Winter Oilseed Rape Plants Research Articles

Mixed-Effects Estimation in Dynamic Models of Plant Growth for the Assessment of Inter-individual Variability

Modeling inter-individual variability in plant populations is a key issue to understand crop heterogeneity and its variations in response to the environment. Being able to describe the interactions among plants and explain the variability observed in the population could provide useful information on how to control it and improve global plant growth. We propose here a method to model plant variability within a field, by extending the so-called GreenLab functional-structural plant model from the individual to the population scale via nonlinear mixed-effects modeling. Parameter estimation of the population model is achieved using the stochastic approximation expectation maximization algorithm, implemented in the platform for plant growth modeling and analysis PyGMAlion. The method is first applied on a set of simulated data and then on a real dataset from a population of 34 winter oilseed rape plants at the rosette stage. Results show that our method allows for a good characterization of the variability in the population with only a limited number of parameters, which is a key point for plant models. Results on simulated data show that parameters associated with a low sensitivity index are inaccurately estimated by the algorithm when considered as random effects, but a good stability of the results can be obtained by considering them as fixed effects. These results open new ways for the analysis of inter-plant variability within a population and the study of plant–plant competition.Supplementary materials accompanying this paper appear online.

Determination of the Titanium Contents in the Winter Oilseed Rape Plants (Brassica napus L.) by the Application of Fertilizer Containing Titanium

In order to obtain the information about changes of titanium contents in the phytomass during the growing season of winter oilseed rape and about the titanium contents drawn by the rape yield during two farming years the small plot field trial was established. In the trial the fertilizer Mg-Titanit (MgTi) containing 8.5 g of titanium in 1 liter was used. The experiment consisted of 5 treatments. 0 – control treatment without MgTi fertilizer; 2xTi0.2 – two applications of MgTi in the dose of 0.2 l/ha; 3xTi0.2 – three applications of MgTi in the dose of 0.2 l/ha; 2xTi0.4 – two applications of MgTi in the dose of 0.4 l/ha; 3xTi0.4 – three applications of MgTi in the dose of 0.4 l/ha. The fertilizer was applied in spring during two, or three different growth stages: BBCH 50, BBCH 59, BBCH 66. The first plant sampling was carried out shortly before the first application of fertilizer (BBCH 50). The second, third and fourth sampling was taken 2–3 weeks after the application of Mg-Titanitu (BBCH 59, BBCH 66, BBCH 71). The obtained results showed that the titanium content in the phytomass of rape was falling during the monitored period. The titanium content in the rape aboveground phytomass varied in the interval from 16.81 to 67.6 mg/kg and in the root in the interval from 56.6 to 258.81 mg/kg. The titanium application on plant leaves in the quantities from 3.4 to 10.2 g per hectare of soil did not have the unambiguous impact on the titanium content in the rape phytomass. In the yield of one tonne of seed and appropriate quantity of rape straw on average 20 grams of titanium was taken in.

Use of petal test in early-flowering varieties of oilseed rape (Brassica napus L.) for predicting the infection pressure of Sclerotinia sclerotiorum (Lib.) de Bary

Sclerotinia sclerotiorum is one of the most important pathogens of winter oilseed rape plants. It causes the white mould disease of rape, thus significantly reducing the yield. The aim of our research was to use a spring oilseed rape variety sown in autumn or an early-flowering variety of winter oilseed rape to predict the infection pressure of S. sclerotiorum in a given year. Field experiments were conducted in 2008–2012 at the experimental station of the Czech University of Life Sciences Prague at Červený Újezd, 20 km west of Prague. In the experiment, we used one variety of spring oilseed rape (Lužnice, LU) and one early-flowering variety of winter oilseed rape (Californium, CA). The methodology of the petal test involved isolating pathogenic fungi from fallen petals on a nutrient medium (potato dextrose agar) in Petri dishes. The first term of collection was the beginning of petal fall (BBCH 61) and the last term was the end of flowering (BBCH 69). The dishes with petals were visually analysed after 1 week. The results were compared with the actual occurrence of white mould of rape in the stand. The occurrence of white mould of rape was strongly influenced by the progress of weather conditions over the given year. Infected petals and stems with symptoms of white mould of rape were found to be moderately correlated (r = 0.80). Spread of white mould spores was mostly observed in two terms (BBCH 62 and BBCH 65). Statistically significant differences were not observed in the infection of petals of spring (LU) and winter (CA) oilseed rape. Spring oilseed rape (LU) and early-flowering varieties of winter oilseed rape (CA) can be used to determine the strength of infection pressure of S. sclerotiorum in the stand in a given year, thereby improving protection against white mould of rape.

Gene flow between imidazolinone‐tolerant and – susceptible winter oilseed rape varieties

Krato C & Petersen J (2012). Gene flow between imidazolinone‐tolerant and – susceptible winter oilseed rape varieties. Weed Research 52, 187–196.SummaryImidazolinone‐tolerant (IT) spring oilseed rape was developed in 1987 using conventional breeding methods and first marketed in Canada in 1996. IT winter oilseed rape will be introduced into the European market. On the one hand, the IT cropping system provides the opportunity for post‐emergence weed control in oilseed rape. On the other hand, the introduction of a new herbicide‐tolerance (HT) trait into the European cropping systems may lead to new challenges for weed control in crop rotations containing winter oilseed rape. In this study, a 2‐year field and glasshouse study was carried out to determine the transfer frequency of the HT trait from IT winter oilseed rape plants to adjacently grown susceptible winter oilseed rape plants. Furthermore, cross‐resistance to sulfonylureas and differences in herbicide response of heterozygous and homozygous IT winter oilseed rape varieties to triflusulfuron‐methyl were examined. The transfer frequency of the resistance trait and zygosity of the F1‐generation was investigated using a real‐time quantitative polymerase chain reaction (qPCR). Outcrossing frequencies ranged from 2.05% in a westerly direction and 0.57% in an easterly direction at the closest distance of 2 m between pollen donor (IT oilseed rape plants) and pollen acceptor (imidazolinone‐susceptible plants). Outcrossing events decreased significantly with increasing distance from the pollen donor, but IT F1‐plants were still found at a distance of 45 m. Of the analysed F1‐oilseed rape plants, 84% showed both independent tolerance genes for imidazolinone‐tolerance (PM1 and PM2) and were heterozygous for both genes. IT winter oilseed rape plants showed a cross‐tolerance against triflusulfuron‐methyl, and the corresponding resistance factors were higher for homozygous biotypes compared with heterozygous ones. Consequently, outcrossing can result practically in IT volunteers with cross‐tolerance to triflusulfuron‐methyl.

Freezing tolerance and proline content of in vitro selected hydroxyproline resistant winter oilseed rape

Twelve doubled haploid (DH) winter oilseed rape plants with altered levels of proline and/or freezing tolerance were obtained by in vitro selection for resistance to trans-4-hydroxy-l-proline (Hyp) in five segregating microspore populations. No significant response to selection either in proline content or in freezing tolerance, compared with the non-selected control populations, was observed. When data from all examined materials were combined, a weak correlation between proline content and freezing tolerance was observed.

The effect of soil and foliar application of sulfur on the yield and mineral composition of winter oilseed rape plants

The effect of soil and foliar application of sulfur on the yield and mineral composition of winter oilseed rape plants

Are Pectins Involved in Cold Acclimation and De-acclimation of Winter Oil-seed Rape Plants?

The hypothesis was tested that pectin content and methylation degree participate in regulation of cell wall mechanical properties and in this way may affect tissue growth and freezing resistance over the course of plant cold acclimation and de-acclimation. Experiments were carried on the leaves of two double-haploid lines of winter oil-seed rape (Brassica napus subsp. oleifera), differing in winter survival and resistance to blackleg fungus (Leptosphaeria maculans). Plant acclimation in the cold (2 degrees C) brought about retardation of leaf expansion, concomitant with development of freezing resistance. These effects were associated with the increases in leaf tensile stiffness, cell wall and pectin contents, pectin methylesterase (EC 3.1.1.11) activity and the low-methylated pectin content, independently of the genotype studied. However, the cold-induced modifications in the cell wall properties were more pronounced in the leaves of the more pathogen-resistant genotype. De-acclimation promoted leaf expansion and reversed most of the cold-induced effects, with the exception of pectin methylesterase activity. The results show that the temperature-dependent modifications in pectin content and their methyl esterification degree correlate with changes in tensile strength of a leaf tissue, and in this way affect leaf expansion ability and its resistance to freezing and to fungus pathogens.

Phenylpropanoid deficiency affects the course of plant acclimation to cold

The effects of phenylpropanoid deficiency on plant growth, photosynthetic efficiency of the photosystem II and freezing tolerance of leaves were studied during acclimation of winter oilseed rape plants (Brassica napus L. var. oleifera L. cv Jantar) at low temperature. Application of 2‐amino‐2‐indanophosphonic acid inhibited phenylalanine ammonia‐lyase (E.C. 4.3.1.5) activity by about 90%. This was followed by a marked reduction of soluble phenolics (in particular hydroxycinnamic acids) and anthocyanins in leaves. Inhibition of the cold‐promoted incorporation of ferulic acid into cell walls was also observed. The reduction of phenylpropanoid contents was associated with: (1) partial abrogation of the cold‐induced growth effects, such as inhibition of leaf fresh weight increments and accumulation of dry matter, proteins and cell walls; (2) decreased photochemical efficiency of photosystem II in low temperature‐affected leaves; and (3) decreased ability of leaves to develop tolerance to the extracellular formation of ice. These findings are discussed in terms of phenylpropanoids' role in plant responses to cold (> 0°C) and freezing temperatures.

Colonization of winter oilseed rape tissues by A/Tox+and B/Tox0Leptosphaeria maculans(phoma stem canker) in France and England

The colonization of winter oilseed rape plants and epidemiology of phoma stem canker differed between A/Tox+and B/Tox0Leptosphaeria maculans. In France and England, where plant colonization was investigated during two and three growing seasons, respectively, there was a difference in timing of leaf infection; A/Tox+L. maculanswas predominant on leaves in the autumn (October/November) but there was an increase in the incidence of B/Tox0in the winter (January/February). In May, June and July both species could be isolated from all external parts of the plant (root to the upper stem) and all crown (stem base) tissues, although they differed in their distribution. At the root and crown, A/Tox+L. maculanswas predominant and was located throughout the cortex, wood and pith tissues, but the rarer B/Tox0was located mainly in the cortex. Approximately equal numbers of A/Tox+and B/Tox0isolates were obtained from the upper stem – there was a greater proportion of B/Tox0isolates than at the crown. In England, after harvest in 1999 and 2000, pseudothecia on the lignified tap root and crown tissues produced predominantly A/Tox+ascospores (94%), while pseudothecia higher up the stem produced more B/Tox0ascospores (60%) than A/Tox+ascospores (40%). The timing of the onset of leaf spotting, earlier in the season for A/Tox+than B/Tox0L. maculans, and the predominance of mycelium of A/Tox+at the crown are consistent with the assumption that A/Tox+is more likely to cause the most damaging stem cankers than B/Tox0L. maculans. Identification as A/Tox+or B/Tox0by cultural characteristics differed only slightly (2·3%) from identification by molecular techniques.

Low temperature-induced modifications of cell wall content and polysaccharide composition in leaves of winter oilseed rape ( Brassica napus L. var. oleifera L.)

Pronounced modifications in cell wall content and polysaccharide composition were observed in the young leaves of winter oilseed rape plants ( Brassica napus L. var. oleifera L. cv Jantar) grown for 3 weeks in cold (2°C) and then exposed to a brief freezing and thawing treatment (−5°C for 18 h). In the cold-grown leaf blades, the increased cell wall content was associated with higher levels of non-covalently bound pectins. The content of galactose, arabinose and glucose in pectins and of galactose and arabinose in hemicelluloses also increased in these leaves. Exposure of cold-acclimated plants to a freeze-thaw treatment resulted in decreased cell wall content, reduced levels of non-covalently bound pectins and decreased contents of xylose and glucose in the hemicellulose fraction. Our findings indicate that the pattern of modifications of cell wall content and polysaccharide composition depends on the range of temperatures the plant has been exposed to. The role of the cell wall in cold-acclimated and freezing treated plants is discussed.

Inositol 1,4,5-trisphosphate formation in leaves of winter oilseed rape plants in response to freezing, tissue water potential and abscisic acid

Inositol 1,4,5-trisphosphate formation in leaves of winter oilseed rape plants in response to freezing, tissue water potential and abscisic acid

Inositol 1,4,5‐trisphosphate formation in leaves of winter oilseed rape plants in response to freezing, tissue water potential aed abscisic acid

Time courses of formation of inositol 1,4,5‐trisphosphate (IP3) were followed in the leaves of non‐acclimated and cold (2°C)‐acclimated winter oilseed rape (Brassica napus L. var. oleifera) plants, subjected to different freezing temperatures or to polyethylene glycol 8000 (PEG) and abscisic acid (ABA) treatments. Changes in water potential (Ψw) and in ABA level in the frost‐ and PEG‐treated tissues were also determined. Results obtained indicate that temperatures sligthly higher than LT50 induced a transient and substantial increase in IP3 level, both in non‐acclimated and cold‐acclimated tissues. At comparable freezing temperature (–5°C) the response of cold‐acclimated leaves was lower than that of non‐acclimated ones. The PEG‐depedent decrease in Ψw to –0.9 MPa or ABA (0.1 mM) treatment gave rise to a transient increase in IP3 content in non‐acclimated tissues only. Collectively, the data indicate that cold acclimation of plants may lead to lower cell responsiveness to the factors studied in terms of induction of IP3 formation. Changes in the IP3 content, observed in the present experiments, support our previous suggestion that non‐killing freezing temperatures may induce the phosphoinositide pathway, both in non‐acclimated and cold‐acclimated tissues. Lowering of tissue water potential to some threshold value or a high exogenous ABA supply may mimic the freezing‐dependent reaction in the non‐acclimated leaves.

Modifications of abscisic acid level in winter oilseed rape leaves during acclimation of plants to freezing temperatures

An almost twofold increase in abscisic acid (ABA) content was observed in the leaves of winter oilseed rape plants (Brassica napus L., var. oleifera L., cv. Jantar) grown in the cold (>0°C). This ABA increase took place during the first three days of cold treatment. After 6 days of plant growth in the cold, the level of ABA started to decline or remained constant, depending on the calculation basis: dry weight or disc area units, respectively. The exposure of cold-acclimated plants to night frost (−5°C for 18 h) induced a further increase (65%) in the ABA level, which begun during the first few hours after thawing. The comparison of time courses of frost resistance increments and ABA content changes showed that modifications of ABA level in the cold-treated leaves preceded those of frost resistance, whereas in the frost-pretreated tissues the ABA increase occurred later than that of frost tolerance. Possible interrelations between ABA content, frost tolerance and tissue water potential modifications in the low temperature-affected tissues are discussed.

The influence of pre-floral growth and development on the pathway of floral development, dry matter distribution and seed yield in oilseed rape (Brassica napus L.)

Patterns of floral development, dry matter distribution and seed yield were examined in winter oilseed rape plants subjected to different pre-floral growth environments. The duration of pre-floral growth and plant size at flower initiation, measured in terms of total mainstem leaf number, were manipulated by varying the temperature between seedling emergence and flower initiation. Exposure of seedlings to low temperatures from cotyledon expansion onwards markedly reduced the duration of pre-floral growth and the number of leaves on the mainstem. The subsequent development pattern of plants was largely dependent on the date of flower initiation and therefore vernalisation requirement. Indeed, the period of growth from flower initiation to maturity, considered on the basis of thermal time, was directly related to the duration of pre-floral growth and mainstem leaf number. The thermal durations of the bud development phase and flowering period in plants exposed to different pre-floral cold treatments but with a common date of flower initiation were similarly linked to these two parameters. Plants exposed to prolonged periods of low temperature treatment from cotyledon expansion onwards initiated fewer mainstem leaves during a relatively short pre-floral growth phase and their yield potential was limited by a reduction in branch and flower numbers. Plants maintained at higher temperatures produced more mainstem leaves during an extended period of pre-floral growth and supported a greater number of branches and flowers. However, this additional yield potential was not realised due to a reduction in seed numbers and mean seed weight. It appeared that seed yield of these plants was limited by increased competition between an excessive number of lower branches and flowers, a problem apparently created by excessive pre-floral growth. Minimal competition for available assimilates between the limited number of branches of plants with a shorter pre-floral growth phase and fewer mainstem leaves, resulted in lower levels of pod abortion, greater seed production and ultimately increased seed yields.

Transfer and segregation of triazine tolerant chloroplasts in Brassica napus L.

Hypocotyl protoplasts of 45 different genotypes of German winter oilseed rape Brassica napus L. (double zero quality: high in yield, seeds low in erucic acid and glucosinolate content) were regenerated to plants. Triazine/triazinone (tri)-tolerant chloroplasts of the Canadian spring oilseed rape variety OAC Triton were introduced into some winter oilseed rapes by means of protoplast fusion. X-ray irradiation was used to limit the transfer of nuclear DNA of Triton protoplasts and to promote the selective transfer of tri-tolerant chloroplasts. Regenerated "cybrid" plants survived a treatment rate of 1000 g/ha metribuzin. The presence and segregation of the tri-tolerant chloroplasts in winter oilseed rape plants, regenerated from fusion products and their progeny, was investigated by restriction fragment length polymorphism (RFLP). Our results indicate that chloroplast segregation was not completed in plants regnerated from fusion products derived from X-irradiated OAC Triton mesophyll protoplasts and German winter oilseed rape hypocotyl protoplasts. In regenerants and their progeny both chloroplast types can still be present. Chloroplasts derived from wintertype protoplasts can outcompete tritolerant chloroplasts during plant development. In some instances, even progeny plants not kept under selective conditions (metribuzin) lost tri-tolerant chloroplasts. A homogenous population of tri-tolerant chloroplasts was necessary to obtain stable tri-tolerant winter oilseed rape plants.