers (158) and chloroplast SSR markers (9) revealed interesting germplasm patterns and trait variations. Diversity groups obtained using distance-based clustering were not fully compliant with structure analysis, especially for the nuclear genetic variation. Association between population structure and phenotypic variation was indicated by significant interactions between chlorotype and seed/biological yields. Thus, there may be a need to factor in the impact of background cytoplasm on population structure in association studies of crops where different cytoplasmic lineages are known.

Very few near-infrared reflectance spectroscopy (NIRS) calibration models are available for non-destructive estimation of seed quality traits in Brassica juncea. Those that are available also fail to adequately discern variation for oleic acid (CCalibrations were based on the reference values of important quality traits estimated from a purposely selected germplasm set comprising 240 genotypes of B. juncea and 193 of B. napus. We were able to develop optimal NIRS-based calibration models for oil, phenols, glucosinolates, oleic acid, linoleic acid and erucic acid for B. juncea and B. napus. Correlation coefficients (RSQ) of the external validations appeared greater than 0.7 for the majority of traits, such as oil (0.766, 0.865), phenols (0.821, 0.915), glucosinolates (0.951, 0.986), oleic acid (0.814. 0.810), linoleic acid (0.974, 0.781) and erucic acid (0.963, 0.943) for B. juncea and B. napus, respectively.The results demonstrate the robust predictive power of the developed calibration models for rapid estimation of many quality traits in intact rapeseed-mustard seeds which will assist plant breeders in effective screening and selection of lines in quality improvement breeding programmes. © 2018 Society of Chemical Industry.

Indian mustard (Brassica juncea (L) Czern & Coss) is naturally indeterminate. Plants with determinate inflorescence were first discovered in the self progenies of B. juncea (AABB; 2n = 36), resynthesized by combining A-genome from B. napus (AACC; 2n = 38) and B-genome from B. carinata (BBCC; 2n = 34). In the determinate plants, apical meristems were transformed into pods. In contrast, the inflorescence in the indeterminate plants continues to grow indefinitely while producing peripheral flowers. Genotyping and morphological characterization of newly developed determinate gene pool (A8) showed a rapid emergence and progression of genetic and phenotypic alterations which continued even after seven generations of selfing. A large number of determinate genotypes (125) were evaluated to establish agronomic potential of determinate B. juncea. A high proportion of determinate genotypes outperformed the best indeterminate checks, suggesting that critical productivity related traits like pod number, seed size and oil content were not a function of indeterminacy. As the gene for determinacy has also been introgressed in B. napus and B. carinata, the stage is now set for future breeding to aim at crop architectural modifications through determinacy in all three types of oilseed Brassicas grown in the world. Our studies emphasized the role of polyploidy as a major force of differentiation at both genotypic and phenotypic level. Although, there was no direct correlation between evolution of genetic and phenotypic diversities following polyploidization. We suggest the use of polyploidy as a plant breeding tool to benefit from de novo variation rather than restricting its use as a method to overcome sterility following wide hybridization alone.

Genetic mitigation needs require a species-by-species and region-by-region analysis of projected environmental issues. This may be done through close interactions among breeders, farmers, and climate change scientists. Although adaptation is highly site specific, sets of sites may exist across the globe that face similar adaptation issues or where the current environment may represent projected future environment for some other regions. Such locations may be extensively utilized to screen available germplasm resources and also for raising crops continuously and naturally, developing crop populations as germplasm conduits for global plant breeding efforts. Comparing adaptation experiences between each of the world's geoclimatic groupings and promoting cross-learning is desirable. Participatory breeding and participatory varietal selection may help fast track the development of climate-resilient crop varieties and cropping systems aimed at multiple breeding targets. Such efforts may further be optimized by ...

Field and controlled environment studies were undertaken to define the range and extent of available host resistances to Pseudocercosporella capsellae (white leaf spot) across diverse oilseed, forage and vegetable crucifers, including some wild and/or weedy species, and also within and/or derived from Brassica carinata. In each experiment, there was a wide range in host response from high resistance to high susceptibility as assessed by four disease parameters, viz. in the field for: (i) Area Under Disease Progress Curve (AUDPC) for percent leaves diseased with values ranging from 0 to 375.5; (ii) Percent Leaf Collapse Index (%LCI) for leaf collapse due to disease with values ranging from 0 to 23.0; and (iii), Percent Pod Area Disease Index (%PADI) for pod area affected with values ranging from 0 to 52.1; and (iv) under controlled environmental conditions for Percent Cotyledon Disease Index (%CDI) for cotyledon lesion size with values ranging from 0 to 27.5. At the Crawley field site, B. carinata ATC 94129 was the most resistant genotype with AUDPC = 1.2, followed by Crambe abyssinica (AUDPC 8.7), Eruca sativa Eruc-01 (AUDPC 19.3) and E. vesicaria Yellow rocket (AUDPC 19.4). B. carinata ATC 94129 and B. oleracea var. capitata had the least leaf collapse, with %LCI = 0.2. At the Shenton Park field site, 21 genotypes of B. carinata and B. oleracea var. acephala Tuscan kale showed total resistance, all with AUDPC values of 0. Of the B. napus genotypes carrying one or more B. carinata B genome introgressions, genotypes NC8 (AUDPC 23.0) and NC9-1 (AUDPC 26.2) were the most resistant. Genotypes as assessed on these disease criteria as having high level resistance generally showed no pod infection; in contrast to %PADI values up to 52 on the most susceptible genotypes. Under controlled environmental conditions, the most resistant genotype was B. carinata ATC 94129 with %CDI values of 0 and 0.2, respectively, across two experiments, along with B. napus genotypes Zhongyou 821 and Hyola 42, with a %CDI value of 0 in one of the two experiments. There was a high degree of correlation both within individual experiments across the different disease parameters and also between field and controlled environment experiments. Within both B. napus and B. juncea genotypes tested, the most resistant genotypes were from China, the most susceptible from India, with those from Australia intermediate.

Current management of Sclerotinia rot (Sclerotinia sclerotiorum) relies heavily upon cultural and chemical control options that provide, at best, only partial, sometimes sporadic control and can be cost prohibitive. Effective host resistance to S. sclerotiorum is urgently needed if Sclerotinia rot is to be successfully managed across diverse oilseed, forage and vegetable crucifer crops worldwide. Differences in resistance across 127 diverse cruciferous genotypes to S. sclerotiorum in one experiment, and a set of 55 Brassica napus lines carrying one or more B. carinata B genome introgressions in a second experiment, were assessed by field-inoculation of stems and natural ascospore infection. Reactions on B. fruticulosa, B. oxyrrhina, B. parachinensis, B. tournefortii, Camelina sativa, Carrichtera annua, Diplotaxis tenuifolia, Eruca vesicaria, Hirschfeldia incana, Raphanus raphanistrum, Raphanus sativus, Rapistrum rugosum, Sinapis arvensis and Sisymbrium irio to this pathogen are reported for the first time. Among these, and across other species previously explored, including B. carinata, B. napus, B. juncea, B. rapa, B. cretica, B. incana, B. insularis, B. nigra, and B. montana, responses ranged from highly resistant (stem lesion length 2 mm) to highly susceptible (155 mm). Against a highly virulent and prevailing pathogen pathotype, R. raphanistrum RRA 41, B. napus Mystic, B. carinata BRA 926/78, B. carinata 054113, R. sativus Krasnodar. Market B, B. carinata PI 193459 and R. raphanistrum WARR 20 all showed very high-level resistance, with stem lesion length 67 mm). There appeared to be separate genetic control for stem vs. leaf resistance, crucial to the understanding needed in developing resistant cultivars across different cruciferous crop types. While this study highlighted individual genotypes that offer great potential for improving resistance to Sclerotinia rot in commercial cruciferous crops, it also demonstrated that assessment of the overall value of a species is only possible when a significant number of genotypes within the species are tested. Overall, while genotypes with high-level stem or leaf resistance identified are of particularly significant value for developing new disease-resistant cultivars of oilseed, forage and vegetable crucifers, even genotypes with moderate levels of resistance, if deployed commercially, offer prospects of improving current integrated disease management strategies compared with current reliance upon cultural and/or chemical controls utilized in conjunction with cultivars lacking any effective resistance. As resistance was identified for the first time across many of these diverse cruciferous species, it is likely that some resistances identified constitute new sources and/or types of host resistance not previously identified.

Climate change, caused by anthropogenic activities, is a universal phenomenon across the globe. There is general consensus that combating climate change will require a set of internationally coordinated policy interventions for reducing greenhouse gas (GHG) emissions besides addressing regional or global vulnerabilities, development patterns, equity distribution, and technology transfer. Agriculture is both a victim and an abettor of climate change. Serious attention is thus required, not only to enhance its adaptation capacity but also to exploit its mitigation potential as a carbon sink. A sustainable policy shift toward enhanced food security, preservation of freshwater resources, prevention of soil degradation, and maintenance of biological diversity and ecosystems remain the hallmark of mitigation strategies. Improved adaptive capacity relative to climate-resilient agriculture needs to be integrated with global developmental paths aimed at reducing social inequalities and alleviating poverty. The Uni...

Flowering is an important phase in the angiosperms life cycle, as it signifies the transition from vegetative to reproductive phase. Recently, increasing number of flowering genes are being cloned and analyzed. However, few studies have focused on the comparative analysis of key candidate genes involved in the regulation of flowering time across species. We explore the common characteristics of key flowering genes across species and compare their diversity and evolutionary divergence. We analyze key flowering candidate genes in three species, Arabidopsis thaliana, Oryza sativa and Zea mays. The homology of flowering genes across the three species was more than 60%. Nucleotide polymorphism analysis for these genes revealed high sequence conservation during evolution, although some small insertion/deletions (InDels) were also detected. Furthermore, these candidate genes harbored simple repeat sequence repeats that perhaps drove genetic variation and divergence of these genes. The flowering genes were expressed preferentially in the organelle and cellular components and participated mainly in metabolic processes with binding and catalytic functionality. These results suggested that key flowering genes have more common characteristics that may allow the identification and analysis of other flowering genes, especially in species where genome sequencing has not yet been performed. Key words: Evolution, flowering gene, simple repeat sequences, homologous genes.