Transcriptome and Physiological Analysis of Rapeseed Tolerance to Post-Flowering Temperature Increase.

Climate-change-induced temperature fluctuations pose a significant threat to crop production, particularly in the Southern Hemisphere. This study investigates the transcriptome and physiological responses of rapeseed to post-flowering temperature increases, providing valuable insights into the molecular mechanisms underlying rapeseed tolerance to heat stress. Two rapeseed genotypes, Lumen and Solar, were assessed under control and heat stress conditions in field experiments conducted in Valdivia, Chile. Results showed that seed yield and seed number were negatively affected by heat stress, with genotype-specific responses. Lumen exhibited an average of 9.3% seed yield reduction, whereas Solar showed a 28.7% reduction. RNA-seq analysis of siliques and seeds revealed tissue-specific responses to heat stress, with siliques being more sensitive to temperature stress. Hierarchical clustering analysis identified distinct gene clusters reflecting different aspects of heat stress adaptation in siliques, with a role for protein folding in maintaining silique development and seed quality under high-temperature conditions. In seeds, three distinct patterns of heat-responsive gene expression were observed, with genes involved in protein folding and response to heat showing genotype-specific expression. Gene coexpression network analysis revealed major modules for rapeseed yield and quality, as well as the trade-off between seed number and seed weight. Overall, this study contributes to understanding the molecular mechanisms underlying rapeseed tolerance to heat stress and can inform crop improvement strategies targeting yield optimization under changing environmental conditions.

Meiosis in Polyploids and Implications for Genetic Mapping: A Review.

Plant cytogenetic studies have provided essential knowledge on chromosome behavior during meiosis, contributing to our understanding of this complex process. In this review, we describe in detail the meiotic process in auto- and allopolyploids from the onset of prophase I through pairing, recombination, and bivalent formation, highlighting recent findings on the genetic control and mode of action of specific proteins that lead to diploid-like meiosis behavior in polyploid species. During the meiosis of newly formed polyploids, related chromosomes (homologous in autopolyploids; homologous and homoeologous in allopolyploids) can combine in complex structures called multivalents. These structures occur when multiple chromosomes simultaneously pair, synapse, and recombine. We discuss the effectiveness of crossover frequency in preventing multivalent formation and favoring regular meiosis. Homoeologous recombination in particular can generate new gene (locus) combinations and phenotypes, but it may destabilize the karyotype and lead to aberrant meiotic behavior, reducing fertility. In crop species, understanding the factors that control pairing and recombination has the potential to provide plant breeders with resources to make fuller use of available chromosome variations in number and structure. We focused on wheat and oilseed rape, since there is an abundance of elucidating studies on this subject, including the molecular characterization of the Ph1 (wheat) and PrBn (oilseed rape) loci, which are known to play a crucial role in regulating meiosis. Finally, we exploited the consequences of chromosome pairing and recombination for genetic map construction in polyploids, highlighting two case studies of complex genomes: (i) modern sugarcane, which has a man-made genome harboring two subgenomes with some recombinant chromosomes; and (ii) hexaploid sweet potato, a naturally occurring polyploid. The recent inclusion of allelic dosage information has improved linkage estimation in polyploids, allowing multilocus genetic maps to be constructed.

Unraveling the impact on agronomic traits of the genetic architecture underlying plant-density responses in canola.

Plant density defines vegetative architecture and the competition for light between individuals. Brassica napus (canola, rapeseed) presents a radically different plant architecture compared to traditional crops commonly cultivated at high density, and can act as a model system of indeterminate growth. Using a panel of 152 spring-type accessions and a double-haploid population of 99 lines from a cross between the cultivars Lynx and Monty, we performed genome-wide association studies (GWAS) and quantitative trait locus (QTL) mapping for 12 growth and yield traits at two contrasting plant densities of 15 and 60 plants m-2. The most significant associations were found for time to flowering, biomass at harvest, plant height, silique and seed numbers, and seed yield. These were generally independent of plant density, but some density-dependent associations were found in low-density populations. RNA-seq transcriptomic analysis revealed distinctive latent gene-regulatory responses to simulated shade between Lynx and Monty. Having identified candidate genes within the canola QTLs, we further examined their influence on density responses in Arabidopsis lines mutated in certain homologous genes. The results suggested that TCP1 might promote growth independently of plant density, while HY5 could increase biomass and seed yield specifically at high plant density. For flowering time, the results suggested that PIN genes might accelerate flowering in plant a density-dependent manner whilst FT, HY5, and TCP1 might accelerate it in a density-independent. This work highlights the advantages of using agronomic field experiments together with genetic and transcriptomic approaches to decipher quantitative complex traits that potentially mediate improved crop productivity.

Transcriptome Analysis of Seed Weight Plasticity in Brassica napus.

A critical barrier to improving crop yield is the trade-off between seed weight (SW) and seed number (SN), which has been commonly reported in several crops, including Brassica napus. Despite the agronomic relevance of this issue, the molecular factors involved in the interaction between SW and SN are largely unknown in crops. In this work, we performed a detailed transcriptomic analysis of 48 seed samples obtained from two rapeseed spring genotypes subjected to different source-sink (S-S) ratios in order to examine the relationship between SW and SN under different field conditions. A multifactorial analysis of the RNA-seq data was used to identify a group of 1014 genes exclusively regulated by the S-S ratio. We found that a reduction in the S-S ratio during seed filling induces the expression of genes involved in sucrose transport, seed weight, and stress responses. Moreover, we identified five co-expression modules that are positively correlated with SW and negatively correlated with SN. Interestingly, one of these modules was significantly enriched in transcription factors (TFs). Furthermore, our network analysis predicted several NAC TFs as major hubs underlying SW and SN compensation. Taken together, our study provides novel insights into the molecular factors associated with the SW-SN relationship in rapeseed and identifies TFs as potential targets when improving crop yield.

Molecular characterization of imidazolinone-resistant Brassica rapa × B. napus hybrids.

Herbicide-resistant oilseed rape (Brassica napus) cultivation in our country entails the risk of gene transfer to related wild species. One of these species is the wild turnip (B. rapa), an important weed of winter crops widely distributed in the Pampas region. Despite hybridization risks, Clearfield ® oilseed rape is available in Argentina. In 2008, a B. rapa population, which was sympatric to an imidazolinone-resistant and a conventional oilseed rape cultivar, was located on a farm in the main cropping area of the country. Herbicide-resistant individuals were found in the progeny of this population in a herbicide screening test. Therefore, a molecular characterization using cleaved amplified polymorphic sequence (CAPS) and simple sequence repeat (SSR) markers was conducted on these plants to determine their hybrid nature and to establish the origin of the imidazolinone resistance trait. The results of this study, along with information of field records, confirmed that the resistant plants were first generation interspecific hybrids. Imidazolinone resistance had been effectively transferred from the herbicide-resistant oilseed rape, even in the particular situation of pollen competition. Oilseed rape resistant cultivars are becoming more common in the country. So, considering that seed loss and crop volunteers are common in these species, it is crucial to avoid the dispersion of new resistant weed biotypes as they reduce the effectiveness of chemical control technologies.

Organic acid effects on Brassica napus L. var. oleifera seed germination and seedling growth / Efeitos de ácidos orgânicos na germinação e crescimento inicial de Brassica napus L. var. oleifera

Canola (Brassica napus L. var. oleifera) is cultivated in the Southern Brazil as an alternative winter crop in the rotation system. No-tillage and hydromorphic soils favor the formation of aliphatic organic acids with short chain and low molecular weight, as acetic, butyric, and propionic acids. These acids may cause negative effects on the canola production. Thus, this study aimed to evaluate the response of five canola hybrid genotypes under the effect of acetic, butyric and propionic acids on the germination and initial phase of seedling growth. The results showed the characters evaluated respond differently to treatments applied within the same genotype. Therefore, the selection of a genotype with a resilient performance for the characters evaluated under stress is complex. Nevertheless, a sensitive profile response was observed in Hyola 433 genotype under different organic acids. Furthermore, acetic acid showed no negative impact on germination and initial growth of the genotypes.

A Canola (Brassica napus L. var. oleifera) é cultivada no Sul do Brasil como uma alternativa para a estação fria no sistema de rotação de culturas. O sistema de plantio direto e a ocorrência de solos hidromórficos favorece a formação de ácidos orgânicos alifáticos com cadeia curta e baixo peso molecular, como os ácidos acético, butírico e propiônico. Estes ácidos podem causar efeitos negativos na produção de canola. Assim, este estudo teve por objetivo avaliar a resposta de cinco genótipos híbridos de canola sob o efeito dos ácidos acético, butírico e propiônico na germinação e na fase inicial do crescimento da plântula. Os resultados demonstraram que os caracteres avaliados respondem de forma diferente em relação aos tratamentos aplicados dentro do mesmo genótipo. Dessa forma, a seleção de um genótipo que manteve um comportamento padrão nos caracteres avaliados sob estresse é dificultado. Entretanto, em uma visão geral, o genótipo Hyola 433 manteve respostas características de sensibilidade nos caracteres avaliados em relação aos ácidos utilizados. Ainda, foi detectado que o ácido acético teve menor efeito na germinação e na fase inicial de crescimento dos genótipos estudados.

Organic acid effects on Brassica napus L. var. oleifera seed germination and seedling growth / Efeitos de ácidos orgânicos na germinação e crescimento inicial de Brassica napus L. var. oleifera

Canola (Brassica napus L. var. oleifera) is cultivated in the Southern Brazil as an alternative winter crop in the rotation system. No-tillage and hydromorphic soils favor the formation of aliphatic organic acids with short chain and low molecular weight, as acetic, butyric, and propionic acids. These acids may cause negative effects on the canola production. Thus, this study aimed to evaluate the response of five canola hybrid genotypes under the effect of acetic, butyric and propionic acids on the germination and initial phase of seedling growth. The results showed the characters evaluated respond differently to treatments applied within the same genotype. Therefore, the selection of a genotype with a resilient performance for the characters evaluated under stress is complex. Nevertheless, a sensitive profile response was observed in Hyola 433 genotype under different organic acids. Furthermore, acetic acid showed no negative impact on germination and initial growth of the genotypes.(AU)

A Canola (Brassica napus L. var. oleifera) é cultivada no Sul do Brasil como uma alternativa para a estação fria no sistema de rotação de culturas. O sistema de plantio direto e a ocorrência de solos hidromórficos favorece a formação de ácidos orgânicos alifáticos com cadeia curta e baixo peso molecular, como os ácidos acético, butírico e propiônico. Estes ácidos podem causar efeitos negativos na produção de canola. Assim, este estudo teve por objetivo avaliar a resposta de cinco genótipos híbridos de canola sob o efeito dos ácidos acético, butírico e propiônico na germinação e na fase inicial do crescimento da plântula. Os resultados demonstraram que os caracteres avaliados respondem de forma diferente em relação aos tratamentos aplicados dentro do mesmo genótipo. Dessa forma, a seleção de um genótipo que manteve um comportamento padrão nos caracteres avaliados sob estresse é dificultado. Entretanto, em uma visão geral, o genótipo Hyola 433 manteve respostas características de sensibilidade nos caracteres avaliados em relação aos ácidos utilizados. Ainda, foi detectado que o ácido acético teve menor efeito na germinação e na fase inicial de crescimento dos genótipos estudados.(AU)

Transgene escape and persistence in an agroecosystem: the case of glyphosate-resistant Brassica rapa L. in central Argentina.

Brassica rapa L. is an annual Brassicaceae species cultivated for oil and food production, whose wild form is a weed of crops worldwide. In temperate regions of South America and especially in the Argentine Pampas region, this species is widely distributed. During 2014, wild B. rapa populations that escaped control with glyphosate applications by farmers were found in this area. These plants were characterized by morphology and seed acidic profile, and all the characters agreed with B. rapa description. The dose-response assays showed that the biotypes were highly resistant to glyphosate. It was also shown that they had multiple resistance to AHAS-inhibiting herbicides. The transgenic origin of the glyphosate resistance in B. rapa biotypes was verified by an immunological test which confirmed the presence of the CP4 EPSPS protein and by an event-specific GT73 molecular marker. The persistence of the transgene in nature was confirmed for at least 4 years, in ruderal and agrestal habitats. This finding suggests that glyphosate resistance might come from GM oilseed rape crops illegally cultivated in the country or as a seed contaminant, and it implies gene flow and introgression between feral populations of GM B. napus and wild B. rapa. The persistence and spread of the resistance in agricultural environments was promoted by the high selection pressure imposed by intensive herbicide usage in the prevalent no-till farming systems.

Detection and Typing of "Candidatus Phytoplasma " spp. in Host DNA Extracts Using Oligonucleotide-Coupled Fluorescent Microspheres.

The use of oligonucleotide-coupled fluorescent microspheres is a rapid, sequencing-independent, and reliable way to diagnose bacterial diseases. Previously described applications of oligonucleotide-coupled fluorescent microspheres for the detection and identification of bacteria in human clinical samples have been successfully adapted to detect and differentiate "Ca. Phytoplasma" species using as a target the chaperonin 60-encoding gene. In this chapter, we describe in detail the design and validation of oligonucleotide capture probes, and their application in the assay aiming to differentiate phytoplasma strains infecting Brassica napus and Camelina sativa plants grown in the same geographic location at the same time.

IMI resistance associated to crop-weed hybridization in a natural Brassica rapa population: characterization and fate.

Wild turnip (Brassica rapa) is a common weed and a close relative to oilseed rape (Brassica napus). The Clearfield® production system is a highly adopted tool which provides an alternative solution for weed management, but its efficiency is threatened by gene transfer from crop to weed relatives. Crop-weed hybrids with herbicide resistance were found in the progeny of a B. rapa population gathered from a weedy stand on the borders of an oilseed rape (B. napus) imidazolinone (IMI)-resistant crop. Interspecific hybrids were confirmed by morphological traits in the greenhouse and experimental field, survival after imazethapyr applications, DNA content through flow cytometry, and pollen viability. The transference of herbicide resistance was demonstrated even in a particular situation of pollen competition between both an herbicide-resistant crop and a non-resistant crop. However, IMI resistance was not found in further generations collected at the same location. These results verify gene transmission from oilseed rape to B. rapa in the main crop area in Argentina where resistant and susceptible varieties are found and seed loss and crop volunteers are common. Hybridization, introgression, and herbicide selection would be associated with the loss of effectiveness of IMI technology.

Identification and cloning of GOLDEN2-LIKE1 (GLK1), a transcription factor associated with chloroplast development in Brassica napus L.

Photosynthesis is the process by which dry matter accumulates, which affects rapeseed yield. In this study, we identified GOLDEN2-LIKE1 (GLK1), located on chromosome A07 and 59.2 kb away from the single nucleotide polymorphism marker SNP16353A07, which encodes a transcription factor associated with the rate of photosynthesis in leaves. We then identified 96 GLK1 family members from 53 species using a hidden Markov model (HMM) search and found 24 of these genes, which were derived from 17 Brassicaceae species. Phylogenetic analysis showed that 24 Brassicaceae proteins were classified into three subgroups, named the Brassica family, Adenium arabicum, and Arabidopsis. Using homologous cloning methods, we identified four BnaGLK1 copies; however, the coding sequences were shorter than the putative sequences from the reference genome, probably due to splicing errors among the reference genome sequence or different gene copies being present in the different B. napus lines. In addition, we found that BnaGLK1 genes were expressed at higher levels in leaves with more chloroplasts than were present in other leaves. Overexpression of BnaGLK1a resulted in darker leaves and siliques than observed in the control, suggesting that BnaGLK1 might promote chloroplast development to affect the rate of photosynthesis in leaves. These results will help to elucidate the mechanism of chloroplast biogenesis by GLK1 in B. napus.

Behavior of canola hybrids and their F2 generations: physiological and sanitary seed quality / Comportamento de híbridos de canola e suas gerações F2: qualidade fisiológica e sanitária de sementes

The objective of this study was to compare the physiological and sanitary quality of canola hybrids and their respective F2 generations. The F2 generation seeds of commercial canola hybrids Hyola 61 and Hyola 433, harvested in July 2014, were evaluated as well as the hybrid seeds. The factorial arrangement (2x2) (Hybrid x Generation) in a completely randomized design was used, with four replications. The germination tests were carried out, tetrazolium, electrical conductivity and seed health, based on the percentage of contaminated seeds. The obtained seedlings had both shoot and root system length measured. The sanitary quality was assessed based on the percentage of seeds contaminated with Aspergillus spp. and Colletotrichum spp. fungi. There was a significant interaction between F2 generations and hybrids for the first count characteristics (PCG), second germination count (SCG) and shoot length (CPA). On the physiological quality, reduction in germination occurred only for hybrid Hyola 61, having approximately 43% less than the hybrid seeds germinated for the F2 generation. There were also differences between generations of abnormal seedlings characteristics and electrical conductivity, and the F1 progeny showed higher values for both. With regards to health quality, Aspergillus spp. and Colletotrichum spp. fungi. were checked, but there was no difference in the the F1 and [...]

Objetivou-se com esse trabalho comparar a qualidade fisiológica e sanitária da geração F2 de híbridos de canola com os seus respectivos híbridos. As sementes da geração F2 dos híbridos comerciais de canola Hyola 61 e Hyola 433, coletadas em julho de 2014, foram avaliadas juntamente com as sementes híbridas em esquema fatorial 2x2 (Híbridos x Gerações) em delineamento inteiramente casualizado com quatro repetições. Foram realizados os testes de germinação, tetrazólio, condutividade elétrica e sanidade das sementes, com base na porcentagem de sementes contaminadas. Nas plântulas obtidas no teste de germinação foi avaliado o comprimento da parte aérea e do sistema radicular. Houve interação significativa entre gerações e híbridos para a primeira contagem de germinação (PCG), segunda contagem de germinação (SCG) e comprimento da parte aérea (CPA). Sobre a qualidade fisiológica, a redução na germinação ocorreu somente para o híbrido Hyola 61, tendo aproximadamente 43% a menos de sementes germinadas do híbrido para a geração F2. Houve também diferenças entre as gerações para as características plântulas anormais e condutividade elétrica, sendo que a geração F1 apresentou valores superiores para ambas. Com relação à qualidade sanitária, foram verificados os fungos Aspergillus spp. e Colletotrichum spp., mas não houve diferença para as sementes da geração F1 e F2 e nem para os híbridos [...]

Behavior of canola hybrids and their F2 generations: physiological and sanitary seed quality / Comportamento de híbridos de canola e suas gerações F2: qualidade fisiológica e sanitária de sementes

The objective of this study was to compare the physiological and sanitary quality of canola hybrids and their respective F2 generations. The F2 generation seeds of commercial canola hybrids Hyola 61 and Hyola 433, harvested in July 2014, were evaluated as well as the hybrid seeds. The factorial arrangement (2x2) (Hybrid x Generation) in a completely randomized design was used, with four replications. The germination tests were carried out, tetrazolium, electrical conductivity and seed health, based on the percentage of contaminated seeds. The obtained seedlings had both shoot and root system length measured. The sanitary quality was assessed based on the percentage of seeds contaminated with Aspergillus spp. and Colletotrichum spp. fungi. There was a significant interaction between F2 generations and hybrids for the first count characteristics (PCG), second germination count (SCG) and shoot length (CPA). On the physiological quality, reduction in germination occurred only for hybrid Hyola 61, having approximately 43% less than the hybrid seeds germinated for the F2 generation. There were also differences between generations of abnormal seedlings characteristics and electrical conductivity, and the F1 progeny showed higher values for both. With regards to health quality, Aspergillus spp. and Colletotrichum spp. fungi. were checked, but there was no difference in the the F1 and [...](AU)

Objetivou-se com esse trabalho comparar a qualidade fisiológica e sanitária da geração F2 de híbridos de canola com os seus respectivos híbridos. As sementes da geração F2 dos híbridos comerciais de canola Hyola 61 e Hyola 433, coletadas em julho de 2014, foram avaliadas juntamente com as sementes híbridas em esquema fatorial 2x2 (Híbridos x Gerações) em delineamento inteiramente casualizado com quatro repetições. Foram realizados os testes de germinação, tetrazólio, condutividade elétrica e sanidade das sementes, com base na porcentagem de sementes contaminadas. Nas plântulas obtidas no teste de germinação foi avaliado o comprimento da parte aérea e do sistema radicular. Houve interação significativa entre gerações e híbridos para a primeira contagem de germinação (PCG), segunda contagem de germinação (SCG) e comprimento da parte aérea (CPA). Sobre a qualidade fisiológica, a redução na germinação ocorreu somente para o híbrido Hyola 61, tendo aproximadamente 43% a menos de sementes germinadas do híbrido para a geração F2. Houve também diferenças entre as gerações para as características plântulas anormais e condutividade elétrica, sendo que a geração F1 apresentou valores superiores para ambas. Com relação à qualidade sanitária, foram verificados os fungos Aspergillus spp. e Colletotrichum spp., mas não houve diferença para as sementes da geração F1 e F2 e nem para os híbridos [...](AU)

Transgenic glyphosate-resistant oilseed rape (Brassica napus) as an invasive weed in Argentina: detection, characterization, and control alternatives.

The presence of glyphosate-resistant oilseed rape populations in Argentina was detected and characterized. The resistant plants were found as weeds in RR soybeans and other fields. The immunological and molecular analysis showed that the accessions presented the GT73 transgenic event. The origin of this event was uncertain, as the cultivation of transgenic oilseed rape cultivars is prohibited in Argentina. This finding might suggest that glyphosate resistance could come from unauthorized transgenic oilseed rape crops cultivated in the country or as seed contaminants in imported oilseed rape cultivars or other seed imports. Experimentation showed that there are alternative herbicides for controlling resistant Brassica napus populations in various situations and crops. AHAS-inhibiting herbicides (imazethapyr, chlorimuron and diclosulam), glufosinate, 2,4-D, fluroxypyr and saflufenacil proved to be very effective in controlling these plants. Herbicides evaluated in this research were employed by farmers in one of the fields invaded with this biotype and monitoring of this field showed no evidence of its presence in the following years.

Discovery of clubroot-resistant genes in Brassica napus by transcriptome sequencing.

Clubroot significantly affects plants of the Brassicaceae family and is one of the main diseases causing serious losses in B. napus yield. Few studies have investigated the clubroot-resistance mechanism in B. napus. Identification of clubroot-resistant genes may be used in clubroot-resistant breeding, as well as to elucidate the molecular mechanism behind B. napus clubroot-resistance. We used three B. napus transcriptome samples to construct a transcriptome sequencing library by using Illumina HiSeq™ 2000 sequencing and bioinformatic analysis. In total, 171 million high-quality reads were obtained, containing 96,149 unigenes of N50-value. We aligned the obtained unigenes with the Nr, Swiss-Prot, clusters of orthologous groups, and gene ontology databases and annotated their functions. In the Kyoto encyclopedia of genes and genomes database, 25,033 unigenes (26.04%) were assigned to 124 pathways. Many genes, including broad-spectrum disease-resistance genes, specific clubroot-resistant genes, and genes related to indole-3-acetic acid (IAA) signal transduction, cytokinin synthesis, and myrosinase synthesis in the Huashuang 3 variety of B. napus were found to be related to clubroot-resistance. The effective clubroot-resistance observed in this variety may be due to the induced increased expression of these disease-resistant genes and strong inhibition of the IAA signal transduction, cytokinin synthesis, and myrosinase synthesis. The homology observed between unigenes 0048482, 0061770 and the Crr1 gene shared 94% nucleotide similarity. Furthermore, unigene 0061770 could have originated from an inversion of the Crr1 5'-end sequence.

Glyphosate-Resistant and Conventional Canola (Brassica napus L.) Responses to Glyphosate and Aminomethylphosphonic Acid (AMPA) Treatment.

Glyphosate-resistant (GR) canola contains two transgenes that impart resistance to the herbicide glyphosate: (1) the microbial glyphosate oxidase gene (gox) encoding the glyphosate oxidase enzyme (GOX) that metabolizes glyphosate to aminomethylphosphonic acid (AMPA) and (2) cp4 that encodes a GR form of the glyphosate target enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase. The objectives of this research were to determine the phytotoxicity of AMPA to canola, the relative metabolism of glyphosate to AMPA in GR and conventional non-GR (NGR) canola, and AMPA pool sizes in glyphosate-treated GR canola. AMPA applied at 1.0 kg ha(-1) was not phytotoxic to GR or NGR. At this AMPA application rate, NGR canola accumulated a higher concentration of AMPA in its tissues than GR canola. At rates of 1 and 3.33 kg ae ha(-1) of glyphosate, GR canola growth was stimulated. This stimulatory effect is similar to that of much lower doses of glyphosate on NGR canola. Both shikimate and AMPA accumulated in tissues of these glyphosate-treated plants. In a separate experiment in which young GR and NGR canola plants were treated with non-phytotoxic levels of [(14)C]-glyphosate, very little glyphosate was metabolized in NGR plants, whereas most of the glyphosate was metabolized to AMPA in GR plants at 7 days after application. Untreated leaves of GR plants accumulated only metabolites (mostly AMPA) of glyphosate, indicating that GOX activity is very high in the youngest leaves. These data indicate that more glyphosate is transformed to AMPA rapidly in GR canola and that the accumulated AMPA is not toxic to the canola plant.

Expression divergence of FRUITFULL homeologs enhanced pod shatter resistance in Brassica napus.

To improve pod shatter resistance in the important oilseed crop Brassica napus, the phenotypic diversity of B. napus was tested using 80 B. napus varieties for pod shatter resistance by a random impact test. Among these varieties, R1-1 was identified as resistant, while R2, 8908B was susceptible to shatter. To understand the molecular basis for this phenotypic difference based on the candidate gene approach, B. napus FRUITFULL (FUL) homologs were identified and characterized. Two FUL loci in the A and C genomes of B. napus were identified. In the susceptible variety, both BnaA.FUL and BnaC.FUL were expressed in the same tissues. However, the expression level of BnaC.FUL differed in varieties with different pod shatter resistance. In the most resistant variety, R1-1, only BnaA.FUL was expressed, while BnaC.FUL was silenced. Therefore, the functional divergence and differing expression of BnaX.FUL homeologs may significantly affect phenotypic variation, which is an important consequence of allopolyploid evolution. This expression level divergence may be useful for selecting pod shatter resistant lines through marker-assisted selection in B. napus-breeding programs.

An insight in the genetic control and interrelationship of some quality traits in Brassica napus.

A study on three leading lines (KN-256, KN-257, and KN-258) of Brassica napus and an approved variety, Punjab-Sarson, was conducted to gain insight into the genetic control of some quality traits using generation mean analysis. Our results showed that additive gene action predominated in the inheritance of oil content and erucic acid in cross KN-256 x KN-257 and in that of glucosinolates in KN-258 x Punjab-Sarson, indicating that these traits may be improved through selection in early segregating generations. Negative dominance can be exploited through heterosis breeding for the development of lines with low glucosinolates in cross KN-256 x KN-257. Protein content and oleic acid in cross KN-256 x KN-257, and oil content, protein content, and erucic acid in cross KN-258 x Punjab-Sarson depicted non-additive gene action and require further improvement in the later segregating generations. Most of the traits displayed high heritability estimates; glucosinolate content in both the crosses and erucic acid in cross KN- 258 x Punjab-Sarson also displayed high genetic advance, reflecting improvement of the trait in the early segregating generations. All the quality traits were positively correlated with oil content and with one another at both (genotypic and phenotypic) levels in KN-256 x KN-257. Negative correlation was observed between glucosinolate and erucic acid, oleic acid and erucic acid, and linolenic acid and oil content in cross KN-258 x Punjab-Sarson. Thus, gene action changed with the material, and cross KN-258 x Punjab-Sarson carried favorable combinations compared to KN-256 x KN-257.

Functional analysis of the Brassica napus L. phytoene synthase (PSY) gene family.

Phytoene synthase (PSY) has been shown to catalyze the first committed and rate-limiting step of carotenogenesis in several crop species, including Brassica napus L. Due to its pivotal role, PSY has been a prime target for breeding and metabolic engineering the carotenoid content of seeds, tubers, fruits and flowers. In Arabidopsis thaliana, PSY is encoded by a single copy gene but small PSY gene families have been described in monocot and dicotyledonous species. We have recently shown that PSY genes have been retained in a triplicated state in the A- and C-Brassica genomes, with each paralogue mapping to syntenic locations in each of the three "Arabidopsis-like" subgenomes. Most importantly, we have shown that in B. napus all six members are expressed, exhibiting overlapping redundancy and signs of subfunctionalization among photosynthetic and non photosynthetic tissues. The question of whether this large PSY family actually encodes six functional enzymes remained to be answered. Therefore, the objectives of this study were to: (i) isolate, characterize and compare the complete protein coding sequences (CDS) of the six B. napus PSY genes; (ii) model their predicted tridimensional enzyme structures; (iii) test their phytoene synthase activity in a heterologous complementation system and (iv) evaluate their individual expression patterns during seed development. This study further confirmed that the six B. napus PSY genes encode proteins with high sequence identity, which have evolved under functional constraint. Structural modeling demonstrated that they share similar tridimensional protein structures with a putative PSY active site. Significantly, all six B. napus PSY enzymes were found to be functional. Taking into account the specific patterns of expression exhibited by these PSY genes during seed development and recent knowledge of PSY suborganellar localization, the selection of transgene candidates for metabolic engineering the carotenoid content of oilseeds is discussed.

Relações de variáveis ambientais e subperíodos na produtividade e teor de óleo em canola / Relations of environments variables and subperiods in yield and content oil in canola

O objetivo do estudo foi avaliar as relações existentes entre a produtividade de grãos, teor de óleo e subperíodos da canola com a soma térmica (ST, ºC dias) e a insolação real acumulada (IAC, horas) durante a fase de enchimento de grãos, além de classificar a importância dessas variáveis sobre as diferenças morfológicas observadas. Foram realizados três experimentos, com espaçamentos entre linhas de 0.20, 0.40 e 0.60m. Durante dois anos de cultivo (2008 e 2009), os genótipos 'Hyola 432' (precoce) e 'Hyola 61' (médio) foram avaliados em três densidades de plantio (20, 40 e 60 plantas m-2), em cada experimento. O delineamento experimental utilizado foi o de blocos ao acaso, em arranjo fatorial 2x2x3 (anos x genótipos x densidades), com quatro repetições. A soma térmica no subperíodo da floração à maturação fisiológica não está diretamente associada ao rendimento e teor de óleo nos grãos, frente ao arranjo de plantas. Os dias da emergência ao início da floração, da emergência à floração final e o tempo de duração da floração em canola são as variáveis que mais contribuem para a variação morfológica total.(AU)

The objective of the study was to evaluate the relationship among grain yield, oil content and subperiods of canola with thermal time and accumulated sunshine hours during of grain-filling phase and classify the importance of this variables about morphological differences observed. Three experiments were carried out with row spacing of 0.20, 0.40 and 0.60m. During two crop years (2008 and 2009), the genotypes 'Hyola 432' and 'Hyola 61' were evaluated in three plant densities (20, 40 e 60 plants m-2) in each experiment. The experimental design was to randomized blocks in factorial arrangement 2x2x3 (years x genotypes x densities), with four replicates. The thermal time in subperiod of flowering to physiological maturation is not associated directly to the yield and oil content in grains by plant arrangement. The days of emergence to the beginning of flowering, of emergence to late flowering and duration time of flowering in canola are variables more contribute to morphological variation total.(AU)